The thesis designs, constructs, and tests an electrically small dipole antenna probe for the measurement of electric field distributions induced by a transcranial magnetic stimulation (TMS) coil. Its unique features include high spatial resolution, large frequency band from 100 Hz to 300 kHz, efficient feedline isolation via a printed Dyson balun, and accurate mitigation of noise. Prior work in this area is thoroughly reviewed. The proposed probe design is realized in hardware; implementation details and design tradeoffs are described. Test data is presented for the measurement of a CW capacitor electric field, demonstrating the probe’s ability to properly measure conservative electric fields caused by a charge distribution. Test data is also presented for the measurement of a CW solenoidal electric field, demonstrating the probe’s ability to measure non-conservative solenoidal electric fields caused by Faraday’s law of induction. Those are the primary fields for the transcranial magnetic stimulation. Advantages and disadvantages of this probing system versus those of prior works are discussed. Further refinement steps necessary for the development of this probe as a valuable TMS instrument are discussed.

Microwave near-field probes (MNPs) confine evanescent fields to regions that are substantially smaller than the wavelength at the operation frequency. Such probes are able to resolve subwavelength features, thus providing resolution much higher than the classical Abb?? limit. These abilities of MNPs are primarily due to the evanescent nature of the field generated at the tip of the probes. In the past, MNPs with ultra-high resolution were designed by tapering a resonant opening to provide high field concentration and high sensitivity. The limitations of these MNPs were subject to low surface roughness and practical realization challenges due to their geometrical features and vibration control constraints. Metamaterials with their ability to enhance evanescent fields, lead to the speculation that they could potentially increase the sensitivity of near-field probe. Periodically arranged metamaterial unit elements such as split-ring-resonators (SRRs) can create negative permeability media. Placing such material layer in the proximity of a probe leads to enhancement of the evanescent waves. Guided by this remarkable feature of metamaterials, I proposed an MNP consisting of a wire loop concentric with a single SRR. The evanescent field behavior of the probe is analyzed using Fourier analysis revealing substantial enhancement of the evanescent field consistent with metamaterial theory predictions. The resolution of the probe is studied to especially determine its ability for sub-surface detection of media buried in biological tissues. The underlying physics governing the probe is analyzed. Variations of the probe are developed by placement of lumped impedance loads. To further increase the field confinement to smaller region, a miniaturized probe design is proposed. This new probe consists of two printed loops whose resonance is tunable by a capacitor loaded in the inner loop. The sensing region is decreased from ??/20 to ??/55, where ?? is the wavelength of the probe???s unloaded frequency. The magnetic-sensitive nature of the new probe makes it suitable for sensing localized magnetostatic surface resonance (LMSR) occurring in electrically very small particles. Therefore, I proposed a sensing methodology for detecting localized magnetostatic surface (LMS) resonant particles. In this methodology, an LMS resonant sphere is placed concentrically with the loops. A circuit model is developed to predict the performance of the probe in the presence of a magnetic sphere having Lorentz dispersion. Full-wave simulations are carried out to verify the circuit model predictions, and preliminary experimental results are demonstrated. The Lorentzian fit in this work implies that the physical nature of LMSR may originate from spin movement of charged particle whose contribution to effective permeability may be analogous to that of bound electron movement to effective permittivity in electrostatic resonance. Detection of LMSR can have strong impact on marker-based sensing applications in biomedicine and bioengineering.

