Ka-band cryogenic low-noise receiver of the Misasa 54 m antenna for deep-space communications and radio astronomy

Abstract We built a Ka-band dual-circular-polarization low-noise receiver for the Misasa 54 m parabola antenna in Misasa, Japan. The antenna is designed to be combined with a transmitter and receiver system at the X band (around 8 GHz) and simultaneously with a receiver system at the Ka band. The Ka band is the frequency band around 30 GHz, which is important for deep-space communications and radio astronomy. The receiver comprises some waveguide components including a feed horn, a circular polarizer, and low-noise amplifiers. The components are installed in a vacuum vessel and are cooled to 4 K with a Gifford–McMahon refrigerator, providing low-noise performance. The receiver is capable of simultaneously handling the left- and right-hand circular-polarization (LHCP and RHCP) channels. The receiver-noise temperature was measured to be TRX ≃ 14 K in both the LHCP and RHCP channels. The system-noise temperature, including the antenna loss and atmospheric attenuation at the zenith, was measured to be Tsys = 36–37 K in both the LHCP and RHCP channels on a clear day in September at Misasa. When the receiver is used with the X-band transmitter, the system-noise temperature is maintained at Tsys ≃ 42 K in the RHCP channel. The degradation in the system-noise temperature is attributed to a frequency-selective reflector, which divides the signals in the X and Ka bands. There is no contamination from the transmitter to damage the receiver. The receiver has already been in use for deep-space communications and radio-astronomy observations. Our team in the radio-astronomy laboratory of ISAS/JAXA is responsible for the development of the receiver and the measurements of its performance.