A 17:1 Dual Band Circularly Polarized Focused Two-Channel Monopulse Tracking System

Abstract

This paper describes a dual circularly polarized feed system for operation In incremental bands over the frequency range from 136 to 2300 MHz. The characteristics of a 60-foot parabola excited by the feed system are discussed. Tracking data for this system have also been obtained using a helicopter, the Apollo VIII vehicle, and Cassiopeia A. It will be shown that the two-channel monopulse technique allows the use of antenna feeds which, in turn, provide sidelobes of greater than -20 db relative to the main lobe peak for all frequencies. This sidelobe performance reflects the fact that the feed is approximately focused at all frequencies, unlike its earlier log periodic type predecessors. The characteristics of a similar feed used in the Apollo Range Instrumented Aircraft (A/RIA) will also be described in this paper.