Improving accuracy of frequency acquisition in spread spectrum system

Frequency acquisition accuracy affects system coherent demodulation, thus affects the performance of communication system. FFT-based frequency estimation can be implemented with high speed and low complexity, but exists picket fence effect. Therefore, using FFT for frequency estimation directly will bring a greater measurement error. Traditional Rife algorithm has the problem of incorrect interpolation direction at low SNRs or with smaller relative offset, whereas traditional Quinn algorithm can obtain the correct interpolation direction. By combining the advantages of Rife algorithm and Quinn algorithm, a Q-Rife algorithm is proposed to achieve higher accuracy estimation. Further, making full use of higher accuracy estimation of joint amplitude-phase interpolation algorithm with small relative offset, an API-Q-Rife algorithm is put forward by combining the advantages of the above two algorithms, which can improve the estimation accuracy of Q-Rife algorithm with small relative offset. The simulation results based on MATLAB show that the improved Q-Rife algorithm can reduce the frequency estimation error while guaranteeing the stability of the algorithm, and the proposed API-Q-Rife algorithm can achieve better performance than Q-Rife algorithm.