Differential phase modulation

摘要

The amplitude of a signal to be modulated on a carrier wave is sampled every T seconds. The sampled amplitudes are converted into phase representative pulses of pulse rate 1/T. Each phase representative pulse corresponds to the difference between a first phase corresponding to the sampled amplitude and the phase of Nth previous phase representative pulse, where N is an interger greater than 1. The discrete phase representative pulses are phase modulated onto the carrier wave. Conversion is accomplished by detecting the sampled amplitudes, applying the detected amplitudes as an address to a ROM to provide corresponding differential phase information, and modulating the differential phase information onto the carrier. To demodulate the signal from the carrier wave, the carrier wave is delayed for NT seconds and the delayed signals are subtracted from the undelayed signals. The resulting signal is linearly detected by an envelope detector to develop an output signal representative of the original modulating signal.