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  • 1.
    Abrahamsson, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Hedlund, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Kamf, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Bernhoff, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    High-Speed Kinetic Energy Buffer: Optimization of Composite Shell and Magnetic Bearings2014In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 61, no 6, p. 3012-3021Article in journal (Refereed)
    Abstract [en]

    This paper presents the design and optimization of a high-speed (30 000 r/min) kinetic energy storage system. The purpose of the device is to function as an energy buffer storing up to 867 Wh, primarily for utility vehicles in urban traffic. The rotor comprises a solid composite shell of carbon and glass fibers in an epoxy matrix, constructed in one curing. The shell is optimized using a combined analytical and numerical approach. The radial stress in the shell is kept compressive by integrating the electric machine, thereby avoiding delamination. Radial centering is achieved through eight active electromagnetic actuators. The actuator geometry is optimized using a direct coupling between SolidWorks, Comsol, and Matlab for maximum force over resistive loss for a given current density. The optimization results in a system with 300% higher current stiffness than the reference geometry with constant flux area, at the expense of 33% higher power loss. The actuators are driven by semipassive H bridges and controlled by an FPGA. Current control at 20 kHz with a noise of less than 5 mA (95% CI) is achieved, allowing position control at 4 kHz to be implemented.

  • 2.
    Abro, Mehwish
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Modelling the exfoliation of graphite for production of graphene2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of my thesis is to make a theoretical model of data obtained from liquid-phase exfoliation of graphene. The production of graphene in the liquid phase exfoliation is a cost efficient method One part of this work is devotedto learn the method of production of graphene by the shear mixing technique from the graphite and to estimate some important parameters which are crucial for the process. Other part of my work is based on studying the liquid-phase exfoliation mechanism of graphene through ultrasonication technique. This method is time consuming as compared to shearmixing.

  • 3.
    Adrian, Ehrnebo
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Single Crystalline CVD Diamond Based Devices for Power Electronics Applications2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Chemical vapor deposited single-crystalline diamond has rare material properties such as thermal conductivity five times as high as copper, a wide band gap, a high breakdown field and high carrier mobilities. This makes it a very interesting material for high power, high frequency and high temperature applications.

    In this thesis work, metal oxide semiconductor (MOS) capacitors of diamond substrate were fabricated and analyzed. The MOS capacitor is a building block of the metal oxide semiconductor field effect transistor (MOSFET). Capacitance-voltage (C-V) measurements can provide useful information of the operation of a MOS. Electrical characterization by C-V and current-voltage (I-V) measurements at temperatures ranging from 20 to 150 degrees Celsius were performed on the MOS capacitors to examine flatband and threshold voltages, oxide charge, and oxide thickness.

    At elevated temperatures, low frequency C-V curves with threshold voltages of approximately 5 V were obtained for MOS capacitors consisting of aluminum gates, a 30 nm layer of aluminum oxide, and boron doped diamond with acceptor concentration 3.1 x 1017 cm-3. The C-V measurements also showed large variations in flatband voltage for different contacts of the MOS capacitor, indicating the presence of oxide charge. Oxide thickness was also extracted from the C-V measurements, typically showing thicknesses around 15-19 nm.

    Also in this  thesis, an alternative method for reducing the electric field strength around the edges of the contact of a Schottky diode has been examined. This method consists of alternating the geometry by etching the semiconductor where the contact is to be placed. Simulations performed in Comsol Multiphysics showed that a reduction of the field strength of approximately 30 % at the contacts could be achieved by etching the substrate.

  • 4.
    Ahlberg, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Graphene Implementation Study in Semiconductor Processing2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Graphene, with its two-dimensional nature and unique properties, has for over a decade captured enormous interests in both industry and academia. This work tries to answer the question of what would happen to graphene when it is subjected to various processing conditions and how this would affect the graphene functionality. The focus is placed on its ability to withstand different thin-film deposition environments with regard to the implementation of graphene in two application areas: as a diffusion barrier and in electronic devices.

    With single-layer graphene films grown in-house by means of chemical vapor deposition (CVD), four techniques among the well-established thin-film deposition methods are studied in detail: atomic layer deposition (ALD), evaporation, sputter-deposition and spray-deposition. And in this order, these methods span a large range of kinetic impact energies from low to high. Graphene is known to have a threshold displacement energy of 22 eV above which carbon atoms are ejected from the lattice. Thus, ALD and evaporation work with energies below this threshold, while sputtering and spraying may involve energies above. The quality of the graphene films undergone the various depositions is mainly evaluated using Raman spectroscopy.

    Spray deposition of liquid alloy Ga-In-Sn is shown to require a stack of at least 4 layers of graphene in order to act as an effective barrier to the Ga diffusion after the harsh spray-processing. Sputter-deposition is found to benefit from low substrate temperature and high chamber pressure (thereby low kinetic impact energy) so as to avoid damaging the graphene. Reactive sputtering should be avoided. Evaporation is non-invasiveness with low kinetic impact energy and graphene can be subjected to repeated evaporation and removal steps without losing its integrity. With ALD, the effects on graphene are of different nature and they are investigated in the field-effect-transistor (FET) configuration. The ALD process for deposition of Al2O3 films is found to remove undesired dopants from the prior processing and the Al2O3 films are shown to protect the graphene channel from doping by oxygen. When the substrate is turned hydrophobic by chemical treatment prior to graphene transfer-deposition, a unipolar transistor behavior is obtained.

    List of papers
    1. A two-in-one process for reliable graphene transistors processed with photolithography
    Open this publication in new window or tab >>A two-in-one process for reliable graphene transistors processed with photolithography
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    2015 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 107, no 20, article id 203104Article in journal (Refereed) Published
    Abstract [en]

    Research on graphene field-effect transistors (GFETs) has mainly relied on devices fabricated using electron-beam lithography for pattern generation, a method that has known problems with polymer contaminants. GFETs fabricated via photo-lithography suffer even worse from other chemical contaminations, which may lead to strong unintentional doping of the graphene. In this letter, we report on a scalable fabrication process for reliable GFETs based on ordinary photo-lithography by eliminating the aforementioned issues. The key to making this GFET processing compatible with silicon technology lies in a two-in-one process where a gate dielectric is deposited by means of atomic layer deposition. During this deposition step, contaminants, likely unintentionally introduced during the graphene transfer and patterning, are effectively removed. The resulting GFETs exhibit current-voltage characteristics representative to that of intrinsic non-doped graphene. Fundamental aspects pertaining to the surface engineering employed in this work are investigated in the light of chemical analysis in combination with electrical characterization.

    National Category
    Physical Sciences Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-269191 (URN)10.1063/1.4935985 (DOI)000365688700049 ()
    Funder
    Knut and Alice Wallenberg Foundation, 2011.0113, 2011.0082Swedish Foundation for Strategic Research , SE13-0061Swedish Research Council, 621-2014-5591
    Available from: 2015-12-14 Created: 2015-12-14 Last updated: 2017-12-01Bibliographically approved
    2. Interface Dependent Effective Mobility in Graphene Field Effect Transistors
    Open this publication in new window or tab >>Interface Dependent Effective Mobility in Graphene Field Effect Transistors
    2018 (English)In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 47, no 3, p. 1757-1761Article in journal (Refereed) Published
    Abstract [en]

    By pretreating the substrate of a graphene field-effect transistor (G-FET), a stable unipolar transfer characteristic, instead of the typical V-shape ambipolar behavior, has been demonstrated. This behavior is achieved through functionalization of the SiO2/Si substrate that changes the SiO2 surface from hydrophilic to hydrophobic, in combination with postdeposition of an Al2O3 film by atomic layer deposition (ALD). Consequently, the back-gated G-FET is found to have increased apparent hole mobility and suppressed apparent electron mobility. Furthermore, with addition of a top-gate electrode, the G-FET is in a double-gate configuration with independent top- or back-gate control. The observed difference in mobility is shown to also be dependent on the top-gate bias, with more pronounced effect at higher electric field. Thus, the combination of top and bottom gates allows control of the G-FET's electron and hole mobilities, i.e., of the transfer behavior. Based on these observations, it is proposed that polar ligands are introduced during the ALD step and, depending on their polarization, result in an apparent increase of the effective hole mobility and an apparent suppressed effective electron mobility.

    National Category
    Engineering and Technology Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Electronics
    Identifiers
    urn:nbn:se:uu:diva-284924 (URN)10.1007/s11664-017-6023-6 (DOI)000424341700002 ()
    Funder
    Knut and Alice Wallenberg Foundation, 2011.0082Swedish Research Council, 2014-5591
    Available from: 2016-04-19 Created: 2016-04-19 Last updated: 2018-04-11Bibliographically approved
    3. Defect formation in graphene during low-energy ion bombardment
    Open this publication in new window or tab >>Defect formation in graphene during low-energy ion bombardment
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    2016 (English)In: APL Materials, ISSN 2166-532X, Vol. 4, no 4, article id 046104Article in journal, Letter (Refereed) Published
    Abstract [en]

    This letter reports on a systematic investigation of sputter induced damage in graphene caused by low energy Ar+ ion bombardment. The integral numbers of ions per area (dose) as well as their energies are varied in the range of a few eV's up to 200 eV. The defects in the graphene are correlated to the dose/energy and different mechanisms for the defect formation are presented. The energetic bombardment associated with the conventional sputter deposition process is typically in the investigated energy range. However, during sputter deposition on graphene, the energetic particle bombardment potentially disrupts the crystallinity and consequently deteriorates its properties. One purpose with the present study is therefore to demonstrate the limits and possibilities with sputter deposition of thin films on graphene and to identify energy levels necessary to obtain defect free graphene during the sputter deposition process. Another purpose is to disclose the fundamental mechanisms responsible for defect formation in graphene for the studied energy range.

    National Category
    Materials Chemistry Nano Technology
    Identifiers
    urn:nbn:se:uu:diva-284702 (URN)10.1063/1.4945587 (DOI)000375846100007 ()
    Funder
    Knut and Alice Wallenberg Foundation, 2011.0082Swedish Research Council, 2014-5591 2014-6463
    Available from: 2016-04-19 Created: 2016-04-19 Last updated: 2017-01-25Bibliographically approved
    4. Toward synthesis of oxide films on graphene with sputtering based processes
    Open this publication in new window or tab >>Toward synthesis of oxide films on graphene with sputtering based processes
    2016 (English)In: Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics, ISSN 2166-2746, E-ISSN 2166-2754Article in journal (Refereed) Submitted
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-284706 (URN)
    External cooperation:
    Available from: 2016-04-19 Created: 2016-04-19 Last updated: 2017-11-30
    5. Graphene as a Diffusion Barrier in Galinstan-Solid Metal Contacts
    Open this publication in new window or tab >>Graphene as a Diffusion Barrier in Galinstan-Solid Metal Contacts
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    2014 (English)In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, Vol. 61, no 8, p. 2996-3000Article in journal (Refereed) Published
    Abstract [en]

    This paper presents the use of graphene as a diffusion barrier to a eutectic Ga-In-Sn alloy, i.e., galinstan, for electrical contacts in electronics. Galinstan is known to be incompatible with many conventional metals used for electrical contacts. When galinstan is in direct contact with Al thin films, Al is readily dissolved leading to the formation of Al oxides present on the surface of the galinstan droplets. This reaction is monitored ex situ using several material analysis methods as well as in situ using a simple circuit to follow the time-dependent resistance variation. In the presence of a multilayer graphene diffusion barrier, the Al-galinstan reaction is effectively prevented for galinstan deposited by means of drop casting. When deposited by spray coating, the high-impact momentum of the galinstan droplets causes damage to the multilayer graphene and the Al-galinstan reaction is observed at some defective spots. Nonetheless, the graphene barrier is likely to block the formation of Al oxides at the Al/galinstan interface leading to a stable electrical current in the test circuit.

    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering Nano Technology
    Research subject
    Engineering Science with specialization in Electronics; Engineering Science with specialization in Microsystems Technology
    Identifiers
    urn:nbn:se:uu:diva-229503 (URN)10.1109/TED.2014.2331893 (DOI)000342906200056 ()
    Available from: 2014-08-10 Created: 2014-08-10 Last updated: 2017-12-05Bibliographically approved
    6. Scalable residue-free graphene for surface-enhanced Raman scattering
    Open this publication in new window or tab >>Scalable residue-free graphene for surface-enhanced Raman scattering
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    2016 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 98, p. 567-571Article in journal (Refereed) Published
    Abstract [en]

    A room-temperature polymer-assisted transfer process is developed for large-area, single-layer graphene grown by means of chemical vapor deposition (CVD). This process leads to transferred graphene layers free of polymer contamination. The absence of polymer residues boosts the surface-enhanced Raman scattering (SERS) of the CVD graphene with gold nanoparticles (Au NPs) deposited atop by evaporation. The SERS enhancement of the CVD graphene reaches similar to 120 for the characteristic 2D peak of graphene, the highest enhancement factor achieved to date, when the Au NPs are at the threshold of percolation. Our simulation supported by experiment suggests that the polymer residues persistently present on the graphene transferred by the conventional polymer-assisted method are equivalent to an ultrathin film of less than 1 nm thickness. The presence of polymer residues drastically reduces SERS due to the separation of the Au NPs from the underlying graphene. The scalability of CVD graphene opens up for the possibility of graphene-based SERS sensors.

