Research On Detection Methods Of Direct Sequence Spread Spectrum Signals

Spread spectrum communication is an important counterreconnaissance technology, which has many advantages such as Low Probability of Intercept (LPI) and high Anti-Jamming (AJ) performance. It is one of the main techniques of secret communication, thus having been widely applied in military communication systems. It is of great significance to study the detection methods of spread spectrum signals under low SNRs to meet the demands of electronic wars.Firstly, the performance of several conventional passive signal detection methods for direct sequence spread spectrum signals are analyzed in this paper, which reveals that the performance of the energy detection is the best in the case of stationary background noises, but it is sensitive to noise and is unable to estimate the parameters of the signal. Both the square carrier detection and the modern spectrum estimation work well in the suppression of noises. They can also estimate the carrier frequency while detecting signals. However, their detection performance comes down dramatically under low SNRs. In order to overcome the weakness that above methods are limited to high SNRs, the multi-correlation integration based carrier detection method and bi-channel signal based cross-power spectrum detection method are presented in this paper. The former works well in the suppression of noise and the improvement of output SNR results by using multiple correlation integration. It also has good detection effects even under low SNRs. While the latter performs detection by estimating the cross-power spectrum of the bi-channel signals, according to the low correlation characteristic of the noises under bi-channel condition. It is shown than this method has good performance of noise suppression and signal detection even in the case of complex noises background.The experimental results verify that the proposed algorithms in this paper are efficient in the detection for direct sequence spread spectrum signals. Moreover, they are easy to implement and are of great practical values.