When the conventional FDTD method is applied to the high-frequency planar circuits, the time step must be very small due to the CFL stability criterion since the structural details of the circuits are usually very small. These results in a prohibitively high computation time since the simulation takes a long time to stabilize. This thesis will focus on implementing an ADI-FDTD algorithm suitable for the analysis and simulation of large-scale high-frequency planar circuits. Realization of the lumped elements befitting the ADI-FDTD algorithm will be developed. Furthermore, active devices will then be incorporated into the algorithm once the models for lumped elements are built up.

Le développement constant des systèmes de communication soulèvent des inquiétudes sur l’influence des ondes électromagnétique sur le corps humain. Une législation existante permet de rassurer la population, mais, l’exposition quotidienne, souvent multi sources implique des interrogations sur ces nouveaux types d’usages. La méthode des Différence Finies dans le Domaine Temporel (FDTD) permet d’évaluer avec précision le niveau d’exposition a été décrit dans ce manuscrit. Cependant, cette méthode présente des limites si on souhaite représenter des structures présentant des courbures du fait de l’usage de mailles orthogonales. Ce manuscrit est une contribution à la problématique en développant une méthode de FDTD conforme dont les mailles suivent la forme des objets à modéliser. Même si, quelques méthodes de FDTD conforme existantes dans la littérature seront au préalable présentées. Dans cette étude, un soin particulier sera porté sur la validation de la méthode développée à travers plusieurs types de maillages différents et en comparant les résultats obtenus avec HFSS et la FDTD classique. Le débit d’absorption spécifique (DAS) sera également calculé en homogénéisant les tissus humains par pondération volumique. Ce qui permettra de réduire les temps de calcul / The constant development of communication systems raises concerns about the influence of electromagnetic waves on human body. Existing legislation helps to reassure population, but daily exposure, often multi-source, involves questions about these new types of use. The Time Domain Finite Difference (FDTD) method allows accurate assessment of the level of exposure described in this manuscript. However, this method has limitations if it is desired to represent structures with curvatures due to the use of orthogonal meshes. This manuscript is a contribution to the problem by developing a conformal FDTD method whose meshes follow the shape of the objects to be modeled. Even so, some existing FDTD compliant methods in the literature will be presented beforehand. In this study, particular attention will be paid to the validation of the method developed through several different types of meshes and comparing results obtained with HFSS and conventional FDTD. The specific absorption rate (SAR) will also be calculated by homogenizing human tissues by volume weighting. This will reduce computing time

FDTD can successfully simulate various kinds of phenomena of electromagnetic waves. Mainly, we use orthogonal Cartesian coordinate in general situations when we deal with the electromagnetic problems, but the curved geometry of the problem makes it difficult to obtain accurate results using conventional FDTD algorithm because of staircasing. To analyze curved geometry using Conformal FDTD can improve this shortcoming. The Conformal FDTD uses the regular FDTD equation for updating the magnetic field by using the electric field values along the distorted contours, that are appropriately weighted with lengths of the contours. The Conformal FDTD technique is well suited for handling such curved geometries. The moment method is used to convert the integral equation into a matrix equation.The major drawback of moment method (MoM) is the full matrix generation and huge computation time. The CFDTD directly approximates the differential operators in the Maxwell curl equation, and avoids using more mathematic formulae. This thesis uses Conformal FDTD to simulate RCS value of the cylinder and sphere and compare Conformal FDTD with Moment Method. We know that Conformal FDTD will save memory requirement and CPU time even more than Moment Method in layered structure.

Perforated metal sheets are frequently used in electric and electronic devices, and in most cases, these metal structures should comply with some electromagnetic compatibility constraints which impose certain conditions on penetrating electromagnetic radiation, quality of shielding, and other characteristics. Currently, many issues in electronic system design could be handled with advanced mathematical and computer models; however, direct reproduction of perforation in these models may result in a significantly increased computational cost. This work is concerned with modeling perforated metal sheets whose apertures have diameters significantly smaller than the wavelength of radiation. We suggest an original approach for computation of intrinsic impedance from the reflection and transmission coefficients obtained by FDTD simulation of the perforated sheet placed in a rectangular waveguide. The calculated impedance can be used to characterize the perforated segment as a solid metal plate which has the same effective material parameters, including electric conductivity. Functionality of the proposed technique is illustrated with a model of a microwave oven that has two perforated wall segments necessary for ventilation and lighting. After computing the impedance of these segments, they are replaced in the model by solid metal with equivalent effective conductivity, which allows for practical simulation of electromagnetic processes in the oven without any increase in the computational resources required. Computations show that the presence of perforated segments on the walls of this microwave oven makes a negligible impact on the frequency characteristics of the systemâ€"so in corresponding full-wave models, the segments can be replaced by solid metal walls without compromising accuracy of simulation.

