LAUSR

In this brief, an ultra-compact broad wall coupler based on slow-wave half-mode substrate integrated waveguide (SW-HMSIW) is presented. The E-plane coupling between different layers of circuits under slow-wave effect is studied for the first time. The slow-wave construction is realized by complementary split ring resonator (CSRR) loaded HMSIW. Moreover, CSRRs could serve as coupling sections at the same time. Hence, the slow-wave effect and energy coupling can support each other and operate well together simultaneously. Furthermore, the slow-wave effect could enhance the coupling level of each aperture and realize coupler size reduction in general. As a result, the presented coupler can operate in a wide band (45%) with 50% size reduction comparing to typical HMSIW fast-wave one, which would be suitable for applications in six-port circuit and Butler matrix with strict size and performance requirements. Simulated results are in good agreement with measured data.