Design of SIW Parallel Coupling Coupler at Q-Band

In order to achieve weak coupling for the applications of 5G communication system, a substrate integrated waveguide (SIW) coupler operating at 36 GHz similar to 42 GHz with four holes opened on narrow wall is designed. The transition structure between microstrip line and SIW adopts traditional gradient line. According to results, the coupling measured by southwest microwave connector reaches 24dB (39 GHz similar to 42 GHz), while the coupling measured by metal structure reaches 19dB (36 GHz similar to 40.5 GHz). The reflection coefficient is less than -20dB and the insertion loss is nearly 3dB. The designed coupler is suitable for the weak coupling in 5G communication system.