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We describe a radiometer intended for use in the spectroradiometric complex for remote sensing of the Earth's atmosphere. The main feature of the radiometer is application of an electrically controlled modulator-calibrator allowing one to perform measurements and thermal calibration in a wide temperature range without using matched loads and means for their connection. The principle of operation and design of the modulator-calibrator are described and the characteristics of the radiometer and its separate units are presented.

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This paper presents a comparison of simple self-consistent theory data and experimental results aimed to study the influence of the anode voltage on the frequency of the subterahertz gyrotron with the goal of frequency stabilization. Numerical simulations of the electron beam formation and beam-wave interaction in a 0.26 THz gyrotron are performed. The experimental dependence of the gyrotron frequency tuning on mod-anode voltage is in agreement with theoretical predictions.

We develop terahertz mixers with monolithic integrated circuits containing balanced, series and antiparallel pairs of Schottky diodes. The designs of these mixers and a method for studying their parameters are described. The best results are obtained for the antiparallel diode pair. In this case, the double-sideband noise temperature of the receiver amounts to 5600-7500 K when operating at the second heterodyne-oscillator harmonic near the frequency 0.71 THz.