PROCESS FOR RECEIVING UNIQUE WORDS

摘要

A method is disclosed for detecting a predetermined code word contained in received signals in a transmission system which operates with four-phase or four-phase difference modulation at the transmitter and coherent demodulation at the receiver and in which successive signal increments are transmitted and received during successive clock periods, the code word being transmitted only as signals in two phases which are 180.degree. apart and the received signals being divided into orthogonal voltage components during demodulation. The method includes monitoring the algebraic signs of the orthogonal voltage components of the signal increment received during each clock period and providing an indication when such signs are opposite during each one of a successive plurality of clock periods one voltage component of a signal increment is then processed in a manner to invert its sign only upon occurence of such indication, i.e. when the signs are opposite, after which the processed one voltage component is algebraically summed with the other voltage component of the same signal increment. A received signal increment is then evaluated in accordance with the algebraic sign of the voltage produced in the summing step.