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. / <p>QC 20120530</p>

This thesis investigates the issues in deriving the Finite Di erence Time Domain Method, including the derivation of a unique method for exciting an FDTD system that is physically realistic in terms of acoustics. It is also the goal of this thesis to use the FDTD method as a tool for investigating various speaker placement con gurations for use in bass equalization. A demerit function is then developed in order to assess how well a particular equalization method performs relative to any others.

This thesis investigates the issues in deriving the Finite Di erence Time Domain Method, including the derivation of a unique method for exciting an FDTD system that is physically realistic in terms of acoustics. It is also the goal of this thesis to use the FDTD method as a tool for investigating various speaker placement con gurations for use in bass equalization. A demerit function is then developed in order to assess how well a particular equalization method performs relative to any others.

In high ¡Vspeed digital circuits, in order to utilize the space of printed circuit boards(PCB) efficiently, the signal via is a heavily used interconnection structure to communicate different signal layers. However, the interconnection discontinuities will result in the degradation of the signal integrity and become a crucial issue for IC designers. To analyze this problem using finite difference time domain(FDTD) method, the stair case approach of interesting structure with curved metallic surface not only introduce errors due to inaccurate approximation, but consume much simulation time and memory required . In this thesis, a conformal FDTD method of locally distorted contours is presented. By modification of Maxwell¡¦s equations in integration form, we simulate the signal via successfully and discuss several interesting issues such as resonance in power/ground plane, the simultaneous switching noise(SSN), the effect of adding ground vias in PCB, and common-mode and differential-mode drives for source, etc.

Rapid development of wireless communications has led to the excessive use of wireless equipments. The purpose of communication is achieved through the transmission and reception of electromagnetic waves by the wireless equipments. Living in the environment of massive electromagnetic exposure coming from these wireless equipments, the health issue is a growing concern among the people who use the equipments and also the general public. The GSM communication system is the most widely used segment of wireless communications currently in Taiwan. The user of the mobile terminal (handset) is in close proximity to the radiating antenna. Most of the EM radiation emitting from the antenna will pass through the body of the user and be absorbed by the human tissue. It is therefore important to consider possible health hazards due to this type of EM exposure. Among all the possible biological effects caused by EM exposure, the heating effect is the most significant and its influence on biological tissues is proven. Currently most countries require the handsets to be tested for SAR values before the handsets are ready for purchasing on the markets. SAR tests require the utilization of expensive measurement facilities. Moreover, even though the phantom used for SAR measurement is prepared according to standards, theoretically the phantom is still not identical to the anatomical constituents of the human head. Henceforth, it is necessary to investigate the field distribution inside the human head, using an anatomical model, due to the exposure of radiation coming from the handset antennas from the theoretical point of view. The whole human body is an inhomogeneous lossy dielectrics as far as EM wave propagation is concerned. This feature renders the problem easy to tackle using the FDTD numerical method. This thesis presents a method to build up a numerical human head model suitable for the FDTD analysis using data set from the ¡§visible human¡¨ project readily available from the internet. The thesis then investigates the field distribution inside the human head, under the exposure of the quarter-wavelength monopole antenna on a dielectric covered metal box. Temperature increases due to the absorption of EM energy by the human head will then be deducted from the bioheat equation.

In the past when we use the FDTD method to analyze electromagnetic problems, it has to properly discretize the structure and time, then analyze by C code. Before analyzing microstrip structures, we have to calculate and draw the distribution of structure on the grid paper. In order to increase the efficiency of drawing structure and coding, we design a GUI that it can draw and discretize the structure properly. This GUI can generate the most appropriate grid size for the user, reduce the distortion. Then, when we are coding the FDTD analysis program according to the output file, we can replace the parts of setting structure and material parameters with reading data and retain the parts of FDTD algorithm and absorbing boundary condition.