Code-shift-keying signal demodulation and tracking method based on the sparse fourier transformation

Code-Shift-Keying (CSK) modulation meets the demand for high-rate information transmission without changing the spectral characteristics of the original signal and has become a candidate for the LEO satellite navigation signal regime. Since the demodulation of CSK signals requires the calculation of the correlation value of each code phase, to reduce the number of operations, the FFT frequency domain demodulation algorithm is generally used instead of the time domain demodulation algorithm. In this paper, the sparse Fourier transform (SFT) process is optimized to achieve high-efficiency demodulation by taking advantage of the sparse correlation values and partial output of CSK signals. In addition, the branch generation method of the tracking loop is improved based on the SFT demodulation algorithm to realize the tracking of dynamic CSK signals. Thus, the problem that the periodicity of the spread spectrum code is destroyed by the CSK modulation, resulting in the inability to track the signal directly is solved. The simulation results show that based on the SFT demodulation algorithm can improve its efficiency to 2.59 times the original, and the improved tracking loop realizes tracking and demodulation of higher dynamic CSK signals, which has certain engineering significance.