NASA ultra low noise X-band microwave feeds for deep space communication

This work describes the configuration, detail design, and final performance of a new ultra low noise diplexed X-band microwave feed system, called X/X diplexing feed, for the deep space network (DSN) 70-m antennas. In this microwave feed, the transmitter signal is combined with the receive signal in a diplexing junction placed near the input of a wide-band feedhorn. This configuration allows the majority of the components in the receive path to be placed in a cryogenically cooled container resulting in a major reduction in the noise temperature of the feed. Combined with a low noise HEMT amplifier this feed provides the lowest noise diplexed feed in the DSN. The total noise temperature of the 70-m antennas at zenith with this feed is approximately 14.6 K.