Polygonal plate modeling of realistic structures

A technique for the electromagnetic modeling of arbitrary perfectly conducting structures using polygonal plates is described. The method is illustrated by three realistic examples.     

A novel electromagnetic bandgap metal plate for parallel plate modesuppression in shielded structures

A novel type of metal plate structure incorporated with electromagnetic bandgap holes for use as metal shields with the capability of suppressing the propagation of unwanted parallel plate mode has been proposed. The holes can be of any shape and the periods of those holes should be selected to half the guided wavelength of the parallel plate mode at a desired center frequency of suppression. To show the validity of the proposal, inert electromagnetic wave simulation, results of a shielded microstrip structure designed for application in the 76 GHz frequency band are demonstrated. Experiments are performed with a prototype designed in the 10 GHz frequency band and parallel plate mode suppression is verified successfully with the excellent agreement between experimental and simulation results     

WIPL: a program for electromagnetic modeling of composite-wire andplate structures

WIPL is a program which allows fast and accurate analysis of antennas. The geometry of any metallic structure (even a very large structure) is defined as a combination of wires and plates. WIPL's analysis features include evaluations of the current distribution, near and far field, and impedance, admittance and s-parameters. The program uses an entire-domain Galerkin method. Efficiency of the program is based on the flexible geometrical model, and sophisticated basis functions. In this paper, the basic theory implemented in the program, and some results concerning TV UHF panel antennas and large horn antennas are given     

Analysis of the time-reversal operator for a small spherical scatterer in an electromagnetic field

The time-reversal operator (TRO) for a planar array of crossed dipole elements illuminating a small conducting and/or dielectric sphere is investigated in order to determine the general properties of an electromagnetic time-reversing array system. The behavior of such a system for a given frequency is analyzed by studying the eigenvalues and eigenvectors of the TRO. Each eigenvector specifies a set of complex driving currents for the array elements that produce received voltages that are proportional to the conjugates of the drive currents. The proportionality constant is equal to the square root of the associated eigenvalue and is the same for all elements. The eigenvalues and eigenvectors can be determined by performing a singular value decomposition (SVD) on the multistatic data matrix of the array. The eigenvalues of the TRO are the squares of the singular values, and the eigenvectors are identical to the singular vectors. We have shown that the maximum number of singular vectors associated with the sphere is equal to the number of orthogonal orientations of the dipole moments induced in the sphere when irradiated by the array, so there is a maximum of six for a conducting sphere but only three are significant when the conductivity is small and the sphere may be considered being just a dielectric. Numerical results are presented for linear and circular arrays to show the general behavior of the system.     

Accurate small-signal modeling of HFET's for millimeter-waveapplications

In this paper we discuss the small-signal modeling of HFET's at millimeter-wave frequencies. A new and iterative method is used to extract the parasitic components. This method allows calculation of a π-network to model the heterojunction field-effect transistor (HFET) pads, thus extending the validity of the model to higher frequencies. Formulas are derived to translate this π-network into a transmission line. A new and general cold field-effect transistor (FET) equivalent circuit, including a Schottky series resistance, is used to extract the parasitic resistances and inductances. Finally, a new and compact set of analytical equations for calculation of the intrinsic parameters is presented. The real part of Y₁₂ is accounted for in these equations and its modeling is discussed. The accounting of Re(Y₁₂ ) improves the S-parameter modeling. Model parameters are extracted for an InAlAs/InGaAs/InP HFET from measured S-parameters up to 50 GHz, and the validity of the model is evaluated by comparison with measured data at 75-110 GHz     

Accurate modeling for drain breakdown current of GaAs MESFET's

Extensive measurements of a drain breakdown current as a function of device bias are reported in this paper. To represent the measured drain breakdown currents accurately, a new modeling function and an equivalent circuit controlled by two voltages are proposed. This model, when integrated into a large-signal analysis program, improves the accuracy of the simulation     

Reduced sized cells for electromagnetic bandgap structures

Electromagnetic bandgap structures of simple squares are compared to convoluted and interleaved elements to reduce bandgap frequency for fixed periodicity. A reduction of 42% in bandgap frequency is obtained for one (Hilbert) convolution. This frequency reduction increases to 55% when adjacent elements in the structure are interleaved.     

