Couplers & Hybrids usually four port passive devices containing two separate transmission lines, each having one port on each end that come into proximity to each other such that microwave energy propogating on one of the lines will couple to the other. The four ports are almost always matched to an impedance of 50 ohms. Midwest Microwave manufactures three basic types of couplers. Directional Couplers, 90° Hybrid Couplers, and 180° Hybrid Couplers.