The calibration and use of directional couplers without standards

Basic principles and suggested techniques are presented for calibrating nonideal four-port couplers without standards. Under the assumption that the complex ratio of the side-arm voltages are known, all the parameters, except one of the directional couplers, can be determined without recourse to known values of impedances, shorts, opens, etc. Also, the surprising number of measurements that can be made with such an incompletely calibrated coupler are discussed.