Research On Anti-Jamming Performance And Synchronization Of Hybrid DS/FH System

As one of the spread spectrum communication schemes with strong anti-jamming performance, hybrid direct sequence / frequency hopping (DS/FH) spread spectrum is of great importance in the modern military communications and electronic warfare. This paper studied the anti-jamming performance and synchronization techniques of hybrid DS/FH spread spectrum system and proposed a rapid synchronization scheme for high-speed DS/FH system.Firstly, DS/FH system's resistance to interference was studied based on theoretical analysis and simulation. Beginning with direct sequence spread spectrum, the impact of the frequency and bandwidth of the interference on the bit error rate of the system was studied. Based on this, the impact of partial spectrum interference on the system and the hopping frequencies under different circumstances on the system processing gain were studied. The paper also analyzed the impact of several factors on synchronization. All these provide good reference to the design of DS/FH system.Secondly, the method of partial matched filter (PMF) plus fast Fourier transform (FFT) for the acquisition of direct sequence was studied. Theoretical analysis and simulation were made, and the various parameters'impacts on the performance of capture were analyzed. Also, some issues regarding the implementation of the system were discussed.Thirdly, two improved capturing methods for frequency hopping were proposed, one based on partial monitoring and the other based on waiting with energy detection. It was proved by theoretical analysis and simulation that, by choosing a reasonable number of monitoring frequencies, the partial monitoring method can have a balance on the capturing time, anti-jamming performance and system resource consumption. Also, the method with energy detection can greatly enhance the anti-jamming performance of the synchronization without a substantial increase of the system resource consumption. Finally, the synchronization scheme that is appropriate for hybrid DS/FH spread spectrum system was proposed based on the discussion of the DS and FH synchronization methods above. The synchronization information is transmitted on time-variant channels, and the receiver can get synchronized by capturing and receiving it in a short time. The synchronization can be achieved rapidly and the method is easily implemented, while the anti-jamming performance being kept.