Echo canceller employing dual-H architecture having variable adaptive gain settings

Abstract

An echo canceller circuit for use in an echo canceller system is set forth that provides sensitive double-talk detection. The echo canceller circuit comprises a second digital filter having adaptive tap coefficients to stimulate an echo response occurring during the call. The adaptive tap coefficients of the second digital filter are updated over the duration of the call using a Least Mean Squares process having an adaptive gain a. A channel condition detector is used to detect channel conditions during the call. The channel condition detector is responsive to detected channel conditions for changing the adaptive gain a during the call. For example, the channel condition detector may detect the presence of a double-talk condition and set the adaptive gain a to zero. Similarly, the channel condition detector may detect the occurrence of a high background noise condition and set the adaptive gain a to a level less than 1 that is dependent on the detected level of the background noise. Other similar channel conditions and corresponding adaptive gain settings may likewise be utilized.

1 . An echo canceller circuit comprising: 
 a switch arranged to supply either a first echo compensated signal based on a first echo response that is modeled using adaptive tap coefficients or a second echo compensated signal based on a second echo response that is modeled using non-adaptive tap coefficients.    
   
   
       2 . The echo canceller circuit of  claim 1 , further comprising: 
 an adaptive filter having taps corresponding to the adaptive tap coefficients; and    a non-adaptive filter having taps corresponding to the non-adaptive tap coefficients.    
   
   
       3 . The echo canceller circuit of  claim 3 , further comprising: 
 a transfer controller arranged to transfer the adaptive tap coefficients from the adaptive filter to the non-adaptive filter.    
   
   
       4 . The echo canceller circuit of  claim 3 , wherein the transfer controller is arranged to transfer the adaptive tap coefficients based on a comparison of a first ERLE value characteristic of the first echo compensated signal with a second ERLE value characteristic of the second echo compensated signal.  
   
   
       5 . The echo canceller circuit of  claim 4 , wherein the transfer controller is arranged to transfer the adaptive tap coefficients when the first ERLE value is greater than the second ERLE value.  
   
   
       6 . The echo canceller circuit of  claim 3 , wherein the adaptive filter is arranged to adapt the adaptive tap coefficients after a transfer has occurred.  
   
   
       7 . An echo canceller circuit comprising: 
 a transfer controller arranged to transfer adaptive tap coefficients to replace non-adaptive tap coefficients to model an echo response using filtering with the adaptive tap coefficients.    
   
   
       8 . The echo canceller circuit of  claim 7 , further comprising: 
 an adaptive filter from which the adaptive tap coefficients are transferred; and    a non-adaptive filter which receives the adaptive tap coefficients.    
   
   
       9 . The echo canceller circuit of  claim 7 , wherein the transfer controller is arranged to transfer the adaptive tap coefficients based on a comparison of a first ERLE value characteristic of a first echo compensated signal with a second ERLE value characteristic of a second echo compensated signal.  
   
   
       10 . The echo canceller circuit of  claim 9 , wherein the transfer controller is arranged to transfer the adaptive tap coefficients when the first ERLE value is greater than the second ERLE value.  
   
   
       11 . The echo canceller circuit of  claim 8 , wherein the adaptive filter is arranged to adapt the adaptive tap coefficients after a transfer has occurred.  
   
   
       12 . A method for echo cancellation comprising: 
 supplying either a first echo compensated signal based on a first echo response that is modeled using filtering with adaptive tap coefficients or a second echo compensated signal based on a second echo response that is modeled using filtering with non-adaptive tap coefficients.    
   
   
       13 . The method of  claim 12 , further comprising: 
 replacing the non-adaptive tap coefficients with the adaptive tap coefficients.    
   
   
       14 . The method of  claim 12 , further comprising transferring the adaptive tap coefficients to replace the non-adaptive tap coefficients.  
   
   
       15 . The method of  claim 12 , further comprising: 
 transferring the adaptive tap coefficients to replace the non-adaptive tap coefficients based on a comparison of a first ERLE value characteristic of the first echo compensated signal and a second ERLE value characteristic of the second echo compensated signal.    
   
   
       16 . The method of  claim 15 , further comprising: 
 determining the first ERLE value; and    determining the second ERLE value.    
   
   
       17 . The method of  claim 14 , further comprising: 
 adapting the adaptive tap coefficients at the adaptive filter after a transfer has occurred.    
   
   
       18 . A method for echo cancellation comprising: 
 transferring adaptive tap coefficients to replace non-adaptive tap coefficients; and    modeling an echo response using the adaptive tap coefficients.    
   
   
       19 . The method of  claim 18 , wherein transferring the adaptive tap coefficients comprises: 
 making a comparison of a first ERLE value characteristic of a first echo compensated signal with a second ERLE value characteristic of a second echo compensated signal; and    transferring the adaptive tap coefficients based on the comparison.    
   
   
       20 . The method of  claim 19 , wherein transferring the adaptive tap coefficients based on the comparison comprises transferring the adaptive tap coefficients if the first ERLE value is greater than the second ERLE value.  
   
   
       21 . The method of  claim 18 , further comprising: 
 adapting the adaptive tap coefficients at the adaptive filter after a transfer has occurred.