Dual-Receiver Radiometric System for Near Field Measurements in Hyperspectral Mode

Abstract

The article presents a schematic of a microwave radiometric system that enables hyperspectral measurements for solving the objectives of near-field measurement. The radiometer functionality is based on the null method of measurement that ensures the invariance of measurements towards changes in the transmission factor and radiometer’s own noise. In the article we have described the newly developed hyperspectral microwave radiometer operation algorithm. The algorithm is based on synchronous amplitude and width pulse modulation that enables the equalization of the signal energy from the antenna in the microwave front-end of the radiometric system. Destabilizing factors in the operation of the developed microwave radiometric system for near-field measurements have been shown. The authors have described the mathematical model that takes into consideration the impact of the losses in passive front-end modules, the precision of thermostat control and the level of reflection coefficient on the measurement results. Based on the results of numeric modeling, it has been shown that to minimize measurement error down to ±0.1 K, equivalent front-end thermostat control precision and minimal losses in the front-end must be ensured and an antenna that allows for lowering the reflection coefficient down to 0.05 must be used.