Wideband Microwave Calibration Target Design for Improved Directional Brightness Temperature Radiation

In this letter, the recent progress in optimizing the microwave calibration target is reported. Based on the former findings on the wideband reflectivity of the target and the analysis model for the directionally radiated brightness temperature, the authors further investigate the comprehensive optimization in both the aspects of electromagnetic and thermal properties. Specifically, a design instance with a thinner coating at the tip and thicker coating at the bottom is concluded and optimized for stable wideband performance, without introducing further difficulties in manufacturing. The performance of the new design is compared to that of traditional uniform coating, in terms of total reflectivity, temperature gradient, and, finally, the brightness temperature toward the normal direction. Results show the comprehensively improved performance of the new design, which can be a good reference for practical applications.