Interference immunity of binary systems with second-order phase-difference modulation in various reception modes

Reception of signals with binary second-order phase-difference modulation is analyzed for interference immunity in various channels with Gaussian noise and, on this basis, second-order phase-difference modulation is compared with first-order phase-difference modulation from the demodulator standpoint. In the case of a channel with deterministic or slowly fluctuating parameters and of correspondingly optimum coherent or quasi-coherent reception, the attainable interference immunity is the same for second-order phase-difference modulated signals as for first-order phase-difference modulated ones, even though errors are not bunched in pairs here but distributed over one element. Two simple demodulators of signals with single second-order phase-difference modulation are proposed for a channel with a widely fluctuating and non a priori estimable random frequency, and an absolutely invariant one with an interference limiting band-pass filter at the input and a relatively invariant one consisting of several parallel autocorrelation demodulators of first-order phase-difference modulated signals.