Modelling of coaxial-fed microstrip patch antenna by finite difference time domain method

A direct three-dimensional finite-difference time-domain (FDTD) method is applied to coaxial-fed microstrip antennas. The model is shown to be an efficient and accurate tool for modelling coaxial-fed structures. The reflection coefficient can be determined from the simulated time-domain wave that is reflected down the coaxial line. Excellent agreement over a wide frequency range is shown in two cases between the measured and FDTD derived results.<>     

Characterization of a 90° microstrip bend with arbitrary mitervia the time-domain finite difference method

A 90° microstrip bend with an arbitrary miter is characterized using the finite difference time-domain (FDTD) method. In this method, to simplify computations, the microstrip structure is enclosed by four electric walls; thus radiation effects are neglected. Time histories generated by FDTD techniques are Fourier-transformed to yield broadband scattering parameters of the microstrip bend. A miter is introduced to improve the transmission characteristics of the bend, and an optimal miter length is found such that the reflection from the microstrip bend over a broad frequency range is minimized     

Analysis of a three-dimensional dielectric mixture with finitedifference method

The present paper reports the results of a numerical analysis of electric fields in random dielectric materials. The effective permittivity of a three-dimensional (3D) dielectric mixture is calculated by the finite difference method. The results show the distribution of the effective permittivity of a mixture with different random inclusion positionings. New empirical mixing models are created as least squares approximations to fit the collection of numerical results. The calculated permittivity distribution is also compared with theoretical mixture models, showing that in case of clustered inclusions, the Bruggeman model is quite reasonable. On the other hand, if the inclusions in the mixture are separate, the results are closer to the Maxwell-Garnett model     

Analysis of microstrip circuits using three-dimensional full-waveelectromagnetic field analysis in the time domain

In this method, the circuit is excited by a raised cosine pulse source that includes broadened frequency components. The frequency characteristics are then computed from the Fourier transform of the output transient responses. To evaluate the validity and capability of the method, a side-coupled microstrip filter is analyzed and the frequency characteristics are calculated. A quasistatic analysis of this filter is also presented and the results compared with measurements. The frequency characteristics calculated with the full-wave analysis in the time domain show excellent agreement with the measured values, thus demonstrating the validity and the power of the analytical method     

Frequency and time domain characterization of microstrip-ridgestructures

Microstrip-ridge structures, i.e., conducting strips which are mounted on ridges and are in the close proximity of other conductors on other ridges, are found in submillimeter/terahertz monolithic circuits in conjunction with layered, ridged dielectric waveguides; in millimeter-wave monolithic circuits as microslab lines; in microwave monolithic circuits as integrated traveling-wave optical modulators; and in VLSI circuits as interconnects. A hybrid full-wave frequency domain technique which uniquely synthesizes well-known integral equation and mode-matching methods is shown to be applicable to the study of microstrip-ridge structures. Unlike most other integral equation techniques, the integral equation-mode matching (IEMM) technique is capable of characterizing a wide variety of nonplanar structures. Time domain results are obtained by utilizing a Fourier transform and an equivalent circuit model to evaluate the response at each frequency point. To introduce this method, several two-dimensional structures-specifically, coupled microstrips on ridges, coupled microstrip with an etched groove, and an electrooptic modulator-are examined     

Numerical solution method of nonlinear guided modes with a finitedifference complex axis beam propagation method

A method to construct modal fields for an arbitrary one- or two-dimensional intensity dependent refractive index structure is described. An arbitrary starting field is propagated along an imaginary axis using the finite difference beam propagation method (FDBPM) based upon the slowly varying envelope approximation (SVEA). First the modes are found for the linear part of the refractive index structure. By suitably choosing the complex value of the propagation step, one mode is maximally increased in amplitude. After the nonlinearity has been put on, two methods are applied to find the modes for the nonlinear structure. One method is the same as the method used for the linear part, in the other method the propagation step is left unchanged. The applicability of the method is discussed and illustrated by a calculation on a waveguide with one-dimensional cross section having Kerr-type nonlinearity     

Experimental validation of microstrip bend discontinuity modelsfrom 18 to 60 GHz

A cavity resonance technique is described and used to experimentally verify microstrip bend discontinuity models over the frequency range 18 to 60 GHz. A novel, dual-cavity method leads to elimination of confounding variables and permits isolation and investigation of the bend model alone. This contrasts to a more standard approach in which the presence of models for several other structures such as microstrip and a coupler complicates study of the specific model under consideration. Optimally mitered, 50% mitered and unmitered bends of three different widths on alumina are included     

Full-wave characterization of the mode conversion in a coplanarwaveguide right-angled bend

A full-wave algorithm is proposed to analyze thoroughly a 90° bend of coplanar waveguide (CPW). Based on the mixed potential integral equation (MPIE) formulation, the equivalent magnetic current distribution on the apertures is solved by the moment method using overlapping rooftop basis functions and the Galerkln weighting procedure. The matrix pencil approach is then utilized to do the de-embedding procedure and extract both the coplanar and slotline modes scattering off the asymmetric discontinuity. Experiments are performed to measure the scattering parameters and the results verify the accuracy of the present algorithm. The full 4×4 scattering matrix between these two modes is presented from which the occurrence of the mode conversion is investigated. The mode conversion is noticed to become almost complete at certain frequencies, which may be useful in the design of CPW to coupled slotline transition     

时域MEI方法初探

对时域ＭＥＩ方法进行了初步探索,根据ＭＥＩ方法的基本原理,建立起时域ＭＥＩ方法的一阶吸收边界条件,应用该条件对线源辐射问题的数值实验和研究表明,它可使截断边界离源更近,同时也证实了时域ＭＥＩ方法的可靠性和精确性。     

A time domain method for producing pulse compression in a plasma

The propagation of a rectangular envelope RF pulse in a lossless homogeneous isotropic plasma is considered. It is desired to produce pulse enhancement by an appropriate choice of the phase variation. A time domain technique is developed for choosing the phase. The resulting enhancement is greater than that reported previously.     

