Research On Nonlinear Feature Extraction Of Noises Radiated From Underwater Targets

Nonlinear theory is one of the most important scientific research in 20th century, taking the chaotic and fractal theory as representations. It's considered to be the 3^rd revolution of physics, proceeding with theory of relativity and quantum mechanics. It has broken down the impassable barrier between the deterministic system and the stochastic system. Nonlinear theory with its application is a challengeable researching subject in world nowadays. The application will be profound.With the increasing development of nonlinear theory, taking the chaotic and fractal theory as representations, applying the nonlinear theory to signal processing, researching the nonlinear characteristic of signal made an increasing attention. Signal is made up with 2 opposite parts-certain signal and stochastic signal in traditional signal processing theory. But chaotic signal is different from the 2 kinds of signal. It's engendered by certain system, acting similar to stochastic signal, and can't be predictable in long term.Underwater acoustic signal processing is an important branch of signal processing. And underwater target radiated noise is a great sort of underwater acoustic signal. The underwater target radiated noise has a complicated nonlinear course. Many recent researches have shown that the underwater acoustic signal including underwater target radiated noise obtains a certain chaotic behavior. So applying the nonlinear analysis method to underwater acoustic signal processing, describing the nonlinear characteristic of target radiated noise is the developing direction of modern underwater acoustic signal processing.Basing on chaotic and fractal theory, this paper is researching nonlinear features extraction of noises radiated from underwater target. The chaotic and fractal theory, relative to feature extraction closely, is introduced first. Then the distilling arithmetic of fractal characteristic parameters, such as phase space...