Dual reflector zoom antenna based on optical imaging theory for satellites in elliptical orbits

This paper describes a Ka band dual reflector zoom antenna where the Half-Power Beamwidth (HPBW) can be varied dynamically. The goal is to compensate the variation of the coverage area as the satellites traveling in highly elliptical orbits. The proposed zoom antenna contains a parabolic main reflector and a spherical subreflector fed by a fundamental mode circular waveguide. By rearranging the location of subreflector and feed, the HPBW can be broadened by about 6.8 times. The design process by using optical imaging theory is also presented. Finally, the GRASP simulation is provided to validate the antenna's performance.

I. Introduction

In the case of a single reflector, zooming can be achieved by defocusing effect [1]. By moving the feed along the boresight of the reflector, the HPBW can be broadened by up to 5 times. However, nulls will appear close to the beam center with the increase of feed displacement, which limits its zoom range.