Frequency domain signal reconstruction compensating for phase adjustments to a sampling signal

An adaptive echo canceller implemented in the frequency domain for use in a digital communications system where transceivers communicate over a communications channel, each transceiver sampling a signal received over the communications channel in accordance with a timing signal, comprising:

• delay stages that receive a transmitted signal to generate a series of input signals;
• a Fourier transformer that transforms the series of input signals into a frequency domain to create series of input spectral components;
• a multiplier multiplying each of the spectral components by a corresponding spectral filter coefficient to generate a corresponding product;
• a summer that sums the products corresponding to each of the spectral components to generate a summed signal corresponding to an expected echo;
• a combiner that subtracts the summed signal from a signal received over the communications channel to cancel echo from the received signal and that generates an error based on an uncancelled echo;
• a signal processor that adapts the spectral filter coefficients of the adaptive filter to minimize the error;
• a compensator that analyzes each spectral filter coefficient as having at least two signal components with a first spectral component including baseband frequency components corresponding to the echo and a second spectral component including aliased frequency components, predicts new values of the spectral filter coefficients in the frequency domain corresponding to an amount of time the timing signal is to be adjusted, and provides the predicted values of the spectral filter coefficients to the one or more multipliers and the signal processor so that the summed signal accurately models an echo in a signal received by the transceiver when the timing signal is adjusted.

In a digital communications system where transceivers communicate over a communications channel, a method implemented in one or more of the transceivers comprising the steps of:

• sampling a signal received over the communications channel in accordance with a sampling signal;
• developing a transfer function corresponding to the impulse response of the communications channel;
• and
• compensating the transfer function in the frequency domain for a phase adjustment in the sampling signal that occurs in the time domain including correcting the spectral coefficients of the transfer function in the frequency domain by an amount corresponding to the adjustment in the sampling signal,
• wherein aliased signal content is taken into account in correcting spectral coefficients of the transfer function by identifying for spectral coefficients of the transfer function at least two spectral components, a first spectral component including baseband frequency components and a second spectral component including aliased frequency components.

In a digital communications system where transceivers communicate over a communications channel, a method implemented in one of the transceivers comprising the step of:

• sampling a signal received over the communications channel in accordance with a timing signal having a sampling rate that is less than twice the highest frequency component of the received signal;
• identifying in the sampled signals aliased frequency components generated as a result of the timing signal having a frequency that is less than twice the highest frequency component of the received signal;
• and
• reconstructing the received signal from the signal samples using the identified aliased frequency components.