Apply Homomorphic Filtering Technology To Underwater Acoustic Channel

Underwater acoustic signals passing through the multi-path fading channel, will suffer a serious distortion, and make it difficult for follow-up positioning solution. So how to pick up the direct sound which is added by the reflected sound in order to reconstruct the original signals, has been of concern in topic. Different disciplines not only develop on their own but also promote each other or even a combination. In speech, images, ultrasonic testing and other scientific fields there are much in common in signal processing. The original intention of this dissertation is trying to apply the homomorphic filtering technology which has been proven mature in the field of speech and image to resolve the underwater acoustic multi-path fading channels.Homomorphic filtering which meets the broad principle of superposition is a nonlinear signal processing technology. The main direction of this dissertation is to apply homomorphic filtering technology to the signal and channel separation. First of all, paper introduces the basic theory of homomorphic filtering technology and the problems which are encountered in the calculation and the corresponding solutions. Then analyzes what is the impact of multi-path fading channel on the positioning systems. The dissertation studies the features of the channel and the signal respectivly in the cepstral domain and the key factors to seprate the signal and the channel.Homomorphic filtering technology has many applications in underwater acoustic signal processing. The dissertation will discusse three applications, they are signal detection, time-delay estimation and target identification. Chapter IV major research in applying homomorphic filtering to detect whether a signal has been added by its delay signal, and to restore the original signal, then simulate the effectiveness of this algorithm under three kinds of typical channel model. The other two applications which are picking passive time delay and picking the frequency of ship radiated noise will be researched in the fifth chapter. There will be detailed simulation and the results showe that homomorphic filtering technique is a simple and convenient anti-multi-path technology. This technique will have a good prospect in underwater acoustic signal processing applications. The dissertation provides a detailed theoretical guidance for future engineering applications.