Analysis of cylindrically conformal microstrip patch arrays via modified method of auxiliary sources

The recently proposed modified method of auxiliary sources (MMAS) is applied to the analysis of conformal microstrip patch arrays. The aim of the technique is to improve the accuracy or/and the computational complexity of standard numerical methods. The radiation patterns are compared to reference data, showing excellent agreement.     

Image compression via joint statistical characterization in thewavelet domain

We develop a probability model for natural images, based on empirical observation of their statistics in the wavelet transform domain. Pairs of wavelet coefficients, corresponding to basis functions at adjacent spatial locations, orientations, and scales, are found to be non-Gaussian in both their marginal and joint statistical properties. Specifically, their marginals are heavy-tailed, and although they are typically decorrelated, their magnitudes are highly correlated. We propose a Markov model that explains these dependencies using a linear predictor for magnitude coupled with both multiplicative and additive uncertainties, and show that it accounts for the statistics of a wide variety of images including photographic images, graphical images, and medical images. In order to directly demonstrate the power of the model, we construct an image coder called EPWIC (embedded predictive wavelet image coder), in which subband coefficients are encoded one bitplane at a time using a nonadaptive arithmetic encoder that utilizes conditional probabilities calculated from the model. Bitplanes are ordered using a greedy algorithm that considers the MSE reduction per encoded bit. The decoder uses the statistical model to predict coefficient values based on the bits it has received. Despite the simplicity of the model, the rate-distortion performance of the coder is roughly comparable to the best image coders in the literature.     

Efficiently convergent novel basis functions for the analysis of microstrip discontinuities by the spectral domain Galerkin method

In this paper, novel efficient basis functions are presented for the rigorous analysis by the spectral domain Galerkin method of geometrically complex Microstrip discontinuities. The numerical performances of these basis functions are very attractive, namely, very rapid convergence and high stability. Moreover, a comparative study of the convergence features of the proposed basis functions with two others widely used in literature, namely, the rooftops and the rectangular pulses, is presented. To illustrate this study, numerical results are presented for a shielded Microstrip bend discontinuity.     

Fast multipole method for time domain PEEC analysis

High-speed electronic circuits are becoming more and more important in modern communication systems, thus leading to an increasing interest in printed circuit boards, interconnect, and packaging. Nowadays, full-wave numerical methods are widely used in order to investigate both signal integrity and electromagnetic compatibility issues arising in PCBs design. When broadband information is desired and transient effects dominate, it is more efficient using time domain numerical techniques, which may scale better than corresponding frequency-domain methods. This paper presents the derivation of the time domain partial element equivalent circuit (PEEC) method enhanced by the three-dimensional (3D) fast multipole method (FMM). It is shown that combining the full-wave time domain PEEC method with the FMM allows performing the analysis of electrically large electronic systems, which reduces both memory and CPU-time requirements. Several examples are presented confirming the capability of the proposed approach to provide a significant reduction of the computational complexity associated with the transient analysis of large systems.     

色散介质中的时域小波Galerkin方法

将基于Daubechies尺度函数的时域小波Galerkin法应用到水和等离子体色散介质中的瞬态传播,给出了一种既适合于Debye模型,又适合于等离子体计算的差分方程方法.计算结果证实了方法的有效性,与(FD)2TD比较,该方法可以增加网格尺寸而不会牺牲精度,因而具有计算效率高的特点.     

Introduction of radiation losses in the time domain transmission line method

Because the transmission line method only allows to study the propagation of a pure tem mode along a line, all radiation phenomena are neglected. These phenomena become important when lines have discontinuities, then in this case radiating losses must be included in the theoretical formalism. This paper introduces an original approach to consider radiation of lines and to include them in a time domain transmission line method. Some comparisons with full modes method results validate the method.     

Quasi-static analysis of a microstrip via through a hole in aground plane

The equivalent circuit of a via connecting two semi-infinitely long transmission lines through a circular hole in a ground plane is found. The π-type equivalent circuit consists of two excess capacitances and an excess inductance. These are quasistatic quantities and thus are computed statically by the method of moments from integral equations. The integral equations are established by introducing a sheet of magnetic current in the electrostatic case and a layer of magnetic charge in the magnetostatic case. Parametric plots of the excess capacitances, the excess inductance, and the characteristic admittance of the via are given     

Full wave modeling of microstrip via holes

A rigorous full-wave analysis of microstrip via hole grounds is performed using a three-dimensional mode-matching method associated with a suitable segmentation technique. Theoretical results are compared with measured data showing excellent agreement.