Demodulator for transmitted phase modulated ternary information

Claim 1

In a communication system having means for transmitting phase shift ternary information wherein each of the items of ternary information is transmitted by introducing through quadri-phase modulation discreet phase shifts in a carrier signal, and demodulator means for demodulating the phase shift information, said demodulator means comprising: means responsive to said carrier signal for deriving first and second reference signals, said first reference signal having a predetermined phase delay with respect to the carrier signal, and said second reference signal having another predetermined phase delay with respect to said first reference signal; means for comparing said carrier signal and said reference signals to provide a pair of output Signals containing said phase shift ternary information; and means for converting said pair of output signals to provide said ternary information comprising: threshold detector means responsive to said pair of output signals for providing polarity signals indicative of the electrical polarities of said pair of output signals; threshold detector and gating circuit means responsive to said pair of output signals for providing absolute value signals indicative of either of said pair of output signals having a greater absolute electrical value than the other; AND gate means responsive to said polarity and absolute value signals for providing phase shift signals indicative of the phase difference between said carrier and reference signals; means responsive to said phase shift signals for generating synchronization signals indicative of the rate of received phase shift information, and squelch signals indicative of the unreliability of said phase shift signals; multivibrator means connected to said AND gate means, and responsive to said phase shift, synchronization, and squelch signals for providing signals only during simultaneous occurrence of said synchronization and phase shift signals, and during the absence of said squelch signals; and gate network means connected to said multivibrator means and responsive to said synchronization signals for providing signals indicative of said ternary information.