    National Category
    Physical Sciences Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-269192 (URN)10.1016/j.carbon.2015.11.043 (DOI)000367233000070 ()
    Funder
    Knut and Alice Wallenberg Foundation, 2011.0113Knut and Alice Wallenberg Foundation, 2011.0082Swedish Foundation for Strategic Research , SE13-0061Swedish Research Council, 621-2014-5591
    Available from: 2015-12-14 Created: 2015-12-14 Last updated: 2017-12-01Bibliographically approved
  • 5.
    Ahlberg, Patrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Seung, Hee Jeong
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jiao, Mingzhi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Zhang, Shi-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zhang, Zhi-Bin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Graphene as a Diffusion Barrier in Galinstan-Solid Metal Contacts2014In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, Vol. 61, no 8, p. 2996-3000Article in journal (Refereed)
    Abstract [en]

    This paper presents the use of graphene as a diffusion barrier to a eutectic Ga-In-Sn alloy, i.e., galinstan, for electrical contacts in electronics. Galinstan is known to be incompatible with many conventional metals used for electrical contacts. When galinstan is in direct contact with Al thin films, Al is readily dissolved leading to the formation of Al oxides present on the surface of the galinstan droplets. This reaction is monitored ex situ using several material analysis methods as well as in situ using a simple circuit to follow the time-dependent resistance variation. In the presence of a multilayer graphene diffusion barrier, the Al-galinstan reaction is effectively prevented for galinstan deposited by means of drop casting. When deposited by spray coating, the high-impact momentum of the galinstan droplets causes damage to the multilayer graphene and the Al-galinstan reaction is observed at some defective spots. Nonetheless, the graphene barrier is likely to block the formation of Al oxides at the Al/galinstan interface leading to a stable electrical current in the test circuit.

  • 6. Ahlgren Peters, Adam
    et al.
    Söderholm, Robin
    Wahlmark, Rickard
    Analog gitarrförstärkare: med rörliknande egenskaper2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 7.
    Ahlström, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Åsktransienter och överspänningar: En spänningsfylld simulering av elkraftsystemet vid Forsmark 32014Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A power system will inevitably be subjected to transient overvoltages, most often produced by switching operations and lightning strikes. These transient overvoltages may harm sensitive equipment without sufficient protection, but it is not an easy task to predict what transients may occur or how they affect the system. A fault occurred in a low voltage system at Forsmark 2012 and overvoltages from lightning were concluded as the probable cause. The three aims with this thesis are to develop and test a model of the power system at Forsmark 3, analyse the transient behaviour of the system when subjected to lightning surges and identify critical parameters, and lastly to provide a tool for investigating the protection of the system. The modelling and simulations were performed in the freely available simulation program LT Spice. Challenges and difficulties have been to obtain parameter values for components that are relevant for the high frequencies produced by the short rise time in lightning surges. The main conclusions are: the maximum current in the lightning discharge has the largest impact on the system voltages and surges in the external grid can produce standing waves in the system, causing significant overvoltages even in low voltage systems. The simulations produced larger overvoltages than would occur in a real system, which also would dampen the high frequency signals to a larger extent. Further work to obtain models better suited for high frequency simulation is suggested.

  • 8.
    Ahmad, Mohd Riduan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. Universiti Teknikal Malaysia Melaka.
    Interaction of Lightning Flashes with Wireless Communication Networks: Special Attention to Narrow Bipolar Pulses2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, the features of electric field signatures of narrow bipolar pulses (NBPs) generated by cloud flashes are investigated and their effects on wireless communication systems are studied. A handful amount of NBPs (14.5%) have been observed to occur as part of cloud-to-ground flashes in South Malaysia. Occurrence of NBPs in Sweden has been reported for the first time in this thesis. The electric field waveform characteristics of NBPs as part of cloud-to-ground flashes were similar to isolated NBPs found in Sweden and South Malaysia and also to those isolated NBPs reported by previous studies from various geographical areas. This is a strong indication that their breakdown mechanisms are similar at any latitudes regardless of geographical areas.

    A comparative study on the occurrence of NBPs and other forms of lightning flashes across various geographical areas ranging from northern regions to the tropics is presented. As the latitude decreased from Uppsala, Sweden (59.8°N) to South Malaysia (1.5°N), the percentage of NBP emissions relative to the total number of lightning flashes increased significantly from 0.13% to 12%. Occurrences of positive NBPs were more common than negative NBPs at all observed latitudes. However, as latitudes decreased, the negative NBP emissions increased significantly from 20% (Sweden) to 45% (South Malaysia). Factors involving mixed-phase region elevations and vertical extents of thundercloud tops are invoked to explain the observed results. These factors are fundamentally latitude dependent.

    In this thesis, the interaction between microwave radiations emitted by cloud-to-ground and cloud flashes events and bits transmission in wireless communication networks are also presented. To the best of our knowledge, this is the first time such effects are investigated in the literature. Narrow bipolar pulses were found to be the strongest source of interference that interfered with the bits transmission.

    List of papers
    1. Signatures of Narrow Bipolar Pulses as Part of Cloud-to-Ground Flashes in Tropical Thunderstorms
    Open this publication in new window or tab >>Signatures of Narrow Bipolar Pulses as Part of Cloud-to-Ground Flashes in Tropical Thunderstorms
    2014 (English)In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824Article in journal (Refereed) Submitted
    Keywords
    Narrow bipolar pulse; Return stroke; Tropical thunderstorm.
    National Category
    Meteorology and Atmospheric Sciences Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-233624 (URN)
    Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2017-12-05
    2. Narrow bipolar pulses and associated microwave radiation
    Open this publication in new window or tab >>Narrow bipolar pulses and associated microwave radiation
    2013 (English)Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Stockholm: , 2013
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Science of Electricity
    Identifiers
    urn:nbn:se:uu:diva-212898 (URN)
    Conference
    Progress in Electromagnetics Research Symposium
    Available from: 2013-12-16 Created: 2013-12-16 Last updated: 2015-01-23
    3. Electric Field Signature of Narrow Bipolar Pulse Observed in Sweden
    Open this publication in new window or tab >>Electric Field Signature of Narrow Bipolar Pulse Observed in Sweden
    Show others...
    2014 (English)In: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895Article in journal (Refereed) Submitted
    Keywords
    Electric field; Narrow bipolar pulse; Sweden.
    National Category
    Meteorology and Atmospheric Sciences Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-233636 (URN)
    Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2017-12-05
    4. Latitude Dependence of Narrow Bipolar Pulse Emissions
    Open this publication in new window or tab >>Latitude Dependence of Narrow Bipolar Pulse Emissions
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    2015 (English)In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 128, p. 40-45Article in journal (Refereed) Published
    Keywords
    Latitude; Narrow bipolar pulse; Thunderstorm.
    National Category
    Meteorology and Atmospheric Sciences Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-233638 (URN)10.1016/j.jastp.2015.03.005 (DOI)000355717500005 ()
    Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2017-12-05Bibliographically approved
    5. Similarity between the Initial Breakdown Pulses of Negative Ground Flash and Narrow Bipolar Pulses
    Open this publication in new window or tab >>Similarity between the Initial Breakdown Pulses of Negative Ground Flash and Narrow Bipolar Pulses
    2014 (English)In: 2014 INTERNATIONAL CONFERENCE ON LIGHTNING PROTECTION (ICLP), IEEE conference proceedings, 2014, p. 810-813Conference paper, Published paper (Refereed)
    Abstract [en]

    In this paper, temporal characteristics of several initial electric field pulses of preliminary breakdown process (PBP) from very close negative cloud-to-ground (CG) flashes are compared to close narrow bipolar pulses (NBPs) to observe any similarity that may exists. Interestingly, we found that the initial PBP pulses are similar to close NBP with zero crossing time less than 5 mu s, do not preceded by any slow field change and followed by pronounce static component. As NBPs are believed to be a result of relativistic runaway electron avalanches discharge, this finding is an indication that the initial electric field pulses of PBP are perhaps the result of the same discharge mechanism.

    Place, publisher, year, edition, pages
    IEEE conference proceedings, 2014
    Keywords
    Narrow bipolar pulse; Preliminary breakdown pulse; Relativistic runaway electron avalanches.
    National Category
    Meteorology and Atmospheric Sciences Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-233639 (URN)000358572100153 ()978-1-4799-3544-4 (ISBN)
    Conference
    International Conference on Lightning Protection (ICLP), OCT 11-18, 2014, Tsinghua Univ, Shanghai, PEOPLES R CHINA
    Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2015-09-03Bibliographically approved
    6. Lightning interference in multiple antennas wireless communication systems
    Open this publication in new window or tab >>Lightning interference in multiple antennas wireless communication systems
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    2012 (English)In: Journal of Lightning Research, ISSN 1652-8034, Vol. 4, p. 155-165Article in journal (Refereed) Published
    Abstract [en]

    This paper analyzes the interference of lightning flashes with multiple antennas wireless communicationsystems operating in the microwave band at 2.4 GHz and 5.2 GHz. A bit error rate (BER) measurement method was usedto evaluate BER and packet error rate (PER) during 5 heavy thunderstorms on January 25 and March 17 to 20, 2011,respectively. In addition, BER measurements also were done on January 21 and March 30, 2011 under fair weather (FW)conditions providing a baseline for comparison. The Transmitter-Receiver separation was fixed at 10 meter with line-ofsight(LOS) consideration. We infer that lightning interfered with the transmitted digital pulses which resulted in a higherrecorded BER. The maximum recorded BER was 9.9·10-1 and the average recorded BER and PER were 2.07·10-2 and2.44·10-2 respectively during the thunderstorms with the average fair weather BER and PER values under the influence ofadjacent channel interference (ACI) and co-channel interference (CCI) being 1.75·10-5 and 7.35·10-6 respectively. Weconclude that multiple antennas wireless communication systems operating at the microwave frequency can besignificantly interfered by lightning.

    Place, publisher, year, edition, pages
    Bentham open, 2012
    National Category
    Meteorology and Atmospheric Sciences Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-190902 (URN)
    Available from: 2013-01-09 Created: 2013-01-09 Last updated: 2016-02-03
    7. Interference from cloud-to-ground and cloud flashes in wireless communication system
    Open this publication in new window or tab >>Interference from cloud-to-ground and cloud flashes in wireless communication system
    2014 (English)In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 113, p. 237-246Article in journal (Refereed) Published
    Abstract [en]

    In this study, cloud-to-ground (CG) flash and intra-cloud (IC) flash events that interfere with the transmission of bits in wireless communication system operating at 2.4 GHz were analyzed. Bit error rate (BER) and consecutive lost datagram (CLD) measurement methods were used to evaluate BER and burst error from 3 tropical thunderstorms on November 27, 28, and 29 during 2012 northeastern monsoon in Malaysia. A total of 850 waveforms from the electric field change recording system were recorded and examined. Out of these, 94 waveforms of very fine structure were selected which matched perfectly with the timing information of the recorded BER. We found that both CG and IC flashes interfered significantly with the transmission of bits in wireless communication system. The severity of the interference depends mainly on two factors namely the number of pulses and the amplitude intensity of the flash. The interference level becomes worst when the number of pulses in a flash increases and the amplitude intensity of pulses in a flash intensifies. During thunderstorms, wireless communication system has experienced mostly intermittent interference due to burst error. Occasionally, in the presence of very intense NBP event, wireless communication system could experience total communication lost. In CG flash, it can be concluded that PBP is the major. source of interference that interfered with the bits transmission and caused the largest burst error. In IC flash, we found that the typical IC pulses interfered the bits transmission in the same way as PBP and mixed events in CG flash and produced comparable and in some cases higher amount of burst error. NBP has been observed to interfere the bits transmission more severely than typical IC and CG flashes and caused the most severe burst error to wireless communication system.

    Keywords
    Bit error rate, Cloud flash, Cloud-to-ground flash, Interference, Microwave radiation, Wireless system
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:uu:diva-228679 (URN)10.1016/j.epsr.2014.03.022 (DOI)000337554200032 ()
    Available from: 2014-07-22 Created: 2014-07-21 Last updated: 2017-12-05Bibliographically approved
  • 9.
    An, Hongbin
    et al.
    Huazhong Univ Sci & Technol, State Key Lab Digital Mfg Equipment & Technol, Wuhan 430074, Hubei, Peoples R China.
    Chen, Liangzhou
    Huazhong Univ Sci & Technol, State Key Lab Digital Mfg Equipment & Technol, Wuhan 430074, Hubei, Peoples R China.
    Liu, Xiaojun
    Huazhong Univ Sci & Technol, State Key Lab Digital Mfg Equipment & Technol, Wuhan 430074, Hubei, Peoples R China.
    Zhao, Bin
    Huazhong Univ Sci & Technol, State Key Lab Digital Mfg Equipment & Technol, Wuhan 430074, Hubei, Peoples R China.
    Ma, Donglin
    Huazhong Univ Sci & Technol, Sch Opt & Elect Informat, Wuhan 430074, Hubei, Peoples R China.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Huazhong Univ Sci & Technol, State Key Lab Digital Mfg Equipment & Technol, Wuhan 430074, Hubei, Peoples R China.
    A method of manufacturing microfluidic contact lenses by using irreversible bonding and thermoforming2018In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 28, no 10, article id 105008Article in journal (Refereed)
    Abstract [en]

    In this paper, we present the development of microfluidic contact lenses, which is based on the advantages of wearable microfluidics and can have great potential in the ophthalmology healthcare field. The development consists of two parts; the manufacturing process and the usability tests of the devices. In the manufacturing process, we firstly extended silane coupling and surface modification to irreversibly bond plastic membranes with microchannel-molded silicone rubber, to form the plastic-PDMS plane assemblies, and then molded the plane into a contact lens by thermoforming. We systematically investigated the effects of thermoforming factors, heating temperatures and the terrace die's sphere radius on channels by using the factorial experiment design. In addition, various tests were conducted to verify the usability of the devices. Through blockage and leakage tests, the devices were proved to be feasible, with no channel-blockages and could stand high pressures. Through a wearing test, the contact lenses were confirmed to be harmless on the living body. Furthermore, by performing the manipulating test, the device was proved to be liquid-controllable. These works provide a foundation for the applications of microfluidic contact lenses in ophthalmology.

