A fast acquisition method of pn code in satellite spread spectrum communication system

Abstract

The invention discloses a method for fast acquisition of PN codes in a satellite spread spectrum communication system, comprising: S1: determining the frequency search step; S2: sequentially compensating and accumulating frequencies of different step lengths on the local signal frequency; S3: calculating the I channel and the full correlation value of the local mixed frequency signal of channel Q and the received signal; S4: the full correlation value is added correspondingly in the complex number domain, and its modulus value is calculated; S5: the one with the largest peak value, it is judged that the Doppler frequency shift is located at this frequency shift In the compensation module; S6: If the frequency compensation step is greater than the preset frequency compensation threshold, execute S7; otherwise, obtain the frequency shift and phase offset; S7: continue to divide the compensation frequency, reduce the search step length, and return to S2. The present invention divides the frequency compensation continuously, gradually narrows the search range, improves the compensation accuracy, shortens the capture time, and obtains the maximum correlation peak value through the calculation of the correlation value, so that the code phase is compensated, and the PN code and Doppler are realized. Two-dimensional capture of frequency shifts.

Description

technical field The invention relates to the technical field of acquisition of spread spectrum codes in a satellite mobile communication system, in particular to a fast acquisition method of a PN code in a satellite spread spectrum communication system. Background technique The direct sequence spread spectrum communication system (Direct Sequence Spread Spectrum, DSSS) has the advantages of anti-multipath fading, anti-interference, high-precision measurement, etc. In order to improve the anti-interference and confidentiality capabilities of the signal in the satellite mobile communication system, satellite spread spectrum is used Technology realizes the spread spectrum processing of satellite signals. Accurate acquisition and synchronization of spreading codes is the basic premise of its superior performance. The acquisition process of the spread spectrum code needs to complete the coarse synchronization of the spread spectrum code, and limit the phase difference of the spr...

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Problems solved by technology

6. The automatic adaptive threshold judgment method based on the constant false alarm rate. The disadvantage of this algorithm is that the detection probability is very low under low signal-to-noise ratio and the capture time is long

However, this scheme separates the frequency and the spreading code for capture. Compared with the two-dimensional simultaneous capture scheme, it will generate a large delay

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