Accurate closed-form formulas for the electromagnetic parameters of squared coaxial lines

This article presents a set of accurate closed-form formulas for the electromagnetic parameters (inductance (L), capacitance (C) and characteristic impedance (Z_c)) for squared coaxial lines with circular and square inner conductor. The analytical expressions, deduced from rigorous analysis by the finite element method (FEM), method of moments (MoM) and curves fitting techniques, can be easily implemented in CAD simulation tools, to design components for wireless communication. This study presents accurate and suitable general expressions for all squared coaxial lines with a wide range of outer to inner conductors ratio between 1.2 and 10. As an application, we present the design of 60 GHz branch line couplers.     

Accurate modeling of an ion-implanted MESFET

An accurate modeling of an ion-implanted silicon MESFET device has been carried out considering a Gaussian-exponential distribution of impurities. Although two-dimensional analysis is essential for the characterization of the short-channel and submicrometer FET devices, one-dimensional analysis is fairly accurate for a moderately long-channel MESFETs fabricated with a shallow implanted channel where the concentration is highly nonlinear with depth. Potential distribution, channel charge, threshold voltage, I–V characteristics, mobility and transconductance of the Si MESFET device have been evaluated. The results show closer agreement with the experimentally obtained values compared to those obtained considering only Gaussian distribution of impurity profile.     

Numerical modeling and electromagnetic resonant modes in complex grating structures and optoelectronic device applications

An extended surface impedance boundary condition algorithm is developed that allows for the optical properties of a wide variety of complex one-dimensional periodic grating structures to be modeled. Wood-Rayleigh anomalies, diffraction, and electromagnetic resonance modes including horizontally oriented surface plasmons and vertical surface resonances are identified and described as well as analyzing their structural and geometrical dependencies. Methods to combine these modes to produce hybrid modes that channel and localize light are described. Application of these modes to metal-semiconductor-metal photodetectors (MSM-PD) is discussed and an example silicon-based MSM-PD with over 30 GHz bandwidth and 0.3 A/W responsivity is described.     

Wavelet packets for fast solution of electromagnetic integralequations

This paper considers the problem of wavelet sparsification of matrices arising in the numerical solution of electromagnetic integral equations by the method of moments. Scattering of plane waves from two-dimensional (2-D) cylinders is computed numerically using a constant number of test functions per wavelength. Discrete wavelet packet (DWP) similarity transformations and thresholding are applied to system matrices to obtain sparsity. If thresholds are selected to keep the relative residual error constant the matrix sparsity is of order O(N^P) with p<2. This stands in contrast with O(N² ) sparsities obtained with standard wavelet transformations. Numerical tests also show that the DWP method yields faster matrix-vector multiplication than some fast multipole algorithms     

Accurate modeling and parameter extraction for meander-line N-well resistors

Accurate modeling and efficient parameter extraction of a scalable lumped-element model for n-well meander-line resistors that are suitable for radio frequency integrated circuit (RF IC) applications is presented. The equivalent circuit is similar to the spiral inductor model but with modifications to the element equations. Direct extraction of component values is performed by analysis of measured Y-parameters. The extracted results of the component values are physically meaningful and match those calculated using the scalable lumped-element model equations. The simulated S-parameter data from the equivalent lumped-element model shows very good agreement with the measured data up to 20 GHz.     

