W-band Microstrip-to-Waveguide Transition without Back-short Structure

A W-band microstrip-to-waveguide transition without back-short structure is presented in the article. It consists of three parts, which are the microstrip line, the coupling-matching structure, and the rectangular waveguide. The planar coupling-matching structure replaces the coupling probe and the back-short end in the traditional waveguide. So this microstrip-to-waveguide transition is fairly compact for W-band applications when integrated with active circuits and chips. The designed model is optimized in full-wave simulations. Simulated results show that the microstrip-to-waveguide transition has good matching characteristics. It achieves an impedance bandwidth from 88.6 GHz to 99.1 GHz when the return loss below -10 dB.