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Gupta, Munish. "Finite Difference Time Domain Analysis of MEMS Transfer Switch." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1132343500.
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Häggblad, Jon. "Modified Stencils for Boundaries and Subgrid Scales in the Finite-Difference Time-Domain Method." Doctoral thesis, KTH, Numerisk analys, NA (stängd 2012-06-30), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-95510.
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This thesis centers on modified stencils for the Finite-Difference Time-Domain method (FDTD), or Yee scheme, when modelling curved boundaries, obstacles and holes smaller than the discretization length. The goal is to increase the accuracy while keeping the structure of the standard method, enabling improvements to existing implementations with minimal effort. We present an extension of a previously developed technique for consistent boundary approximation in the Yee scheme. We consider both Maxwell's equations and the acoustic equations in three dimensions, which require separate treatment, unlike in two dimensions. The stability properties of coefficient modifications are essential for practical usability. We present an analysis of the requirements for time-stable modifications, which we use to construct a simple and effective method for boundary approximations. The method starts from a predetermined staircase discretization of the boundary, requiring no further data on the underlying geometry that is being approximated. Not only is the standard staircasing of curved boundaries a poor approximation, it is inconsistent, giving rise to errors that do not disappear in the limit of small grid lengths. We analyze the standard staircase approximation by deriving exact solutions of the difference equations, including the staircase boundary. This facilitates a detailed error analysis, showing how staircasing affects amplitude, phase, frequency and attenuation of waves. To model obstacles and holes of smaller size than the grid length, we develop a numerical subgrid method based on locally modified stencils, where a highly resolved micro problem is used to generate effective coefficients for the Yee scheme at the macro scale. The implementations and analysis of the developed methods are validated through systematic numerical tests.<br><p>QC 20120530</p>
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Rouf, Hasan. "Unconditionally stable finite difference time domain methods for frequency dependent media." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/unconditionally-stable-finite-difference-time-domain-methods-for-frequency-dependent-media(50e4adf1-d1e4-4ad2-ab2d-70188fb8b7b6).html.
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The efficiency of the conventional, explicit finite difference time domain (FDTD)method is constrained by the upper limit on the temporal discretization, imposed by the Courant–Friedrich–Lewy (CFL) stability condition. Therefore, there is a growing interest in overcoming this limitation by employing unconditionally stable FDTD methods for which time-step and space-step can be independently chosen. Unconditionally stable Crank Nicolson method has not been widely used in time domain electromagnetics despite its high accuracy and low anisotropy. There has been no work on the Crank Nicolson FDTD (CN–FDTD) method for frequency dependent medium. In this thesis a new three-dimensional frequency dependent CN–FDTD (FD–CN–FDTD) method is proposed. Frequency dependency of single–pole Debye materials is incorporated into the CN–FDTD method by means of an auxiliary differential formulation. In order to provide a convenient and straightforward algorithm, Mur’s first-order absorbing boundary conditions are used in the FD–CN–FDTD method. Numerical tests validate and confirm that the FD–CN–FDTD method is unconditionally stable beyond the CFL limit. The proposed method yields a sparse system of linear equations which can be solved by direct or iterative methods, but numerical experiments demonstrate that for large problems of practical importance iterative solvers are to be used. The FD–CN–FDTD sparse matrix is diagonally dominant when the time-stepis near the CFL limit but the diagonal dominance of the matrix deteriorates with the increase of the time-step, making the solution time longer. Selection of the matrix solver to handle the FD–CN–FDTD sparse system is crucial to fully harness the advantages of using larger time-step, because the computational costs associated with the solver must be kept as low as possible. Two best–known iterative solvers, Bi-Conjugate Gradient Stabilised (BiCGStab) and Generalised Minimal Residual (GMRES), are extensively studied in terms of the number of iteration requirements for convergence, CPU time and memory requirements. BiCGStab outperforms GMRES in every aspect. Many of these findings do not match with the existing literature on frequency–independent CN–FDTD method and the possible reasons for this are pointed out. The proposed method is coded in Fortran and major implementation techniques of the serial code as well as its parallel implementation in Open Multi-Processing (OpenMP) are presented. As an application, a simulation model of the human body is developed in the FD–CN–FDTD method and numerical simulation of the electromagnetic wave propagation inside the human head is shown. Finally, this thesis presents a new method modifying the frequency dependent alternating direction implicit FDTD (FD–ADI–FDTD) method. Although the ADI–FDTD method provides a computationally affordable approximation of the CN–FDTD method, it exhibits a loss of accuracy with respect to the CN-FDTD method which may become severe for some practical applications. The modified FD–ADI–FDTD method can improve the accuracy of the normal FD–ADI–FDTD method without significantly increasing the computational costs.
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Maloney, James G. "Analysis and synthesis of transient antennas using the Finite-Difference Time-Domain (FDTD)." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/15052.
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Hao, Yang. "The development and characterisation of a conformal FDTD method for oblique electromagnetic structures." Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285559.
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Turer, Ibrahim. "Specific Absorption Rate Calculations Using Finite Difference Time Domain Method." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605200/index.pdf.
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This thesis investigates the problem of interaction of electromagnetic radiation with
human tissues. A Finite Difference Time Domain (FDTD) code has been developed to
model a cellular phone radiating in the presence of a human head. In order to implement
the code, FDTD difference equations have been solved in a computational domain
truncated by a Perfectly Matched Layer (PML). Specific Absorption Rate (SAR)
calculations have been carried out to study safety issues in mobile communication.
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Çapoğlu, İlker R. "Techniques for Handling Multilayered Media in the FDTD Method." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16179.
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We introduce supplemental methods for the finite-difference time-domain (FDTD) analysis of planar multilayered media. The invariance is allowed to be disturbed by any imperfection, provided that these imperfections are local and therefore can be contained within an FDTD simulation grid. We specifically investigate two FDTD methods that were not previously developed for general multilayered media: the near-field-to-far-field transform (NFFFT) and the total-field/scattered-field (TF/SF) boundary (or the plane-wave injector). The NFFFT uses the FDTD output on a virtual surface surrounding the local imperfections and calculates the radiated field. The plane wave injector builds an incident plane wave inside a certain boundary (TF/SF boundary) while allowing any scattered fields created by the imperfections inside the boundary to exit the boundary with complete transparency. The NFFFT is applicable for any lossless multilayered medium, while the plane-wave injector is applicable for any lossy multilayered medium. After developing the respective theories and giving simple examples, we apply the NFFFT and the plane-wave injector to a series of problems. These problems are divided into two main groups. In the first group, we consider plane-wave scattering problems involving perfectly-conducting objects buried in multilayered media. In the second group, we consider problems that involve radiating structures in multilayered media. Specifically, we investigate the reciprocity of antennas radiating in the presence of an ungrounded dielectric slab using the methods developed in this study. Finally, we present our previous work on an entirely different subject, namely, the theoretical analysis of the input admittance of a prolate-spheroidal monopole fed by a coaxial line through a ground plane.
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Ajaz, Mahnoor. "Finite Difference Time Domain Modelling of Ultrasonic Parametric Arrays in Two-Dimensional Spaces." The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1619109761801613.
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Saario, Seppo Aukusti, and n/a. "FDTD Modelling For Wireless Communications: Antennas and Materials." Griffith University. School of Microelectronic Engineering, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030602.101319.
