A Compact Folded Patch Coupler Based on SISL Platform

In this paper, a compact patch coupler based on substrate integrated suspended line (SISL) platform is proposed. By folding the square patch on the middle substrate, and connecting its edges with via holes, the implemented coupler features a much smaller size as compared to conventional single-layer counterpart. The coupling degree is controlled by the slots etched on the edges. The folded patch coupler is embedded inside the multi-layer SISL structure, which helps to reduce the radiation loss. A 3-dB SISL folded patch coupler is designed in sub-6 GHz band, and good results are obtained.