| 摘要 |
<p>A transmitter generates a transmit signal to a communications channel in a frequency band outside a voice frequency band. A receiver receives signals from the communications channel within or outside the voice frequency band. A programmable scaler is connected to the transmitter and generates a scaled replica of the transmit signal based upon a scaled control signal. The receiver is connected to the scaler and reduces the undesired local echo by subtraction of a scaled replica of the transmit signal. An echo reducing circuit senses the received signal power and generates the scaled control signal to reduce the undesired local echo. Alternatively, an estimate of the transfer function from the transmitter digital-to-analog converter to the input of a canceller is used to replicate the local echo path used to replicate the local echo path so that a cancelling signal can be generated. <IMAGE></p> |
