Study On Frequency Modulation In Radar Signal Based On Map Chaos And Photonic Generation Chaos

As the development of information technology, electronic warfare are playing an more and more important role in modern wars, which requires a higher and higher level on radar technology. Faced with complicate and diversified environments of war, chaos radar has been emerged. Not only is chaos radar easy to control and produce the signal source, but also it has strong anti-interference and anti-interception performance, which make chaos radar gradually embarked on the front end of information warfare. This dissertation mainly focuses on design of signal source for wideband chaos radar, and main contributions are summarized as follows:(1) Two different chaos generation ways: chaotic map and fiber laser are studied. Firstly, the iterative mode of chaotic map and several common one-dimensional chaotic maps are introduced; then chaos generation principle in fiber laser is presented by adopting the erbium-doped fiber ring laser as the main model and nonlinear Kerr effect as the main technology.(2) Focused on some disadvantages of one-dimensional chaotic map sequences such as simple phase space, high equilibrium value, low Appropriate Entropy(ApEn) and easy destroyed by short quantization word length when realized digitally and so on, a combination map model based on Bernoulli is proposed. The model gets parameters B from other single maps, then B sequences are brought into Bernoulli map for chaos generation. The simulation demonstrates that chaotic sequences of this model in comparison with one-dimensional maps, combination maps based on Logistic and maps combined with Bernoulli itself, have more complex phase space, lower equilibrium value, higher approximate entropy,and still keep chaotic behavior when realized in digital device with short quantization word length.(3) Since there is a strong periodic problem in chaos generated by fiber laser due to the presence of cavity length, sampling and recombining methods are proposed. Through sampling with different intervals or recombining the original chaotic sequences, the chaos generation mode is changed in different levels. The simulation indicates the periodicity in auto-correlation and power spectrum has been effectively reduced and even eliminated.(4) The chaos-based frequency-modulated(FM) radar signal is designed, simultaneously, the frequency spectrum and ambiguity function are deduced and analyzed. The simulation results show that the FM radar signal with combined chaotic sequences based on Bernoulli map, compared with one-dimensional and other combination maps, has better autocorrelation, flatter frequency spectrum and better thumbtack ambiguity function; the FM radar signal based on random sampled or recombined photonic generation chaos has low side-lobes of auto-correlation, average energy distribution of cross-correlation, wide bandwidth of frequency spectrum and great performance of ambiguity function.