New slot-coupled directional couplers between double-sided substrate microstrip lines, and their applications

A slot-coupled directional coupler between two microstrip lines that couples through a rectangular slot in the common ground plane has been proposed and fabricated for the 1.5-GHz band. The design method and the experimental results for this directional coupler are described, as well as its application to a planar multiport directional coupler (MDC). The measured 3-dB coupling results agreed well with the calculated results, as do the experimental results for a four-port MDC. A planar MDC configuration consisting of a combination of slot-coupled directional couplers has also been proposed.<>