Study On Communications Jamming Technology In A Complex Electromagnetic Environment

In the battlefield of joint operation filled with information, control over information is critical for decision making and manoeuver. However, during the process of fighting for ownership of information, the electromagnetic environment is quite complex for the widely-used anti-jamming technique. This dissertation takes signals'separability, separating principle and search algorithms as main clues and makes some heuristic research on communication anti-jamming technique, including signal separation technique, signal extraction technique and anti-jamming system construction, in order to solve the problems of inter-symbol interference and white noise interference due to the wide frequency band and lack of spectrum resource in the application of Frequency-Hopping Spread Spectrum and Spread Spectrum. The main task and contribution of this dissertation are as follows:(1)This dissertation introduces the background and significance of this subject, summarizes the present status of development communication anti-jamming technique and proposes the problem to be solved in anti-jamming technique.(2)This dissertation researches on signal separating technique in communication anti-jamming in order to solve the problem of inter-symbol interference due to the wide frequency band and lack of spectrum resource. The simulation result of Informax algorithm based on linear simultaneous mixing model shows that the estimation of probability density is critical for separating signals. Furthermore, an algorithm named switching algorithm is introduced to solve the above problem and is compared with Informax algorithm in Matlab. The simulation results indicate that Informax algorithm could only separate the signals following super-Gaussian distribution due to the selection of probability density function, but switching algorithm decides the choice of probability density function through calculating normalized kurtosis. And the results also prove that switching algorithm could separate the mixed signals of super-Gaussian signals and sub-Gaussian signals which solves the inter-symbol interference problem. Then a further modification is made to the switching algorithm to improve its stability and simulation in Matlab is again used to prove the validity and effectiveness.(3)This dissertation proposes a new sequential extraction algorithm based on the available sequential extraction algorithm using normalized kurtosis. This new algorithm nullifies the white noise interference and successfully solves the problem introduces by the Gaussian white nose. Furthermore, an improvement is made to avoid the constrictive cells, and the simulation shows the validity of the revised algorithm.(4)This dissertation builds an experimental platform to test the communication anti-jamming algorithms based on the previous research as a reliable reference for practical application. The platform applies high-speed data acquisition card to sample mixed signals of communication anti-jamming system and separates the signals in Matlab with different algorithms. Besides, a friendly GUI with functions like sampling, analysis and storage is designed. On this platform, some experiments using separating algorithms and extraction techniques are done to prove that the system is able to separate communication signals from the interference signals efficiency which is quite significant in communication anti-jamming technique.