RF Directional CouplerA RF directional coupler is an electronic device that is used to sample the power of a radio frequency (RF) signal in a transmission line. It is called a directional coupler because it is designed to only allow the RF signal to be measured in one direction, and to isolate the measurement from any reflections or other signals on the transmission line. RF directional couplers are commonly used in RF communication systems and other applications where it is important to measure the power of an RF signal accurately and without interference.