Communication receiving apparatus

摘要

Receiving apparatus for processing differential quadrature phase shift keyed (DQPSK) signals. Received 70 MHz IF signals are mixed with a 70 MHz reference frequency to provide quadrature components of each received signal. The resultant of the quadrature components of each signal is converted to a digital representation. The digital representations are sampled at sixteen times the baud rate. Samples are subtracted by two's complement addition and the difference produced by samples from two successive received signals is read out as the data encoded in the signal. The resultant of each two's complement addition is monitored to determine if there is no difference indicating that the samples are from the same received signal or if there is a difference indicating that the samples are from different received signals. The timing of signals which control the operation of the apparatus are adjusted with respect to the timing of received signals so that half the number of resultants of the two's complement addition occurring during a period equal to a baud indicate no difference and half indicate a difference.