Half Mode Substrate Integrated Waveguide and Microstrip Rectangular Patch Hybrid Integrated Coupler

In this paper, a half mode substrate integrated waveguide (HMSIW) and microstrip rectangular patch (MRP) hybrid integrated coupler with two HMSIW ports and two microstrip ports is presented. The HMSIW ports are compatible with HMSIW components (e.g. HMSIW antennas), while the microstrip ports are compatible with active devices (e.g. power amplifiers). Due to the compact geometry and great compatibility with various topologies, the proposed hybrid integrated coupler is attractive for the design of active antennas, balanced amplifiers, six-port receivers, etc. To verify the proposed scheme, a 3-dB prototype coupler is designed, fabricated and measured, which achieves a fractional bandwidth (FBW) of 21% with 1 dB amplitude imbalance and 4 degrees phase imbalance.