  • 10.
    Anderås, Emil
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Advanced MEMS Pressure Sensors Operating in Fluids2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Today’s MEMS technology allows manufacturing of miniaturized, low power sensors that sometimes exceeds the performance of conventional sensors. The pressure sensor market today is dominated by MEMS pressure sensors.

    In this thesis two different pressure sensor techniques are studied. The first concerns ways to improve the sensitivity in the most commonly occurring pressure sensor, namely such based on the piezoresistive technique. Since the giant piezoresistive effect was observed in silicon nanowires, it was assumed that a similar effect could be expected in nano-thin silicon films. However, it turned out that the conductivity was extremely sensitive to substrate bias and could therefore be controlled by varying the backside potential. Another important parameter was the resistivity time drift. Long time measurements showed a drastic variation in the resistance. Not even after several hours of measurement was steady state reached. The drift is explained by hole injection into the buried oxide as well as existence of mobile charges. The piezoresistive effect was studied and shown to be of the same magnitude as in bulk silicon. Later research has shown the existence of such an effect where the film thickness has to be less than around 20 nm. 

    The second area that has been studied is the pressure sensitivity of in acoustic resonators. Aluminium nitride thin film plate acoustic resonators (FPAR) operating at the lowest-order symmetric (S0), the first-order asymmetric (A1) as well as the first-order symmetric (S1) Lamb modes have been theoretically and experimentally studied in a comparative manner. The S0 Lamb mode is identified as the most pressure sensitive FPAR mode. The theoretical predictions were found to be in good agreement with the experiments. Additionally, the Lamb modes have been tested for their sensitivities to mass loading and their ability to operate in liquids, where the S0 mode showed good results.

    Finally, the pressure sensitivity in aluminium nitride thin film bulk wave resonators employing c- and tilted c-axis texture has been studied. The c-axis tilted FBAR demonstrates a substantially higher pressure sensitivity compared to its c-axis oriented counterpart. 

    List of papers
    1. Resistance Electric Field Dependence and Time Drift of Piezoresistive Single Crystalline Silicon Nanofilms
    Open this publication in new window or tab >>Resistance Electric Field Dependence and Time Drift of Piezoresistive Single Crystalline Silicon Nanofilms
    2009 (English)In: Proceedings of Eurosensors May 2009, Procedia Chemistry vol 1 (1), 2009, p. 80-83Conference paper, Published paper (Refereed)
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-122014 (URN)
    Conference
    Eurosensors May 2009, Proceedings of Eurosensors May 2009, Procedia Chemistry vol 1 (1)
    Projects
    WISENETVR-621-2006-5881
    Available from: 2010-04-06 Created: 2010-04-06 Last updated: 2016-04-14Bibliographically approved
    2. Drift in thin film SOI piezoresistors
    Open this publication in new window or tab >>Drift in thin film SOI piezoresistors
    Show others...
    2010 (English)In: Proc. of EUROSOI Workshop, 2010 Jan 25-27, Grenoble, France, 2010, p. 71-72Conference paper, Oral presentation only (Refereed)
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-136179 (URN)
    Conference
    EUROSOI 2010 Jan 25-27, Grenoble, France
    Available from: 2010-12-10 Created: 2010-12-10 Last updated: 2016-04-18Bibliographically approved
    3. Sensitivity Features of Thin Film Plate Acoustic Wave Resonators
    Open this publication in new window or tab >>Sensitivity Features of Thin Film Plate Acoustic Wave Resonators
    2011 (English)In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 11, no 12, p. 3330-3331Article in journal (Refereed) Published
    Abstract [en]

    Thin film plate acoustic resonators devices operating in the lowest order symmetric Lamb wave mode (S0) in coriented aluminum nitride (AlN) membranes on Si were fabricated and tested for their sensitivities to pressure and mass as well as for their ability to work in liquid environment.

    Place, publisher, year, edition, pages
    IEEE Sensors Council, 2011
    Keywords
    Film bulk acoustic resonators, Resonant frequency, Sensitivity, Sensors, Surface acoustic waves
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Microsystems Technology; Engineering Science with specialization in Electronics
    Identifiers
    urn:nbn:se:uu:diva-157877 (URN)10.1109/JSEN.2011.2158094 (DOI)000301878500019 ()
    Projects
    VR "Thin Film Guided Microacoustic Waves in Periodical Systems: Theory and Applications"
    Funder
    Swedish Research Council, 2009-5056
    Available from: 2011-08-24 Created: 2011-08-24 Last updated: 2017-12-08Bibliographically approved
    4. Lamb wave resonant pressure micro-sensor utilizing a thin-film aluminium nitride membrane
    Open this publication in new window or tab >>Lamb wave resonant pressure micro-sensor utilizing a thin-film aluminium nitride membrane
    2011 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 21, no 8, p. 085010-Article in journal (Refereed) Published
    Abstract [en]

    In this work, pressure sensitivities of aluminium nitride (AlN) thin film plate acoustic resonators (FPAR) operating at the lowest-order symmetric (S0), the first-order asymmetric (A1) as well as the first-order symmetric (S1) Lamb modes are theoretically and experimentally studied in a comparative manner. The finite element method analysis has also been performed to get a further insight into the FPAR pressure sensitivity. The theoretical predictions are found to be in good agreement with the experiment. The S0 Lamb mode is identified as the most pressure-sensitive FPAR mode, while the A1 and S1 modes are found to be much less sensitive. Further, the S0 and the A1 modes exhibit almost equal temperature sensitivities, which can be exploited to eliminate the temperature drift by comparing the resonance frequencies of the latter two modes.

    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Electronics
    Identifiers
    urn:nbn:se:uu:diva-157028 (URN)10.1088/0960-1317/21/8/085010 (DOI)000293163700010 ()
    Funder
    Swedish Research Council, 2009-5056
    Available from: 2011-08-16 Created: 2011-08-15 Last updated: 2017-12-08
    5. Thin Film Plate Wave Resonant Sensor for Pressure and Gravimetric Measurements
    Open this publication in new window or tab >>Thin Film Plate Wave Resonant Sensor for Pressure and Gravimetric Measurements
    2011 (English)In: Procedia Engineering 25, Eurosensors XXV: Proc. Eurosensors XXV, September 4-7, 2011, Athens, Greece, Elsevier, 2011, p. 571-574Conference paper, Published paper (Refereed)
    Abstract [en]

    Thin film plate acoustic resonators (FPAR) devices operating in the lowest order symmetric Lamb wave mode (S0),the first order asymmetric Lamb wave mode (A1) and the first order symmetric Lamb wave mode (S1), propagatingin c-oriented aluminum nitride (AlN) membranes on Si were fabricated and tested for their sensitivities to pressureand mass. Systematic data on frequency shifts versus rigid mass (layer) thickness and ambient pressure variations arepresented for the different Lamb wave resonances. Further the ability to work in liquid environment of the S0, A1 andS1 modes, respectively, has been tested in view of Bio-sensor applications.

    Place, publisher, year, edition, pages
    Elsevier, 2011
    Series
    Procedia Engineering, ISSN 1877-7058 ; 25
    Keywords
    Micro, prssure, sensor, radio frequency
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Microsystems Technology; Engineering Science with specialization in Electronics
    Identifiers
    urn:nbn:se:uu:diva-167002 (URN)10.1016/j.proeng.2011.12.142 (DOI)000300512400139 ()
    Conference
    25th Eurosensors Conference, SEP 04-07, 2011, Athens, GREECE
    Projects
    VR Granted
    Funder
    Swedish Research Council, 2009-5056
    Available from: 2012-01-18 Created: 2012-01-18 Last updated: 2013-03-13
    6. Tilted c-Axis Thin-Film Bulk Wave Resonant Pressure Sensors With Improved Sensitivity
    Open this publication in new window or tab >>Tilted c-Axis Thin-Film Bulk Wave Resonant Pressure Sensors With Improved Sensitivity
    2012 (English)In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 12, no 8, p. 2653-2654Article in journal (Refereed) Published
    Abstract [en]

    Aluminum nitride thin film bulk wave resonant pressure sensors employing c- and tilted c-axis texture, have been fabricated and tested for their pressure sensitivities. The c-axis tilted FBAR pressure sensors demonstrate substantially higher pressure sensitivity compared to its c-axis oriented counterpart. More specifically the thickness plate quasi-shear resonance has demonstrated the highest pressure sensitivity while further being able to preserve its performance in liquid environment.

    Keywords
    AlN, FBAR, pressure sensor, sensitivity, micro-acoustic
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Electronics
    Identifiers
    urn:nbn:se:uu:diva-173179 (URN)10.1109/JSEN.2012.2199482 (DOI)000305584300003 ()
    Available from: 2012-04-20 Created: 2012-04-20 Last updated: 2017-12-07Bibliographically approved
  • 11.
    Anderås, Emil
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Arapan, Lilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Katardjiev, Ilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Yantchev, Ventsislav
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Thin Film Plate Wave Resonant Sensor for Pressure and Gravimetric Measurements2011In: Procedia Engineering 25, Eurosensors XXV: Proc. Eurosensors XXV, September 4-7, 2011, Athens, Greece, Elsevier, 2011, p. 571-574Conference paper (Refereed)
    Abstract [en]

    Thin film plate acoustic resonators (FPAR) devices operating in the lowest order symmetric Lamb wave mode (S0),the first order asymmetric Lamb wave mode (A1) and the first order symmetric Lamb wave mode (S1), propagatingin c-oriented aluminum nitride (AlN) membranes on Si were fabricated and tested for their sensitivities to pressureand mass. Systematic data on frequency shifts versus rigid mass (layer) thickness and ambient pressure variations arepresented for the different Lamb wave resonances. Further the ability to work in liquid environment of the S0, A1 andS1 modes, respectively, has been tested in view of Bio-sensor applications.

  • 12.
    Anderås, Emil
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Katardjiev, Ilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Yantchev, Ventsislav
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Tilted c-Axis Thin-Film Bulk Wave Resonant Pressure Sensors With Improved Sensitivity2012In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 12, no 8, p. 2653-2654Article in journal (Refereed)
    Abstract [en]

    Aluminum nitride thin film bulk wave resonant pressure sensors employing c- and tilted c-axis texture, have been fabricated and tested for their pressure sensitivities. The c-axis tilted FBAR pressure sensors demonstrate substantially higher pressure sensitivity compared to its c-axis oriented counterpart. More specifically the thickness plate quasi-shear resonance has demonstrated the highest pressure sensitivity while further being able to preserve its performance in liquid environment.

  • 13.
    Ankarcrona, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    High Frequency Analysis of Silicon RF MOS Transistors2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Today, the silicon technology is well established for RF-applications (f~1-100 GHz), with emphasis on the lower frequencies (f < 5 GHz). The field of RF power devices is extensive concerning materials and devices. One of the important RF-devices is the silicon LDMOS transistor. A large extent of the research presented in the thesis concerns studies of this device, which have resulted in increased understanding of the device behavior and improved performance. The thesis starts with a brief survey of the RF-field, including the LDMOS transistor, followed by a description of the methods used in the investigations; simulations, modeling and measurements. Specific results presented in the appended papers are also briefly summarized.

    A new concept for LDMOS transistors, which allows for both high frequency and high voltage operation, has been developed and characterized. World-record performance in terms of output power density was obtained: over 1 W/mm at 50 V and 3.2 GHz. Further understanding and improvements of the device are achieved using simulations and modeling. For determination of model parameters a new general parameter extraction technique was developed. The method has been successfully used for a large variety of high-frequency devices, and has been frequently used in the modeling work in this thesis.

    Important properties of RF-power devices are the device linearity and power efficiency. Extensive studies regarding the efficiency were conducted using numerical simulations and modeling of the off-state output resistance, which is correlated to the efficiency. The results show that significant improvements can be obtained for devices on both bulk- and SOI-substrates, using thin high-resistivity substrates and very low-resistivity SOI-substrates, respectively.

