Analysis of a four parallel wire antenna system by the spatialFourier transform method

The electromagnetic fields and currents associated with an infinite four parallel wire transmission line are analyzed through the use of the spatial Fourier transform method. The near and far electromagnetic fields and currents that are associated with frill and gap voltage excitations are analyzed by the Fourier transform method. Possible VHF compact range applications of a four parallel wire antenna system are discussed, including the possibility of simulating an off-axis EM plane wave by the appropriate adjustment of the exciting voltage phase on each of the four parallel wires. Comparisons of Fourier transform method solutions with method-of-moments solutions and finite-difference-time-domain solutions are made for an infinite four parallel wire antenna system     

J. H. Kulick, J. M. Jarem, R. G. Lindquist, S. T. Kowel, and M. W. Friends are with the Department of Electrical and Computer Engineering, University of Alabama in Huntsville, Huntsville, Alabama 35899

The development and modeling of a liquid-crystal phase grating for real-time diffractive three-dimensional displays are discussed. The system being developed, which is called the ICVision system, utilizes a number of ideas that will result in a rugged, low-power three-dimensional display offering both vertical and horizontal parallax and eventually full color. Fringing fields created between interdigitated electrodes formed on top of VLSI die will induce a diffraction pattern in a thin layer of liquid crystal that will cover the die. A detailed electrostatic and diffraction analysis of liquid-crystal phase-grating regions that will make up the final display is given here. The electrostatic analysis is developed by use of the method of moments. The diffraction analysis is developed by use of rigorous coupled-wave diffraction theory. The numerical results obtrained from the mathematical model are compared with experimental diffraction results from preliminary LCD cells that have been assembled as prototype ICVision devices.     

A bound on the multiple scattered power from a plasma medium

A measure of the validity of the first Born approximation for scattering from an inhomogeneous plasma is obtained. This measure is derived using the inequalities appropriate to quadratically summable functions and bounded operators. A simple upper bound for the ratio of multiple scattered power to first Born power is derived as a function ofB, the sufficiency condition for the convergence of the series.     

Electromagnetic field analysis of a four-wire anechoic chamber

The electromagnetic field characteristics and plane-wave generating ability of a parallel four-wire anechoic chamber which is to be operated in the VHF range is analyzed. The analysis considers three cases: the first is a four-wire chamber when only a thin layer of absorber material covers the chamber walls, the second is a four-wire chamber when only free space surrounds the four wires of the system, and the third is a four-wire chamber when a thick layer of absorber material covers the anechoic chamber walls. The three cases are analyzed by a variety of mathematical methods including the method of moments, waveguide theory, and a finite-difference time-domain method. Numerical results for the propagation constants and electromagnetic fields that are generated in the chamber in the three cases are presented     

The input impedance of a hollow-probe-fed, semi-infiniterectangular waveguide

Image theory is used to determine the input impedance of a coaxial feed in a short-circuited, semi-infinite, rectangular waveguide. The analysis is applicable to hollow antenna probes of variable height and lends itself well to accurate numerical evaluation. The numerical results are compared to results obtained from other methods and show the efficacy of using image theory to determine the waveguide input impedance     

Pattern synthesis of cylindrical slot antenna

A constrained synthesis procedure is applied to the cylindrical slot antenna. Sets of orthogonal eigenfunctions are generated to represent the aperture and radiation fields. The error criterion is that of the minimum mean-square match and the super-gain ratio represents the source constraint. The method is illustrated for the cosecant pattern.     

A method of moments analysis and a finite-difference time-domainanalysis of a probe-sleeve fed rectangular waveguide cavity

A multifilament method of moments (MOM) analysis and a finite-difference time-domain (FE-TD) analysis are used to numerically calculate the input impedance of a probe-sleeve fed rectangular waveguide which has been short-circuited on one side. The input impedance of the system is determined by using the above methods for several probe-sleeve configurations, and reasonable agreement between the two methods for the cases studied is found. An MOM Green's function formulation which is based on scattering superposition and which allows the input impedance of a probe-sleeve feed to be calculated when the waveguide is terminated in a given load is derived. The MOM results and FD-TD numerical results are compared for this loaded waveguide input impedance case, and reasonable agreement between the methods is found. A comparison of theory and experiment is given for when the waveguide is terminated in a ground plane aperture     

Strip and line source synthesis with a quality factor constraint

Rhodes' antenna synthesis method is extended and modified to include strip source antenna systems that are optimized for a given value of a quality factor. A set of biorthogonal aperture functions, which happen to minimize the quality factor functional of the antenna, are shown to have a finite Fourier transform that is doubly orthogonal over the invisible and visible ranges of the radiation pattern. The biorthogonality properties of the above functions as well as the double orthogonality properties of the finite Fourier transforms of these functions are shown to lead to a synthesis method that is numerically identical to Rhodes' but which handles a more general class of antennas.