Noise-Temperature Measurements of Deep Space Network Dichroic Plates at 8.4 Gigahertz

The addition of 7.2-GHz (X-band) uplink capability to Deep Space Network (DSN) 70-m antennas required the development of a new dual-band dichroicplate-type frequency-selective surface. This plate passes both the uplink and the 8.4-GHz (X-band) downlink signals. The plate contributes to the overall noise temperature of the antenna receiving system as well as e‐ciency loss. Tests were performed to measure the noise-temperature contribution of the plate. This article describes the measurements and the results. The results of noise-temperature measurements of the new dual-band plate and the existing narrowband design are presented. The efiect of the plate on antenna e‐ciency is also discussed. I. Introduction The Deep Space Network (DSN) 70-m antennas use dichroic-plate-type frequency-selective surfaces to separate the 2.3-GHz (S-band) and 8.4-GHz (X-band) downlink signals to achieve simultaneous S-/Xband operation. The 2.3-GHz energy is re∞ected ofi the flrst surface of the plate, and the 8.4-GHz energy is passed through. Until recently the plates only needed to pass 8.4-GHz downlink signals. The 70-m X-Band Uplink Project added the capability of 7.2-GHz (X-band) uplink operation. The addition of the uplink using the X-/X-band diplexed feed required a dual-band plate that will pass both the uplink signals at 7.2 GHz and the downlink at 8.4 GHz [1]. This article reports the results of measurements of the noise-temperature contribution of both the new dual-band plate and the existing plate.