Abstract: A compact apparatus for the accurate measurement of complex reflection coefficients and VSWR of a device over a bandwidth of an octave or greater by preferably measuring three power levels at detectors associated with the device. The device is formed by the junction of 5 transmission lines two of which are used for receiving a test signal and for transmitting the signal to the device being measured. The other three transmission lines are connected to detector arms each having a detector associated therewith. The techniques of the invention are embodied herein in a waveguide embodiment, a stripline embodiment and a microstrip embodiment of the invention.