    Finally a new approach to drastically reduce substrate crosstalk by using very low-resistivity SOI substrate is proposed. Experimentally, a reduction of 20-40 dB was demonstrated in the GHz range compared to high-resistivity SOI substrate.

    List of papers
    1. Sub-Circuit Based SPICE Model for High Voltage LDMOS Transistors
    Open this publication in new window or tab >>Sub-Circuit Based SPICE Model for High Voltage LDMOS Transistors
    2002 (English)In: Physica Scripta, no T101, p. 7-9Article in journal (Refereed) Published
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Electronics
    Identifiers
    urn:nbn:se:uu:diva-93398 (URN)
    Available from: 2005-09-02 Created: 2005-09-02 Last updated: 2012-09-26
    2. A General Small-Signal Series Impedance Extraction Technique
    Open this publication in new window or tab >>A General Small-Signal Series Impedance Extraction Technique
    2002 (English)In: IEEE Microwave and Wireless Components Letters, ISSN 1531-1309, E-ISSN 1558-1764, Vol. 12, no 7, p. 249-251Article in journal (Refereed) Published
    Abstract [en]

    A new technique for extracting the series inductances and resistances in a small-signal equivalent circuit is presented. The technique does not rely on approximation and should therefore be as accurate as the measured data. The technique can also be used to extract the intrinsic parameters if they are not easily achieved using other methods. The method is exemplified with a microwave LDMOS transistor

    Keywords
    S-parameters, microwave LDMOS transistor, parameter estimation, series inductances, series resistances, small-signal equivalent circuit, small-signal series impedance extraction technique
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:uu:diva-93400 (URN)10.1109/LMWC.2002.801134 (DOI)
    Available from: 2005-09-02 Created: 2005-09-02 Last updated: 2017-12-14Bibliographically approved
    3. Analysis and Design of a Low-Voltage High-Frequency LDMOS Transistor
    Open this publication in new window or tab >>Analysis and Design of a Low-Voltage High-Frequency LDMOS Transistor
    2002 (English)In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, Vol. 49, no 6, p. 976-980Article in journal (Refereed) Published
    Abstract [en]

    For a low voltage lateral double-diffused MOS (LDMOS) transistor, the output performance has been improved in terms of fMAX. This is done by decreasing the output capacitance and thus decreasing the total output conductance. Extraction of the model parameters has been made and the most efficient parameter to improve was identified and linked to a specific part of the transistor structure. Layout changes in the n-well/p-base region were done as the result of the model analyses and finally, the modified devices were processed. Measurements on the improved devices showed results that closely, matched the expected, and fMAX was increased with 30% and only a slight decrease in f T. Finally, the capacitance reduction in the n-well/p-base junction was measured by direct. measurements

    Keywords
    LV HF LDMOS transistor, S-parameter, current-voltage characteristics, equivalent circuits, layout changes, microwave FET, model parameters, n-well/p-base junction, output capacitance, output performance, small-signal parameters, total output conductance
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:uu:diva-93401 (URN)10.1109/TED.2002.1003715 (DOI)
    Available from: 2005-09-02 Created: 2005-09-02 Last updated: 2017-12-14
    4. Simulation and modeling of the substrate contribution to the output resistance for RF-LDMOS power transistors
    Open this publication in new window or tab >>Simulation and modeling of the substrate contribution to the output resistance for RF-LDMOS power transistors
    2004 (English)In: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 48, no 5, p. 789-797Article in journal (Refereed) Published
    Abstract [en]

    High frequency substrate losses for RF MOSFETs are analyzed using numerical device simulation. The results show that losses in devices made on low resistivity substrate occur through the substrate while losses in devices made on high resistivity substrate in the high frequency region occur along the surface through the device (source–drain). An equivalent circuit model is developed which accurately describes the off-state losses. Based on the model significant improvements in terms of output resistance are demonstrated, using an improved device on high resistivity substrate.

    Keywords
    Substrate losses, Modeling, RF MOSFET, LDMOS
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-93402 (URN)10.1016/j.sse.2003.12.005 (DOI)
    Available from: 2005-09-02 Created: 2005-09-02 Last updated: 2017-12-14
    5. Improved Output Resistance in RF-power MOSFETs using Low Resistivity SOI Substrate
    Open this publication in new window or tab >>Improved Output Resistance in RF-power MOSFETs using Low Resistivity SOI Substrate
    Show others...
    (English)Manuscript (Other academic)
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-93403 (URN)
    Available from: 2005-09-02 Created: 2005-09-02 Last updated: 2015-07-21Bibliographically approved
    6. Low Resistivity SOI for Substrate Crosstalk Reduction
    Open this publication in new window or tab >>Low Resistivity SOI for Substrate Crosstalk Reduction
    2005 (English)In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, IEEE Trans on Electronic Devices, Vol. 52, no 8, p. 1920-1922Article in journal (Refereed) Published
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-93404 (URN)
    Available from: 2005-09-02 Created: 2005-09-02 Last updated: 2017-12-14Bibliographically approved
    7. 1 W/mm RF Power Denisty at 3.2 GHz for a Dual-Layer RESURF LDMOS Transistor
    Open this publication in new window or tab >>1 W/mm RF Power Denisty at 3.2 GHz for a Dual-Layer RESURF LDMOS Transistor
    Show others...
    2002 (English)In: IEEE Electron Device Letters, ISSN 0741-3106, Vol. 23, no 4, p. 206-208Article in journal (Refereed) Published
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:uu:diva-41678 (URN)10.1109/55.992840 (DOI)
    Available from: 2007-02-23 Created: 2007-02-23 Last updated: 2010-07-09Bibliographically approved
  • 14.
    Ankarcrona, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Eklund, Klas-Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Vestling, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Olsson, Jörgen
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Analysis and improvments of high frequency substrate losses for RF MOSFETs2003In: Proceedings of IEEE SISPAD, 2003, p. 319-322Conference paper (Refereed)
  • 15.
    Ankarcrona, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Eklund, Klas-Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Vestling, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Olsson, Jörgen
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Simulation and modeling of the substrate influence on the high frequency performance for RF LDMOS2003In: GHz2003 Symposium, Nov. 4-5, 2003Conference paper (Refereed)
  • 16.
    Ankarcrona, Johan
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Materials Science. Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Olsson, Jörgen
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Materials Science. Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    SPICE Modeling of High Voltage LDMOS Transistors2001In: The 19th Nordic Semiconductor Meeting, Copenhagen, Denmark, May, 2001Conference paper (Refereed)
  • 17.
    Ankarcrona, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Olsson, Jörgen
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Sub-Circuit Based SPICE Model for High Voltage LDMOS Transistors2002In: Physica Scripta, no T101, p. 7-9Article in journal (Refereed)
  • 18. Anthon, Jonsson
    et al.
    Vincent, Ricknell
    Project in Electrical Engineering: Electric Skateboard2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 19.
    Apelfröjd, Senad
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Bülow, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Kjellin, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Eriksson, Sandra
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Laboratory verification of system for grid connection of a 12 kW variable speed wind turbine with a permanent magnet synchronous generator2012In: EWEA 2012 Annual Event, Copenhagen, Denmark, 2012, 2012Conference paper (Refereed)
    Abstract [en]

    In this paper the first laboratory tests of the gridconnection system, connected to a resistiveload, for a vertical axis wind turbine (VAWT)with a permanent magnet generator arepresented. The system is based on a taptransformertopology with a voltage sourceinverter and an LCL-filter. The use of a taptransformer topology eliminates the need for aDC-DC converter to handle the variations inDC voltage. The harmonic content of thecurrents from experiments and simulationsperformed in Simulink using different taps onthe transformer are presented. The simulatedcurrents, fed to the resistive load, have a totalharmonic distortion (THD) of 0.5% to 0.9% forthe different taps. The experimental systemhas a current THD ranging from 1.8% to 2.8%.The difference is expected to be due tounbalances, delays and dead times in theexperimental set-up as the major THDcontribution is from harmonic orders below 11.The results show that an LCL filter can bedesigned to meet the demands on powerquality for grid connection of the system withall the taps of the tap transformer inaccordance with IEEE 519-1992.

  • 20.
    Arapan, Lilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Thin Film Plate Acoustic Resonators for Frequency Control and Sensing Applications2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The recent development of the commercially viable thin film electro-acoustic technology has triggered a growing interest in the research of plate guided wave or Lamb wave components owing to their unique characteristics. In the present thesis i) an experimental study of the thin film plate resonators (FPAR) performance operating on the lowest symmetrical Lamb wave (S0) propagating in highly textured AlN membranes versus a variety of design parameters has been performed. The S0 mode is excited through an Interdigital Transducer and confined within the structure by means of reflection from metal strip gratings. Devices operating in the vicinity of the stop-band center exhibiting a Q-value of up to 3000 at a frequency around 900MHz have been demonstrated. Temperature compensation of this type of devices has been studied theoretically and successfully realized experimentally for the first time. Further, integrated circuit-compatible S0 Lamb based two-port FPAR stabilized oscillators exhibiting phase noise of -92 dBc/Hz at 1 kHz frequency offset with feasible thermal noise floor below -180 dBc/Hz have been tested under high power for a couple of weeks. More specifically, the FPARs under test have been running without any performance degradation at up to 27 dBm loop power. Further, the S0 mode was experimentally demonstrated to be highly mass and pressure sensitive as well as suitable for in-liquid operation, which together with low phase noise and high Q makes it very suitable for sensor applications; ii) research in view of FPARs operating on other types of Lamb waves as well as novel operation principles has been initiated. In this work, first results on the design, fabrication and characterization of two novel type resonators: The Zero Group Velocity Resonators (ZGVR) and The Intermode-Coupled Thin Film Plate Acoustic Resonators (IC-FPAR), exploiting new principles of operation have been successfully demonstrated. The former exploits the intrinsic zero group velocity feature of the S1 Lamb mode for certain combination of design parameters while the latter takes advantage of the intermode interaction (involving scattering) between S0 and A1 Lamb modes through specially designed metal strip gratings (couplers). Thus both type of resonators operate on principles of confining energy under IDT other than reflection.

    List of papers
    1. Micromachined Thin Film Plate Acoustic Wave Resonators (FPAR) Part II
    Open this publication in new window or tab >>Micromachined Thin Film Plate Acoustic Wave Resonators (FPAR) Part II
    2009 (English)In: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, ISSN 0885-3010, E-ISSN 1525-8955, Vol. 56, no 12, p. 2701-2710Article in journal (Refereed) Published
    Abstract [en]

    Improved performance thin-film plate acousticwave resonators (FPAR) using the lowest order symmetricLamb wave (S0) propagating in highly textured AlN membraneshave been previously demonstrated for the first time.In this work, an experimental study of the resonators’ performancevs. a variety of design parameters is performed. Devicesoperating in the vicinity of the stopband center exhibiting aQ-value of up to 3000 at a frequency of around 875 MHz aredemonstrated. Further, low-loss high-Q micromachined 2-portlongitudinally coupled thin-film resonators using the S0 modeare demonstrated for the first time. For the analysis of theproposed structures, the coupling-of-modes (COM) approachis successfully employed. Initially, the COM model is used forthe extraction of physical parameters from one-port FPARmeasurements. Subsequently, using the COM model, a satisfactoryagreement with the proposed experimental frequencycharacteristics of S0 2-port FPARs has been achieved, andpossibilities for further improvements in the performance discussed.Finally, the frequency spectrum of the one-port deviceshas been studied and the excited plate modes at differentfrequencies identified and presented with their Q-factors andtemperature coefficients of frequency (TCF).

    Keywords
    Thin films, Resonator, Micromachining, MEMS, NEMS
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Microsystems Technology
    Identifiers
    urn:nbn:se:uu:diva-111379 (URN)10.1109/TUFFC.2009.1361 (DOI)000272593100011 ()
    Projects
    VR Funded "Thin Film Guided Microacoustic Waves in Periodical Structures: Theory and Applications"
    Funder
    Swedish Research Council, 2009-5056
    Available from: 2009-12-12 Created: 2009-12-12 Last updated: 2017-12-12
    2. Micromachined thermally compensated thin film Lamb wave resonator for frequency control and sensing applications
    Open this publication in new window or tab >>Micromachined thermally compensated thin film Lamb wave resonator for frequency control and sensing applications
    2009 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 19, no 3, p. 035018-Article in journal (Refereed) Published
    Abstract [en]

    Micromachined thin film plate acoustic wave resonators (FPAR) utilizing the lowest order symmetric Lamb wave (S0) propagating in highly textured 2μm thick Aluminum Nitride (AlN) membranes have been successfully demonstrated [1]. The proposed devices have a SAW-based design and exhibit Q factors of up to 3000 at a frequency around 900MHz as well as design flexibility with respect to the required motional resistance. However, a notable drawback of the proposed devices is non-zero temperature coefficient of frequency (TCF) which lies in the range -20 ppm/K to –25 ppm/K. Thus, despite the promising features demonstrated, further device optimization is required. In this work temperature compensation of thin AlN film Lamb wave resonators is studied and experimentally demonstrated. Temperature compensation while retaining at the same time the device electromechanical coupling is experimentally demonstrated. The zero TCF Lamb wave resonators are fabricated onto composite AlN/SiO2 membranes. Q factors of around 1400 have been measured at a frequency of around 755 MHz. Finally, the impact of technological issues on the device performance is discussed in view of improving the device performance.

