Circularly Polarised X-Band H11- and H21-Modes Antenna Feed for Monopulse Autotracking Ground Station : Invited Paper

This paper covers results of full wave analysis and optimization of electrical performance of key components of the multimode circularly polarised X-band monopulse feed, namely, the wideband circular corrugated horn supporting propagation of hybrid modes HE11 and HE21, the wideband multiholes directional coupler of orthogonal modes H21 and the wideband compact septum polariser. Also, results of design and laboratory testing in anechoic chamber of the whole manufactured monopulse feed prototype in the frequency range 7.7-8.5 GHz are presented. The simulated and measured results show that the developed feed has excellent sum and difference channels radiation patterns, high isolation between these channels and high crosspolar discrimination. Therefore the proposed feed can be considered as a promising candidate for application in ground station reflector antennas to provide capability of high accuracy autotracking and reception of high data rate information in both right hand circular polarisation (RHCP) and left hand circular polarisation (LHCP) from low Earth orbit (LEO) satellites.