In accordance with an embodiment, a method of operating a directional coupler includes determining a coupled power variation by applying an input signal at an input port of the directional coupler, applying a first impedance at a transmitted port of the directional coupler, measuring a first coupled power at a coupled port of the directional coupler after applying the first impedance, applying a second impedance at the transmitted port of the directional coupler, measuring a second coupled power after applying the second impedance, and determining a difference between the first coupled power and the second coupled power to form the coupled power variation.