METHOD OF MITIGATING THE EFFECTS OF CLIPPING OR QUANTIZATION IN THE D/A CONVERTER OF THE TRANSMIT PATH OF AN ECHO CANCELLER

摘要

A transmission system includes transmit and receive paths coupled via a hybrid circuit (16) to a bidirectional transmission path (18). The transmit path includes a DAC (14) having a given rang and precision. The transmit path signal is limited and truncated (28) to this range and precision before the DAC. An echo canceller (26) can be coupled between the transmit and receive paths, a difference of the transmit path signal before and after limiting and truncation being used to produce an estimated echo response which is subtracted (32) from the receive path signal, or all of the inputs to the echo canceller can be derived from the transmit path after the limiting and truncation. The amplitudes of transmit path signal samples can be shaped in conjunction with the limiting. If the system uses multicarrier modulation, the amplitudes can be scaled to reduce clipping, with an indication of the scaling being transmitted to a remote receiver.