A Blind Estimation Method of QPSK/OQPSK Symbol Rate

In digital communications, the accurate estimation of symbol rate is extremely important for both blind demodulation of non-cooperative communications and radio spectrum monitoring. An instantaneous frequency symbol rate estimation method is proposed in this paper for the QPSK signals. The method determines the symbol rate of the signal by detecting the position of the spectral peak of the instantaneous frequency power spectrum. The instantaneous frequency power spectrum of the OQPSK signal does not have a distinct symbol rate spectrum due to the offset between the in-phase (I) and quadrature (Q) components of the signal. To address this issue, this paper also proposes a symbol rate estimation method based on the signal envelope spectrum. This method performs spectrum analysis on the envelope of the analytical signal and has high estimation accuracy for the symbol rate of the OQPSK signal. The simulation analysis and practical signal verify the feasibility and validity of this algorithm.