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The application of the finite-difference time-domain (FDTD) method for the numerical analysis of complex electromagnetic problems related to wireless communications is considered. Since exact solutions to many complex electromagnetic problems are difficult, if not impossible, the FDTD method is well suited to modelling a wide range of electromagnetic problems. Structures considered include single and twin-slot antennas for millimetre-wave applications, monopole antennas on mobile handsets and chokes for the suppression of currents on coaxial cables. Memory efficient techniques were implemented for the split-field perfectly matched layer (PML) absorbing boundary condition. The frequency-domain far-field transformations were used for the calculation of far-field radiation patterns. Dipole, slot and mobile handset antenna benchmark problems verified the accuracy of the FDTD implementation. The application of slot antennas for millimetre-wave imaging arrays was investigated. An optimal feed network for an offset-fed single-slot antenna was designed for the X band with numerical and experimental results in excellent agreement. A twin-slot antenna structure reduced surface wave coupling by 7.6 dB in the substrate between coplanar waveguide-fed slot antenna elements in a planar array. The reduction of substrate surface waves for the twin-slot antenna allows for closer element spacings with less radiation pattern degradation in array applications. Suppression techniques for currents flowing on the exterior surface of coaxial cables were investigated. These include the use of ferrite beads and a quarter-wave sleeve balun. The frequency dependent behaviour of ferrite based chokes showed highly resonant effects which resulted in less than 5 dB of isolation at the resonant frequencies of the bead. An analysis of air-gaps between the ferrite bead and cable are shown to be extremely detrimental in the isolation characteristics of ferrite bead chokes. An air-gap of 0.5 mm can reduce the isolation effectiveness of a bead by 20 dB. The first rigorous analysis of a quarter-wave sleeve balun is presented, enabling an optimal choke design for maximum isolation. A standard 0.25[symbols] sleeve balun achieved 10.9 dB isolation with [symbols]=4, whereas a choke of optimal length 0.232[symbols] had an isolation of better than -20 dB. Several techniques for the measurement of antenna characteristics of battery powered handsets were compared and perturbation effects associated with the direct connection of a coaxial cable to a mobile handset was quantified. Significant perturbation in both return loss and radiation pattern can occur depending on cable location on the handset chassis. The effectiveness of ferrite chokes in any location was marginal. However, the application of an optimal quarter-wave sleeve balun in the centre of the largest plane of the handset, orthogonal to the primary polarisation resulted in minimal perturbation of both radiation patterns and return loss.
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Saario, Seppo Aukusti. "FDTD Modelling For Wireless Communications: Antennas and Materials." Thesis, Griffith University, 2003. http://hdl.handle.net/10072/366188.
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The application of the finite-difference time-domain (FDTD) method for the numerical analysis of complex electromagnetic problems related to wireless communications is considered. Since exact solutions to many complex electromagnetic problems are difficult, if not impossible, the FDTD method is well suited to modelling a wide range of electromagnetic problems. Structures considered include single and twin-slot antennas for millimetre-wave applications, monopole antennas on mobile handsets and chokes for the suppression of currents on coaxial cables. Memory efficient techniques were implemented for the split-field perfectly matched layer (PML) absorbing boundary condition. The frequency-domain far-field transformations were used for the calculation of far-field radiation patterns. Dipole, slot and mobile handset antenna benchmark problems verified the accuracy of the FDTD implementation. The application of slot antennas for millimetre-wave imaging arrays was investigated. An optimal feed network for an offset-fed single-slot antenna was designed for the X band with numerical and experimental results in excellent agreement. A twin-slot antenna structure reduced surface wave coupling by 7.6 dB in the substrate between coplanar waveguide-fed slot antenna elements in a planar array. The reduction of substrate surface waves for the twin-slot antenna allows for closer element spacings with less radiation pattern degradation in array applications. Suppression techniques for currents flowing on the exterior surface of coaxial cables were investigated. These include the use of ferrite beads and a quarter-wave sleeve balun. The frequency dependent behaviour of ferrite based chokes showed highly resonant effects which resulted in less than 5 dB of isolation at the resonant frequencies of the bead. An analysis of air-gaps between the ferrite bead and cable are shown to be extremely detrimental in the isolation characteristics of ferrite bead chokes. An air-gap of 0.5 mm can reduce the isolation effectiveness of a bead by 20 dB. The first rigorous analysis of a quarter-wave sleeve balun is presented, enabling an optimal choke design for maximum isolation. A standard 0.25[symbols] sleeve balun achieved 10.9 dB isolation with [symbols]=4, whereas a choke of optimal length 0.232[symbols] had an isolation of better than -20 dB. Several techniques for the measurement of antenna characteristics of battery powered handsets were compared and perturbation effects associated with the direct connection of a coaxial cable to a mobile handset was quantified. Significant perturbation in both return loss and radiation pattern can occur depending on cable location on the handset chassis. The effectiveness of ferrite chokes in any location was marginal. However, the application of an optimal quarter-wave sleeve balun in the centre of the largest plane of the handset, orthogonal to the primary polarisation resulted in minimal perturbation of both radiation patterns and return loss.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Microelectronic Engineering<br>Full Text
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Turati, Paolo. "FDTD modelling of nanostructures at microwave frequency." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/9062.
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The thesis which is hereby presented describes a study of the numerical modelling of the coupled interaction of nanostructures with electromagnetic fields in the range of microwaves. This is a very ambitious task and requires a thorough and rigorous implementation of new algorithms designed to this purpose. The first issue to be encountered is the characterisation and the physical understanding of the behaviour of a nanostructure. The term itself, nanostructure, defines any device which has a nanometric size in at least one dimension, regardless of its material and geometry, hence it is a very wide definition. Carbon Nanotubes (CNT), quantum dots and quantum wells fall into this category, for example, and in electronics these structures are generally composed of semiconductor materials, like Silicon or Gallium Arsenide. The first step to take, in order to model such objects from an electronics point of view, is to solve the Schrodinger equation. The Schrodinger equation is a very general formula, widely used in quantum physics, which, when provided with a certain electrical potential in a material, determines the behaviour of the electrons in this material. Needless to say, the electrical potential is the DNA of a material or, in other words, it is the physical property which affects the propagation of electrons and therefore makes a material conducting or non-conducting. Nanostructures are often composed of several materials, hence the potential is not constant and, with opportune geometries, it is possible, in principle, to guide the electron currents through the device, as, for example, a channel in a MOSFET. This principle holds for very small structures where the electron transport can be considered ballistic, i.e. when the structures are smaller than the free mean path of the particle. The behaviour of the electrons is affected both by external factors, such as temperature or applied electric and magnetic fields, and internal factors, such as the electron mobility or the doping concentration, which are dependent on the used materials. This parameters play a very important role whilst modelling the behaviour of particles such as electrons and in this work the main focus is the study of the impact of external electromagnetic fields. The electromagnetic fields (EM fields) are composed of an electric field component and of a magnetic field component, which can be analysed separately in order to better understand the response of nanostructures to their application. A rigorous analysis is presented by showing numerical results, obtained with the modelling of the Schrodinger equation, compared with the expected theoretical results, exploiting simple structures, where it is possible to calculate the solutions analytically. The second part of thesis focuses on the impact of the EM fields on the nanostructure, hence the combined effect of both electric and magnetic fields affecting the electrons' propagation, and the mutual coupling of the fields with the quantum effects. Indeed the study of nanodevices for microwave applications requires to consider the contribution of a parameter called quantum current density, which accounts for the quantum effects generated by the structure. This is normally ignored in conventional devices because the quantum contributions are negligible but, by using opportune materials and opportune geometries, these currents become relevant and they may have an impact on the propagation of the EM fields. For this reason a consistent part of the thesis is dedicated to investigate the mutual coupling between EM fields and quantum effects, by implementing the Maxwell-Schrodinger coupled model. A chapter is dedicated to the novel approaches taken in order to tackle the issues and the limits of the numerical implementation; in particular two solutions are presented, nonuniform domains and the parallelisation of the algorithm. These approaches are vital whilst modelling numerically such physical problems since the required computational capacity increases with the accuracy requirements. Solving the presented algorithms conventionally would limit the potential of the method and thus a thorough study has been made in order to improve the efficiency of the simulations. In the last chapter, three different scenarios are presented, each one of them showing different features of the coupled model. The results are illustrated and discussed, including the limits due to the chosen approximations. References to the analytical solutions are provided in order to validate the obtained numerical results.
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Wu, Shuguang. "FPGA Implementation of the FDTD Algorithm Using Local Sram." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1131732782.
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Ow, Say Cheoh. "An investigation of alternating-direction implicit finite-difference time-domain (ADI-FDTD) method in numerical electromagnetics." Thesis, University of Hull, 2003. http://hydra.hull.ac.uk/resources/hull:5496.
