No / A heterogeneous hybrid computational electromagnetics method is presented, which enables different parts of an antenna simulation problem to be treated by different methods, thus enabling the most appropriate method to be used for each part. The method uses a standard frequency-domain moment-method program and a finite-difference time-domain program to compute the fields in two regions. The two regions are interfaced by surfaces on which effective sources are defined by application of the Equivalence Principle. An extension to this permits conduction currents to cross the boundary between the different computational domains. Several validation cases are examined and the results compared with available data. The method is particularly suitable for simulation of the behavior of an antenna that is partially buried, or closely coupled with lossy dielectric volumes such as soil, building structures or the human body.

Yes / The main objective of this work is to investigate the combinatory effects of both uniaxial magnetic and electrical anisotropies on the input impedance, resonant length and the mutual coupling between two dipoles printed on an anisotropic grounded substrate. Three different configurations: broadside, collinear and echelon are considered for the coupling investigation. The study is based on the numerical solution of the integral equation using the method of moments through the mathematical derivation of the appropriate Green’s functions in the spectral domain. In order to validate the computing method and evaluated Matlab® calculation code, numerical results are compared with available literature treating particular cases of uniaxial electrical anisotropy; good agreements are observed. New results of dipole structures printed on uniaxial magnetic anisotropic substrates are presented and discussed, with the investigation of the combined electrical and magnetic anisotropies effect on the input impedance and mutual coupling for different geometrical configurations. The combined uniaxial (electric and magnetic) anisotropies provide additional degrees of freedom for the input impedance control and coupling reduction. / This work is part of the POSITION-II project funded by the ECSEL joint Undertaking under grant number Ecsel-7831132-Postitio-II-2017-IA,www. position-2.eu and partly funded by FCT/MCTES through national funds and when applicable co-funded EU funds under the project UIDB/50008/2020- UIDP/50008/2020. This work was also supported in part by the DGRSDT (General Directorate of Scientific Research and Technological Development) - MESRS (Ministry of Higher Education and Scientific Research), Algeria, and RTI2018-095499-B-C31, Funded by Ministerio de Ciencia, Innovación y Universidades, Gobierno de España (MCIU/AEI/FEDER,UE).

An experimental method for determination and analysis of the impulse response function of linear, elastic, vibrating systems is developed. A deconvolution method is developed for estimation of the impulse response function. The estimator is shown to be unbiased in the presence of measurement noise. Modal parameters are extracted from impulse response estimates using a modification of the Pisarenko harmonic decomposition method. The advantages of a time-domain approach over traditional Fourier analysis procedures, including avoidance of leakage and enhanced statistical significance, are described. Several tests used to determine the performance of the impulse response estimator are described, and the results of these tests, are presented. It is shown that the method can provide accurate estimates of modal parameters even for short data sets or high noise levels. / Master of Science

The development of the High Frequency Power MOSFET has brought about a need for accurate models. Now that the frequency range of these MOSFETs is in domains where typically scattering parameter measurements are used, a broad band device model can prove to be extremely useful. This thesis summarizes the research performed towards the development of a wideband Gate model for the Motorola MRF162 High Frequency Power Transistor. The device theory for typical MOSFETs will be explained. This theory will lead into the development of the Power MOSFET and its associated frequency limitations. The benefits of Time Domain Techniques will be explained and how a wideband model is achieved from this technique. The result from the analysis of the measurements and the device theory is a wideband Gate model developed for the frequency range from 100MHz to 400MHz. Verification is achieved by curve matching the measured Time Domain Reflected waveforms with the simulated waveforms generated using a proprietary program Modified Transient Analysis Program (MTCAP) and by comparison of expected and simulated parasitic values. / Master of Science

A calibration technique for time domain reflectometry and transmission (TDR and TDT) measurement system as applied to network analysis is presented. The calibration corrects for the errors caused by the response of the measurement system. A complete physically-based model has been established for the system. A set of calculable standards has been developed to satisfy the time domain requirements for calibration. The calibration technique was applied to determining the model parameters of a commercial TDR and TDT system. The errors of modeling and de-embedding are analyzed. The calibration enhanced the system bandwidth from 8 GHz to about 20 GHz. Experimental verification is given to demonstrate the validity and accuracy of the calibration technique. / Ph. D.

Several methods for evaluating the permittivity of soil samples using measurements in the time domain were studied. A number of algorithms for inverting the measured data to obtain epsilon were investigated and three different types of sampling devices were examined. The investigation examined the positive and negative aspects of three different types of sample holders to determine a method of obtaining dielectric information from in-situ time domain measurements. A scheme using a twin lead balun driven ground probe was proposed and analysed with regard to accuracy and sensitivity to measurement error. / Ph. D.

