New high performance non-data-aided frequency estimation and implementation of QPSK

A new scheme for modulation removal for Non-Data-Aided(NDA) QPSK signals is proposed.The algorithm based on this new scheme can make a large range of frequency estimation cooperated with the DFT coarse frequency estimation method.Compared with the estimation algorithm using DFT and interpolation,the new scheme can endure more frequency fluctuation and estimate accurately the frequency offset when the effset varies slowly.Simulations and FPGA implementation prove the new scheme's good performance that it closes to CRB even at a low SNR.