A Zero-Balance Microwave Radiometer with Additional Postdetection Pulse-Width Modulation of the Reference Signal

摘要

A switching radiometer operating in the zero-measurement mode is considered. This operating mode is produced by postdetection separation of the antenna signal and the signal from the reference noise generator into two channels and an additional pulse-width modulation of the reference signal. High-frequency symmetrical and low-frequency pulse-width modulations are synchronized by a digital control unit. The duration of the width-modulated signal is shown to be directly proportional to the measured antenna signal and linearly related to it. After calibration by two reference (standard) noise generators, the radiometer is tuned to operate in the desired measurement range by adjusting the signal attenuation in low-frequency channels.