Dual-mode analog/digital adaptive echo cancellation in communication systems with asymmetric spectrum

In a full-duplex communication system having a transmit path and a receive path, a system for echo cancellation comprising:

• a digital echo estimator unit for generating a digital echo estimate signal based on the transmit path;
• a switch communicatively coupled to the digital echo estimator unit, the switch configured to select between an analog echo cancellation path and a digital echo cancellation path;
• a digital to analog converter (DAC) communicatively coupled to the analog echo cancellation path of the switch for converting the digital echo estimate signal to an analog echo estimate signal;
• an analog subtractor communicatively coupled to the DAC for receiving the analog echo estimate signal and communicatively coupled to the receive path of the communication system for receiving a received signal superimposed with a local echo signal, wherein the analog subtractor creates an error signal by differencing the analog echo estimate signal and the received signal;
• and
• a digital subtractor communicatively coupled to the digital echo cancellation path of the switch for receiving the digital echo estimate signal and communicatively coupled to the receive path of the communication system for receiving a received signal superimposed with a local echo signal, wherein the digital subtractor creates an error signal by differencing the digital echo estimate signal and the received signal.