Research On Weak Signal Reception Based On Non-linear Theory

Nowadays, aeronautical communications in the exchange of aircraft flightinformation, accessing to meteorological indicators and in the field of militaryreconnaissance, etc. play an increasingly important role. In Space Communication,long communication link will reduce the strength of the received signal. Further,since the need for secure communication, the signal transmission is often buried innoise.Therefore, there is an urgent need to find out a way to apply to receive lowSNR signal extraction techniques.The traditional methods of weak signal reception were divided into the timedomain and the frequency domain method for receiving two categories.However,these methods required for adding a pre-amplifier in front of the system,resulting in a signal with the noise is amplified at the same time. Furthermore, thesemethods required the input SNR (Signal to Noise Ratio) is high.Therefore, thesemethods for weak signal processing are almost powerless.Low SNR signal receivertechnology, is to study to distinguish the weak signal from the strong noise andextract technology.It is able to adapt to aeronautical communications applications.This paper is mainly research on the theory of wavelet transform and chaostheory. And propose a receiver technology that can extract the high-frequency weaksignal from noise effectively. The wavelet transform canaccumulate weak signalenergy, while discrete noise energy, thusmost of the noise will be subtracted fromthe weak signal.As chaos theory has a dependence on initial small-signal, andexclusion to noise, the weak signal submerged in strong noise can rapid andeffective identification. Combines the advantages of both technologies, this paperpresents a reception technology for high frequency weak signal,that meets the needsof aeronautical communications Firstly, this article describes the basic theory ofwavelet transform, analyzes the basic principles of wavelet threshold method toextract weak signals. According to the characteristics of wavelet threshold method,we design reasonable denoising parameters, and we verify the validity of waveletthreshold method denoising low SNR signal through simulation. Additionally, weintroduces the concepts of chaos theory, focusing on analysis of the dynamicscharacteristics of Duffing equation. Then it introduces a self-adaptivesynchronization controlling algorithm-Speed Gradient Methodology. Thesimulation results show that the algorithm can effectively control the chaotic system,and make dual chaotic systems produced by double Duffing equation achievesynchronization. Finally combining wavelet threshold method and advantages of dual Duffing synchronous control system, we design a suitable model for weaksignal reception. Simulation results prove that the model can extract QPSK signalswhose SNR is more than-20dB, thus verifying reliability and validity of themethods mentioned in the text.