Research On High Precision Carrier Synchronization Technology Of GMSK Signal

In recent years,communication systems have become increasingly demanding for integration and scalability.Compared with analog communication systems,digital communication systems are easier to reconstruct the system.Therefore,all digital receivers have become a research hotspot.The signal processing technology in the receiver,including carrier synchronization technology,has also become the main point of research.The signal received by the receiver usually has a certain frequency offset,which directly affects the reliability of the demodulation.The purpose of synchronization is to eliminate the influence of the frequency offset.Achieving good synchronization performance requires a high-performance frequency offset estimation algorithm.The factors that measure the performance of an estimation algorithm include accuracy,complexity,and signal-to-noise ratio(SNR)working threshold.Gaussian minimum shift keying(GMSK)signal is often used in space communication,and the signal needs to be transmitted in a very low SNR environment.It is the key to consider the SNR working threshold and accuracy of the frequency offset estimation algorithm.factor.In this paper,the digital carrier synchronization technology of GMSK signal is deeply analyzed and studied.Aiming at reducing the SNR threshold and improving the accuracy of the estimation algorithm,a quadratic search interpolation algorithm based on fast Fourier transform(FFT)is proposed.The spectral line of the signal is obtained by FFT,and the peak spectral line is used to obtain a rough estimate of the frequency.Spectral line values of the adjacent quantized frequency center points on both sides of the peak line are obtained,and the obtained center point spectral line value is compared with the original peak value to obtain a maximum new peak spectral line,which reduces the occurrence of correction direction misjudgment and the impact of noise on useful signals.The value of the center line spectrum of the frequency of the new peak line is quantized to improve the estimation accuracy of the algorithm.Finally,the hardware design and implementation of the secondary search interpolation algorithm.Experimental results show that the proposed frequency estimation algorithm is superior to Rife and Candan interpolation algorithms in estimating accuracy,and has a stable estimation effect under different frequency offset factors.When the FFT point is64,the SNR threshold of the proposed algorithm is 2 d B,and when the FFT point is1024,the threshold is-9 dB.