| In modern warfare, confront between electronic system will become increasingly fierce; communication system anti-interference function becomes the inevitable request for modern military communication system. Spread spectrum communication (SSC) is superior-performance modulation theories and new technology, which is to improve the reliability of the information transmission. As its biggest characteristic is strong anti-jamming capability, it is widely used in military anti-jamming communication and mobile communications. And the direct sequence spread spectrum (DSSS) technology has become the research hot spot in the military field because of its good capabilities of anti-interference and resistance to intercept. Burst communication can effectively avoid interference, and improve the anti-interference ability of the system in a certain extent, because the signal sending time is short and the sending time is not sure. Burst communication technology combines with direct sequence spread spectrum technology, which can effectively improve the capabilities of anti-interference and resistance to intercept of communication system.This paper presents a burst-type DS signal digital receiver PN code despreading correlation peaks decision feedback superposition program based on FFT parallel one-dimensional capture search algorithm. At the same time it designs and simulates the scheme on the Matlab/Simulink platform which makes it more convenient and accurate to describe the impact on the receiver PN code despreading by relevant correlation peaks decision feedback superposition method based on FFT. The program can significantly improve the probability of capture in the case of low SNR, and ensure the receiver to work properly in the same time.The paper firstly studies the technologies of serial despreading, parallel despreading, digital matched filter despreading and parallel one-dimensional despreading based on FFT and analyses their advantages and disadvantages. The results show that the serial despreading technology takes too long time and fits for the PN code despreading of a short period, parallel despreading technology requires more equipment, digital matched filter despreading demands less equipment but fits for PN code despreading of a shorter period, while parallel one-dimensional technology based on FFT is more easily to achieve PN code despreading of a longer period. Parallel one-dimensional solution based on FFT is obtained through the Fourier transform of the serial two-dimensional despreading technology. In the meantime of searching the PN code phase, the parallel one-dimensional despreading based on FFT also achieves the Doppler frequency offset and improves the capture speed.Then we design and simulate the proposed FFT parallel one-dimensional despreading program based on relevant correlation peaks decision feedback superposition in the receiver. The system increases the delayed feedback loop and the relevant correlation peaks superimposes after a feedback. It can increase the SNR. The increasing of SNR can improve the detection probability of the system and speed up the capture speed, and the system capture probability can be significantly improved in the case of low SNR.Finally we design the burst-type DS system and carry out simulation, and obtain the results that the factors affecting the acquisition probability and false-alarm probability are associated with the selection of the threshold and SNR. The lower threshold and the greater SNR there are, the more easily the system captures, but low threshold will also increase the false-alarm probability. So we should take into account comprehensive consideration when select the threshold. The use of the FFT parallel one-dimensional despreading program based on relevant correlation peaks decision feedback superposition with MF-FFT is of certain practical value in the White Gaussian Noise (WGN) environment of High Dynamic Range and low SNR and narrowband interference. |
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