Design and emissivity meterage of 3mm microwave blackbody

The configuration design and the meterage data of 3 mm microwave blackbody are presented. The blackbody can be used in 75 GHz to 110 GHz or higher frequency and its emissivity is more than 0.996. Because the emissivity of microwave blackbody is close to one, namely its reflectance almost equals zero, the directivity error of directional coupler and the antenna reflection will make it is difficult to measure the emissivity directly. Hence, we use the space reflection method of moving DUT to measure reflectance of microwave blackbody. In this method, the reflectance of measurement system is equivalent to a big stationary wave and the reflectance of black body is equivalent to a small stationary wave. By using moving blackbody, we can separate the two stationary waves. The emissivity of blackbody is given by friis formula including some near field parameters. The measurement results are presented in section 5.