Microwave coherent demodulator for phase-shift-keyed signals

A coherent demodulator for p.s.k. signals at microwave-carrier frequencies using an open-squaring phase-locked loop is described and evaluated experimentally. The circuit has been operated at a 50 Mbit data rate, and should operate at much higher data rates. Error measurements in the presence of Gaussian noise confirm that the circuit performs as an ideal coherent detector until the phase-locked-loop threshold is reached.