Power dividers and directional couplers are in all essentials the same class of device . " Directional coupler " tends to be used for 4-port devices that are only loosely coupled that is, only a small fraction of the input power appears at the coupled port . " Power divider " is used for devices with tight coupling ( commonly, a power divider will provide half the input power at each of its output ports a divider ) and is usually considered a 3-port device.