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In this thesis, the alternating-direction implicit method (ADI) is investigated in conjunction with the finite difference time-domain method (FDTD) to allow crossing of the Courant-Friedrich-Levy (CFL) stability criterion while maintaining stability in the FDTD algorithm. The main reason for this is to be able to use a larger numerical time step than that governed by the CFL criterion. The desired effect is a significant reduction in numerical run-times. Although the ADI-FDTD method has been used in the literature, most analysis and application have been performed on simple three-dimensional cavities. This work makes original contribution in two aspects. Firstly, a new modified alternating-direction implicit method for a three-dimensional FDTD algorithm has been successfully developed and implemented in this research. This new method allows correct modelling of a realistic physical structure such as a microstrip patch with the ADI scheme without causing instability even when the CFL criterion is not observed. However, due to the inherent property of this modified ADI-FDTD method, a decreasing reflection coefficient is observed using this scheme. The second and more important contribution this research makes in the field of numerical electromagnetics is the development of a new method of simulating realistic complex structures such as geometries comprising copper patch antennas on a dielectric substrate. With this new method, for the first time, the ADl-FDTD algorithm remains stable while still in violation of the CFL criterion, even when complex structures are being modelled. However, there is a trade-off between accuracy and computational speed in ADI-FDTD and modified ADI-FDTD methods. The larger the numerical time step, the shorter is the simulation run-time but an increase in numerical time step causes a degradation in accuracy of numerical results. Comparison between speed and accuracy is shown in this thesis and it has to be mentioned here that these values are very much dependent on the structure being modelled.
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Gorunmez, Zohre. "Finite-Difference Time-Domain (FDTD) Modeling of Nanoscale Plasmonic Substrates for Surface-Enhanced Raman Spectroscopy (SERS)." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563296001850111.
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Petit, Frédéric. "Reverberation Chamber Modeling Using Finite-Difference Time-Domain Method." Diss., University of Marne la Vallée, 2002. http://hdl.handle.net/10919/71555.
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Since the last few years, the unprecedented growth of communication systems involving the propagation of electromagnetic waves is particularly due to developments in mobile phone technology. The reverberation chamber is a reliable bench-test, enabling the study of the effects of electromagnetic waves on a specific electronic appliance. However, the operating of a reverberation chamber being rather complicated, development of numerical models are of utmost importance to determine the crucial parameters to be considered.This thesis consists in the modelling and the simulation of the operating principles of a reverberation chamber by means of the Finite-Difference Time-Domain method. After a brief study based on field and power measurements performed in a reverberation chamber, the second chapter deals with the different problems encountered during the modelling. The consideration of losses being a very important factor in the operating of the chamber, two methods of implementation of these losses are set out in this chapter. Chapter~3 consists in the analysis of the influence of the stirrer on the first eigenmodes of the chamber; the latter modes can undergo a frequency shift of several MHz. Chapter~4 shows a comparison of results issued from high frequency simulations and theoretical statistical results. The problem of an object placed in the chamber, resulting in a field disturbance is also tackled. Finally, in the fifth chapter, a comparison of statistical results for stirrers having different shapes is set out.
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Holt, Jennifer Jane. "Finite difference time domain modeling of dispersion from heterogeneous ground properties in ground penetrating radar." Columbus, Ohio : Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1080136001.
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Thesis (Ph. D.)--Ohio State University, 2004.<br>Title from first page of PDF file. Document formatted into pages; contains xxii, 212 p.; also includes graphics. Includes abstract and vita. Advisor: Jeffrey Daniels, Dept. of Geological Sciences. Includes bibliographical references (p. 152-154).
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Donderici, Burkay. "Time-Domain Solvers for Complex-Media Electrodynamics and Plasma Physics." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1216744283.
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Rial, Alvaro Valcarce. "Applying the finite-difference time-domain to the modelling of large-scale radio channels." Thesis, University of Bedfordshire, 2010. http://hdl.handle.net/10547/295748.
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Finite-difference models have been used for nearly 40 years to solve electromagnetic problems of heterogeneous nature. Further, these techniques are well known for being computationally expensive, as well as subject to various numerical artifacts. However, little is yet understood about the errors arising in the simulation of wideband sources with the finitedifference time-domain (FDTD) method. Within this context, the focus of this thesis is on two different problems. On the one hand, the speed and accuracy of current FDTD implementations is analysed and increased. On the other hand, the distortion of numerical pulses is characterised and mitigation techniques proposed. In addition, recent developments in general-purpose computing on graphics processing units (GPGPU) have unveiled new methods for the efficient implementation of FDTD algorithms. Therefore, this thesis proposes specific GPU-based guidelines for the implementation of the standard FDTD. Then, metaheuristics are used for the calibration of a FDTD-based narrowband simulator. Regarding the simulation of wideband sources, this thesis uses first Lagrange multipliers to characterise the extrema of the numerical group velocity. Then, the spread of numerical Gaussian pulses is characterised analytically in terms of the FDTD grid parameters. The usefulness of the proposed solutions to the previously described problems is illustrated in this thesis using coverage and wideband predictions in large-scale scenarios. In particular, the indoor-to-outdoor radio channel in residential areas is studied. Furthermore, coverage and wideband measurements have also been used to validate the predictions. As a result of all the above, this thesis introduces first an efficient and accurate FDTD simulator. Then, it characterises analytically the propagation of numerical pulses. Finally, the narrowband and wideband indoorto-outdoor channels are modeled using the developed techniques.
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Kim, Jae Hwan (Eric). "Finite-Difference Time-Domain (FDTD) simulations and fabrication of a Fabry-Perot cavity using photonic crystal arrays." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/32578.
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In this thesis, Fabry-Perot (FP) cavity structures aimed at a 850nm wavelength are modeled and analyzed by Finite-Difference Time-Domain (FDTD) simulations, for the purpose of fabricating resonant cavity detectors and Vertical-Cavity Surface-Emitting Lasers (VCSELs). The structures are based on square-lattice photonic crystals.
In designing a VCSEL, different types of highly reflective mirrors such as GaAs/AlGaAs Distributed Bragg Reflectors (DBRs), and a GaAs-based Sub-Wavelength Grating (SWG) or a Photonic Crystal (Phc) Slab are used to form a FP cavity. FDTD phase analysis is implemented to estimate resonant conditions in a simple but very effective technique.
For the fabrication of a resonant cavity detector, square-lattice photonic crystal arrays are written by (1) Focused Ion Beam (FIB) and (2) e-beam lithography, followed by dry-etching. The quality of air holes, etching depths, and sidewalls are scrutinized by Scanning Electron Microscopy (SEM) imaging and Atomic Force Microscopy (AFM).
Post-patterning, a sacrificial layer is etched away by Buffered Oxide Etch (BOE) and a suspended photonic crystal membrane is released by Critical Point Drier (CPD).
The SWG and Phc slab used as one of the mirrors in the FP cavity structures are beneficial for achieving a compact-sized resonator, as well as forming multi-wavelength arrays, in which the resonance can be widely tuned by lithographically defined parameters (i.e., for the SWG: period and duty factor and for the Phc slab: lattice constant and radius of the air hole).<br>Applied Science, Faculty of<br>Electrical and Computer Engineering, Department of<br>Graduate
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Chilton, Ryan Austin. "H-, P- and T-Refinement Strategies for the Finite-Difference-Time-Domain (FDTD) Method Developed via Finite-Element (FE) Principles." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1219064270.
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Svensson, Mattias. "Simulating Low Frequency Reverberation in Rooms." Thesis, KTH, Marcus Wallenberg Laboratoriet MWL, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-290038.
