High performance echo canceller for high speed modem

A system for performing echo cancellation in a communications network, comprising:

• a local bi-directional two-wire communication line;
• a remote bi-directional two-wire communication line;
• a four-wire communication line interposed between said local line and said remote line, said four-wire communication line having a transmit path and a receive path, wherein said transmit path is adapted to transfer a transmit signal from said local line to said remote line, and said receive path is adapted to transfer a receive signal from said remote line to said local line;
• a local hybrid transformer coupled between said local line and said four-wire line and configured to perform two-wire to four-wire circuit conversion to transfer the transmit signal from said local line to said four-wire line and transfer the receive signal from said four-wire line to said local line, wherein the local hybrid transformer imputes a near echo of the transmit signal upon the receive signal;
• a remote hybrid transformer coupled between said four-wire line and said remote line and configured to perform four-wire to two-wire circuit conversion to transfer the transmit signal from said four-wire line to said remote line and transfer the receive signal from said remote line to said four-wire line, wherein the remote hybrid transformer imputes a far echo of the transmit signal upon the receive signal;
• a modem which comprises:
• a transmitter configured to accept a sequence of input data and thereafter provide said transmit signal;
• an echo canceler comprising:
• a symbol buffer coupled to receive said sequence of input data;
• a first filter operatively coupled to receive a modulated output from said symbol buffer for providing a replica of said far echo in a real domain;
• a second filter coupled to said symbol buffer and configured to provide a replica of an analytic representation of said far echo in a complex domain;
• a third filter operatively coupled to receive a second modulated output from said symbol buffer for providing a replica of said near echo;
• a first summer configured to accept said receive signal and the replica of said near echo for providing a near-echo canceled signal;
• and
• a summer configuration coupled to said first filter to accept the replica of said far echo, coupled to said third filter to accept the replica of said near echo, configured to accept said receive signal, and configured to provide an error signal which is coupled to update coefficients of said first and third filters in accordance with an adaptation algorithm.