A Ku/Ka dual-band dual-CP tracking feed

The current NASA TDRSS (Telemetry Data Relay Satellite System) provides service at S- and Ku-bands. The next generation TDRSS will extend the service to Ka-band, in addition to the existing S- and Ku-bands. One approach to achieve this enhancement is to replace the Ku-band feed assembly of the existing single access antennas (SAAs) with a new Ku/Ka dual-band feed. This approach has the advantage of minimum breakage to the existing hardware, which has seven flight heritage. The new Ku/Ka dual-band feed is required to provide efficient illumination on the deployable mesh reflector and perform the tracking function (in both Ku- and Ka-bands) and be capable of both RHCP and LHCP operations. In addition, the new feed assembly has to be sufficiently compact to fit into the existing feed tower so that the costly redesign of the reflector system and the deployment mechanism is avoided. This paper describes the design approach, the breadboard model fabrication, and the measured performance of such a feed assembly. The new feed is designed for the following operating frequencies: 13.775 to 13.805 GHz for Ku-transmit, 14.888 to 15.113 GHz for Ku-receive, 22.55 to 23.55 GHz for Ka-transmit, and 25.255 to 27.505 GHz for Ka-receive.