An All Solid-State 1 THz Radiometer For Space Applications

Abstract

A heterodyne receiver at 1 THz is described, whose components are waveguide mixer and frequency multipliers with Schottky-diodes as mixing and multiplying elements. Most important is the breakthrough in local-oscillator development: The power at the fundamental frequency is generated by an InP-Gunn-Oscillator which delivers 70 mW at 111.2 2 GHz. The output power from two cascade triplers (at the 9th-harmonic) was 60 1.1W (min.) Coupling of signaland I—O.-power is achieved by a Martin-Puplett Interferometer. System noise temperature was determined with absorbers at room temperature and 77 K yielding Tsys = 8800 K (DSB) and total conversion loss = 13dB. Atmospheric losses appear to account for half of the noise temperature and 3dB conversion loss. The mixer is prepared for cooling to liquid nitrogen from which we hope for a further reduction in system noise of approximately a factor of two.