Miniaturized Broadband Coupler Made of Slow-Wave Half-Mode Substrate Integrated Waveguide

In this work, a size-reduced wideband coupler is presented and demonstrated, which explores the slow-wave half-mode substrate integrated waveguide (SW-HMSIW) technique on a printed circuit board process. The SW-HMSIW coupler is composed of two SW-HMSIW transmission lines loaded with a polyline network. Along the coupler, energy is coupled by the electric and magnetic field between the two parallel SW-HMSIW lines. Compared with conventional microstrip coupler, the proposed coupler presents lower loss owning to the HWSIW structure performance. In addition, the proposed SW-HMSIW coupler exhibits a smaller size against its SIW and HWSIW counterparts, thanks to slow-wave effects of the loaded polyline. Measured and simulated results are in a good agreement.