Wideband Hybrid Ring Coupler Based on Half-Mode Substrate Integrated Waveguide

A substrate integrated waveguide ring coupler and a half-mode substrate integrated waveguide ring coupler in X-band are designed from the principle of traditional 180 ^° hybrid ring coupler. The HMSIW hybrid ring coupler, adopted closed side to closed side designing for connections of HMSIW branches, is proposed for the first time. It has 24.6% bandwidth for the amplitude imbalance of coupling coefficient less than ±0.5 dB and phase differences between outputs are 15.0^° ~ -5.8^° and 175.5^° ~ 189.7^° for the in-phase and the out-of-phase operations, respectively, which shows much better performance than SIW coupler.