RF Waveguide Couplers

RF waveguide couplers are circuits that sample radio frequency (RF) transmissions by coupling signals asymmetrically. There are three basic types of products: unidirectional, bidirectional, and dual directional. Unidirectional couplers are three-port devices with two lines: a main line with a separate input and output, and a coupled line with a coupled output and internal termination. Power that passes along the main line is combined with the coupled output. Power that is reflected from the main line output is coupled with the termination.  Bidirectional RF waveguide couplers are similar to unidirectional devices, but remove termination from the fourth port. Main line power is coupled to the forward output of the secondary line. Reflected power is coupled with the reflected output. Dual directional couplers are also available. These four-port devices can be connected back-to-back in series or integrated into one device with a single main line and two secondary lines. The use a single main line reduces insertion loss and increases isolation.