A 3-dB Coupler in Slow Wave Substrate Integrated Waveguide Technology

This letter presents the design, simulation, and measurement results of a 3-dB coupler in slow wave (SW) substrate integrated waveguide technology at 11 GHz. It shows the possibility of reducing by 70% of the surface area without significant increase in insertion loss. The topology relies on a uniform distribution of blind via-holes, creating a distributed SW effect. It is therefore applicable to already existing coupling structures, in this case, the short-slot coupler. An equivalent homogeneous substrate defined by an increased permittivity is used to simplify the optimization of the structure. Finally, a good agreement is obtained between simulation and measurement.