Accurate high speed empirically based predictive modeling of deeplyembedded gridded parallel plate capacitors fabricated in a multilayerLTCC process

A novel technique is presented for the accurate, rapid, high frequency, predictive modeling of parallel plate capacitors with gridded plates manufactured in a multilayer low temperature cofired ceramic (LTCC) process. The method is empirical in nature and is based on the concept of incrementally constructing the model for a structure from well characterized individual building blocks. Building blocks are characterized by the use of test structures and measurements, and are modeled using passive lumped circuit elements. This method is applied to the predictive modeling of deeply embedded gridded parallel plate capacitor structures. The procedure has been experimentally verified, with accurate predictions of behavior obtained up to the second self resonance for large area gridded parallel plate capacitors. Since lumped element circuits are generated by this method, structure prediction speed is determined by circuit size and simulator small signal analysis time. The method is versatile and is well suited for circuit design applications     

Numerical solution of electromagnetic problems

Modern high-speed digital computers have made possible the solution, by theoretical-numerical techniques, of many problems in electromagnetics that have traditionally been solvable only by experimental methods. Formulated in terms of integral equations, the techniques described yield answers, with an accuracy and completeness unobtainable by experimental methods, in a small fraction of the time and at much less cost than by the experimental approach. Computer programs utilizing these techniques have been developed in the areas of radiation and scattering from arbitrary wire-antenna structures, bodies of revolution, and cylindrical bodies of arbitrary cross section.     

Dual electromagnetic bandgap CPW structures for filter applications

A novel coplanar waveguide (CPW) low pass filter based on electromagnetic bandgaps (EBG) with double periodicity has been designed and fabricated. The device consists on a CPW with T-shaped loading capacitances at periodic positions and slot width modulation. By properly choosing the ratio between the two periods of the structure, a huge band gap (more than five times the bandwidth) is obtained through the suppression of spurious frequencies. The fabricated prototypes also exhibit very sharp cutoff, very low insertion loss in the passband and slow wave effect.     

Accurate modeling of line-defect photonic crystal waveguides

An accurate three-dimensional method to calculate the Bloch modes of photonic crystal (PhC) waveguides is proposed. Good agreement with available experimental and numerical data is obtained. The originality of the method lies in the fact that the Bloch modes are seen as the electromagnetic fields associated to the complex poles of an in-plane transversal scattering matrix. In comparison with previous approaches, the computational domain discretized is smaller and a higher accuracy for the losses of PhC waveguides is achieved.     

Accurate silicon dummy structure model for nonlinear microwave FinFET modeling

The dummy test structures based de-embedding techniques allow one to quickly subtract out part of the parasitic contributions from the microwave transistor measurements without the need of explicit determination of the associated circuit model. But this means that the problem of determining the complex network representing the dummy structures is only by-passed rather than solved. Consequently, this paper is aimed at extracting accurate lumped element models for silicon “open” and “short” structures in order to extend the nonlinear microwave modeling of on-wafer FinFETs at the calibration plane corresponding to the probe tips without need of any shift of the reference plane.     

Higher order hierarchical Legendre basis functions for electromagnetic modeling

This paper presents a new hierarchical basis of arbitrary order for integral equations solved with the method of moments (MoM). The basis is derived from orthogonal Legendre polynomials which are modified to impose continuity of vector quantities between neighboring elements while maintaining most of their desirable features. Expressions are presented for wire, surface, and volume elements but emphasis is given to the surface elements. In this case, the new hierarchical basis leads to a near-orthogonal expansion of the unknown surface current and implicitly an orthogonal expansion of the surface charge. In addition, all higher order terms in the expansion have two vanishing moments. In contrast to existing formulations, these properties allow the use of very high-order basis functions without introducing ill-conditioning of the resulting MoM matrix. Numerical results confirm that the condition number of the MoM matrix obtained with this new basis is much lower than existing higher order interpolatory and hierarchical basis functions. As a consequence of the excellent condition numbers, we demonstrate that even very high-order MoM systems, e.g., tenth order, can be solved efficiently with an iterative solver in relatively few iterations.     

近场电磁散射特点及其对建模要求

介绍了近场电磁散射问题,从电磁散射角度阐释当前对近场特性认识上的分歧,分析近场电磁散射问题中局部照射与探测器及动态过程关联密切等特点.根据近场特点提出了对建模中目标模型、电磁算法以及计算特性类型等的一般要求,同时提出了一种基于基础近场散射问题与探测器去相关的建模方式,并针对典型弹载雷达探测情况,给出了近场动态散射建模中运动模型、天线模型以及动态采样等具体要求.