Six-port reflectometer circuit comprising three directional couplers

A six-port reflectometer circuit, assembled from three directional couplers and covering a waveguide passband, is described. Experimental results obtained from a WG 22 wave-guide version show that about 1 mW source power is sufficient for thermistor detectors to be used with the circuit, a level obtainable from millimeter-wave solid-state sources.