A blind carrier frequency estimation algorithm for digitally modulated signals

In this paper, we consider estimation of the carrier frequency of a single-tone digitally modulated signal in the automatic modulation recognition (AMR) environment. This issue is quite different from that in the cooperative communications systems since the AMR receiver works in a non-cooperative mode with the transmitter. That is, the AMR receiver does not have any priori knowledge of the transmitted signal such as symbol rate, shaping pulse, modulation type, and constellation size. A blind carrier frequency estimation algorithm is presented in this paper based on the phase information of the autocorrelations of the received signal. The phase distribution has been analyzed, and an iterative mechanism has been employed to improve the accuracy of carrier frequency estimation. Simulations show that the algorithm works well for amplitude-shift keying (ASK), phase-shift keying (PSK), and quadrature amplitude modulation (QAM) signals.