Novel Substrate Integrated Waveguide fixed phase shifter for 180-degree Directional Coupler

Substrate integrated waveguide (SIW) is a new type of guided wave structure which could be used in both microwave and millimeter wave integrated circuits. The study found that SIW's metallic via structure is very suitable for achieving fixed phase difference by different SIW widths. In this principle, a very simple way was used to realize the fixed phase shifter in equal length SIW firstly, and designed a 23 GHz 3 dB 180-degree H-plane directional coupler in this technique. It can achieve an over 8.7% bandwidth with plusmn0.25 dB power equality, -19.2 dB isolation and 180 degrees phase shift between the output and coupled ports.