Electric and magnetic fields in the vicinity of strong sources of radiation (e.g. radar and broadcasting) can exceed the limits mentioned in the national standards for the exposition of persons. Field probes are needed to warn personnel if they are going too close to the RF-sources. For acceptance reasons the field probes should be universal in such a way that no user adjustment of frequency is required. The limits for power density, electric and magnetic field strength depend on the frequency. In contrast, field probes covering a large frequency range, e.g. 1 MHz to 18 GHz or even larger, normally have a flat frequency response. Therefore, the person using the field probe has to know the frequency of the electromagnetic field and to evaluate fieldstrength with respect to the frequency dependent limit value defined by law. Human mistakes while making that evaluation can lead to expositions above the limit value. On the other hand, the evaluation of the power density in the presence of multiple strong sources of radiation at different frequencies with different limit values also leads to measurement problems. A new approach has been undertaken to overcome these difficulties in the development of a rectifying field probe. It consists in shaping the antenna factor of the probe inversely proportional to the limit value. The isotropic response of field probes can be achieved, if three dipole antennas are arranged perpendicular to each other. The presence of dielectric supporting material leads to degradation of the isotropic response of such a field probe. The effect will be investigated. For typical substrates the isotropic response is degraded by up to 3.8 dB. An compensation for this effect will be proposed that leads to a residual unisotropic response of less than 0.2 dB.

Electric and magnetic fields in the vicinity of strong sources of radiation (e.g. radar and broadcasting) can exceed the limits mentioned in the national standards for the exposition of persons. Field probes are needed to warn personnel if they are going too close to the RF-sources. For acceptance reasons the field probes should be universal in such a way that no user adjustment of frequency is required. The limits for power density, electric and magnetic field strength depend on the frequency. In contrast, field probes covering a large frequency range, e.g. 1 MHz to 18 GHz or even larger, normally have a flat frequency response. Therefore, the person using the field probe has to know the frequency of the electromagnetic field and to evaluate fieldstrength with respect to the frequency dependent limit value defined by law. Human mistakes while making that evaluation can lead to expositions above the limit value. On the other hand, the evaluation of the power density in the presence of multiple strong sources of radiation at different frequencies with different limit values also leads to measurement problems. A new approach has been undertaken to overcome these difficulties in the development of a rectifying field probe. It consists in shaping the antenna factor of the probe inversely proportional to the limit value. The isotropic response of field probes can be achieved, if three dipole antennas are arranged perpendicular to each other. The presence of dielectric supporting material leads to degradation of the isotropic response of such a field probe. The effect will be investigated. For typical substrates the isotropic response is degraded by up to 3.8 dB. An compensation for this effect will be proposed that leads to a residual unisotropic response of less than 0.2 dB.

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Cette thèse est une contribution à l’étude d’un système de biotélémesure par gélule ingérable. L’étude concerne les problèmes de télétransmission d’énergie et d’informations entre la gélule ingérable et le système extracorporel de télécommande.Nous exposons des méthodes de conception théoriques et de caractérisation expérimentales du système de télécommande sans fil de la mise sous tension des gélules. Une deuxième partie concerne la conception du système de télétransmission d’énergie et d’informations par induction magnétique, suivi de la réalisation d’un système d’accord automatique par capacité commutée synchrone. La caractérisation d’antennes miniatures a fait l’objet d’une troisième partie dans laquelle nous avons proposé des solutions basées sur des techniques de mesure des paramètres Sij en différentiel.Enfin, nous présentons la conception d’une sonde de champ magnétique destinée à valider les résultats de simulation. / This thesis is a contribution to study of intracorporeal measure of ingestible capsule. It concerns more specifically the problems of wireless transmission of energy and information between the capsule and ingestible extracorporeal control and monitoring system. Thus we first set of design methods and theoretical characterization of the experimental system of wireless remote power up capsules. A second part was dedicated to wireless transmission of energy and information design through magnetic induction, it led to the creation of an original system of tuning by synchronous switched capacitor. The problem of miniature antennas characterization has been a third party in which we have proposed innovative solutions based on techniques for measuring parameters Sij in differential (or transmission). Finally, we presented in the last part the design and characterization of a magnetic field probe designed to validate the simulation results.

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No description available.

