All Solid-State Radimeter at 557 GHz

An all solid-state radiometer is described, for detecting the 557 GHz transition of the water molecule in galactic molecular clouds. The radiometer will be mounted in a high altitude balloon, and is the first of several such units for different experiments in the 550-700 GHz range. The key semiconductor elements are a gunn diode and three Schottky-barrier diodes - two varactors and a low-capacitance low-noise varistor. The double-sideband system noise temperature ature is 2000 K over a 1.1-1.7 GHz i.f. band, and 1500 K over 100 MHz at midband.