Time domain analysis in vector network analyzers (VNAs) is a method to represent the frequency response, stated by the S-parameters, in time domain with apparent high resolution. Among other utilities time domain option from Agilent allows to measure microwave devices into a specific frequency range and down till DC as well with the two time domain mode: band-pass and low-pass mode. A special feature named gating is of important as it allows representing a portion of the time domain representation in frequency domain.   This thesis studies the time domain option 010 from Agilent; its uncertainties and sensitivity. The task is to find the best method to measure the antenna element matching taking care to reduce the influence of measurement errors on the results.   The Agilent 8753ES is the instrument used in the thesis. A specific matching problem in the antenna electric down-tilt (AEDT) previously designed by Powerwave Technologies is the task to be solved. This is because it can not be measured directly with 2-port VNAs. It requires adapters, extra coaxial cables and N-connectors, all of which influences the accuracy. The AEDT connects to the array antenna through cable-board-connectors (CBCs). The AEDT and the CBCs were designed before being put into the antenna-system. Their S-parameters do not coincide with the ones measured after these devices were put in the antenna block.   Time domain gating and de-embedding algorithms are two methods proposed in this thesis to measure the S-parameters of the desired antenna element while reducing the influence of measurement errors due to cables CBCs and other connectors. The aim is to find a method which causes less error and gives high confidence measurements.   For the time domain analysis, reverse engineering of the time domain option used in the Agilent VNA 8753ES is implemented in a PC for full control of the process. The results using time-domain are not sufficiently reliable to be used due to the multiple approximations done in the design. The methodology that Agilent uses to compensate the gating effects is not reliable when the gate is not centered on the analyzed response. Big errors are considered due to truncation and masking effects in the frequency response.   The de-embedding method using LRL is implemented in the AEDT measurements, taking away the influences of the CBCs, coaxial cables and N-connector. It is found to have sufficient performance, comparable to the mathematical model. Error analysis of both methods has been done to explaine the different in measurements and design.

In the road transportation industry development is moving towards more advanced technology and the use of automation in the driving environment is increasing. Regarding the safety risks associated with an unconsidered use of a high degree of automation, it is expensive to develop automatic systems dealing with complex situations. As there is still much improvement to do in this area, this thesis aims to contribute to developing safe autonomic systems to assist truck drivers. The aim of the study was twofold, namely 1) to use Cognitive Work Analysis to identify opportunities for enhancing human-heavy vehicle system performance and 2) to contribute to improving the possibilities for identifying opportunities for enhancing system performance through the development of a method of prioritizing Activities using a Contextual Activity Template. To identify the opportunities for improvement, the first two phases of a Cognitive Work Analysis (CWA) – Work Domain Analysis (WDA) and Control Task Analysis (ConTA), were conducted. To complete the WDA, five hours of interviews were conducted with a senior technical adviser from Scania CV AB as well as a two hour interview with an experienced commercial driver. Additionally, an observation study was conducted during which three video cameras were used to capture sixteen hours of footage (per camera) from 35 hours (2500kms) of observation (one driver/day over a four day period). During the observation study, drivers were asked to talk out loud about the information needed, decisions made and to provide some rational for their behavior at that time with respect to their driving activities. A total of 40 minutes of talk out loud video data was collected per driver. Finally, around five hours of follow-up interviews were conduct-ed during which these drivers reviewed the videos collected during the observation study. The results from the WDA were presented in an Abstraction Hierarchy. The overall functional purpose of the system was defined as Goods Distribution via Road Transportation with the values and priorities being Effectivity and Efficiency, Safety, Comfort, Laws/regulations, Reputation, and Organizational Regulations. For the WDA in the current thesis, the AH was completed for the first three values listed above. In total the AH included 343 nodes (39 at the Purpose Related Functions level, 77 at the Object Related Processes level, and 211 at the Physical Objects level). The means by which the physical objects were used in different situations was described using a Contractual Activity Template. The object related processes defined in the AH were crosschecked with 42 situations identified during the observation study. Eight hours of further interviews were conducted with the previously-observed drivers to better understand the relationship between the object related processes and the situations. The object related process-situations matrix was then prioritized according to importance and frequency. On the basis of this prioritization, a set of potential improvement areas were identified, as for example communication and visibility during highway driving. / Transportindustrins utveckling går mot mer avancerad teknik och högre automationsgrad i förarmiljön. Det är kostsamt att utveckla automatiska system som klarar att hantera komplexa situationer på grund av de säkerhetsrisker som är förknippade med ogenomtänkt införande av automation. Eftersom det fortfarande finns mycket förbättring att göra inom området syftar denna studie till att bidra i utvecklingen av säkra autonoma system som stödjer lastbilschauffören. Studien hade ett tvåfaldigt syfte, nämligen 1) att använda Cognitive Work Analysis för att identifiera möjligheter att förbättra människa-fordonssystemsprestandan för tunga lastbilar och 2) att bidra till att förbättra möjligheterna att identifiera möjliga systemförbättringar genom utveckling av en metod för prioritering av aktiviteterna i en Contextual Activity Template. För att identifiera förbättringsmöjligheterna genomfördes de två första faserna av Cognitive Work Analysis – Work Domain Analysis (WDA) och Control Task Analysis (ConTA). För WDA utfördes fem timmar av intervjuer med en senior technical adviser från Scania VC AB och en två timmars intervju med en erfaren kommersiell lastbilschaufför. Utöver detta genomfördes en observationsstudie där tre videokameror användes för att samla 16 timmars inspelning (per kamera) från 35 timmars (2500 km) observation (en förare/dag under en fyradagarsperiod). Under observationsstudien berättade förarna högt om informationsbehov, beslut som tas och förklarade beteendet under de olika köraktiviteterna. Totalt 40 minuter av videodata när förarna berättade högt insamlades per förare. Slutligen genomfördes ungefär fem timmar av efterföljande intervjuer där samma förare fick återge körningen utifrån videomaterialet från observationsstudien. Resultatet från WDA presenterades i en abstraktionshierarki. Det övergripande funktionella syftet med systemet var definierat som godsdistribution via vägtransport med värdena och prioriteringarna Effektivitet, Säkerhet, Komfort, Lagar/Regler, Rykte och Organisatoriska regler. För WDA:n i detta examensarbete gjordes en AH för de tre första värdena nämnda ovan. Totalt bestod AH av 343 noder, (39 på nivån med syftesrelaterade funktioner, 77 på nivån med objektrelaterade processer och 211 på nivån med fysiska objekt). I vilka situationer de fysiska objektens funktioner användes beskrevs med en Contractual Activity Template (CAT; Naikar et al., 2006). De objektrelaterade processer definierade i AH:n undersöktes utifrån 42 situationer identifierade under observationsstudien. Åtta timmar av vidare intervju genomfördes med förarna från observationsstudien för att erhålla en bättre förståelse för förhållandet mellan de objektrelaterade processerna och situationerna. Matrisen med objektrelaterade processer och situationer prioriterades sedan enligt betydelse och frekvens. Baserat på prioriteringen identifierades ett antal potentiella förbättringsområden, exempelvis kommunikation och synlighet under landsvägskörning.

