| In modern communication, direct sequence spread Spectrum communications was widely used in the fields of both military and civil communication systems, because of its low interception probability, high noise resistance and good security. This thesis is focused on research on interference suppression of burst-mode direct sequence spread spectrum communications, as well as related simulations with Matlab.The thesis first introduced the basis principle, the construction framework, the performance parameters and the channel model of spread spectrum system; Being on this foundation put forward predicting with the Longley-Rice model the spread spectrum signal path attenuation with the Longley-Rice model, and discussed the anti-interference ability of the burst-mode direct sequence spread spectrum system with processing gain; Analyzed to the composition of receive signal after, carried on setting up the model and analysis to the interference environment and the interference signals; Then introduced the theory of time-domain and frequency-domain narrow-band interference suppression, presented a frequency-domain trap-filtering algorithm based on the estimation of mean and variance after the analysis of the statistic characteristic to the spectrum of receive signal, and then some computer simulations are made to test the algorithm; As for the LFM sweeping interference, a numbers of researches have been done in time-frequency domain, so an analysis of detecting and removing the LFM signal with FRFT is given, and besides, a LFM interference suppression method found on the discrete observed data is put forward; In the end, techniques of pulse interference suppression are theoretically studied from the following aspects: amplitude related processing, AGC, error correction and interleaving coding/decoding technique. Then,a project synthesizing AGC, FEC and interleaving coding/decoding techniques is presented to reduce the BERs caused by pulse interferences. |
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