RF directional couplers are often used in RF design applications. Directional couplers are RF passive devices used to couple a specific proportion of the power travelling in one transmission line out through another connection or port. Directional couplers find many applications in RF design , ranging from through line power sensors to transmitter automatic levels controls. As such they are particularly useful, enabling power levels to be sensed without making a direct connection to the transmission line carrying the power.
RF directional couplers can be implemented using a variety of techniques including stripline, coaxial feeder and lumped or discrete elements. They may also be contained within a variety of packages from blocks with RF connectors, or solder pins, or they may be contained on a substrate carrier, or they may be constructed as part of a larger unit containing other functions.