Weak Signal Detection Under Chaotic

Weak signal is not only a signal with very small amplitude,but also a signal existing in the background of noise.The application of weak signal detection technology covers communication,radar,magnetics,vibration measurement,medicine and other fields.In the practical engineering application field,because of the complex environment and various noises,the traditional weak signal detection method will fail.So the urgent task is to find some new weak signal detection methods.According to chaos theory,chaotic system is very sensitive to weak signals and immune to noise,so it has great advantages in signal detection.Therefore,Duffing oscillator system is used to detect weak signals.The main research contents and achievements are as follows:(1)Several definitions of chaos and basic characteristics of chaos are introduced.Several classical chaotic systems are introduced,and simulated experimental diagrams are given.In these classical chaotic systems,Duffing oscillator system is selected to detect weak signals.The method of judging the state of chaotic system is analyzed,and Lyapunov exponent is chosen as the criterion of chaos in these methods.(2)The dynamic characteristics and detection principle of the Duffing oscillator system are studied in detail.The influence of signal frequency and Gauss white noise on Duffing oscillator system is analyzed.A single Duffing oscillator system may fail when detecting unknown frequency signals.To solve this problem,two improved methods are proposed.One is to improve the parameters of the oscillator when constructing the Duffing oscillator array,secondly,a spectrum-based Duffing oscillator detection method based on sliding mode variable structure control is presented.The simulation results show that the two improved methods can detect the frequency of weak signals and have high estimation accuracy.(3)An improved method for detecting the amplitude and initial phase of weak signals is proposed,and the PSO is used to optimize the Wolf method.By using the improved method proposed in this paper,the simulation experiment is carried out and compared with the traditional amplitude detection method.The results show that the improved method proposed in this paper is superior to the traditional amplitude detection method in detection accuracy.The paper has 73 Figures,3 Tables and 81 references.