Weak Signal Detection Based On Chaos Theory And Its Application On DSP

An important aspect in information science field is to acquire real information of objective world, but there exists noise in all systems, especially it is difficult to detect weak signal in strong noise, so more attention has been paid to the problem of how to measure the weak signal in strong noise. In recent years, the rapid development of nonlinear science, particularly the introduction of chaos theory and the stochastic resonance theory, puts a new complexion on weak signal detection. It is proved that chaotic systems are sensitive to certain signals but immune to noise at the same time, the properties of which demonstrate their tremendous potential application in weak signal detection.The thesis starts by introducing the definition of chaos, chaotic characteristics, methods for distinguishing chaotic motion and ways leading to chaos, and then the intermittent chaos theory of the Duffing oscillator and its periodic characteristic are expounded for practical purpose. A new measurement method of frequency of weak signal is presented based on intermittent chaotic phenomenon resulting from minute change of system parameters. The key of above method is to increase the frequency of internal periodic alternate force in Duffing oscillator by degrees, which establishes the theoretical basis of weak signal detection by use of the intermittent chaos. Simultaneity the numerical experiment study is carried out for distinguishing intermittent chaotic motion and evaluating its period, and a brand-new method is advanced using zero-pass ratio. The thesis places emphasis on analysing the computer simulation by taking the weak sinusoidal periodic signal in strong noise as an example. The results of experiments show that above method has many merits such as simple, effective, easy to be applied, less error etc compared with other detection methods.Combined with author's experience on DSP, the thesis also further explores the application of DSP in weak signal detection based on chaos theory, including building a utilizing TMS320C6211B experiment platform, developing corresponding software, giving the revelant optimization codes of C language when mutli-language programming with assembly language and measuring the frequency of the input signal in order to demonstrate the feasibility, practicability of above theory and the validity of DSP system.At the end, some valuable advice of weak signal detection based on chaos theory and its implement on DSP system are proposed.