On the Reflectivity Measurements of Microwave Blackbody in Bistatic Near-Field Configuration

Determining the total reflectivity of a manufactured microwave blackbody is a significant problem for the microwave radiometer calibration. In this work, the authors report the progress in testing the standard facility for microwave blackbody reflectivity determination in China. Following a bistatic configuration, the facility is designed to measure the Floquet scattering properties of the array-shaped microwave blackbody, and then based on that, the total reflectivity is extracted, covering a vast frequency range from 6 to 500 GHz. In this work, the key configurations of the facility design, the testing procedures, and the data processes are demonstrated. And the measured results validate the ability of the standard facility in capturing weak Floquet scattering from blackbody targets. Two typical types of array-shaped blackbodies, coated cones, and coated pyramids are included in this study. In the results, the effects of manufacturing imperfections on the measured scattering as well as the total reflectivity are investigated. Furthermore, it is shown in the results of 364, 380, and 452 GHz that the issue of referencing target is worthy of further investigation at very high frequencies. The presented design, testing procedure, and measured scattering properties provide direct reference for the blackbody reflectivity determination in the microwave radiometer calibration applications.