Miniaturized Terahertz Heterodyne Radiometer With 183-GHz Subharmonic Mixer and 91-GHz Frequency Tripler for Water Vapor Sensing in CubeSat

Terahertz (THz) radiometers are prominent tools in water vapor sensing in space applications. In this work, a 183-GHz heterodyne radiometer payload is proposed for detecting water vapor on extraterrestrial planets. The THz radiometer is based on Schottky diodes and an optimized design. It mainly consists of a 183-GHz subharmonic mixer (SHM) and a 91-GHz frequency tripler. The 1<sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</small>–11-dB conversion loss of the mixer and 5% conversion efficiency of the frequency tripler could be competent in the detection application. The practical THz radiometer is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10\times 10\times 10$ </tex-math></inline-formula> cm3, less than 500 g, 1.3 W power consumption, 0.1 K radiometric sensitivity, and 1 K accuracy for detecting water vapor. Subsequently, compared with the existing radiometers, the proposed THz radiometer is miniaturized, has low power consumption, and has reliable sensitivity in a CubeSat.