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A new finite plane wave series expansion for spherical wave functions of the first kind is presented in this paper. The formulation converts the spherical wave function described in the spherical coordinate system into a series of plane wave functions represented in the Cartesian coordinate system. The series expansion will be very useful in modal analysis of three dimensional guided wave structures and scatterers containing planar boundary surfaces. For a given range of orders m and degree n and for a region with [bar]r < R, the same set of plane waves can be used. The theory is numerically verified for a wide range of parameters, showing its fast convergence characteristics. The plane wave expansions of the vector multipole fields can also be obtained. Index Terms--Electromagnetic theory, guided waves, modal analysis, scattering, waveguide.

A new technique for the design of a thinned, linear, multiplicative array which directly measures the principal solution of a radio source distribution is described. The original filled multiplicative array with uniform element spacing l is first generalized to an array of [N.sub.1] + 1 subarrays each with [M.sub.1] + 1 elements. A thinning factor of 1/2 is shown to be possible if [M.sub.1] = [N.sub.1]. Finally, if each subarray is further divided into smaller subarrays until the smallest are simple two element interferometers, then the principal solution can be directly measured but with far fewer elements. Significant thinning factors are achieved when the array is very large. The method can also be used to measure the principal solution with planar arrays with very strong thinning occurring for large arrays. Index Terms--Multiplicative phased arrays, radio source mapping, thinned arrays.

A study was conducted to analyze a full-wave electromagnetic framework for examining the waveguide discontinuities of arbitrarily shaped piecewise planar boundaries. The finite plane-wave series expansion of circular cylindrical modal functions was utilized to carry out the analysis. Several waveguide components were then examined. Results indicated that the analytical expressions for the elements of the field-matching matrix supported the accuracy and efficiency of a full-wave model.

An efficient numerical technique based on the modal-expansion method in conjunction with a recursive algorithm is developed for a multilayer insulated monopole antenna fed by a coaxial transmission line. The modal-expansion analysis is facilitated by introducing a perfectly matched boundary (PMB) at a variable height over the ground plane of the monopole. The current distribution and input admittance are computed by finding the expansion coefficients of the electromagnetic field expressions. Numerical results for the input admittance of a dielectric-coated monopole antenna and an air-insulated monopole are compared with experimental ones available in the literature. Good agreement is achieved. Calculated results for the effects of various parameters on the input admittance of an air-insulated monopole antenna are presented and discussed. Index Terms - Monopole antennas.

A formally exact full-wave solution is presented for the problem of scattering at a nonchiral-chiral interface in a coaxial waveguide. The field components for the axisymmetric modes in a coaxial chirowaveguide are initially obtained. A new orthogonality relation for the modes is then proposed and used to find expansion coefficients for the electromagnetic fields in the coaxial chirowaveguide. The scattering matrix for the nonchiral-chiral dielectric discontinuity in a coaxial waveguide is finally derived by enforcing the continuity conditions of the tangential field components across the interface. Numerical results for the reflection and transmission coefficients at the nonchiral - chiral interface in a coaxial waveguide are presented. Index Terms - Chiral material, mode-matching method, waveguide discontinuity.

A rigorous analysis is obtained for the problem of scattering at the junction of a cross-shaped waveguide and a larger circular waveguide. The general case of an arbitrary offset and orientation of the cross waveguide axes is considered. The fields matching over the cross aperture of the smaller guide is facilitated by using the transformation of the circular cylindrical Bessel-Fourier modal fields of the circular guide into a finite series of exponential plane wave functions. This permits an analytical finite series solution for the elements of the fields mode matching matrix, from which the general scattering matrix of the junction is obtained. The application of the formulation to circular waveguide filter design is emphasized in the numerical examples. Excellent agreements between theoretical and experimental results are obtained in all the numerical examples. Index Terms - Modal analysis, waveguide filter design, waveguide junction.

A rigorous modal-expansion analysis. is developed for obtaining the current distribution and input impedance of a sleeve-monopole antenna fed through an infinite ground plane by a coaxial line. A 'perfectly matched boundary,' which is simply the combination of an electric wall and a magnetic wall, is initially proposed to facilitate the modal-expansion analysis. The walls are parallel to the ground plane at a variable height above it. Expansion coefficients of the electromagnetic fields are then determined by enforcing the boundary conditions at conducting surfaces and regional interfaces. Numerical results for the current distribution and input impedance of the sleeve monopole are presented and compared with available data in the literature. Very good agreement is observed. Also examined are the radiation pattern for different sleeve lengths and the effects of the length and finite thickness of the sleeve conductor on the antenna's input impedance.

An improved modal expansion method is described for the scattering matrix of a cascaded network which consists of an enlargement junction combined with a reduction junction. The new method can significantly reduce computation time and requirement of computer memory. Application to iris coupled waveguide cavity filters is demonstrated. Numerical results for a rectangular waveguide cavity filter are given.

The input admittance of a thin prolate spheroidal dipole antenna of major and minor axes a, b and fed by a gap of finite width 2d operating at the wavelength [Lambda] (k - 2[Pi]/[Lambda]) is expressed as a very slowly convergent sum of symmetric prolate spheroidal angle and radial modal functions whose computation in this paper is facilitated by a novel method for evaluating radial functions of the second kind for small and large order with high accuracy. Then, by using Infeld's method of replacing a sum by an integral, the slowly convergent part of the admittance is evaluated. Three different types of distributions for the gap electric field are considered, and numerical results for the admittance are given as a function of the spheroidal dipole's length (0 [less than or equal to] 2a [less than or equal to] [Lambda]) with its thickness (2b [greater than or equal to] 2 x [10.sup.-5] [Lambda]), as well as the gap ratio d/b, as parameters.

This paper presents a simple but effective method for the analysis of open-ended waveguides. The method begins with the introduction of a large waveguide to approximate the half-space. In order to avoid the convergence problem lossy dielectric is assumed to homogeneously fill the large waveguide. After obtaining a number of convergent data for different values of the loss tangent an extrapolation technique is employed to calculate the solution to the original problem - a waveguide terminated by an infinite conducting flange and radiating into a lossless or low-loss half-space. Numerical results are given to show the validity of the proposed method. The behavior of the effect of the loss tangent on the size of the large waveguide and on the final results are also examined. Index Terms - Modal analysis, open-ended waveguide, waveguide junction.

A full-wave analysis of an inhomogeneous waveguide region with both planar and circular cylindrical boundaries is presented in this paper. Circular cylindrical modal functions are used to represent the fields. Field matching on the planar walls and apertures is rigorously achieved by the finite plane-wave series expansion of each modal field, whereas the addition theorem for cylindrical waves is used for rigorous field matching on the circular cylindrical boundaries. Numerical results are given for rectangular waveguides with 90 [degrees] bends and rounded outer corners. Index Terms--Full-wave modal analysis, inhomogeneous waveguide functions.

The input impedance of a monopole antenna partially buried in an infinite grounded dielectric substrate and fed by a coaxial transmission line is calculated by the modal expansion method. The effect of the dielectric substrate on the antenna's radiated power and input impedance is numerically examined.

This paper describes a rigorous analysis of asymmetrical cylindrical dipole antennas by the modal-expansion method. The analysis is facilitated by introducing two parallel conducting plates to enclose the dipole antenna. Field expressions for all the subregions of the resulting structure can be readily derived, and the expansion coefficients are found by enforcing the continuity conditions of tangential field components across the regional interfaces. Comparison of computed results with experimental data shows an excellent agreement. Numerical results are also presented for the input impedances, current distributions, and radiation patterns of various dipole antennas. Index Terms--Antennas, asymmetrical dipole, modal-expansion method.