Design of waveguide to microstrip directional coupler with rectangular apertures as fishbone shape for high power applications

A compact directional coupler with rectangular apertures, which are arranged in a fishbone configuration for high power systems, is designed. The proposed design can be applied to small size microwave interspaces and realize low coupling between waveguide and microstrip line with parallel axes by multi-aperture. In this paper, we present a C band novel directional coupler with low coupling of 40 dB with the deviation of 1 dB, directivity of 20 dB and low return loss over a operation band of 1.4 GHz.