Radiation by sources on perfectly conducting convex cylinders with an impedance surface patch

Abstract

Abstract : This report deals with an asymptotic high frequency analysis of the radiation patterns of a magnetic line source, or a magnetic line dipole, located on a uniform impedance surface patch which partly covers an electrically large perfectly conducting convex cylinder. This work is relevant, for example, to the analysis of fuselage mounted airborne antennas for satellite communication purposes. In the latter application impedance surface patches may be employed to increase the radiation intensity near the horizon over that which would ordinarily exist in the absence of any such impedance loading. In the present analysis, the impedance surface patch is represented as an equivalent aperture in the rest of the perfectly conducting convex cylinder. Approximate asymptotic expressions for the 'equivalent aperture distribution;' i.e., for the 'currents on the impedance surface patch' are developed in this work for the two source types; these expressions for the currents are valid in the neighborhood of the source. The radiation pattern of this configuration is then found in a straightforward manner by numerically integrating this current distribution in conjunction with a simple and accurate asymptotic high frequency form of the perfectly conducting, convex cylinder Green's function. Radiation pattern calculations based on this analysis are found to compare quite well with a numerical moment method type solution, a previous GTD solution for those impedances which support an Elliot mode, and also with some presently available experimental results.