A microwave radiometer for measuring signals with a low effective noise temperature

Abstract

A modulation microwave radiometer using a combined pulse modulation with automatic zero balance control is described. For measurements of signals with a low noise temperature, the radiometer realizes the method of shifting a measurement range toward lower temperatures by using reference noise signals with a high effective temperature. The whole measurement range in a low-temperature region up to 0 K is divided into subranges. The subrange width is 20 K, and the measured resolution is 0.075 K, which corresponds to the fluctuation sensitivity of the radiometer for a 1-s acquisition time.