Receiver for psk digital signals

Abstract

In a phase-shift-keying (PSK) signaling system with or without amplitude modulation, using two conjugate channel carriers of like frequency, the signals incoming at a receiver input over the two channels are coherently detected and filtered to supply a pair of coordinates defining a point on an orthogonal matrix divided into eight sectors, each sector representing a respective signal level. The coordinate values are quantized and translated into selective energization of two mutually orthogonal matrix leads whereby an associated AND gate conducts and emits a signal identifying the sector encompassing the intersection of these leads. The sector-identifying signal addresses a read-only memory which delivers a corresponding output signal to a processor and feeds back corrective signals to a pair of summing circuits for superposition upon the next input signals in order to compensate for both intrachannel and interchannel distortion. If adjacent levels are distinguished not only by the phase shifts of the channel carriers but also by changes in their amplitudes, the corrective signals fed back by the memory are of correspondingly different amplitudes.