FORFARANDE FOR ATT AV EN MODULERAD BERVAGSSIGNAL ERHALLA EN FELTTIDGIVNINGSSIGNAL SAMT ANORDNING FOR UTFORANDE AV FORFARANDET

摘要

A demodulator useful for demodulating multi-phase differentially coherent phase shift keyed (PSK) signals. In the four phase case, a pair of correlators operate upon the identity and non-identity of the PSK signal and two replicas of itself derived from the preceding baud or frame interval to produce first and second correlation signals. The first and second correlation signals are then filtered by means of first and second digital counter type filters with the direction of counting being controlled by corresponding ones of the correlation signal. The output of the filters are then compared with one another in sign and magnitude to detect the modulating information.