Study On Heterodyne Terahertz Quasi-optical Receiver Front-end And Its Test Method

Terahertz (THz) electromagnetic wave refers to frequency of0.3-10THz, thatcorresponding wavelength range of1mm-30um, which located in the middle ofmillimeter wave and infrared waves. The THz wave is difficult to generate and bedetected by the traditional method both electronic and optical. Terahertz band isbelieved to be a blank final electromagnetic spectrum, and called the THz gap. Withthe rapid development of THz technology, it has been applied in radio astronomy, theearth’s atmospheric observations, THz communication, high sensitivity of short-rangeradar system, medical and biological imaging, the earth’s environment monitoring andhigh-speed wireless network field. At present, THz imaging technology is a hotresearch field. THz detector with high sensitivity is an important part of THz imagingsystem. The development of infrared detectors and millimeter-wave receivers havebeen relatively mature, which detection theory based on Wien radiation law and thelaw of Rayleigh-Jones. The test methods of THz quasi-optical receiver front-end noisetemperature and THz quasi-optical mixer conversion loss and noise temperature isstill in the development stage. Therefore, study the test methods that apply to noisetemperature of THz optical receiver front-end and noise temperature and conversionloss of THz quasi-optical mixer is particularly important.This paper introduces the basic theory and the development of THz receiver atdomestic and abroad. Blackbody radiation theory has been studied to analyze theradiation characteristics of the THz waves. The test method of the noise temperatureof THz quasi-optical receiver front-end noise temperature and conversion loss andnoise temperature of THz quasi-optical mixer is optimized. The test system isdesigned and built successfully. This paper also studies the theory of weak signaldetection. The lock-in amplifier detect the IF signal by the technology of moving thespectrum. In this paper, the design of THz quasi-optical receiver front-end noisetemperature test platform is given to obtain noise temperature and conversion loss ofTHz quasi-optical mixer. Through preliminary theoretical analysis and experimentalverification, this paper analyzes the impact of external infrared wave to THzheterodyne room temperature quasi-optical receiver front-end work status.