Pseudocode-Doppler combined capturing method of direct sequence spread spectrum MSK signal

Abstract

The invention provides a pseudocode-Doppler combined capturing method of a direct sequence spread spectrum MSK signal. The method comprises the following steps of converting the direct sequence spread spectrum MSK signal to an appropriate direct sequence spread spectrum BPSK signal through intermediate-frequency matching processing; performing Doppler compensation on sampling data of the appropriate direct sequence spread spectrum BPSK signal; capturing the code phase error, the Doppler channel and Doppler displacement value of the BPSK signal after Doppler compensation through a pseudocode parallel capturing method, and acquiring a Doppler frequency offset according to the Doppler channel and the pseudocode displacement value. The pseudocode-Doppler combined capturing method can realize capturing of the direct sequence spread spectrum MSK signal in a high dynamic condition and furthermore finishes combined estimation for the pseudocode phase and the Doppler frequency offset. On the condition of relatively low signal-to-noise ratio, not only is relatively low Doppler frequency offset estimation error realized, but also high pseudocode phase capturing performance is obtained, thereby ensuring relatively good coarse synchronization of a received signal before entering a signal tracking processing module.

Description

technical field [0001] The invention relates to a digital communication technology, in particular to a pseudo-code-Doppler joint acquisition method of a direct spread MSK signal. Background technique [0002] At present, BPSK and QPSK modulation methods are mostly used in spread spectrum systems, but these two modulation methods cannot be applied to the application fields with severe nonlinear distortion, Doppler frequency shift and multipath fading. The direct spread MSK communication system has the advantages of low interception of the spread spectrum system, multi-user random site selection capability, strong anti-interference performance, constant envelope of the MSK signal, high spectrum utilization, energy concentration, fast sidelobe attenuation, and band With the advantages of low external radiation power and insensitivity to nonlinear distortion, it has been widely used in tactical data link, civil aviation ground-air data link, missile guidance command transmission...

AI Technical Summary

Problems solved by technology

[0004] G.J.R.Povey and others first proposed a capture model based on the combination of digital partial matched filter and FFT (PMF-FFT). Two-dimensional acquisition of pseudo-code phase and carrier frequency offset, but this method is mainly suitable for MPSK signals, and the capture range of Doppler frequency offset is small, and it is still not applicable in high dynamic environments

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