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The aim of this thesis was to make a practical tool for low frequency analysis in room acoustics.The need arises from Acad’s experience that their results from simulations using raytracing software deviate in the lower frequencies when compared to field measurements inrooms. The tool was programmed in Matlab and utilizes the Finite Difference Time Domain (FDTD) method, which is a form of rapid finite element analysis in the time domain.A number of tests have been made to investigate the practical limitations of the FDTD method, such as numerical errors caused by sound sources, discretization and simulation time. Boundary conditions, with and without frequency dependence, have been analysed bycomparing results from simulations of a virtual impedance tube and reverberation room to analytical solutions. These tests show that the use of the FDTD method appears well suited for the purpose of the tool.A field test was made to verify that the tool enables easy and relatively quick simulations of real rooms, with results well in line with measured acoustic parameters. Comparisons of the results from using the FDTD method, ray-tracing and finite elements (FEM) showed goodcorrelation. This indicates that the deviations Acad experience between simulated results and field measurements are most likely caused by uncertainties in the sound absorption data used for low frequencies rather than by limitations in the ray-tracing software. The FDTDtool might still come in handy for more complex models, where edge diffraction is a more important factor, or simply as a means for a “second opinion” to ray-tracing - in general FEM is too time consuming a method to be used on a daily basis.Auxiliary tools made for importing models, providing output data in the of room acoustic parameters, graphs and audio files are not covered in detail here, as these lay outside the scope of this thesis.<br>Målet för detta examensarbete var att undersöka möjligheten att programmera ett praktisktanvändbart verktyg för lågfrekvensanalys inom rumsakustik. Behovet uppstår från Acadserfarenhet att resultat från simuleringar med hjälp av strålgångsmjukvara avviker i lågfrekvensområdeti jämförelse med fältmätningar i färdigställda rum. Verktyget är programmerati Matlab och använder Finite Difference Time Domain (FDTD) metoden, vilket är en typav snabb finita elementanalys i tidsdomänen.En rad tester har genomförts för att se metodens praktiska begräsningar orsakade av numeriskafel vid val av ljudkälla, diskretisering och simuleringstid. Randvillkor, med och utanfrekvensberoende, har analyserats genom jämförelser av simulerade resultat i virtuella impedansröroch efterklangsrum mot analytiska beräkningar. Testerna visar att FDTD-metodentycks fungerar väl för verktygets tilltänkta användningsområde.Ett fälttest genomfördes för att verifiera att det med verktyget är möjligt att enkelt och relativtsnabbt simulera resultat som väl matcher uppmätta rumsakustiska parametrar. Jämförelsermellan FDTD-metoden och resultat beräknade med strålgångsanalys och finita elementmetoden(FEM) visade även på god korrelation. Detta indikerar att de avvikelser Acaderfar mellan simulerade resultat och fältmätningar troligen orsakas av osäkerheter i den ingåendeljudabsorptionsdata som används för låga frekvenser, snarare än av begränsningar istrålgångsmjukvaran. Verktyget kan fortfarande komma till användning för mer komplexamodeller, där kantdiffraktion är en viktigare faktor, eller helt enkelt som ett sätt att få ett”andra utlåtande” till resultaten från strålgångsmjukvaran då FEM-analys generellt är en förtidskrävande metod för att användas på daglig basis.Kringverktyg skapade för t.ex. import av modeller, utdata i form av rumsakustiska parametrar,grafer och ljudfiler redovisas inte i detalj i denna rapport eftersom dessa ligger utanförexamensarbetet.
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DESAI, ASHISH R. "PERFORMANCE IMPROVEMENT OF AN FPGA-BASED FDTD SOLVER FOR RECONFIGURABLE HIGH PERFORMANCE COMPUTING." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1141333144.
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Torin, Alberto. "Percussion instrument modelling in 3D : sound synthesis through time domain numerical simulation." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/31029.
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This work is concerned with the numerical simulation of percussion instruments based on physical principles. Three novel modular environments for sound synthesis are presented: a system composed of various plates vibrating under nonlinear conditions, a model for a nonlinear double membrane drum and a snare drum. All are embedded in a 3D acoustic environment. The approach adopted is based on the finite difference method, and extends recent results in the field. Starting from simple models, the modular instruments can be created by combining different components in order to obtain virtual environments with increasing complexity. The resulting numerical codes can be used by composers and musicians to create music by specifying the parameters and a score for the systems. Stability is a major concern in numerical simulation. In this work, energy techniques are employed in order to guarantee the stability of the numerical schemes for the virtual instruments, by imposing suitable coupling conditions between the various components of the system. Before presenting the virtual instruments, the various components are individually analysed. Plates are the main elements of the multiple plate system, and they represent the first approximation to the simulation of gongs and cymbals. Similarly to plates, membranes are important in the simulation of drums. Linear and nonlinear plate/membrane vibration is thus the starting point of this work. An important aspect of percussion instruments is the modelling of collisions. A novel approach based on penalty methods is adopted here to describe lumped collisions with a mallet and distributed collisions with a string in the case of a membrane. Another point discussed in the present work is the coupling between 2D structures like plates and membranes with the 3D acoustic field, in order to obtain an integrated system. It is demonstrated how the air coupling can be implemented when nonlinearities and collisions are present. Finally, some attention is devoted to the experimental validation of the numerical simulation in the case of tom tom drums. Preliminary results comparing different types of nonlinear models for membrane vibration are presented.
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Haque, Amil. "Modeling of the excited modes in inverted embedded microstrip lines using the finite-difference time-domain (FDTD) technique." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26582.
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Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.<br>Committee Chair: Tentzeris, Emmanouil; Committee Member: Andrew Peterson; Committee Member: Laskar, Joy; Committee Member: Papapolymerou, Ioannis. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Hemmi, Tadashi. "Locally one dimensional finite difference time domain method with frequency dependent media for three dimensional biomedical applications." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/locally-one-dimensional-finite-difference-time-domain-method-with-frequency-dependent-media-for-three-dimensional-biomedical-applications(f5fc769a-7dc4-4cce-80f0-755054cb4bab).html.
Full textAbstract:
The finite difference time domain (FDTD) method is commonly used for numerical simulations of the electromagnetic wave propagation in time domain. The FDTD method is easy to implement and the computational results are highly relevant to the analytical solution, so that the FDTD method is applied to variety application problems. However, the computational efficiency of the FDTD method is constrained by the upper limit of the temporal discretisation. The Courant Friedrich Lewy (CFL) stability condition limits the time step for the computation of the FDTD method, so that if the spatial discretisation of the computation is set to be small in order to obtain high accurate results, the size of the temporal discretisation need to be satisfy the CFL stability condition. The locally one dimensional FDTD (LOD-FDTD) method is unconditionally stable. The time step and the spatial step can be independently chosen for the computation of the LOD-FDTD method. The arithmetic operations of the LOD-FDTD method is fewer than that of the other implicit FDTD method, such as the Crank Nicolson FDTD (CN-FDTD) method and the alternating direction implicit FDTD (ADI-FDTD) method. Although the implementation of the LOD-FDTD method is simpler than that of the ADI-FDTD method,the numerical error in the computational results of the LOD-FDTD method is equivalent to that in the computational results of the ADI-FDTD method. In this thesis, a new three dimensional (3D) frequency dependent (FD) LOD-FDTD method is proposed. The one pole Debye model is incorporated into the 3D-FD-LOD-FDTD method in order to deal with practical applications. The proposed method is implemented in Fortran 90 and parallelised with OpenMP. A simulation model of the human phantom is developed in the 3D-FD-LOD-FDTD method with fine structures and frequency dependent dielectric properties of the human tissues, and numerical simulation of electromagnetic wave propagation inside the human head is shown.
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Belkhir, A. "Extension de la modélisation par FDTD en nano-optique." Phd thesis, Université de Franche-Comté, 2008. http://tel.archives-ouvertes.fr/tel-00373606.
Full textAbstract:
Cette thèse constitue un ensemble de travaux et de réflexions sur la question de la modélisation des applications électromagnétiques en nano-optique en utilisant la méthode des différences finies dans le domaine temporel (FDTD). Dans un premier temps, des codes FDTD bidimentionnels pour le calcul de bandes interdites photoniques ont été mis en oeuvre. Ces algorithmes tiennent comptes de la dispersion des métaux nobles dans la gamme optique décrite par le modèle de Drude ou de Drude-Lorentz. Ces programmes FDTD permettent de tenir compte de la propagation soit dans le plan perpendiculaire au plan d'invariance (appelé "cas dans le plan" ou "in-plane" en anglais) pour les deux polarisations TE et TM ainsi que le cas d'une propagation quelconque hors du plan (ou off-plane). Plusieurs diagrammes de bandes sont calculés et présentés pour les structures carrées et triangulaires dans les cas diélectriques et métalliques. Ensuite, nous avons implémenté un code BOR-FDTD, basé sur la discrétisation des équations de Maxwell exprimées en coordonnées cylindriques, pour la modélisation des guides d'ondes (ou d'autres objets) à symétrie de révolution. Les conditions absorbantes PML pour décrire l'espace libre sont intégrées à la BOR-FDTD ainsi que les deux modèles de Drude et de Drude-Lorentz. Des simulations ont été effectuées pour le calcul de modes propres de guides d'ondes coaxiaux et cylindriques sub-longueurs d'ondes faits en métal parfait et en métal réel (argent par exemple). Les résultats montrent la possibilité de guider des signaux optiques sans beaucoup de pertes dans un guide coaxial fait en argent de dimensions sublongueur d'onde. Ce dernier résultat est original et constitue une très importante avancée dans le domaine de la "nanoconnectique" en optique, plus particulièrement pour l'optique intégrée. Puis, un autre code numérique FDTD-3D a été élaboré pour la modélisation des structures périodiques (type cristaux photoniques tridimensionnels) éclairées en incidence oblique. Ce code intègre aussi les couches absorbantes PML ainsi que les modèles de dispersion de Drude et de Drude-lorentz. Les résultats obtenus sont comparés à ceux issus d'autres modèles théoriques. Les applications de ce code à l'étude de radôme, à l'excitation du mode TEM de la structure métallique à ouvertures annulaires et aux calculs des spectres d'extinction Raman montrent l'efficacité de la FDTD pour la modélisation de telles structures.