    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Electronics
    Identifiers
    urn:nbn:se:uu:diva-89404 (URN)10.1088/0960-1317/19/3/035018 (DOI)000263678200019 ()
    Projects
    WISENET
    Funder
    Swedish Research Council, 2009-5056
    Available from: 2009-02-12 Created: 2009-02-12 Last updated: 2018-06-26Bibliographically approved
    3. Thin film plate acoustic resonators for integrated microwave power oscillator applications
    Open this publication in new window or tab >>Thin film plate acoustic resonators for integrated microwave power oscillator applications
    2011 (English)In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 47, no 7, p. 452-453Article in journal (Refereed) Published
    Abstract [en]

    Two-port film plate acoustic resonators (FPAR) devices operating on the lowest order symmetric Lamb wave mode (S0) in C-oriented AlN membranes on Si were fabricated and tested for their power handling capabilities in a feedback-loop power oscillator circuit. The FPAR was operated at an incident power level of 24 dBm for several weeks without performance degradation. Its flicker noise constant was calculated from close-in phase noise data as αR=2.1×10^−36/Hz. The results indicate that IC-compatible S0 FPARs are well suited for integrated microwave oscillators with thermal noise floor (TNF) levels below −175 dBc/Hz.

    Keywords
    Powe oscillator, low noise, MEMS, piezo
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Microsystems Technology; Engineering Science with specialization in Electronics
    Identifiers
    urn:nbn:se:uu:diva-150468 (URN)10.1049/el.2011.0381 (DOI)000288893100023 ()
    Projects
    VR "Thin Film Guided Microacoustic Waves in Periodical Systems: Theory and Applications"
    Funder
    Swedish Research Council, 2009-5056
    Available from: 2011-03-30 Created: 2011-03-30 Last updated: 2017-12-11Bibliographically approved
    4. Sensitivity Features of Thin Film Plate Acoustic Wave Resonators
    Open this publication in new window or tab >>Sensitivity Features of Thin Film Plate Acoustic Wave Resonators
    2011 (English)In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 11, no 12, p. 3330-3331Article in journal (Refereed) Published
    Abstract [en]

    Thin film plate acoustic resonators devices operating in the lowest order symmetric Lamb wave mode (S0) in coriented aluminum nitride (AlN) membranes on Si were fabricated and tested for their sensitivities to pressure and mass as well as for their ability to work in liquid environment.

    Place, publisher, year, edition, pages
    IEEE Sensors Council, 2011
    Keywords
    Film bulk acoustic resonators, Resonant frequency, Sensitivity, Sensors, Surface acoustic waves
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Microsystems Technology; Engineering Science with specialization in Electronics
    Identifiers
    urn:nbn:se:uu:diva-157877 (URN)10.1109/JSEN.2011.2158094 (DOI)000301878500019 ()
    Projects
    VR "Thin Film Guided Microacoustic Waves in Periodical Systems: Theory and Applications"
    Funder
    Swedish Research Council, 2009-5056
    Available from: 2011-08-24 Created: 2011-08-24 Last updated: 2017-12-08Bibliographically approved
    5. Highly Mass-Sensitive Thin Film Plate Acoustic Resonators (FPAR)
    Open this publication in new window or tab >>Highly Mass-Sensitive Thin Film Plate Acoustic Resonators (FPAR)
    Show others...
    2011 (English)In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 11, no 7, p. 6942-6953Article in journal (Refereed) Published
    Abstract [en]

    The mass sensitivity of thin aluminum nitride (AlN) film S0 Lamb wave resonators is theoretically and experimentally studied. Theoretical predictions based on modal and finite elements method analysis are experimentally verified. Here, two-port 888 MHz synchronous FPARs are micromachined and subsequently coated with hexamethyl-disiloxane(HMDSO)-plasma-polymerized thin films of various thicknesses. Systematic data on frequency shift and insertion loss versus film thickness are presented. FPARs demonstrate high mass-loading sensitivity as well as good tolerance towards the HMDSO viscous losses. Initial measurements in gas phase environment are further presented.

    Keywords
    resonator, aluminum nitride, membrane, HMDSO, gravimetric, sensitivity
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Microsystems Technology; Engineering Science with specialization in Electronics
    Identifiers
    urn:nbn:se:uu:diva-157836 (URN)10.3390/s110706942 (DOI)000293069200027 ()
    Projects
    VR "Thin Film Guided Microacoustic Waves in Periodical Systems: Theory and Applications"
    Available from: 2011-08-24 Created: 2011-08-23 Last updated: 2017-12-08Bibliographically approved
    6. Thin-film zero-group-velocity Lamb wave resonator
    Open this publication in new window or tab >>Thin-film zero-group-velocity Lamb wave resonator
    2011 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, no 3, article id 033505Article in journal (Refereed) Published
    Abstract [en]

    A concept for the development of thin film micro-acoustic resonators is demonstrated. The basicprinciples for the design and fabrication of zero-group-velocity Lamb acoustic wave resonators onc-textured thin aluminum nitride films are presented. The experimental results demonstrate that thezero-group-velocity waves can be employed in high frequency resonators with small form factors.

    Keywords
    acoustic resonators, aluminium compounds, micromechanical resonators, surface acoustic waves
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Microsystems Technology; Engineering Science with specialization in Electronics
    Identifiers
    urn:nbn:se:uu:diva-157833 (URN)10.1063/1.3614559 (DOI)000293679000069 ()
    Projects
    VR, "Thin Film Guided Microacoustic Waves in Periodical Systems: Theory and Applications"
    Funder
    Swedish Research Council, 2009-5056
    Available from: 2011-08-23 Created: 2011-08-23 Last updated: 2017-12-08Bibliographically approved
    7. An intermode-coupled thin-film micro-acoustic resonator
    Open this publication in new window or tab >>An intermode-coupled thin-film micro-acoustic resonator
    2012 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 22, no 8, p. 085004-Article in journal (Refereed) Published
    Abstract [en]

    A novel concept for the development of thin-film micro-acoustic resonators based on the coupling between different plate acoustic modes was demonstrated. The basic principles for the design and fabrication of intermode-coupled plate acoustic wave resonators on c-textured thin AlN films were presented and first experimental proof of coupling between laterally propagating waves and BAW was demonstrated. The experimental results demonstrate that the grating-assisted intermode coupling can be employed in high-frequency resonators inheriting the low dispersive nature of the S0 mode in combination with the energy localization in the plate bulk typical for the fundamental thickness shear resonance.

    Keywords
    acoustic resonator, aluminium nitride, Lamb wave, mode conversion
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Electronics; Engineering Science with specialization in Microsystems Technology
    Identifiers
    urn:nbn:se:uu:diva-178590 (URN)10.1088/0960-1317/22/8/085004 (DOI)000306649000004 ()
    Funder
    Swedish Research Council, 2009-5056
    Available from: 2012-08-01 Created: 2012-08-01 Last updated: 2017-12-07Bibliographically approved
  • 21.
    Arapan, Lilia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Anderås, Emil
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Katardjiev, Ilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Yantchev, Ventsislav
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Sensitivity Features of Thin Film Plate Acoustic Wave Resonators2011In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 11, no 12, p. 3330-3331Article in journal (Refereed)
    Abstract [en]

    Thin film plate acoustic resonators devices operating in the lowest order symmetric Lamb wave mode (S0) in coriented aluminum nitride (AlN) membranes on Si were fabricated and tested for their sensitivities to pressure and mass as well as for their ability to work in liquid environment.

  • 22.
    Arapan, Lilia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Avramov, Ivan
    Inst Solid State Physics, Bulgarian Academy of Sciences.
    Yantchev, Ventsislav
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Thin film plate acoustic resonators for integrated microwave power oscillator applications2011In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 47, no 7, p. 452-453Article in journal (Refereed)
    Abstract [en]

    Two-port film plate acoustic resonators (FPAR) devices operating on the lowest order symmetric Lamb wave mode (S0) in C-oriented AlN membranes on Si were fabricated and tested for their power handling capabilities in a feedback-loop power oscillator circuit. The FPAR was operated at an incident power level of 24 dBm for several weeks without performance degradation. Its flicker noise constant was calculated from close-in phase noise data as αR=2.1×10^−36/Hz. The results indicate that IC-compatible S0 FPARs are well suited for integrated microwave oscillators with thermal noise floor (TNF) levels below −175 dBc/Hz.

  • 23.
    Arapan, Lilia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Katardjiev, Ilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Yantchev, Ventsislav
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    An intermode-coupled thin-film micro-acoustic resonator2012In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 22, no 8, p. 085004-Article in journal (Refereed)
    Abstract [en]

    A novel concept for the development of thin-film micro-acoustic resonators based on the coupling between different plate acoustic modes was demonstrated. The basic principles for the design and fabrication of intermode-coupled plate acoustic wave resonators on c-textured thin AlN films were presented and first experimental proof of coupling between laterally propagating waves and BAW was demonstrated. The experimental results demonstrate that the grating-assisted intermode coupling can be employed in high-frequency resonators inheriting the low dispersive nature of the S0 mode in combination with the energy localization in the plate bulk typical for the fundamental thickness shear resonance.

  • 24.
    Arapan, Lilia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Katardjiev, Ilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Yantchev, Ventsislav
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Alexieva, Gergana
    Dept of Solid State Physics and Microelectronics, University of Sofia.
    Strashilov, Vesseline
    Dept of Solid State Physics and Microelectronics, University of Sofia.
    Avramov, Ivan
    Georgy Nadjakov Institute of Solid State Physics, Sofia, Bulgarian Academy of Sciences.
    Radeva, Ekaterina
    Georgy Nadjakov Institute of Solid State Physics, Sofia, Bulgarian Academy of Sciences.
    Polymer coated thin film plate acoustic resonators (FPAR) for gas sensing applications2011In: 2011 Joint Conference of the IEEE International Frequency Control Symposium and European Frequency and Time Forum Proceedings, San Fransisco, CA, USA, 2011Conference paper (Refereed)
    Abstract [en]

    Mass sensitivity of thin aluminum nitride (AlN) film S0 plate wave resonators is theoretically and experimentally studied. Here, two-port 888MHz synchronous thin film plate acoustic resonators (FPAR) are micromachined and subsequently coated with plasma-polymerized hexamethyldisiloxane (pp-HMDSO) thin films of various thicknesses. Systematic data on frequency shift and insertion loss versus film thickness are presented in a comparative manner. Measurements in gas phase environment are further presented in a comparative manner.

  • 25.
    Arevalo, Liliana
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Numerical Simulations of Long Spark and Lightning Attachment2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The research work presented here is concerned with numerical simulations of two different electrical phenomena: Long gap electrical discharges under switching impulses and the lightning attachment process associated with positive upward leaders. The development of positive upward leaders and the progression of discharges in long gaps are attributable to two intertwined physical phenomena, namely, the leader channel and the streamer zone. The physical description and the proposed calculations of the above-mentioned phenomena are based on experimental tests conducted in long spark gaps.

    The methodology presented here proposes a new geometrical approximation for the representation of the streamer and the calculation of the accumulated electrical charge. Furthermore, two different approaches to representing the leader channel are applied and compared. Statistical delays before the inception of the first corona, and random distributions to represent the tortuous nature of the path taken by the leader channel were included based on the behavior observed in experimental tests, with the intention of ensuring the discharge behaved in a realistic manner. A reasonable agreement was found between the physical model and the experimental test results.

    A model is proposed to simulate the negative discharges produced by switching impulses using the methodology developed to simulate positive leader discharges and the physics underlying the negative leader phenomena. The validation of the method demonstrated that phenomena such as the pilot leader and negative leader currents are successfully represented.

    In addition, based on previous work conducted on the physics of lightning and the lightning attachment process, a new methodology is developed and tested. In this new approach, the background electric field and the ionized region, considered in conjunction with the advance of the leader segment, are computed using a novel method. The proposed methodology was employed to test two engineering methods that are accepted in international standards, the mesh method and the electro-geometrical method. The results demonstrated that the engineering approximations are consistent with the physical approach.

    In addition to the electrical phenomena mentioned above, one should remember that, to simplify the calculation, there are certain real effects arising from the lightning attachment process that have not been considered. In fact, when a structure is subjected to a strong electric field, it is possible to generate multiple upward leaders from that structure. This effect has not been taken into account in the numerical models available previously, and therefore the process of generating multiple upward leaders incepted over a structure is incorporated here. The results have shown that a slight advantage from the background electric field is enough for one upward connecting leader to take over, thereby forcing the others to abort the attachment process.

