QPSK Carrier Tracking Method with a Large Pull-in Range for Satellite Communications

A novel quadrature phase shift keying (QPSK) carrier tracking method used in coherent demodulation is proposed for satellite communications. Frequency ambiguity is always ignored by the traditional ones which results in that the maximum pull-in range of the carrier tracking loop is limited to one eighth of the symbol rate. A novel low complexity QPSK frequency/phase discriminator and a frequency estimation and compensation (FEC) module are presented in this paper to enlarge the frequency pull-in range, which can resolve the phase jump and frequency ambiguity problem in carrier tracking process and also has the few calculation complexity comparing with the traditional QPSK detector. A parallel FLL-assisted-PLL is adopted to simplify the design structure through the module reuse. Comparing with the state-of-the-arts, this method has lower complexity, smaller variance and larger pull-in range.