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タン, チャン フー, and Huu Thang Tran. "Modeling of corona discharge and Its application to a lightning surge analysis in a power system." Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12863878/?lang=0, 2014. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12863878/?lang=0.
Full textAbstract:
This thesis has proposed a simplified model of corona discharge from an overhead wire struck by lightning for surge computations using the FDTD method. In the corona model, the progression of corona streamers from the wire is represented as the radial expansion of cylindrical conducting region around the wire. The validity of this corona model has been tested against experimental data. Then, its applications to lightning electromagnetic pulse computations have been reviewed.<br>博士(工学)<br>Doctor of Philosophy in Engineering<br>同志社大学<br>Doshisha University
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Denanot, Francis. "Techniques de sous-maillage dans la méthode FDTD : apports de l'approche variationnelle." Limoges, 2006. http://aurore.unilim.fr/theses/nxfile/default/82d08f51-8ead-4da0-b529-8f4d0b6c370b/blobholder:0/2006LIMO0014.pdf.
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Dans ce rapport nous commençons par élaborer un schéma de sous-maillage 3D basé sur des relations d’interpolation. Le facteur de raffinement utilisé est égale à deux. La réflexion numérique et la stabilité que nous obtenons nous permettent alors de traiter des problèmes de diffraction. Nous étudions ensuite séparément les parties temporelle et spatiale de ce schéma puis nous montrons la stabilité numérique de l’algorithme temporel. Ainsi nous prouvons que les instabilités produite par le schéma sont dues à l’algorithme spatial seul, de plus nous mettons à jour une nouvelle façon de concevoir les schémas de sous-maillage, puisque dorénavant ces derniers sont conçus comme la succession d’un algorithme temporel stable et d’un certain schéma de raffinement spatial. Nous montrons finalement que cette nouvelle méthode de construction peut s’appliquer aussi à des schémas de sous-maillage possédant des facteurs de raffinement plus élevés (3, 4 et 5), en particulier nous démontrons la stabilité numérique des schémas de raffinement temporels en 1/3, 1/4 et 1/5. Dans la seconde partie de ce rapport nous expliquons en détail la formulation variationnelle de la méthode des éléments finis présentée par T. Fouquet dans sa thèse. Par la suite nous proposons une version simplifiée de cette formulation basée sur le théorème de Poynting, puis nous l’appliquons avec succès à la stabilisation des schémas de sous-maillage 2DTE et 2D-TM<br>In this report we first derive a consistent three-dimensional subgridding scheme for the Finite Difference Time Domain method by using spatial and temporal interpolations. The refinement factor used is equal to two. Then, numerical reflexion and stability which have been obtained allow us to deal with scattering problems. We also study temporal and spatial algoritms separately, and we demonstrate the stability of the temporal algorithm by performing a large number of time steps for a scattering structure. Ln this way we show the instability of the spatial refinement algorithm, and we obtain a new method for constructing subgridding schemes. To finish this part we generalize our constructing method to schemes which have refinement factors more important like three, four, and five, and especially we demonstrate the stability of temporal algorithms which have this previous refinement factors. Ln the second part of this report we explain the fini te element method and the variational formulation presented by T. Fouquet in this thesis. Especially we propose a « traduction» of these mathematical methods by using a formulation based on the Ponyting theorem. This formulation is applied to derive two stable two-dimensional subgridding schemes in TE and TM propogating mode
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Senarath, Aditha Srikantha. "Finite Different Time-Domain Simulation of Terahertz Waves Propagation Through Unmagnetized Plasma." Wright State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=wright1629431383655508.
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ElSherbini, Khaled Mohammad. "Contrawound toroidal helical antenna modeling using the FDTD method." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1363.
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Thesis (Ph. D.)--West Virginia University, 2000.<br>Title from document title page. Document formatted into pages; contains xiii, 325 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 138-144).
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GANDHI, SACHIN. "AN FPGA IMPLEMENTATIN OF FDTD CODES FOR RECONFIGURABLE HIGH PERFORMANCE COMPUTING." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1100550013.
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Vazquez, Javier. "Analysis and design of planar active and passive quasi-optical components using new FDTD techniques." Thesis, Queen Mary, University of London, 2002. http://qmro.qmul.ac.uk/xmlui/handle/123456789/28583.
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New Quasi-optical sensor technology, based on the millimetre and submillimetre band of the electromagnetic spectrum, is actually being implemented for many commercial and scientific applications such as remote sensing, astronomy, collision avoidance radar, etc. These novel devices make use of integrated active and passive structures usually as planar arrays. The electromagnetic design and computer simulation of these new structures requires novel numerical techniques. The Finite Difference Time Domain method (FDTD) is well suited for the electromagnetic analysis of integrated devices using active non-linear elements, but is difficult to use for large and/or periodic structures. A rigorous revision of this popular numerical technique is performed in order to permit FDTD to model practical quasi-optical devices. The system impulse response or discrete Green's function (DGF) for FDTD is determined as a polynomial then the FDTD technique is reformulated as a convolution sum. This new alternative algorithm avoids Absorbing Boundary Conditions (ABC's) and can save large amounts of memory to model wire or slot structures. Many applications for the DGF can be foreseen, going beyond quasi-optical components. As an example, the exact ABC based on the DGF for FDTD is implemented for a single grid wall is presented. The problem of time domain analysis of planar periodic structures modelling only one periodic cell is also investigated. Simple Periodic Boundary Conditions (PBC) can be implemented for FDTD, but they can not handle periodic devices (such as phased shift arrays or dichroic screens) which produce fields periodic in a 4D basis (three spatial dimensions plus time). An extended FDTD scheme is presented which uses Lorentz type coordinate transformations to reduce the problem to 3D. The analysis of non-linear devices using FDTD is also considered in the thesis. In this case, the non linear devices are always model using an equivalent lumped element circuit. These circuits are introduced into the FDTD grid by means of the current density following an iterative implicit algorithm. As a demonstration of the technique a quasi-optically feed slot ring mixer with integral lens is designed for operation at 650 GHz.
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Hill, Jonathan. "Efficient Implementation of Mesh Generation and FDTD Simulation of Electromagnetic Fields." Digital WPI, 1999. https://digitalcommons.wpi.edu/etd-theses/1055.
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"This thesis presents an implementation of the Finite Difference Time Domain (FDTD) method on a massively parallel computer system, for the analysis of electromagnetic phenomenon. In addition, the implementation of an efficient mesh generator is also presented. For this research we selected the MasPar system, as it is a relatively low cost, reliable, high performance computer system. In this thesis we are primarily concerned with the selection of an efficient algorithm for each of the programs written for our selected application, and devising clever ways to make the best use of the MasPar system. This thesis has a large emphasis on examining the application performance."
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Fernandes, Leandro Carísio. "Representação de ambientes urbanos para o cálculo da perda de propagação nas faixas de 1 mhz e 900 mhz." reponame:Repositório Institucional da UnB, 2012. http://repositorio.unb.br/handle/10482/12007.
