Compact V-band overmoded mode-selective coupler with diamond apertures

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.