Abstract: Two signals received by spaced antennas or equivalent diversity receiving systems and having identical data signals, phase modulated on frequency-identical suppressed carrier signals, are combined to produce a more nearly error-free data output. Each input signal, after heterodyning, is multiplied by a distinct feedback signal to produce a phase-coherent carrier and a recovered data signal. Each carrier is filtered by a narrow bandpass filter and connected to a separate adder. The two multiplier outputs are also added together, then filtered in a low pass filter to provide a combined recovered data signal. This combined data signal is added separately to each coherent-phase carrier to provide the two distinct feedback signals for the input multipliers. When each carrier is phase modulated in quadrature with the same two data signals, the signals are phase shifted, after heterodyning, to separate the quadrature components.

Abstract: Digital data, differentially phase shift keyed on a suppressed carrier, double side band transmission, is recovered by multiplying the input signal by a signal derived from regenerative feedback and consisting of the sum of a phase-coherent carrier and the recovered data signal. The phase-coherent carrier is derived by alternate phase reversals of the incoming carrier, produced by the polarity changes in the data. The phase-coherent carrier and the recovered data signal are components of the multiplier output and are separated by bandpass and low pass filters respectively, the output terminal of the low pass filter also being the data output terminal. When a carrier has been phase modulated with two distinct signals in quadrature, the received carrier is phase shifted to produce two signals in quadrature, then each of the resultant modulated carriers is demodulated as with the single signal carrier, using one common bandpass filter.