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Tese (doutorado)—Universidade de Brasília,
Faculdade de Tecnologia, Departamento de Engenharia Elétrica, 2012.<br>Submitted by Alaíde Gonçalves dos Santos (alaide@unb.br) on 2013-01-25T12:20:01Z
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2012_LeandroCarisioFernandes.pdf: 11244387 bytes, checksum: 56968dbdb42928aca7dfd8945faf01cd (MD5)<br>A demanda por serviços de comunicações móveis cresce ano após ano. A implantação
de sistema que ofereça esse tipo de serviço requer mecanismos de predição de cobertura
de sinal, a fim de otimizar parâmetros usados na fase de planejamento. E importante
considerar que, em um enlace de comunicação via rádio, a propagação do sinal não
ocorre em situações ideais, na maioria das vezes. A quantidade de fenômenos que influenciam a propagação do sinal é proporcional a complexidade do ambiente. Em regra, em áreas urbanas existe um número maior de obstáculos do que em localidades rurais, o que torna mais complicado estimar a perda de propagação em cidades e metrópoles. Melhorar a estimativa da perda de propagação pode assegurar mais qualidade ao serviço oferecido por operadoras de telecomunicações. Este trabalho mostra como o
ambiente urbano pode ser considerado no cálculo da perda de propagação em duas
faixas de freqüência. Para a faixa de 900 MHz, são propostos métodos que analisam situações em que a altura da antena transmissora é menor do que a altura média das construções. Os resultados demonstram uma melhora signicativa quando comparados com aqueles obtidos por meio do modelo COST-Walfisch-Ikegami. Em ondas médias, na faixa de 1MHz, propõe-se uma correção da Recomendação ITU-R P.368 de forma a se incluir informações sobre a densidade de área ocupada por construções na localização do receptor. Os valores estimados do campo elétrico estão mais próximos dos dados de medidas do que os obtidos usando-se apenas a recomendação do ITU. O estudo da propagação em ambientes indoor também e um problema de grande interesse prático. Nesse caso, devido a complexidade do ambiente, o uso de equações analíticas torna-se impraticável. Uma forma de contornar essa restrição e usando métodos numéricos. Nesse sentido, será mostrado também como problemas de propagação em ambientes indoor podem ser analisados via métodos numéricos. _______________________________________________________________________________________ ABSTRACT<br>The demand for mobile communications services grows year after year. Path loss
prediction models are necessary to deploy any system that o ers this service. In a
wireless communication link, the propagation of the signal occurs mostly over a non
line of sight path. The more complex the environment, the greater the number of
phenomena that a ect the propagation of the signal. In urban areas, the number of
obstacles is greater than in rural areas, and therefore it is more di cult to estimate the path loss in those sites. However, improve estimates of path loss in urban environment can also improve the quality of service o ered by telecommunications operators. Thus, this thesis shows how the urban environment can be considered to calculate the path loss in two frequency bands. Two path loss models are proposed at 900 MHz, when transmitting antenna is lower than the average height of the buildings. The results show a signi cant improvement when compared with COST-Wal sch-Ikegami model. For medium waves, at 1 MHz, a correction of Recommendation ITU-R P.368 is proposed to include information of area occupied by buildings in the receiver's location. The estimated values of the electric fi eld are better than those obtained using the Recommendation ITU-R P.368. Propagation in indoor environments is also a problem with practical interest. Due
to the complexity of the environment, the use of analytical equation is impractical.
Numerical methods solve this limitation. Thus, it will be shown how to analyse indoor
environments using numerical methods.
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Sirbu, Marina. "Couplage des équations de Maxwell avec l'équation de Boltzmann en 3D : appliqué à la modélisation d'un photocommutateur THz." Paris 11, 2005. http://www.theses.fr/2005PA112255.
Full textAbstract:
Cette thèse traite le couplage des équations du transport et des équations de l'électromagnétisme dans un photocommutateur visant la génération des signaux TeraHertz. Dans un premier temps, les équations relatives au transport des porteurs sont résolues avec un modèle " dérive diffusion ". Ensuite une résolution plus complexe basée une approche Monte Carlo est présentée. Le photocommutateur est situé dans un guide coplanaire dont les dimensions sont proches de celles des structures existantes. Les contraintes numériques sont liées à la résolution dans le domaine temporel du système d'équations couplées, au maillage spatial, à la taille du domaine de simulation nécessaire, aux conditions aux limites et aux non- linéarités supplémentaires introduites par la variation temporelle et spatiale des différents coefficients. Le système 3D est entièrement résolu par la méthode FDTD (Finite Difference Time Domain) à pas variable, ce qui nous permet d'avoir un maillage suffisamment fin au sein du dispositif. Nous avons étudié la manière dont est générée la réponse du photocommutateur à une excitation optique femto seconde. Nous avons d'abord mis en évidence l'origine électromagnétique de cette réponse, avant d'effectuer une étude paramétrique permettant l'identification des paramètres clefs qui la contrôlent. La confrontation des résultats de modélisation avec les résultats de mesure existants a montré un bon accord. Les résultats préliminaires obtenus avec la méthode de Monte Carlo ont permis de mettre en évidence des effets inertiels entre les variations du champ électromagnétique et la réponse des porteurs<br>This PhD thesis presents the coupling between the Boltzmann transport equations and the electromagnetic field equations in a photoconductive switch generating THz signals. First, the transport equations are solved in the drift diffusion approximation. Then, a more complex resolution is made with a Monte Carlo based model. The photoconductive switch is located is coplanar wave guide whose dimensions are comparables with the existents structures. The numerical constraints come from the time dependant resolution, the necessarily space mesh, the simulation domain dimensions, boundary conditions and non linearity introduced by the time and space coefficients variation. The 3D equation system is solved with the variable space step FDTD (Finite Difference Time Domain) method, which allows a sufficiently refined mesh inside the switch. We have studied the photoconductive switch response when a femto second optic excitation is applied. We have shown the electromagnetic field implication in the device response origin. We also made a parametric analysis identifying the main parameters controlling the electromagnetic THz pulse. There is a good agreement between the modelling results and the experimental data. The Monte Carlo method allows taking into account the inertial effects between the electromagnetic field variation and the carrier response. This method is still in developing phase, but we have obtained good preliminary results
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Lee, Richard Todd. "A novel method for incorporating periodic boundaries into the FDTD method and the application to the study of structural color of insects." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29772.
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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.<br>Committee Chair: Smith, Glenn; Committee Member: Buck, John; Committee Member: Goldsztein, Guillermo; Committee Member: Peterson, Andrew; Committee Member: Scott, Waymond. Part of the SMARTech Electronic Thesis and Dissertation Collection.
37
Riedinger, Christophe. "Proposition of a new FDTD (Finite Difference Time Domain) algorithm for modelling a rotating Sagnac gyroscope and its applications to the reduction of perturbations." Université Louis Pasteur (Strasbourg) (1971-2008), 2007. http://www.theses.fr/2007STR13217.
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Proposition of a new FDTD (Finite Difference Time Domain) algorithm for modelling a rotating Sagnac gyroscope and its applications to the reduction of perturbations [. . . ]<br>Proposition d'un nouvel algorithme FDTD (Finite Difference Time Domain) simulant un gyroscope Sagnac en rotation : application à la réduction des perturbations [. . . ]
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Zhai, Pengwang. "A fourth-order symplectic finite-difference time-domain (FDTD) method for light scattering and a 3D Monte Carlo code for radiative transfer in scattering systems." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1839.
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Spivey, David Jeremiah. "FDTD analysis of passive structures in RF IC'S." Honors in the Major Thesis, University of Central Florida, 2001. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/248.
Full textAbstract:
This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.<br>Bachelors<br>Engineering<br>Electrical Engineering
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Ramli, Khairun Nidzam. "Modelling and analysis of complex electromagnetic problems using FDTD subgridding in hybrid computational methods : development of hybridised Method of Moments, Finite-Difference Time-Domain method and subgridded Finite-Difference Time-Domain method for precise computation of electromagnetic interaction with arbitrarily complex geometries." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5443.
