Two-dimensional joint acquisition method for direct sequence spread spectrum MSK signals in high dynamic condition

Abstract

The invention provides a two-dimensional joint acquisition method for direct sequence spread spectrum MSK signals in a high dynamic condition. The method comprises the following steps: intermediate frequency direct sequence spread spectrum MSK signals are subjected to a receiving conversion filter, down conversion, low pass filter and extraction processing, and approximate direct sequence spread spectrum BPSK signals are obtained; joint acquisition is carried out on the approximate direct sequence spread spectrum BPSK signals and a local code, and the estimated value of a code phase error and the estimated value of Doppler frequency shift are acquired; and after Doppler compensation is carried out on the approximate direct sequence spread spectrum BPSK signals based on the above estimated values, accurate code tracking and despreading and demodulation can be carried out subsequently, and information is acquired. The two-dimensional joint acquisition method for direct sequence spread spectrum MSK signals in a high dynamic condition is extremely applicable to a high-dynamic low-signal-to-noise ratio application environment, and has the advantages that the algorithm complexity is little; pseudo-code phase and Doppler frequency offset acquisition can be completed at the same time; and the estimation error is little in the high dynamic condition.

Description

technical field [0001] The invention relates to a digital communication technology, in particular to a two-dimensional joint acquisition method of direct-spread MSK signals under high dynamics. Background technique [0002] At present, spread spectrum systems mostly use BPSK and QPSK modulation methods, but these two modulation methods cannot be applied to the application environment 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 ...

AI Technical Summary

Problems solved by technology

The capture correlation peaks of these two methods are highly susceptible to Doppler frequency shift, and are obviously not suitable for high dynamic capture

[0004] In a highly dynamic environment, the most classic estimation method for Doppler frequency offset is nonlinear transformation combined with FFT. The specific method is to perform square or multiple nonlinear transformation on the received signal, and then process the peak value of the spectrum according to the signal FFT The index of the frequency offset estimate is obtained, but this method cannot work under low signal-to-noise ratio

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 search range of Doppler frequency offset is small, and it is still not applicable in high dynamic environment

In recent years, some scholars have successively proposed code acquisition methods under high dynamics such as differential acquisition and two-step acquisition, but it is difficult to strike a balance between low signal-to-noise ratio and estimation accuracy

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