Concept of a Radiometer for Measurements of the Optical Depth of the Atmosphere in a 1.3-mm Window of Atmospheric Transparency

The article presents a concept of an uncooled subterahertz radiometer designed for estimating the atmospheric absorption in the 1.3-mm atmospheric transparency window, which can possibly operate under mountain expedition conditions. Estimation of the atmospheric absorption is based on radiometric measurements of the sky brightness temperature. A comparative analysis of two typical schemes of radiometer receivers (heterodyne and tuned radio frequency receiver schemes) was carried out based on the modern stage of development of the subterahertz electronic components. The noise temperature and fluctuation sensitivity of both schemes were estimated. The results of designing a horn–lens antenna with a radiation pattern of 3° at a level of –3 dB at a frequency of 230 GHz are presented. The general structure of the high-frequency part of the radiometer is described, including some design features that are necessary to provide continuous measurements in a wide range of climatic conditions.