Full textAbstract:
The main objective of this research is to model and analyse complex electromagnetic problems by means of a new hybridised computational technique combining the frequency domain Method of Moments (MoM), Finite-Difference Time-Domain (FDTD) method and a subgridded Finite-Difference Time-Domain (SGFDTD) method. This facilitates a significant advance in the ability to predict electromagnetic absorption in inhomogeneous, anisotropic and lossy dielectric materials irradiated by geometrically intricate sources. The Method of Moments modelling employed a two-dimensional electric surface patch integral formulation solved by independent linear basis function methods in the circumferential and axial directions of the antenna wires. A similar orthogonal basis function is used on the end surface and appropriate attachments with the wire surface are employed to satisfy the requirements of current continuity. The surface current distributions on structures which may include closely spaced parallel wires, such as dipoles, loops and helical antennas are computed. The results are found to be stable and showed good agreement with less comprehensive earlier work by others. The work also investigated the interaction between overhead high voltage transmission lines and underground utility pipelines using the FDTD technique for the whole structure, combined with a subgridding method at points of interest, particularly the pipeline. The induced fields above the pipeline are investigated and analysed. FDTD is based on the solution of Maxwell's equations in differential form. It is very useful for modelling complex, inhomogeneous structures. Problems arise when open-region geometries are modelled. However, the Perfectly Matched Layer (PML) concept has been employed to circumvent this difficulty. The establishment of edge elements has greatly improved the performance of this method and the computational burden due to huge numbers of time steps, in the order of tens of millions, has been eased to tens of thousands by employing quasi-static methods. This thesis also illustrates the principle of the equivalent surface boundary employed close to the antenna for MoM-FDTD-SGFDTD hybridisation. It depicts the advantage of using hybrid techniques due to their ability to analyse a system of multiple discrete regions by employing the principle of equivalent sources to excite the coupling surfaces. The method has been applied for modelling human body interaction with a short range RFID antenna to investigate and analyse the near field and far field radiation pattern for which the cumulative distribution function of antenna radiation efficiency is presented. The field distributions of the simulated structures show reasonable and stable results at 900 MHz. This method facilitates deeper investigation of the phenomena in the interaction between electromagnetic fields and human tissues.
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Ramli, Khairun N. "Modelling and analysis of complex electromagnetic problems using FDTD subgridding in hybrid computational methods. Development of hybridised Method of Moments, Finite-Difference Time-Domain method and subgridded Finite-Difference Time-Domain method for precise computation of electromagnetic interaction with arbitrarily complex geometries." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5443.
Full textAbstract:
The main objective of this research is to model and analyse complex electromagnetic problems
by means of a new hybridised computational technique combining the frequency domain
Method of Moments (MoM), Finite-Difference Time-Domain (FDTD) method and a subgridded
Finite-Difference Time-Domain (SGFDTD) method. This facilitates a significant advance in the
ability to predict electromagnetic absorption in inhomogeneous, anisotropic and lossy dielectric
materials irradiated by geometrically intricate sources. The Method of Moments modelling
employed a two-dimensional electric surface patch integral formulation solved by independent
linear basis function methods in the circumferential and axial directions of the antenna wires. A
similar orthogonal basis function is used on the end surface and appropriate attachments with
the wire surface are employed to satisfy the requirements of current continuity. The surface
current distributions on structures which may include closely spaced parallel wires, such as
dipoles, loops and helical antennas are computed. The results are found to be stable and showed
good agreement with less comprehensive earlier work by others.
The work also investigated the interaction between overhead high voltage transmission lines and
underground utility pipelines using the FDTD technique for the whole structure, combined with
a subgridding method at points of interest, particularly the pipeline. The induced fields above
the pipeline are investigated and analysed.
FDTD is based on the solution of Maxwell¿s equations in differential form. It is very useful for
modelling complex, inhomogeneous structures. Problems arise when open-region geometries
are modelled. However, the Perfectly Matched Layer (PML) concept has been employed to
circumvent this difficulty. The establishment of edge elements has greatly improved the
performance of this method and the computational burden due to huge numbers of time steps, in
the order of tens of millions, has been eased to tens of thousands by employing quasi-static
methods.
This thesis also illustrates the principle of the equivalent surface boundary employed close to
the antenna for MoM-FDTD-SGFDTD hybridisation. It depicts the advantage of using hybrid
techniques due to their ability to analyse a system of multiple discrete regions by employing the
principle of equivalent sources to excite the coupling surfaces. The method has been applied for
modelling human body interaction with a short range RFID antenna to investigate and analyse
the near field and far field radiation pattern for which the cumulative distribution function of
antenna radiation efficiency is presented. The field distributions of the simulated structures
show reasonable and stable results at 900 MHz. This method facilitates deeper investigation of
the phenomena in the interaction between electromagnetic fields and human tissues.<br>Ministry of Higher Education Malaysia and Universiti Tun Hussein Onn Malaysia
(UTHM)
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Ireland, David John. "Dielectric Antennas and Their Realisation Using a Pareto Dominance Multi-Objective Particle Swarm Optimisation Algorithm." Thesis, Griffith University, 2010. http://hdl.handle.net/10072/365312.
Full textAbstract:
Antennas utilising a dielectric medium are technologies that have become popular in modern wireless platforms. They offer several desirable features such as high efficiency, electrically small and resistance to proximity detuning. Being a volumetric radiator however, realising a final, commercially competitive solution, often requires the use of a computational optimisation algorithm.
In the realm of antenna design the practice of optimisation typically involves an automated routine consisting of a heuristic algorithm and a forward solving engine such as the finite element method (FEM) or finite difference time domain (FDTD) method. The solving engine is used to derive a post-processed performance value typically referred to as an objective or
fitness function, while the heuristic method uses the objective function data to determine the next trial solution or solutions that approach a design goal.
Nowadays, commercially viable antenna platforms are not characterised by a single performance value, but rather, a series of objective functions that are often inherently conflicting. Thus, an increase in one objective function results in a decrease in another. The optimisation algorithm is therefore required to seek a solution dictated by the preferences of the designer.
Classical literature dominantly featured preference articulation, a priori, where the set of objectives are transformed into a scalar using a predefined preference arrangement. Contemporary theory implements the articulation a posteriori, where the complete set of compromise solutions are sought by the optimisation algorithm.
It is hypothesised that modern multi-objective optimisation (MOO) theory, using a posteriori preference articulation, can be more useful for contemporary antenna design. By treating the objectives as individual dimensions in a mathematical space, it allows for independent, simultaneous optimisation. At the time of writing this dissertation, all commercial simulation software that include an optimisation algorithm use a predefined preference to the performance criteria. Thus, where a large set of equally potential solutions exist, only one final solution is delivered.
This thesis examines two novel dielectric antenna technologies and uses modern MOO theory to obtain new solutions that supersede their prototypes. Taking a commercial perspective by optimising the electromagnetic performance and the physical size of the antenna simultaneously, it is hypothesised this allows an unprecedented insight into the inherent tradeoffs of practical antenna configurations.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>Griffith School of Engineering<br>Science, Environment, Engineering and Technology<br>Full Text
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Tuerxunjiang, Abulikemu. "FDTD measurement of the reflection coefficient associated with total internal reflection from gainy Lorentzian media." Pullman, Wash. : Washington State University, 2008. http://www.dissertations.wsu.edu/Thesis/Fall2008/A_Tuerxunjiang_120108.pdf.
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Thesis (M.S. in physics)--Washington State University, December 2008.<br>Title from PDF title page (viewed on July 10, 2009). "Department of Physics and Astronomy." Includes bibliographical references (p. 64-68).
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陽紀, 池田, та Yoki Ikeda. "垂直導体のサージ伝搬特性を考慮した風力発電タワー周波数依存回路解析モデル". Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12902988/?lang=0, 2015. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12902988/?lang=0.
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風力発電システムは、現在世界中で普及しているが、その地上高と立地条件からしばしば落雷の被害を受け、稼働率の低下が問題視されている。本論文は、垂直導体である風力発電タワーにおける雷サージ解析の高精度化、高速化を目的とした垂直導体回路解析モデルの提案、およびその有用性のについて述べるとともに、風力発電所や洋上風車への拡張性についてまとめたものである。<br>博士(工学)<br>Doctor of Philosophy in Engineering<br>同志社大学<br>Doshisha University
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Lee, Kwan-Ho. "Development of four novel UWB antennas assisted by FDTD method." Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1103659688.
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Thesis (Ph. D.)--Ohio State University, 2004.<br>Title from first page of PDF file. Document formatted into pages; contains xvii, 165 p.; also includes graphics (some col.). Includes bibliographical references (p. 158-165).
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Xu, Yang. "Performance Analysis of Point Source Model with Coincident Phase Centers in FDTD." Digital WPI, 2014. https://digitalcommons.wpi.edu/etd-theses/214.
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The Finite Difference Time Domain (FDTD) Method has been a powerful tool in numerical simulation of electromagnetic (EM) problems for decades. In recent years, it has also been applied to biomedical research to investigate the interaction between EM waves and biological tissues. In Wireless Body Area Networks (WBANs) studies, to better understand the localization problem within the body, an accurate source/receiver model must be investigated. However, the traditional source models in FDTD involve effective volume and may cause error in near field arbitrary direction. This thesis reviews the basic mathematical and numerical foundation of the Finite Difference Time Domain method and the material properties needed when modeling a human body in FDTD. Then Coincident Phase Centers (CPCs) point sources models have been introduced which provide nearly the same accuracy at the distances as small as 3 unit cells from the phase center. Simultaneously, this model outperforms the usual sources in the near field when an arbitrary direction of the electric or magnetic dipole moment is required.
