Applied Physics
 
 
 
 
Adaptive signal processing and neural networks

Adaptive signal processing systems refer to systems for processing of data, which based on some recursive algorithm, are able to operate in an unknown or time-varying environment or possibly both. Hence, the basic nature of the problem is that some elements of it is unknown and must be learned from the data, or some components of the system is changing in an unknown manner, and therefore must be tracked. So far most of these problems have been formulated as linear filtering problems. Nevertheless, adaptive filters are commonly classified as linear or non-linear. An adaptive filter is said to be linear if the estimated quantity of interest is computed adaptively as a linear combination of the observable applied data. Else, the adaptive filter is characterized as non-linear. In this project we are studying algorithms for non-linear adaptive signal processing. Basically, we are studying a model consisting of three sections: a bank of linear filters followed by an array of non-linear elements and a linear combiner. The objective is to find effective, stable algorithms for adjusting the parameters of the system. Presently, we are studying two applications: adaptive speech enhancement and non-linear time series prediction.

A neural network is a large system of interconnected non-linear processing elements called neurons. Its motivation comes from the way the human brain performs its operations. Neural networks have the following characteristics: they have non-linear processing elements, they make few or no assumptions about the environment, they have learning and generalization capabilities, and they have fault tolerance. We are interested in the design of neural networks for specific application, such as: adaptive signal processing, time series prediction, clustering and pattern recognition. 

For more information please contact Torbjørn Eltoft.
 
 
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Department of Physics, Faculty of Science  
University of Tromsø, N-9037 Tromsø, tel. 77 64 51 50 
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Web responsible: Svein Jacobsen; Last update: September 11th, 2002