A phase shifter has been designed to give a constant phase over the octave bandwidth 70-140 GHz in dielectric guide. The phase shifter was designed for use in a multistate reflectometer in dielectric guide, though other applications are possible. The multistate reflectometer required two less power meters than a previous six-port reflectometer. The whole device enabled very accurate measurement of phase and amplitude in the range 70-140 GHz for little more than the cost of a swept source.