Abstract: A system is provided for extracting the proper carrier phase from a single sideband suppressed carrier signal. A received signal is equalized and then product demodulated by estimated in-phase and quadrature carriers produced by a voltage controlled oscillator (VCO). The outputs of the in-phase and quadrature product demodulators are low-pass filtered producing corresponding in-phase and quadrature baseband signals. An estimator compares the in-phase baseband signal with reference levels, samples the output of the comparing circuit at the band rate and generates a sequence of estimated data signals. The error signal, which forms the input to the VCO, is produced by multiplying the recovered quadrature baseband signal with the estimated data signals and is proportional to the product of the square of the low pass filtered baseband signal and the sine of the difference between the phases of the received carrier and estimated carrier.

Abstract: A multi-phase, multi-amplitude level modulation method, and modulator, is provided which produces a three-level, ten-phase modulated carrier. The carrier is modulated in three amplitude levels, viz., off, intermediate and high and in ten phase positions, to produce sixteen signal states, one state corresponding to the carrier being off, five intermediate amplitude level states having five equally spaced phase positions, and ten high amplitude level states having ten equally spaced phase positions. A number of different four digit binary coding schemes for the sixteen signal states are disclosed together with other different coding and modulation techniques.