Parameters Estimation Of Phase-coded Signals

With the advantages of solving the contradiction between the effective distanceand distance distinguish ability, agile alteration to waveform, flexible encoding scheme,strong anti-interference, low probability of intercept(LPI), and high tracking accuracy,phase-coded signals have been widely used in radar systems. Hence, it is of importantpractical significance to estimate the parameters and recognize the modulation ofphase-coded signals.In this paper, the parameters estimation and modulation recognition of phase-codedsignals are studied. Firstly, the fundamental knowledge of phase-coded signals andcyclic cumulants are discussed. Secondly, several algorithms of frequency estimation ofcomplex sine signal and BPSK signal are introduced, such as frequency estimationalgorithm using phase difference, Rife algorithm, a blind carrier frequency estimationalgorithm of BPSK signal and so on. With any of all these algorithms, the carrierfrequency can be estimated without prior knowledge. However, the frequencyestimation algorithm using phase difference is sensitive to noise. The RMSE(root meansquare error) of Rife algorithm is fluctuate with the distribution of the frequency ofsignals to be measured, and that of the blind carrier frequency estimation algorithm ofBPSK signal is not low enough. Then a new algorithm based on four-order cycliccumulants is proposed for frequency estimation of complex sine signal and BPSK signal.Simulation results show that the performance of the new algorithm doesn’t fluctuatewith the distribution of signal frequency. The results of simulation also show that thefrequency of complex sine signal and BPSK signal can be accurately estimated with thealgorithm without any prior knowledge. Thirdly, several algorithms of estimating thesymbol rate of multi-phase-shift keying(MPSK) signals are introduced, along withsimulation results. Finally, a modified algorithm based on two-order and four-ordercyclic cumulants is put forward to make it more efficient for modulation classificationof MPSK signals. The performance of the modified algorithm is proved by thesimulation results.