    List of papers
    1. Modelling of Positive Discharges in Laboratory Gaps under Switching impulses
    Open this publication in new window or tab >>Modelling of Positive Discharges in Laboratory Gaps under Switching impulses
    2008 (English)Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Cardiff, UK: , 2008
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-113403 (URN)
    Conference
    XVII International Conference on Gas Discharges and Their applications
    Available from: 2010-01-28 Created: 2010-01-28 Last updated: 2016-04-12Bibliographically approved
    2. Breakdown effect on long gaps under switching impulses statistical variation
    Open this publication in new window or tab >>Breakdown effect on long gaps under switching impulses statistical variation
    2008 (English)Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Uppsala, Sweden: , 2008
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-113402 (URN)
    Conference
    29th International Conference on Lightning Protection
    Available from: 2010-01-28 Created: 2010-01-28 Last updated: 2016-04-12Bibliographically approved
    3. Breakdown times and voltages probability calculation using a simplified numerical methodology
    Open this publication in new window or tab >>Breakdown times and voltages probability calculation using a simplified numerical methodology
    2008 (English)Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Florianopolis Brazil: , 2008
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-113401 (URN)
    Conference
    International Conference on Grounding and Earthing and 3rd International Conference on Lightning Physics and Effects
    Available from: 2010-01-28 Created: 2010-01-28 Last updated: 2016-04-12Bibliographically approved
    4. Numerical simulation of long laboratory sparks generated by positive switching impulses
    Open this publication in new window or tab >>Numerical simulation of long laboratory sparks generated by positive switching impulses
    2009 (English)In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 67, no 2-3, p. 228-234Article in journal (Refereed) Published
    Abstract [en]

    A numerical methodology using two different leader channel criteria has been implemented. The methodology is based on Bondiou and Gallimberti's proposition [A. Bondiou, I. Gallimberti, Theoretical modelling of the development of the positive spark in long spark, J. Phys. D: Appl. Phys. 27 (1994) 1252-1266]. The leader channel criteria used are Rizk engineering criterion [Rizk, A model for switching impulse leader inception and breakdown of long air gaps, IEEE Trans. Power Deliv., 4(1) (1989)] and Local thermodynamic - L.T.E. - physical concept [I. Gallimberti, The mechanism of the long spark formation, Colloque C7, J. Phys. (supplement au nro 7, Tome 40) (July 1979) C7-193]. The methodology was tested in three different cases; a deterministic case, a statistical variation and a typical constant level test. Deterministic calculation considered corona inception using stabilization corona electric field criterion of Gallimberti [I. Gallimberti, The mechanism of the long spark formation, Colloque C7, J. Phys. (supplement au nro 7, Tome 40) (July 1979) C7-193] and the leader moving as segments. The statistical simulation has two different statistical delays, one at inception and the other due to the tortuous characteristics of the leader channel. The constant level test consists of 200 positive switching impulses with the same characteristics such as maximum applied voltage, time to crest and time to fall. Time to breakdown and breakdown voltage were found based on the results obtained from the constant level test characteristics. All the numerical results presented are based on experimental conditions reported in [Les Renardières Group, Research on long gap discharges at Les Renardières, Electra N 35 (1973)] from the world class research group namely Les Renardieres Group.

    Keywords
    Discharge, Leader, Modeling, Switching
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-113133 (URN)10.1016/j.elstat.2008.12.022 (DOI)000266019500029 ()0304-3886 (ISBN)
    Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2017-12-12Bibliographically approved
    5. LABORATORY LONG GAPS SIMULATION CONSIDERING A VARIABLE CORONA REGION
    Open this publication in new window or tab >>LABORATORY LONG GAPS SIMULATION CONSIDERING A VARIABLE CORONA REGION
    2010 (English)Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Cagliary, Italy: , 2010
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-140390 (URN)
    Conference
    30TH International Conference on Lightning Protection, ICLP
    Available from: 2011-01-05 Created: 2011-01-05 Last updated: 2016-03-03
    6. A RELIABLE NUMERICAL METHOD FOR THE CALCULATION OF BREAKDOWN VOLTAGES
    Open this publication in new window or tab >>A RELIABLE NUMERICAL METHOD FOR THE CALCULATION OF BREAKDOWN VOLTAGES
    2010 (English)Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Cagliary, Italy: , 2010
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-140391 (URN)
    Conference
    30TH International Conference on Lightning Protection, ICLP
    Available from: 2011-01-05 Created: 2011-01-05 Last updated: 2014-12-10
    7. A new static calculation of the streamer region for long spark gaps
    Open this publication in new window or tab >>A new static calculation of the streamer region for long spark gaps
    2012 (English)In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 70, no 1, p. 15-19Article in journal (Refereed) Published
    Abstract [en]

    Different electrostatic approximations have been proposed to calculate the streamer region without going in deep details of the behavior of density of particles under the effect of high electric fields; this kind of approximations have been used in numerical calculations of long spark gaps and lightning attachment. The simplifications of the streamer region are achieved by considering it to be a geometrical region with a constant geometrical shape. Different geometrical shapes have been used, such as cones or several parallel filaments. Afterward, to simplify the procedures, the streamer region was approximated by two constants, one denoted K-Q, called the geometrical constant and in other cases K named as geometrical factor. However, when a voltage that varies with time is applied to an arrangement of electrodes (high voltage and grounded electrodes), the background electric field will change with time. Thus, if the background electric field is modified, the streamer zone could cover a larger or smaller area. With the aim of reducing the number of assumptions required in the calculation of long gap discharges, a new electrostatic model to calculate the streamer region is presented. This model considers a variable streamer zone that changes with the electric field variations. The three-dimensional region that fulfills the minimum electric field to sustain a streamer is identified for each time step, and the charge accumulated in that region is then calculated. The only parameter that is being used in the calculation is the minimum electric field necessary for the propagation of streamers.

    Keywords
    charge, leader, Streamer, Electrical charge, Electric field, Corona inception, Discharge
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Electricity, Esp The Study Of Transients and Discharges; Engineering Science with specialization in Science of Electricity
    Identifiers
    urn:nbn:se:uu:diva-150528 (URN)10.1016/j.elstat.2011.07.013 (DOI)000300804300003 ()
    Available from: 2011-03-31 Created: 2011-03-31 Last updated: 2017-12-11Bibliographically approved
    8. The development of long spark gaps: Simulation including a variable streamer region
    Open this publication in new window or tab >>The development of long spark gaps: Simulation including a variable streamer region
    (English)Article in journal (Refereed) Submitted
    Keywords
    Breakdown, streamer, discharge
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-150531 (URN)
    Available from: 2011-03-31 Created: 2011-03-31 Last updated: 2016-03-03
    9. Reliable model for the calculation of negative leader discharges under switching impulses
    Open this publication in new window or tab >>Reliable model for the calculation of negative leader discharges under switching impulses
    2010 (English)Conference paper, Published paper (Refereed)
    Keywords
    negative streamer, space leader, breakdown
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-150533 (URN)
    Conference
    36th grounding and 4th Lightning Physics conference GND&LPE
    Available from: 2011-03-31 Created: 2011-03-31 Last updated: 2016-04-18
    10. A preliminary model to simulate negative leader discharges
    Open this publication in new window or tab >>A preliminary model to simulate negative leader discharges
    (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463Article in journal (Refereed) Submitted
    Keywords
    Negative streamer, pilot system, breakdown
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-150532 (URN)
    Available from: 2011-03-31 Created: 2011-03-31 Last updated: 2017-12-11
    11. On the interception of lightning flashes by power transmission lines
    Open this publication in new window or tab >>On the interception of lightning flashes by power transmission lines
    2011 (English)In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 69, no 3, p. 220-227Article in journal (Refereed) Published
    Abstract [en]

    The design of the lightning protection system LPS of transmission lines is based on the well knownelectro-geometrical model. The electro-geometrical model assumes that the first point on a powertransmission line that will come within striking distance of the tip of a down-coming stepped leaderchannel is the strike point of the lightning flash. The model neglects almost all of the physics associatedwith the lightning attachment.Nowadays, as it is possible to use modern hardware and software tools and several different numericalmethods, it is feasible to apply the physics of the discharge process to the study of lightning attachment.Such models take into account the movement of the downward and the resulting upward leaders fromdifferent points on the structures under consideration.In this paper, a procedure based on lightning physics was used to analyze the lightning attachmentphenomena in EHV transmission lines of 230 kV and 500 kV and the results were compared with thepredictions of the electro-geometrical method.

    Keywords
    power system, lightning attachment, breakdown, downward leader
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-150534 (URN)10.1016/j.elstat.2011.03.013 (DOI)000292230300012 ()
    Available from: 2011-03-31 Created: 2011-03-31 Last updated: 2017-12-11
    12. 'The mesh method' in lightning protection standards - Revisited
    Open this publication in new window or tab >>'The mesh method' in lightning protection standards - Revisited
    2010 (English)In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 68, no 4, p. 311-314Article in journal (Refereed) Published
    Abstract [en]

    At present the design of the Lightning protection systems (LPS) for structures as stipulated in standards is based on the electro - geometrical method, which was initially used to protect power lines from lightning. A derivative of the electro-geometrical method is the rolling sphere method. This method together, with the protection angle method and mesh method are used almost in all lightning standards as the measure in installing the lightning protection systems of grounded structures. In the mesh method, the dimension of the cell size in different levels of protection is determined using the rolling sphere method. Since the rolling sphere method does not take into account the physics of the lightning attachment process there is a need to evaluate the validity of the stipulated value in standards of the minimum lightning current that can penetrate through the mesh in different levels of protection. In this paper, meshes of different sizes as stipulated in the lightning protection standards were tested for their ability to intercept lightning flashes using a lightning attachment model that takes into account the physics of connecting leaders on. The results are in reasonable agreement with the specifications given in the lightning protection standards.

    Keywords
    Dynamic leader, Electro-geometrical method, Lightning inception, Mesh method, Upward leader, Standards
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-135183 (URN)10.1016/j.elstat.2010.03.003 (DOI)000281211700004 ()
    Available from: 2010-12-06 Created: 2010-12-06 Last updated: 2017-12-12Bibliographically approved
    13. Influence of multiple upward connecting leaders initiated from the same structure on the lightning attachment process
    Open this publication in new window or tab >>Influence of multiple upward connecting leaders initiated from the same structure on the lightning attachment process
    2009 (English)Conference paper, Published paper (Refereed)
    Keywords
    electric field, inhibit discharge, breakdown, streamer, lightning, attachment
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-150535 (URN)
    Conference
    X International symposium on lightning protection - SIPDA
    Available from: 2011-03-31 Created: 2011-03-31 Last updated: 2016-04-14
    14. Interaction of multiple connecting leaders issued from a grounded structure simulated using a self consistent leader inception and propagation model SLIM
    Open this publication in new window or tab >>Interaction of multiple connecting leaders issued from a grounded structure simulated using a self consistent leader inception and propagation model SLIM
    2010 (English)In: 30TH International Conference on Lightning Protection, ICLP, Cagliary, Italy, 2010Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Cagliary, Italy: , 2010
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-142452 (URN)
    Conference
    30TH International Conference on Lightning Protection, ICLP
    Available from: 2011-01-14 Created: 2011-01-14 Last updated: 2016-04-19Bibliographically approved
  • 26.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    A preliminary model to simulate negative leader dischargesIn: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463Article in journal (Refereed)
  • 27.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Influence of multiple upward connecting leaders initiated from the same structure on the lightning attachment process2009Conference paper (Refereed)
  • 28.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    On the interception of lightning flashes by power transmission lines2011In: Journal of Electrostatics, ISSN 0304-3886, E-ISSN 1873-5738, Vol. 69, no 3, p. 220-227Article in journal (Refereed)
    Abstract [en]

    The design of the lightning protection system LPS of transmission lines is based on the well knownelectro-geometrical model. The electro-geometrical model assumes that the first point on a powertransmission line that will come within striking distance of the tip of a down-coming stepped leaderchannel is the strike point of the lightning flash. The model neglects almost all of the physics associatedwith the lightning attachment.Nowadays, as it is possible to use modern hardware and software tools and several different numericalmethods, it is feasible to apply the physics of the discharge process to the study of lightning attachment.Such models take into account the movement of the downward and the resulting upward leaders fromdifferent points on the structures under consideration.In this paper, a procedure based on lightning physics was used to analyze the lightning attachmentphenomena in EHV transmission lines of 230 kV and 500 kV and the results were compared with thepredictions of the electro-geometrical method.

  • 29.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Reliable model for the calculation of negative leader discharges under switching impulses2010Conference paper (Refereed)
  • 30.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Wu, Dong
    Jacobson, Björn
    The development of long spark gaps: Simulation including a variable streamer regionArticle in journal (Refereed)
  • 31.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Wu, Dong
    ABB Power Systems HVDC.
    A consistent approach to estimate the breakdown voltage of high voltage electrodes under positive switching impulses2013In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 114, no 8Article in journal (Refereed)
  • 32.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. ABB Power Systems HVDC.
    Wu, Dong
    ABB Power Systems HVDC.
    Coated large electrodes for corona prevention2013In: International Symposium on High Voltage Engineering ISH, At Seoul Korea, 2013Conference paper (Refereed)
  • 33.
    Arevalo, Liliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. ABB Power Systems HVDC.
    Wu, Dong
    ABB POwer Systems HVDC.
    INFLUENCE OF RAIN ON THE SWITCHING IMPULSE BREAKDOWN BEHAVIOUR OF POST INSULATOR WITH LARGE ELECTRODE2013In: CIGRE Symposium "Best practice in generation, transmission and distribution in a changing environment", At Auckland, New Zealand / [ed] CIGRE, 2013Conference paper (Refereed)
  • 34.
    Arvidsson, Mari
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Analys av mellanspänningsnätet i centrala delar av Västerås stad2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The dependency of continuous electricity supply is high in the Swedish society today, at the same time no one is willing to pay for a too costly or over dimensioned power distribution system. The owners of the distribution systems are the ones responsible for this balance act of maintaining a high quality of electricity delivery to customers at a reasonable cost.

