Sub-band adaptive signal processing in an oversampled filterbank

An adaptive signal processing system for improving a quality of a signal, comprising:

• a first analysis filterbank for receiving a primary information signal in the time domain and transforming the primary information signal into a plurality of oversampled sub-band primary signals in the frequency domain;
• a second analysis filterbank for receiving a reference signal in the time domain and transforming the reference signal into a plurality of oversampled sub-band reference signals numerically equal to the number of primary signal sub-bands;
• a plurality of sub-band processing circuits for processing these signals to improve a quality of an output signal;
• and
• a synthesis filterbank for combining the outputs of the sub-band processing circuits to generate the output signal,
• wherein the sub-band processing circuit minimizes some error metric, which includes The value of the squared error E2 as described in the following equation:
• E2=(YW−X)(YW−X)*
• wherein the “Y” denotes the sub-band primary signals, the “X” denotes the sub-band reference signals, the “W” denotes an adaptive weighting filter, the “E” denotes a summation of the “X” and “Y” filtered by the “W”, and the “*” operator denotes complex conjugation.

A method of improving a quality of a signal, comprising the steps of:

• at a first weighted-overlap-add (WOLA) analysis filterbank, implementing block processing including a weighting window limited in length to transform a primary information signal in the time domain into a plurality of oversampled sub-band primary complex signals in the frequency domain;
• at a second WOLA analysis filterbank, implementing block processing including a weighting window limited in length to transform a reference signal in the time domain into a plurality of oversampled sub-band reference complex signals numerically equal to the number of primary signal sub-bands;
• at each of sub-band processing circuits, adaptively processing the over-sampled sub-band complex signals, including performing adaptive filtering at a complex adaptive filter which has adjustable parameters, the processing step including, at a feedback circuit included in the sub-band processing circuit, implementing adaptive algorithm to adjust the adjustable parameters based on the result of the processing, and improving convergence of the adaptation algorithm;
• and
• at a WOLA synthesis filterbank, combining the outputs of the sub-band processing circuits to generate an output signal having a signal of interest of improved quality and in the time domain.