Master’s thesis is focused on making the acquaintance of EMC issues and ways of electromagnetic field scanner RS321 utilization for pre-compliance measurements. First part contains analysis of available equipment’s influence on measurement results on the basis of gathered specification. Next part includes an example measurement used as operational manual for scanner and its controlling program. The most important part is correction evaluation for performed EMI measurement of signal generator using its EMC certification protocol and application of gained correction curve on independent EMI measurement of device tested by EMC testing laboratory. Other possibilities of scanner utilization are mentioned in the next chapters. Last part of the thesis contains suitability evaluation of EMC scanner on the basis of findings from performed measurements.

With power generation and consumption placed further away from each other, with for example increased offshore power production, the need for HVDC transmission systems increases. As voltage levels in the HVDC transmission system are raised, the losses can be decreased, enabling efficient power transfer over longer distances. Such an increase in voltage levels comes with questions regarding insulation performance due to increased electrical field stress in high voltage apparatus, particularly in and around cable terminations. Thus, physical measurements of electrical fields or voltage potentials in air are of interest to improve the understanding of the electrical fields around cable terminations as well as to verify and develop simulation models for use at ultra high voltage. In this thesis, different measurement systems and sensors for electrical field measurements are investigated, and their benefits and drawbacks are compared to a known previously implemented reference measurement system with known strengths and limitations. Two new conceptual measurement systems with a sensor concept and positioning system are developed and proposed for a set of given conditions, such as measurement around cable terminations in air. The first proposed system is based on a shutter field mill sensor placed on variable electric potential. The second system is based on the reference system's sensor design modified to remove the need for a large positioning system. The feasibility of the two measurement systems is investigated further utilizing a COMSOL model and a mechanical prototype. The simulation model is used for electrical field simulations around cable terminations in a 2D-axisymmetric geometry as well as a 3D geometry to verify the first measurement system. The mechanical prototype is utilized to test and verify the possibility of implementing the second system's positioning system. The two final proposed measurement systems can be further developed and used as a foundation for a future implemented measurement system. / Ökad elproduktion i form av exempelvis vindkraftsverk placerade till havs leder till elproduktion och konsumtion placerad med större avstånd från varandra, vilket skapar ett behov av HVDC transmissionssystemm. Genom att höja spänningsnivåerna i transmissionssystemet kan förluster minskar, vilket möjligör effektiv kraftöverföring över längre avstånd. En sådan ökning av spänningsnivåerna i transmissionssystemet kommer med obesvarade frågor angående isoleringsprestanda i högspänningsutrustningen på grund av en höjd elektrisk stress, med särskilt intresse gällande påverkan på kabelavslut. Därför är fysiska mätningar av elektriska fält eller potentialer i luft av intresse för att förbättra förståelsen av det elektriska fältet kring kabelavslut, samt att verifiera och utveckla simuleringsmodeller för användning vid ultrahög spänningspotentialer. I detta examensarbete har olika mätsystem och sensorer för elektriska fältmätningar utredits och deras fördelar och nackdelar jämförts med ett känt tidigare implementerat rereferensmätsystem med kända styrkor och begränsningar. Två nya konceptuella mätsystem med sensorkoncept med tillhörande positioneringssystem utvecklas och föreslås för en uppsättning givna förhållanden, som t.ex mätning kring kabelavslutningar i luft. Det första föreslagna systemet är baserat på en fältkvarnssensor placerad på variabel elektrisk potential. De andra systemet är baserat på referenssystemets sensordesign modifierad för att ta bort behovet av ett stort positioneringssystem. Genomförbarheten av de två mätsystem undersöks vidare med användning av en COMSOL-modell och en mekanisk prototyp. Simuleringsmodellen används för elektriska fält simuleringar kring ett kabelavslut i en 2D-axelsymmetrisk geometri samt i en 3D-geometri för att verifiera det första mätsystemet. Mekaniska prototypen används för att testa och verifiera möjligheten att implementera andra systemets positioneringssystem. De två föreslagna mätsystemen kan vidareutvecklas och användas som en grund för ett framtida implementerat mätsystem.