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Long, Zeyu. "Introduction of the Debye media to the filtered finite-difference time-domain method with complex-frequency-shifted perfectly matched layer absorbing boundary conditions." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/introduction-of-the-debye-media-to-the-filtered-finitedifference-timedomain-method-with-complexfrequencyshifted-perfectly-matched-layer-absorbing-boundary-conditions(441271dc-d4ea-4664-82e6-90bf93f5c2b7).html.
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The finite-difference time-domain (FDTD) method is one of most widely used computational electromagnetics (CEM) methods to solve the Maxwell's equations for modern engineering problems. In biomedical applications, like the microwave imaging for early disease detection and treatment, the human tissues are considered as lossy and dispersive materials. The most popular model to describe the material properties of human body is the Debye model. In order to simulate the computational domain as an open region for biomedical applications, the complex-frequency-shifted perfectly matched layers (CFS-PML) are applied to absorb the outgoing waves. The CFS-PML is highly efficient at absorbing the evanescent or very low frequency waves. This thesis investigates the stability of the CFS-PML and presents some conditions to determine the parameters for the one dimensional and two dimensional CFS-PML.The advantages of the FDTD method are the simplicity of implementation and the capability for various applications. However the Courant-Friedrichs-Lewy (CFL) condition limits the temporal size for stable FDTD computations. Due to the CFL condition, the computational efficiency of the FDTD method is constrained by the fine spatial-temporal sampling, especially in the simulations with the electrically small objects or dispersive materials. Instead of modifying the explicit time updating equations and the leapfrog integration of the conventional FDTD method, the spatial filtered FDTD method extends the CFL limit by filtering out the unstable components in the spatial frequency domain. This thesis implements filtered FDTD method with CFS-PML and one-pole Debye medium, then introduces a guidance to optimize the spatial filter for improving the computational speed with desired accuracy.
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Diamanti, Nectaria. "An efficient ground penetrating radar finite-difference time-domain subgridding scheme and its application to the non-descructive testing of masonry arch bridges." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/3491.
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This thesis reports on the application of ground penetrating radar (GPR) as a non-destructive technique for the monitoring of ring separation in brick masonry arch bridges. In addition, research is reported on the assessment of the clay capping layer often used in construction as a waterproof backing to arches. The thrust of the research is numerical modelling, verified by large laboratory experiments. Due to the heterogeneity of these structures, the resultant signals from the interaction between the GPR system and the bridge are often complex and hence, hard to interpret. This highlighted the need to create a GPR numerical model that would allow the study of the attributes of reflected signals from various targets within the structure of the bridge. The GPR numerical analysis was undertaken using the finite-difference time-domain (FDTD) method. Since micro regions in the bridge structure need to be modelled, the introduction of subgrids of supporting finer spatial resolution into the standard FDTD method was considered essential in order to economise on the required computational resources. In the main part of this thesis, it is demonstrated how realistic numerical modelling of GPR using the FDTD method could greatly benefit from the implementation of subgrids into the conventional FDTD mesh. This is particularly important when (a) parts of the computational domain need to be modelled in detail (i.e., ring separation between the mortar layers and the brick units, which is the case studied in this thesis); and also (b) when there are features or regions in the overall computational mesh with values of high relative permittivity supporting propagation of waves at very short wavelengths. A scheme is presented that simplifies the process of implementing these subgrids into the traditional FDTD method. This scheme is based on the combination of the standard FDTD method and the unconditionally stable alternating-direction implicit (ADI) FDTD technique. Given that ADI-FDTD is unconditionally stable, its time-step can be set to any value that facilitates the accurate calculation of the electromagnetic fields. By doing so, the two grids can efficiently communicate information across their boundary without requiring to use a time-interpolation scheme. The performance of ADI-FDTD subgrids when implemented into the traditional FDTD method is discussed herein. The developed algorithm can handle cases where the subgrid crosses dielectrically inhomogeneous and/or conductive media. In addition, results from the comparison between the proposed scheme and a commonly employed purely FDTD subgridding technique are presented. After determination of the optimum ADI-FDTD scheme, numerical experiments were conducted and calibrated using GPR laboratory experiments. Good correlations were obtained between the numerical experiments and the actual GPR experiments. It was shown both numerically and experimentally that significant mortar loss between the masonry arch rings can be detected. Dry hairline delaminations between the mortar and the brick masonry are difficult to detect using standard GPR procedures. However, hairline faults containing water produce distinct and detectable GPR responses. In addition, the clay layer was successfully identified and its thickness calculated to a satisfactory accuracy.
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Ha, Myunghyun. "EM simulation using the Laguerre-FDTD scheme for multiscale 3-D interconnections." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42850.
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As the current electronic trend is toward integrating multiple functions in a single electronic device, there is a clear need for increasing integration density which is becoming more emphasized than in the past. To meet the industrial need and realize the new system-integration law [1], three-dimensional (3-D) integration is becoming necessary. 3-D integration of multiple functional IC chip/package modules requires co-simulation of the chip and the package to evaluate the performance of the system accurately. Due to large scale differences in the physical dimensions of chip-package structures, the chip-package co-simulation in time-domain using the conventional FDTD scheme is challenging because of Courant-Friedrich-Levy (CFL) condition that limits the time step. Laguerre-FDTD has been proposed to overcome the limitations on the time step. To enhance performance and applicability, SLeEC methodology [2] has been proposed based on the Laguerre-FDTD method. However, the SLeEC method still has limitations to solve practical 3-D integration problems.
This dissertation proposes further improvements of the Laguerre-FDTD and SLeEC method to address practical problems in 3-D interconnects and 3-D integration. A method that increases the accuracy in the conversion of the solutions from Laguerre-domain to time-domain is demonstrated. A methodology that enables the Laguerre-FDTD simulation for any length of time, which was challenging in prior work, is proposed. Therefore, the analysis of the low-frequency response can be performed from the time-domain simulation for a long time period. An efficient method to analyze frequency-domain response using time-domain simulations is introduced. Finally, to model practical structures, it is crucial to model dispersive materials. A Laguerre-FDTD formulation for frequency-dependent dispersive materials is derived in this dissertation and has been implemented.
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Lacroux, Fabrice. "Contribution à la modélisation d'éléments localisés pour les simulations électromagnétiques en transitoire : Application en millimétrique et au transport d'énergie sans fil." Limoges, 2005. http://aurore.unilim.fr/theses/nxfile/default/b0c5314e-251a-454a-a365-a395d8c2b349/blobholder:0/2005LIMO0001.pdf.
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Ce travail a permis de définir de nouvelles possibilités pour l'algorithme LE-FDTD (Lumped Element – Finite Difference Time Domain), puis de l'exploiter pour deux applications originales. La première permet de représenter une structure passive distribuée par son impédance équivalente. Pour cela, ce travail met tout d'abord en évidence les différents phénomènes parasites qui sont associés à l'insertion d'un élément localisé dans le volume de calcul FDTD. Puis, une solution est proposée afin de s'en affranchir. Cette technique est ensuite validée en remplaçant une transition ligne microruban / ligne coaxiale par son impédance équivalente jusqu'à 80GHz. La deuxième application est consacrée à l'étude d'un système de réception dédiée au transport d'énergie sans fil. Ce système a été modélisé de façon globale : antenne, système de redressement et charge. Le rendement de conversion d'une telle structure a pu être calculé en tenant compte des problèmes d'adaptation et d'interaction entre les différentes parties<br>This work has enabled to define new possibilities for the LE-FDTD algorithm (Lumped Element – Finite Difference Time Domain), and use it on two original applications. The first one allows to represent a distributed passive structure with its equivalent impedance. In this way, this work underscore parasitic phenomenon which are present with the insertion of the lumped elements into the FDTD meshgrid. Then, a solution is proposed to compensate them. As result, a transition from a microstrip line to a coaxial line is replaced by its equivalent impedance until 80GHz. The second application is dedicated to the reception system used in a wireless power transmission. This system has been studied in a global electromagnetic simulation (antenna, rectifier and load) in order to take all couplings and radiations into account. So, this global approach permits to determinate the conversion efficiency of such a system