Total Power Radiometer for Microwave Noise Measurement

Abstract

Two types of radiometers are generally used for microwave noise measurements. One is a total power type and the other is the Dicke type. The former is theoretically the most sensitive and more broadband in frequency, but it is slightly unstable and worse in the linearity of the receiver gain. From the viewpoint of realizing a broadband radiometer, the total power type has been adopted for precision noise measurements. In order to reduce the influence of non-linearity, a differential detection scheme has been employed in the detection section. And also in order to reduce the instability of the gain, the temperature of the front end section and the IF and detection section has been stabilized with circulated warmed water. Based on these ideas, a new microwave radiometer has been built. In addition a new equation of the output indication for the total power radiometer has been derived. By using this equation, an equation has been derived for making noise calibration and several equations have been derived for measuring parameters indicating the characteristics of the radiometer, which are important to perform precision noise measurements. And the effectiveness of the radiometer has been proven experimentally using these equations.

Evaluation of a cryogenic coaxial noise source based on the calibration method by single auxiliary transmission line

“…In this paper, we have proposed an improving method of [3] by using an auxiliary transmission line (ATL), and constructed a cryogenic 7-mm coaxial noise source for experimental evaluation. The totalpower radiometer developed by NMIJ [4] was used for verifying the ATL method, and basic properties of the noise source were evaluated over the range of 8-12 GHz. The available power ratio of the transmission line of the noise source was estimated by a vector network analyzer (VNA) using the ATL in cryogenic condition.…”