Research On Weak Signal Detection Method Based On Chaos And FPGA Implementation Of Chaotic System

Information interaction makes matter closely linked.Noise affects the effective transmission of information in the transmission,transmission,reception and processing of information.Weak signal detection technology is a method to suppress noise.It has many branches.As a system sensitive to specific frequency signals and immune to noise,chaotic system is widely used in weak signal detection.In this paper,intermittent chaos is used to detect weak signals with unknown frequencies,chaotic synchronization is used to recover waveforms of signals with low signal-to-noise ratio(SNR),and the realization of chaotic system in FPGA is studied.Firstly,the characteristics of Duffing chaotic system and Liu chaotic system are analyzed,and the convergence state of Liu chaotic system is highlighted.The Chua's chaotic system is analyzed by using the bifurcation graph,and the relationship between the parameter change and the state of the chaotic system is obtained.The working principle of phase-locked loop(PLL)is analyzed,which provides theoretical guidance for parameter design of PLL.Then,aiming at the problem that the conditions of intermittent chaos are not clear,the intermittent chaos phenomena of Duffing chaotic system are studied,and the influence of noise on the conditions of intermittent chaos phenomena is illustrated by simulation experiments.Aiming at the problem that the chaos-periodic transition intermittent chaos phenomenon of Duffing chaotic system is not obvious,the chaos-convergence transition intermittent chaos of Liu chaotic system is debugged by using the characteristics of convergence state of Liu chaotic system.The two chaotic systems are compared by the experiment of detecting noisy waves.The experimental results show that Liu chaotic system has the advantage of high detection accuracy.Then,the driver-response Chua's chaotic synchronization system is realized by the controller,and the weak signal detection function is verified.To overcome the shortcoming that Chua's chaotic synchronization system can only detect weak signals at specific frequencies,the idea of scale transformation is introduced to improve the system.By adjusting the scale transformation factor in the system,the improved system can detect weak signals at different frequencies.In order to obtain more pure signals,PLL is designed and connected with the improved Chua's chaotic synchronization system in series to achieve low SNR sinusoidal signal waveform recovery.Finally,Duffing chaotic digital system and Liu chaotic digital system are designed based on the FPGA platform,and the basic functions of the two digital chaotic systems are verified by experiments.Two digital chaotic systems and corresponding analog chaotic systems are compared for threshold stability of state transition.The advantages and disadvantages of the two digital chaotic systems are analyzed.