Directional Couplers are passive devices used for sampling incident and reflected microwave power, conveniently and accurately, with minimal disturbance to the transmission line. Directional couplers are used in many different testing applications where power or frequency needs to be monitored, leveled, alarmed or controlled. These include providing a signal sample for measurement or monitoring, feedback, combining feeds to and from antennas, antenna beam forming, providing taps for cable distributed systems such as cable TV, separating transmitted and received signals on telephone lines, in addition to electronic warfare (EW) systems and the emerging mmWave and 5G wireless communications systems.