A new carrier frequency estimator for modem signals

ABSTRACT A novel carrier frequency estimation scheme for a relatively broad class of voiceband data signals (modem signals) is presented in this paper. The class of signals being studied includes different types of phase-shift-keyed (PSK) and frequency-shift-keyed (FSK) signals. The frequency estimates are obtained by averaging the estimates of the derivative of the instantaneous signal phase after discarding the estimates at the baud boundaries. Experimental results illustrate that the frequency estimates obtained from our scheme are unbiased and have small variances. Results also show that the carrier frequency estimation scheme presented here is superior to two other techniques in terms of both the mean and variance of the carrier frequency estimates.