Photoconductive antenna (PCA) array based THz near-field imager incorporating Hadamard multiplexing method is developed in this work. By using a 2 × 2 dipole antenna array as the THz transmitter, the system signal-to-noise ratio (SNR) is demonstrated to be improved by a factor of 2 as the theory predicts. Additionally, a 2-D scanning of a metallic structure on a THz-transparent substrate (with a total scanning area of 1 × 1 mm2) is experimentally implemented. Correlation coefficient estimation is made afterwards to quantify the reconstructed image quality.

O objetivo deste trabalho é apresentar uma metodologia de cálculo da distribuição de correntes e dos campos eletromagnéticos e tensões induzidas associadas em estruturas atingidas diretamente por descargas atmosféricas que, agregada à filosofia geral de compatibilidade eletromagnética (CEM), constitua uma abordagem inovadora e abrangente quando comparada às recomendações de proteção contra descargas atmosféricas atuais. Propõe-se, portanto, desenvolver uma metodologia que: · Constitua uma ferramenta de auxílio nas tomadas de decisões, aplicável desde a etapa de definição da arquitetura da estrutura e do leiaute dos equipamentos até a definição final da configuração do sistema de proteção contra descargas atmosféricas (S.P.C.D.A); · Possibilite a implementação de uma filosofia de proteção dos equipamentos e sistemas elétricos e eletrônicos contra descargas atmosféricas na qual se integre as recomendações tradicionais às necessidades atuais relacionadas à área de compatibilidade eletromagnética; · Seja abrangente e com grau de precisão satisfatório, quando comparadas com as recomendações atuais, com possibilidade de exploração dos valores das grandezas elétricas envolvidas no domínio do espaço e do tempo, e · Apresente simplicidade na implementação em computadores pessoais. / The main purpose of this work is to present a suitable method for calculating the current distribution, the electric and magnetic field, and the induced voltage on electric circuits regarding a structure directly struck by lightning. Moreover, when the method is used together with the electromagnetic compatibility (EMC) requirements, it can provide the designer with a new and helpful methodology meeting the recent aspects or the state of the art on lightning protection systems (L.P.S). Thus, a methodology is proposed, which provides the L.P.S. design team with: · The availability to take technical decisions in all steps of the project, from the definition of the architecture of the structure to the definition of the best layout of L.P.S.; · Recommendations to achieve the EMC of the electric and electronic system, in addition to the traditional ones; · Reliable numerical results concerning simulations in the space and time-domain, and · Simple implementation in personal computers.