Cryogenically cooled K‐band high electron mobility transistor receiver for radio astronomical observation
ABSTRACT A K‐band receiver using cooled high‐electron mobility‐transistor (HEMT) amplifiers was developed at the Nobeyama Radio Observatory (NRO). Remarkable reduction of receiver noise temperature T rec was obtained when it was cooled down to cryogenic temperature. The lowest T rec of 75 K was obtained at 23.4 GHz. This low noise characteristic reveals that the cooled HEMT amplifier is promising as a sensitive receiver for radio astronomical observations.