设计了一种用于测量V波段过模高功率毫米波源在线功率的选模耦合器。利用小孔耦合理论和微元法对菱形耦合缝隙进行了理论分析, 采用两组相同的菱形耦合缝隙实现选模功能, 缩短了耦合器长度, 增加了工作带宽。采用数值模拟的方法对耦合器结构进行优化设计, 模拟结果表明: 在60 GHz频点处, TM01模耦合度约为50 dB, TM02模耦合度仅为75 dB, 对TM02模的抑制度为25 dB; 在500 MHz带宽内对TM02模的抑制度大于15 dB, 1 GHz带宽内的抑制度大于10 dB, 可满足工作于TM01模的V波段高功率毫米波测试需求。同时针对工作于高次模TM0n(n=2,3,4,…)的器件设计了可抑制TM01模的耦合器, 为高次模工作的高功率毫米波器件的在线功率测量和模式诊断提供了技术方案。

A V-band mode-selective coupler is designed for measuring the output power of overmoded high power millimeter-wave generators. The small-hole coupling theory and infinitesimal dividing method are adopted to analyze the coupling characteristics of the diamond aperture which is applied to decrease the length of the coupler and increase the operating bandwidth. Meanwhile, mode selection can be achieved by setting two identical apertures. At the frequency of 60 GHz, the simulation results show that the coupling coefficient and directivity of TM01 mode are 50 dB and 75 dB respectively, and the suppression of TM02 mode is more than 10 dB. Besides, a coupler for measuring the output power of generators operating in high order mode is also presented in this paper, which is used to couple TM01 mode and suppress TM02 mode. The numerical calculation and simulation results show a good coherency.