Study On Interference Rejection Techniques In Spread-spectrum System

Spread spectrum communication is one of newly-developed and high-tech communication technology. Because of its large capacity, anti-interference ability, security, as well as multi-access ability, etc., this communication technology has been widely used in both civil and military areas. Due to its wide range of applications, the corresponding interference and anti-jamming technology on spread spectrum communication have been rapidly developed. On the one hand, in the military application, many associations have committed to interference research and anti-jamming technology of the system, in order to destroy enemy communications to obtain the initiative in wars; On the other hand, in the civil application, ours demanding towards high quality and security of communications, also has largely promoted the interference and interference suppression development of the system. Although the system itself has a strong anti-interference ability, because processing gain of the system can not be arbitrarily increased which is restricted by the spectrum resources. Therefore, when the external interference, imposed on the system, exceed the jamming margin of the system, the performance will reduced sharply, which is another reason for the research of the interference and interference suppression from the perspective of technology. At present, a large number of relevant studies have appeared at home and aboard, and great achievements have been made out. However, most of the researches and achievements mainly concentrated on the narrow-band interference and its suppression. Whereas, recently, with the maturity of narrowband interference suppression, the interference on spread spectrum system transfer gradually from narrowband interference to non-stationary broadband interference, which is getting more and more attentions. Therefore, following the tide of times, the LFM interference suppression technology is mainly discussed in paper, on the basis of the introduction on narrow-band interference suppression.Firstly, an introduction of spread spectrum communication system and its anti-jamming performance are made at the beginning. The current state of interference and interference suppression studies are summarized then. On this basis, according to the current situation demand, the non-stationary broadband interference suppression is researched deeply. Linear frequency modulation--LFM signal, the presentation of the typical non-stationary signal, is treated as the interference of the system in paper. However, since this kind of study currently is relatively small, so the discussions begin from the research results of LFM signal itself. LFM interference suppression methods based on STFT, WHT and FRFT are researched respectively then. At last, according to the characteristics of LFM signals, a new method of LFM interference suppression, based on parametric time-frequency analysis, is proposed. And the performance analysis on the output SNR is also given out. Simulation analysis shows this method can realize LFM interference suppression and improve the output SNR, and the amount computation can also be reduced with the help of FFT.