Dual Circularly Polarized X-Band Feed of 3.6m Radial Rib Reflector Antenna for Payload Data Download Application

In this paper, the design of X-Band dual circularly polarized data transmission feed for a 3.6m Radial Rib Antenna (RRA) is presented. The RRA as a common reflector in cassegrain configuration can be used for both payload and data transmission application. The configuration comprises of a nine antenna feed system where the eight linear polarized elements provides payload data and the extreme 9
^th
element is used to download the payload date to ground stations. The data transmission is in dual circular polarization for frequency reuse. The designed central feed has good circularly symmetric co-pol patterns with a taper of -1.7dB at ±17.5° and isolation better than 20dB over 10% bandwidth. This element provides cross-pol isolation by better than 25dB at the required frequency (8-8.4 GHz) to support dual circular polarization for frequency reuse application. The criticalities involved in the design associated with the feed location are thoroughly discussed in this paper.