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.