    In this master thesis a limited part of the primary distribution system (10 kV), owned by Mälarenergi Elnät AB and located in the city centre of Västerås, was chosen for a deeper analysis of its reliability. Its ability to handle outages of system components (N-1 and N-2 contingency analysis) was investigated to find out potential weak spots and parts of the grid that showed signs of being overdimensioned.

    The results of the performed simulations showed that in 74 % of the studied N-1 contingencies cases, consisting of outages of a bus bar in a distribution substation, the system could handle this without causing outages in other parts of the grid. For the N-2 contingencies 61 % passed the test. It was also found that one of the two included high voltage substations could alone supply the investigated part of the grid. Some cables and transformers were found to be more or less unnecessary, whereas other components proved to be overloaded in several situations.

  • 35. Ask, Simon
    et al.
    Lindh, Rickard
    Design och konstruktion av roterande LiDAR-system för 360 graders objektdetektering2017Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Although laser rangefinder technologies have been around for decades in military, cartography, building, industrial and research applications it is only in recent years that more generally applicable and cheaper consumer grade laser range finder sensors have become available. This project investigates the possibilities and limitations of creating a mobile 360 degree, two-dimensional obstacle detection system using off-the-shelf available electronic components.

    Using a Lidar Lite 3 from Garmin Ltd., an Arduino compatible microcontroller based on Atmel 328P, a Raspberry Pi 3 from The Raspberry Pi Foundation and an electronic speed controlled brushless DC motor driving the rotation, it is shown how range data measurements can be collected, communicated, processed and displayed at measurement rates between 500 and 1000 Hz. At 5 Hz update rate of a complete 360-degree data set, this translates to a worst case angular resolution of 2.5 degrees at ranges reaching 10 meters depending on target reflectivity. Configured for these faster measurement rates, at static measurements of a white painted wall, the measurements show a standard deviation of 0.06 m at a five-meter range, going up to 0.19 m at a range of 10 meters.

    A modular and mobile prototype was designed and built. The modularity allowed testing and verification of two configurations. Configuration A uses a slip ring for power and data transfer to the rotating sensor. Configuration B allows the laser range finder to be stationary and instead rotates a first surface aluminum mirror positioned at 45 degrees above the sensor.

    The measurement results show that increasing range has a notable adversely effect on the number of successful readings in a setting demanding faster measurement rates of above 500 Hz. The number of successful readings decreases at ranges above 5 meters, and this decrease of successful readings is more pronounced in the configuration using a mirror to reflect the measurement. The mirror reflected version does on the other hand allow an electromechanically simpler, more silent and durable system.

    Using a density based clustering algorithm it is shown how person sized objects in the point cloud data can be robustly detected at ranges up to 5 meters. 

  • 36.
    Augustine, Robin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Rydberg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Complex dielectric permittivity measurements of human skin and biological solution in 2-67GHz range2012Conference paper (Refereed)
  • 37.
    Avramov, Ivan
    et al.
    Bulgarian Academy of Sciences.
    Arapan, Lilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Katardjiev, Ilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Strashilov, Vesseline
    University of Sofia.
    Yantchev, Ventsislav
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    IC-compatible Power Oscillators Using Thin Film Plate Acoustic Resonator (FPAR)2009In: Proceedings 2009 IEEE International Ultrasonics Symposium, 2009Conference paper (Refereed)
    Abstract [en]

    In this study, two-port 880MHz FPAR devicesoperating on the lowest order fast symmetric Lamb wave mode(S0) in c-oriented AlN membranes on Si, were fabricated andsubsequently tested for their power handling capabilities in afeedback-loop power oscillator circuit. The S0 Lamb waves wereexcited and detected by a classical two-port resonator structure,as in Rayleigh SAW (RSAW) resonators. Incident power levels ofup to 24 dBm (250 mW) for the FPARs were provided by a high powersustaining amplifier in the loop. No measurable performance degradation was observed. The results from this study indicate that IC-compatible S0 FPAR devices can dissipate orders of magnitude higher RF-power levels than their RSAWcounterparts on quartz and are well suited for integrated microwave power oscillators with thermal noise floor (TNF) levelsbelow -175 dBc/Hz.

  • 38.
    Back, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    A new DC-DC converter technology suitable to support grid connection of wave power energy converter2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Since 2002, the department of electricity at Uppsala university has pushed the Lysekil project. The project has a number of wave energy converters installed in the sea southwest of Lysekil.

    The purpose of this work is to design, build and test a DC-DC converter, which will later be used as a necessary part of the grid connection of a wave energy converter.

    Since a wave energy converter does not generate electricity at a constant frequency, it is not possible to use a gearbox. Instead, power is rectified and, if there are several wave power energy converters, are put together with the others before it is inverted and transformed to the correct voltage level, and finally connected to the grid [1].

    The designed DC-DC converter is a converter of the type "inverting buck-boost", i.e. a converter that can both lower and raise the voltage, and inverts the polarity of the output. Although the voltage in normal circumstances will only be increased, the simulations showed that the efficiency and cost of components did not differ much between a "boost" and "buck-boost" converter, thus considered flexibility to be able to lower the voltage if needed.

    The project also includes a small part to the construction of a bridge rectifier, but as the most difficult moment in the project is the DC-DC converter, the greatest focus will be there.

  • 39.
    Backlund, Ludvig
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Martin, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Svantesson, Gustaf
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Methods for calibration of the vibration measurement system EVME used on the JAS 39 Gripen engine.2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This project investigates methods for calibrating and functional testing an Engine Vibration Measurement Equipment. The equipment uses accelerometers to measure vibrations on the JAS 39 Gripen aircraft engine to ensure that the engine is correctly installed. A model for emulating the electronic signals generated by the accelerometers was created in Simulink and different ways for utilizing the model as a part of a complete test system were examined. Upon examination of different calibration methods it was found that a complete test system needs to have the ability to both send electrical signals directly into the EVME as well as a way of testing the accelerometers mechanically. Both short- and long-term solutions fulfilling these requirements were prepared.

  • 40.
    Baharudin, Zikri Abadi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Characterizations of ground flashes from tropic to northern region2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis portrays new information concerning the cloud-to-ground (CG) lightning flashes or ground flashes produced by thunderclouds. It emphasizes the importance of characterizing lightning studies as the relationship between lightning mechanisms, and of incorporating the influence of geographical location, latitude and storm type. Sweden, Malaysia and USA were chosen as the main locations for field experiments in 2009 to 2011 to gather a significant number of negative and positive CG flashes. This work provided data on a total of 1792 CG lightning flashes (1685 negative and 107 positive ones) from a total of 53 thunderstorms by monitoring both the slow and the fast electric field and the narrowband radiation field at 3 and 30 MHz signals simultaneously. This thesis is comprised of: (i) the relationship of the Low Positive Charge Region (LPCR) and Preliminary Breakdown Pulse (PBP) trains to the occurrence of negative CG, (ii) slow field changes generated by preliminary breakdown processes in positive and negative ground flashes, and (iii) the occurrence of positive and negative ground flashes. It was revealed that the PBP train appeared have a higher strength in the in Sweden. The strength of the PBP train was caused by the LPCR; in contrast,  weak PBP trains were characteristic in tropical countries constituting insignificant LPCR and needing little energy to break the “blocking” agent to allow the flash to propagate downward to the ground. The second contribution concerns the characteristics of the PBP train mentioned; this includes novel information for Malaysia. Further, it is stated that there are some different characteristics in the PBP trains in Johor, Malaysia and Florida, USA. The studies of slow field changes generated by preliminary breakdown processes clarifies unclear features concerning the starting position of slow field changes generated by preliminary breakdown processes in positive and negative ground flashes. It was found that the slow field changes did not occur before the initial process of the commencement of preliminary breakdown. Single-station electric field measurements incorporating narrowband radiation field measurement and high resolution transient recording (12 bits) with an accuracy of several nanoseconds, allows one to distinguish between the intracloud activities and the preceding processes of ground flashes. The results for the interstroke intervals, amplitude distribution of subsequent return-stroke (SRS) and the number of strokes per flash in the tropics, subtropics and northern regions were similar. Finally, a significant number of positive return-stroke (RS) electric fields provided statistically significant information on the characteristics of these strokes.

    List of papers
    1. Comparative study on preliminary breakdown pulse trains observed in Johor, Malaysia and Florida, USA
    Open this publication in new window or tab >>Comparative study on preliminary breakdown pulse trains observed in Johor, Malaysia and Florida, USA
    Show others...
    2012 (English)In: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895, Vol. 117, p. 111-121Article in journal (Refereed) Published
    Abstract [en]

    In this paper, the preliminary breakdown (PB) pulse train preceding the negative first return stroke (RS) is recorded using a broad band antenna system. These analyses were carried out in Johor Bahru, Malaysia and Florida, United States. This is a novel initiative at examining and identifying the characteristics of the PB pulse trains in the negative cloud-to-ground flashes observed in Malaysia. The arithmetic mean of the total pulse train duration is 12.3 ms and the weighted arithmetic mean of the pulse durations and interpulse intervals are 11 mu s and 152 mu s, respectively. The arithmetic mean ratio between the maximum peak amplitude of the PB pulse and the peak RS electric field was 27.8%, and the corresponding value in Florida was 29.4%. The arithmetic mean of the time duration between the most active part of the pulse train, and the RS was 57.6 ms in Malaysia and 22 ms in Florida. A qualitative comparison of our results with those obtained earlier in Sri Lanka. Sweden and Finland supports the hypothesis that the PBP/RS ratio is higher in the northern regions compared to the tropical regions. (C) 2012 Elsevier B.V. All rights reserved.

    Keywords
    Preliminary breakdown pulses, PB/RS ratio, PB-RS separation
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Science of Electricity
    Identifiers
    urn:nbn:se:uu:diva-184450 (URN)10.1016/j.atmosres.2012.01.012 (DOI)000309300100015 ()
    Available from: 2012-11-09 Created: 2012-11-07 Last updated: 2017-12-07Bibliographically approved
    2. Electric field changes generated by the preliminary breakdown for the negative cloud-to-ground lightning flashes in Malaysia and Sweden
    Open this publication in new window or tab >>Electric field changes generated by the preliminary breakdown for the negative cloud-to-ground lightning flashes in Malaysia and Sweden
    Show others...
    2012 (English)In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 84-85, p. 15-24Article in journal (Refereed) Published
    Abstract [en]

    We present the study of the electric field changes generated by the preliminary breakdown for negative cloud-to-ground lightning flashes in Malaysia and Sweden concerning the association of slow field changes associated in preliminary breakdown process. We examined the total of 1685 negative cloud-to-ground lightning flashes from the total of 39 thunderstorms by recording the slow electric field, fast electric field and narrowband radiation field at 3 and 30 MHz signals simultaneously. Our results show that there is a pre-starting time, i.e. the duration between the first preliminary breakdown pulse and slow field changes starting point, which is found to be after the first preliminary breakdown pulse. The pre-starting time has the arithmetic and geometric mean range from 1.4-6.47 and 1-3.36 ms, respectively. The mean values of pre-starting time in Malaysia are greater than the values observed in Sweden by more than a factor of 3. From the two data sets it shows that the slow field changes never start before the preliminary breakdown. Furthermore, the use of single-station electric fields measurement with high resolutions of 12 bits transient recorder with several nanosecond accuracy allow one to distinguish the slow field changes generated by preliminary breakdown, which preceded the negative first return stroke, between tens to hundreds of milliseconds of pre-return stroke duration.

    Keywords
    Initiation position, Slow field changes, Close ground flashes, Preliminary breakdown process
    National Category
    Meteorology and Atmospheric Sciences Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-182547 (URN)10.1016/j.jastp.2012.04.009 (DOI)000308512100003 ()
    Available from: 2012-10-11 Created: 2012-10-11 Last updated: 2017-12-07
    3. Electric field changes generated by preliminary breakdown pulse for positive lightning ground flashes in Sweden
    Open this publication in new window or tab >>Electric field changes generated by preliminary breakdown pulse for positive lightning ground flashes in Sweden
    Show others...
    (English)Manuscript (preprint) (Other academic) [Artistic work]
    Abstract [en]

    This is the new study of the electric field changes generated by the preliminary breakdown for positive cloud-to-ground flashes which concerning on the association of slow field changes in preliminary breakdown process. In this study, a 107 positive cloud-to-ground lightning flashes recorded from the total of 14 thunderstorms generated by the whole flash were examined. The electric fields were measured with nanosecond resolution by using the slow electric field, fast electric field and narrowband radiation field at 3 and 30 MHz signals simultaneously. Our result shows that there is a pre-starting time, i.e. the duration between the first preliminary breakdown pulse and slow field changes starting point, which is found to be after the first preliminary breakdown pulse. The pre-starting time has the arithmetic mean – 3.0 ms and geometric mean – 1.8 ms, ranging from 0.3 to 21.7 ms. This study is consistent with the latest finding for the slow field changes in negative ground flashes where the slow field changes never start before the preliminary breakdown process.

