Ray phase verification at the Cassegrain antenna aperture

Abstract

Large sections in textbooks and monographs on antenna technology, as well as publications in numerous periodicals are devoted to Cassegrain two-mirror antennas. In them it is possible to find various ratios for calculating the dimensions of the structural elements of the antenna system, which, at the same time, need preliminary verification of their accuracy by checking of the ray phase at the exit of the paraboloid aperture. In addition, it is necessary to develop a procedure for assessing the sensitivity of the system to the phase mismatch of the output rays at the antenna aperture caused by the deviation of the actual dimensions of the structural elements from the calculated ones. The purpose of the article is to develop a methodology for estimating the in-phase output rays at the aperture of the Cassegrain antenna parabolic mirror at the calculated values of the design parameters, as well as when they deviate from the nominal values. A simple method of computer-aided configuration construction of the ray structure in a two-mirror Cassegrain antenna has been developed. The influence of the deviation of the emitter position from a given starting point, as well as the shift of the focus of the counter-reflector from the focus of the parabola on the phasing of the rays has been investigated. The presented methodology makes it possible to verify the applicability of the calculated ratios borrowed from the literature. The presented method of estimating the common phase of the rays at the aperture of the Cassegrain antenna may be useful for the rapid verification of the ratios used in the design of its geometric structure. Also it can be used to estimate the permissible deviations of the geometric dimensions of the elements from the nominal values. Finally, the visibility of the focus graphic illustration facilitates the rejection of obviously unacceptable antenna implementation options.