Patent ID: 6147979
Filing Date: 2000-11-14
Classification: H04M

Abstract:
An echo canceller for reducing an echo component in an analog output signal, the echo canceller comprising:a digital echo canceller for digitally processing the analog output signal after being converted to digital form to reduce the echo component before transmission;an analog echo canceller for reducing the echo component in the analog output signal when in analog form before digital processing by the digital echo canceller; wherein the analog echo canceller includes:means for generating an analog cancellation signal which is substantially the same as the echo component in the analog output signal before digital processing by the digital echo canceller; andmeans for combining the analog echo cancellation signal with the analog output signal to reduce the echo component before digital processing by the digital echo canceller wherein the combining means produces an echo reduced analog output signal and includes means interposed between the combining means and the digital echo canceller to automatically amplify the echo reduced analog output signal to a level for substantially maximum resolution digitization of the echo reduced analog output signal;wherein said automatically amplifying means includes:a variable gain amplifier,means for setting the amplifier gain at a level below a digitization saturation level,means for training the analog echo canceller until substantially maximum echo reduction is achieved, andmeans for increasing the gain of the variable gain amplifier after training is completed to obtain maximum digital resolution during conversion.