Equivalent Circuit Synthesis Research Articles

Transient simulation of nonuniform coupled lossy transmission lines characterized with frequency-dependent parameters. I. Waveform relaxation analysis

Presents a waveform relaxation technique for simulating the transient response of nonuniform coupled transmission lines which are characterized with frequency-dependent parameters. The method consists of iterative waveform relaxation analysis of asymmetric disjoint resistive networks constructed with voltage-dependent voltage sources generated by applying the fast Fourier transform (FFT). The method requires neither convolution integration nor synthesis of lumped equivalent circuits for the simulation of the frequency-dependence of transmission-line parameters. Transient responses of uniform and nonuniform coupled transmission lines with and without skin-effect parameters and terminated with linear and nonlinear loads are simulated for illustration. The accuracy and efficiency of the relaxation technique are substantiated with exact analytical solutions and experimental data.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Optimal second-order small-signal model for long- and short-channel three-terminal MOSFET/MODFET wave equation

An optimal second-order small-signal model is developed for the long-channel three-terminal MOSFET/MODFET wave equation. The resulting Y parameters admit the correct fourth-order frequency power series expansion and exhibit a graceful degradation at high frequencies compared to a previously reported second-order model. This model can be integrated in the velocity-saturated MOSFET/MODFET equivalent circuit and is demonstrated to greatly improve the frequency range of validity of this short-channel model. The excellent results obtained demonstrate the validity of both the equivalent-circuit synthesis procedure and the correctness of the equivalent circuit proposed. >

Synthesis of equivalent circuits for inductive strips in homogeneous finline: W/b = 1

AbstractThis article describes a procedure for synthesizing equivalent circuits for inductive strips in homogeneous finline with W/b = 1. Values of strip scattering coefficients predicted by the circuit model are shown to be in excellent agreement with the scattering coefficients predicted by a spectral domain electromagnetic model.

Equivalent circuit synthesis for a loop antenna based on the singularity expansion method

The singularity expansion method (SEM) is used to derive active equivalent circuits for a plane-wave-excited loop antenna immersed in a lossless and homogeneous medium. The circuits consist of simple modules associated with the dominant pole pairs of the loop, and circuit element values are expressed in terms of the SEM data. Particular attention is paid to the issue of physical realizability. The synthesized circuits have been analyzed under various excitation and loading conditions by a general-purpose circuit analysis code, and the results agree favorably with the responses of the loop computed by other means

Analysis and Design of A High Directivity Compact Waveguide Coupler Using 3-Hole Aperture Array

A new approach for designing a multi-hole-waveguide coupler for X-band is proposed. Levy analysed two-hole aperture and used it for designing a high directivity multi-hole coupler. The present analysis is done for 3-hole aperture and it has been incorporated in designing a multi-hole high directivity compact coupler. The method of analysis and design is partly from Shelton, Hensperger and Levy. An equivalent circuit synthesis technique and distributed low-pass prototype Alter design method was followed for the analysis of 3-hole aperture and for designing the multi-hole compact coupler respectively. It has been possible to achieve a directivity greater than 38 dB in a length of 17.5 cm.

ON THE CLASS 1 COUPLING COEFFICIENT PERFORMANCE IN THE SEM EXPANSION FOR THE CURRENT DENSITY ON A SCATTERING OBJECT

ABSTRACT It has been pointed out by several workers that the class 1 coupling coefficient form of the SEM expansion for the current density on a scattering object tends to be numerically unstable in the early time, before the leading edge of the incident field clears the object. The class 1 form is computationally more attractive than the more reliable class 2 form; it is also the form mandated in some applications as, for example, in the SEM equivalent circuit synthesis. This paper presents a numerical evidence that the class 1 coupling coefficient form yields good results provided the time origin of the problem is placed at the observation point. It is concluded that the assessment of the practical utility of the class 1 coupling coefficient form prevailing in the literature is, perhaps, too pessimistic.

Application of Prony's method to time-domain reflectometer data and equivalent circuit synthesis

The singularity expansion of time-domain reflectometer data has been computed and used to calculate lumped-element equivalent circuits for the impedance of some typical antennas. Prony's algorithm was used to obtain the poles of the antennas' terminal voltage waveform due to a step-like excitation. The residues, however, were calculated subject to the uniform-error norm instead of the least-squared-error norm. Although it requires much longer to calculate, the uniform-error norm approximation is often orders of magnitude better than the least-squared-error approximation. The physical realizability of impedance functions obtained from experimental data has been investigated. Also, the procedures necessary to synthesize the lumped-element network have been evaluated. A simple partial-fraction expansion of a realizable impedance function representing an antenna was found to yield nonrealizable element values. A general network synthesis procedure, such as Brune's method, is required.

Transformer Couplings for Equivalent Network Synthesis

It may be shown that regardless of the type of analogy chosen (“impedance” versus “mobility”), disconformity will be encountered in synthesizing the equivalent network of a mechano-acoustic array. A method is described employing transformer couplings for getting around this difficulty. As a result, it becomes possible to construct equivalent circuits of mechanical arrays in a simple and straightforward manner by the method of impedance analogy. Similar benefits are achieved for the method of mobility analogy in the synthesis of equivalent circuits of acoustic arrays. Equivalent networks for certain mechano-acoustic arrays which cannot be conventionally synthesized become feasible through this method.

Transformer Couplings for Equivalent Network Synthesis

It may be shown that regardless of the type of analogy chosen (“direct” versus “inverse” or “mobility”), topological disconformity will be encountered in synthesizing the equivalent network of an mechano-acoustic array. A method is described employing transformer couplings for getting around this difficulty. As a result, it becomes possible to construct equivalent circuits of mechanical arrays in a simple and straightforward manner by the method of direct analogy. Similar benefits are achieved for the method of inverse analogy in the synthesis of equivalent circuits of acoustic arrays. Equivalent networks for certain mechano-acoustic arrays which cannot be conventionally synthesized become feasible through this method.

Transformer Analogs of Diaphragms

The use of the conventional analog for diaphragms in equivalent circuits often causes serious difficulties. The action of a diaphragm is shown to be analogous to that of a system of ideal transformers, each corresponding to an area of the diaphragm. The ancillary concept of “acoustical ground” analogy is introduced to facilitate synthesis of equivalent electrical circuits. The analysis includes equivalent circuit representations of a piston diaphragm, multiple diaphragms, diaphragms with subdivided sides, and articulated diaphragms, etc., together with examples. Simultaneous use of the transformer analogy of diaphragms and the transformer analogy of transducer couplings is treated in the Appendix.