Low-noise 460 GHz waveguide Schottky mixer radiometer for radioastronomy

We report measurements on a cryogenically cooled Schottky barrier diode mixer system at 460 GHz. The mixer and horn are electroformed in a single block, and the carcinotron local oscillator is coupled in through a polarisation diplexer. A double-sideband system noise temperature of 870 K was obtained at midband at 12 K ambient. The total RF/IF double-sideband conversion loss was 9.0 dB, measured at 295 K ambient.