    Keywords
    Positive cloud-to-ground lightning flashes, Initiation position, slow field changes, close ground flashes, preliminary breakdown process
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-222826 (URN)
    Funder
    Swedish Research Council, 621-2006-4299Swedish Foundation for Strategic Research , IG2004–2031
    Available from: 2014-04-15 Created: 2014-04-14 Last updated: 2017-11-09Bibliographically approved
    4. Negative cloud-to-ground lightning flashes in Malaysia
    Open this publication in new window or tab >>Negative cloud-to-ground lightning flashes in Malaysia
    Show others...
    2014 (English)In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 108, p. 61-67Article in journal (Refereed) Published
    Abstract [en]

    The characteristics of the negative cloud-to-ground lightning flashes in Malaysia are studied by analyzing the electric fields generated by the whole flash in nanosecond resolution. A total of 405 strokes obtained from 100 successive negative cloud-to-ground lightning flashes were analyzed, which were recorded from seven convective thunderstorms during the southwest monsoon period, i.e. from April to June 2009. It was found that the total number of interstroke intervals has an arithmetic mean value of 86 ms, a geometric mean value of 67 ms and does not depend on the return stroke order. Of the 100 negative ground flashes, 38 flashes (38%) have at least one subsequent return-stroke (SRS) whose electric field peak was greater than that of the first return-stroke (RS). Furthermore, 58 (19%) out of 305 SRS have electric field peak larger than those of the first RS. The arithmetic and geometric mean ratio between the peak electric field of the SRS and the peak electric field of the first RS are 0.7 and 0.6, respectively. The percentage of single-stroke flashes was 16% while the mean number of strokes per flash and maximum number of stroke per flash were 4 and 14, respectively.

    Keywords
    Negative cloud-to-ground lightning flashes, Number of strokes per flash and interstroke interval
    National Category
    Natural Sciences Engineering and Technology
    Research subject
    Engineering Science with specialization in Science of Electricity
    Identifiers
    urn:nbn:se:uu:diva-221965 (URN)10.1016/j.jastp.2013.12.001 (DOI)000331684900007 ()
    Available from: 2014-04-10 Created: 2014-04-07 Last updated: 2017-12-05Bibliographically approved
    5. On the characteristics of positive lightning ground flashes in Sweden
    Open this publication in new window or tab >>On the characteristics of positive lightning ground flashes in Sweden
    Show others...
    2016 (English)In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 138, p. 106-111Article in journal (Refereed) Published
    Abstract [en]

    In this study the stroke characteristics of positive cloud-to-ground flashes in Sweden were obtained from the electric field records measured from 14 thunderstorms. The electric fields were measured with nanosecond resolution. Together with the fast and the slow electric field records, the narrowband radiation field at 3 and 30 MHz signals were also measured simultaneously. Out of a total of 107 flashes, 30 flashes had two strokes, 7 had three strokes and 3 flashes had four strokes. The arithmetic and geometric means of the interstroke intervals were found to be 116 and 70 ms, respectively. The arithmetic and geometric mean ratio between the peak electric field of the Subsequent Return Stroke (SRS) and the first Return Stroke (RS) were 0.48 and 0.36, respectively. Of the 40 positive multiple-stroke ground flashes, 5% have at least one SRS with field peak higher than the first RS. The percentage of SRS with field peaks greater than the first RS was 6%. In our best of our knowledge, this is the first time a large sample of positive return strokes in Sweden was analysed. It was found to be statistically more significant than the previous studies.

    Keywords
    Lightning flashes, Positive ground flashes, Positive return strokes, Electromagnetic fields
    National Category
    Meteorology and Atmospheric Sciences Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-274994 (URN)10.1016/j.jastp.2015.12.014 (DOI)000370769900011 ()
    Funder
    Swedish Research Council, 621-2006-4299
    Available from: 2016-01-27 Created: 2016-01-27 Last updated: 2017-11-30Bibliographically approved
    6. Comparative Study on Preliminary Breakdown Pulse Trains Observed in Malaysia and Florida
    Open this publication in new window or tab >>Comparative Study on Preliminary Breakdown Pulse Trains Observed in Malaysia and Florida
    Show others...
    2010 (English)Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Cagliary, Italy: , 2010
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-140393 (URN)
    Conference
    30TH International Conference on Lightning Protection, ICLP
    Available from: 2011-01-05 Created: 2011-01-05 Last updated: 2018-05-28
    7. The first electric field pulse of cloud and cloud-to-ground lightning discharges
    Open this publication in new window or tab >>The first electric field pulse of cloud and cloud-to-ground lightning discharges
    Show others...
    2010 (English)In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 72, no 2-3, p. 143-150Article in journal (Refereed) Published
    Abstract [en]

    In this study, the first electric field pulse of cloud and cloud-to-ground discharges were analyzed and compared with other pulses of cloud discharges. Thirty eight cloud discharges and 101 cloud-to-ground discharges have been studied in this analysis. Pulses in cloud discharges were classified as [`]small', [`]medium' and [`]large', depending upon the value of their relative amplitude with respect to that of the average amplitude of the five largest pulses in the flash. We found that parameters, such as pulse duration, rise time, zero crossing time and full-width at half-maximum (FWHMs) of the first pulse of cloud and cloud-to-ground discharges are similar to small pulses that appear in the later stage of cloud discharges. Hence, we suggest that the mechanism of the first pulse of cloud and cloud-to-ground discharges and the mechanism of pulses at the later stage of cloud discharges could be the same.

    Keywords
    Cloud discharges, Electromagnetic field, Lightning, Electric field pulses
    National Category
    Meteorology and Atmospheric Sciences Engineering and Technology
    Research subject
    Engineering Science with specialization in Atmospheric Discharges
    Identifiers
    urn:nbn:se:uu:diva-140337 (URN)10.1016/j.jastp.2009.11.001 (DOI)
    Available from: 2011-01-05 Created: 2011-01-05 Last updated: 2017-12-11
    8. Radiation Field Spectra of Long-duration Cloud Flashes
    Open this publication in new window or tab >>Radiation Field Spectra of Long-duration Cloud Flashes
    (English)In: IEEE transactions on electromagnetic compatibility (Print), ISSN 0018-9375, E-ISSN 1558-187XArticle in journal (Refereed) Submitted
    Abstract [en]

    The radiation electric fields produced by long-duration cloud flashes have been Fourier analyzed to determined the frequency spectrum in the range of 10 kHz to 10 MHz. The flashes were recorded within a distance of less than 20 km. The spectrum was normalized to 50 km distance and it shows a f-1 dependence within the entire frequency range.

    Identifiers
    urn:nbn:se:uu:diva-150952 (URN)
    Available from: 2011-04-08 Created: 2011-04-08 Last updated: 2017-12-11
    9. Characteristics of narrow bipolar pulses observed in Malaysia
    Open this publication in new window or tab >>Characteristics of narrow bipolar pulses observed in Malaysia
    Show others...
    2010 (English)In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 72, no 5-6, p. 534-540Article in journal (Refereed) Published
    Abstract [en]

    Narrow bipolar pulses (NBPs) are considered as isolated intracloud events with higher peak amplitude and strong high frequency emission compared to the first return strokes and other intracloud discharges. From 182 NBPs recorded in Malaysia in the tropic, 75 were narrow negative bipolar pulses (NNBPs) while 107 were narrow positive bipolar pulses (NPBPs). The mean duration of NNBPs was 24.6 +/- 17.1 mu s, while 30.2 +/- 12.3 mu s was observed for NPBPs. The mean full-width at half-maximum (FVVHM) was 2.2 +/- 0.7 and 2.4 +/- 1.4 mu s for NNBPs and NPBPs, respectively. The mean peak amplitude of NPBPs normalized to 100 km was 22.7 V/m, a factor of 1.3 higher than that of NNBPs which is 17.6 V/m. In contrast to the previous studies, it was observed that the electric field change was characterized by a bipolar pulse with a significant amount of fine structures separated by a few tens of nanoseconds intervals, embedded on it. (C) 2010 Elsevier Ltd. All rights reserved.

    Keywords
    Narrow bipolar pulses, Lightning, Cloud discharges, Electric field
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-137067 (URN)10.1016/j.jastp.2010.02.006 (DOI)000276428600020 ()
    Available from: 2010-12-15 Created: 2010-12-15 Last updated: 2017-12-11Bibliographically approved
    10. Some features of electric field waveform of Narrow Bipolar Pulses
    Open this publication in new window or tab >>Some features of electric field waveform of Narrow Bipolar Pulses
    (English)In: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895Article in journal (Refereed) Submitted
    Abstract [en]

    Narrow Bipolar Pulses (NBPs) are generated by intra-cloud discharge processes and they are of interest due to their strong broadband and high frequency (HF) emissions. In this study, we present some features of electric field waveform of NBPs which have not been reported in the literature.  The HF emission was observed to begin simultaneously with the onset of NBPs indicating no streamers or stepped-leader process was taking place before the initiation of NBPs. The electric field waveforms of NBPs were characterized by many fine peaks embedded intermittently on the rising and decaying edge of NBPs suggesting that some small scale electrical discharges were involved during the formation of NBPs.

     

    Identifiers
    urn:nbn:se:uu:diva-150953 (URN)
    Available from: 2011-04-08 Created: 2011-04-08 Last updated: 2017-12-11
  • 41.
    Baharudin, Zikri Abadi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Cooray, Vernon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Rahman, Mahbubur
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Hettiarachchi, Pasan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Ahmad, Noor Azlinda
    Universiti Teknologi Malaysia.
    Electric field changes generated by preliminary breakdown pulse for positive lightning ground flashes in SwedenManuscript (preprint) (Other academic)
    Abstract [en]

    This is the new study of the electric field changes generated by the preliminary breakdown for positive cloud-to-ground flashes which concerning on the association of slow field changes in preliminary breakdown process. In this study, a 107 positive cloud-to-ground lightning flashes recorded from the total of 14 thunderstorms generated by the whole flash were examined. The electric fields were measured with nanosecond resolution by using the slow electric field, fast electric field and narrowband radiation field at 3 and 30 MHz signals simultaneously. Our result shows that there is a pre-starting time, i.e. the duration between the first preliminary breakdown pulse and slow field changes starting point, which is found to be after the first preliminary breakdown pulse. The pre-starting time has the arithmetic mean – 3.0 ms and geometric mean – 1.8 ms, ranging from 0.3 to 21.7 ms. This study is consistent with the latest finding for the slow field changes in negative ground flashes where the slow field changes never start before the preliminary breakdown process.

  • 42.
    Bahceci, Mesut
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Simulation of an Electrical Machine: with superconducting magnetic bearings2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis investigates if there is an induction motor configuration that can be used with a flywheel energy storage system, that uses passve superconducting magnetic bearings (SMBs). The configurations should be able to be designed with induction motor building blocks that are commercially available. The method used to investigate this was simulations of different induction motor configurations in the finite element analysis software COMSOL.

    The simulations show that when larger air-gaps than that of a commercial IM unit are used it is possible to use SMBs in the IM. SMBs have the advantage of having zero resistance which makes it possible to store energy without resistance losses. However it was found that by using and IM with SMBs the generated power would be lower than that of a commercial unit.

  • 43.
    Bajramovic, Azur
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Val av överlastskydd för elektriska ventilmanöverdon på kärnkraftverket i Forsmark2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    At nuclear power plants, electrical valve actuators are important for ensuring that the reactor core is water covered and the pressure in the reactor tank and containment is limited. The electrical actuators are provided with overload protection in case of drawing higher current then the motors are rated for. When safety manoeuvres are needed, the overload protection must not trig and cause the valve to stop before completing the manoeuvre. Analyses have showed that the current settings of the overload protection may cause an illegitimate trig at the worst theoretically possible accident. A new method has been developed with conservative assumptions and applies overload protections for all electrical valve actuators at the three reactors in Forsmark.

  • 44. Bakke, T
    et al.
    Köhler, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science. ÅSTC. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electronics.
    Bäcklund, Ylva
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science. Fasta tillståndets elektronik. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electronics.
    Mukherjee, S
    Silicon semi-circular tapered structures made by diffusion limited HF:HNO3 wet etching1998In: Micromechanics Europe 1988, MME'98, Ulvik Norge, 1998Conference paper (Refereed)
  • 45.
    Barankova, Hana
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Materials Science. Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Bardos, Ladislav
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Materials Science. Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Cold atmospheric plasma sources2002In: INVITED PAPER, ANZIO 2002, 5th Symp.Europ.Vac.Coaters, September 30, Rome-Anzio, Italy, abstract only, 2002Conference paper (Refereed)
  • 46.
    Barankova, Hana
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Materials Science. Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Bardos, Ladislav
    Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Cold atmospheric plasma sources based on hollow cathodes2002In: INVITED presentation at 1st Topical Meeting on Pulsed and Atmospheric Pressure Plasma Processing, FMT - Forschungszentrum für Mikrostrukturtechnik, Univestity of Wuppertal, Wuppertal, March 2002, 2002Conference paper (Refereed)
  • 47.
    Barankova, Hana
    et al.