Calibration of a Tri-Band Microwave Radiometric System with Background Noise Compensation

Abstract

It is shown that for microwave radiometric systems for remote sensing of natural environments, the issue of unambiguous determination of the correspondence of the output signal to the value of the radio brightness temperature of the probed region, from which the physical parameters are estimated, is important. Microwave radiometric systems operate under external noise and background noise. This article explores the effect of background noise on the external calibration of a microwave radiometric system using an external “deterministic” noise signal source. The conditions for performing calibration in a system with compensation for the influence of background noise are analyzed. The analysis of the output signal of the microwave radiometric system showed a significant effect of background noise on the parameter that determines the reference origin of the receiver scale. The possibility of reducing the interference effect of background noise on the measurement results in a microwave radiometric system with a two-channel antenna operating on two modes of a circular waveguide is considered. It is shown that an additional compensation signal is formed at the antenna output. An analytical assessment of the degree of compensation of the influence of background noise on the output difference signal of the system is carried out. We perform a numerical analysis of the error of external calibration of a three-band microwave radiometric system with compensation of background noise when receiving thermal radiation to a common aperture of the antenna.