Method of extracting a signal

Abstract

A method is provided of extracting desired signals s t from contaminated signals y t measured via respective communication channels. The system comprising the desired signals s t and the channels is modelled as a state space model. In the model, the desired signals have time-varying characteristics which vary more quickly than second time-varying characteristics of the channels.

1 - 38 . (canceled)  
   
   
       39 . A method of extracting at least one desired signal from a system comprising at least one measured contaminated signal and at least one communication channel via which the at least one contaminated signal is measured, comprising modelling the at least one desired signal as a first dynamical state space system with at least one first time-varying parameter and modelling the at least one communication channel as a second state space system having at least one second parameter.  
   
   
       40 . A method as claimed in  claim 39 , in which the at least one desired signal is generated by a physical process.  
   
   
       41 . A method as claimed in  claim 40 , in which the at least one first parameter models the physical generation process.  
   
   
       42 . A method as claimed in  claim 39 , in which the at least one second parameter is time-varying.  
   
   
       43 . A method as claimed in  claim 39 , in which the at least one desired signal comprises a plurality of desired signals, each of which is modelled as a respective state space system.  
   
   
       44 . A method as claimed in  claim 39 , in which the second parameter is known.  
   
   
       45 . A method as claimed in  claim 43 , in which the at least one communication channel comprises a plurality of communication channels and the at least one contaminated signal comprises a plurality of contaminated signals.  
   
   
       46 . A method as claimed in  claim 45 , in which the number of communication channels is greater than or equal to the number of desired signals.  
   
   
       47 . A method as claimed in  claim 43 , in which the at least one contaminated signal comprises a linear combination of time-delayed versions of at least some of the desired signals.  
   
   
       48 . A method as claimed in  claim 39 , in which the at least one contaminated signal comprises the at least one desired signal contaminated with noise.  
   
   
       49 . A method as claimed in  claim 39 , in which the at least one channel comprises a plurality of signal propagation paths of different lengths.  
   
   
       50 . A method as claimed in  claim 39 , in which the at least one desired signal comprises an analog signal.  
   
   
       51 . A method as claimed in  claim 50 , in which the analog signal is a temporally sampled analog signal.  
   
   
       52 . A method as claimed in  claim 50 , in which the at least one desired signal comprises a sound signal.  
   
   
       53 . A method as claimed in  claim 52 , in which the least one sound signal comprise speech.  
   
   
       54 . A method as claimed in  claim 52 , in which the contaminated signals are measured by spatially sampling a sound field.  
   
   
       55 . A method as claimed in  claim 52 , in which the at least one first parameter comprises a noise generation modelling parameter.  
   
   
       56 . A method as claimed in  claim 52 , in which the at least one first parameter comprises a formant modelling parameter.  
   
   
       57 . A method as claimed in  claim 39 , in which the at least one desired signal is modelled as a time-varying autoregression.  
   
   
       58 . A method as claimed in  claim 39 , in which the at least one desired signal is modelled as a moving average model.  
   
   
       59 . A method as claimed in  claim 39 , in which the at least one desired signal is modelled as a non-linear time-varying model.  
   
   
       60 . A method as claimed in  claim 39 , in which the at least one communication channel is modelled as a finite impulse response model.  
   
   
       61 . A method as claimed in  claim 39 , in which the at least one communication channel is modelled as an infinite impulse response model.  
   
   
       62 . A method as claimed in  claim 39 , in which the at least one communication channel is modelled as a non-linear time-varying model.  
   
   
       63 . A method as claimed in  claim 39 , in which the first state space system has at least one parameter which is modelled using a probability model.  
   
   
       64 . A method as claimed in  claim 63 , in which the at least one desired signal is extracted by a Bayesian inversion.  
   
   
       65 . A method as claimed in  claim 63 , in which the at least one desired signal is extracted by maximum likelihood.  
   
   
       66 . A method as claimed in  claim 63 , in which the at least one desired signal is extracted by a last squares fit.  
   
   
       67 . A method as claimed in  claim 64 , in which the signal extraction is performed by one of a sequential Monte Carlo method and a particle filter.  
   
   
       68 . A method as claimed in  claim 64 , in which the signal extraction is performed by one of a Kalman filter and an extended Kalman filter.  
   
   
       69 . A program for controlling a computer to perform a method as claimed in  claim 39 .  
   
   
       70 . A carrier containing a program as claimed in  claim 69 .  
   
   
       71 . A computer programmed by a program as claimed in  claim 69.