Recovery of a carrier signal from a modulated input signal

摘要

The present invention relates to the recovery of a carrier phase from a modulated input signal where the modulation is in accordance with the M-PSK modulation format, M has a value greater than 4 and the signal-to-noise ratio in the channel is low. A voltage controlled oscillator is employed to generate first and second oscillations in phase quadrature with respect to each other. The modulated input signal is mixed with the first of the oscillations to detect the (I) signal component and the modulated input signal is mixed with the second of the oscillations to detect the (Q) signal component. A control signal is derived from the (I) and (Q) signal components as an estimate of the phase difference between the input signal carrier and the voltage controlled oscillator. The control signal conforms to the relationship: $where\; \text{'}a\text{'}\; is\; the\; control\; signal,\; \text{'}k\text{'}\; is\; an\; odd\; integer\; between\; 1\; and\; M,\; and\; Ck\_m\; represent\; binominal\; coefficients.\; The\; frequency\; of\; the\; voltage\; controlled\; oscillator\; is\; controlled\; by\; the\; control\; signal\; to\; recover\; the\; carrier\; phase.\mathop{\mathrm{image}}$