Sub-band adaptive signal processing in an oversampled filterbank

• US 20030108214A1
• Filed: 08/07/2002
• Published: 06/12/2003
• Est. Priority Date: 08/07/2001
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: AMI Semiconductor Inc (ON Semiconductor Corporation)
• Inventors: Nadjar, Hamid Sheikhzadeh, Brennan, Robert L., Hermann, David, Schneider, Todd, Tam, King
• Granted Patent: US 7,110,554 B2
• Time in Patent Office: Days
• US Class Current: 381/94.7
• CPC Class Codes: H03H 17/0266 Filter banks
• CPC Class Codes: H03H 2021/0096 with input-sampling frequency and output-delivery frequency which differ, e.g. extrapolation; anti-aliasing
• CPC Class Codes: H03H 21/0027 filtering in the frequency domain

Abstract

An adaptive signal processing system for improving a quality of a signal. The system includes an analysis filterbank for transforming a primary information signal in time domain into oversampled sub-band primary signals in frequency domain and an analysis filterbank for transforming a reference signal in time domain into oversampled sub-band reference signals. Sub-band processing circuits process the signals output from the filterbanks to improve a quality of an output signal. A synthesis filterbank can combine the outputs of the sub-band processing circuits to generate the output signal.

Claims

1. 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.

2. The adaptive signal processing system of claim 1 wherein each processing circuit includes a digital filter having adjustable parameters, and a feedback circuit for adjusting the adjustable parameters of the digital filter based on the result of the processing.

3. The adaptive signal processing system of claim 2 wherein the filter is a FIR filter for filtering the sub-band reference signal, and the feedback circuit includes a summer for summing the output of the FIR and the sub-band primary signal, and a LMS circuit for receiving the output of the summer and the sub-band reference signal to adjust the adjustable parameters of the FIR filter.

4. The adaptive signal processing system of claim 1 wherein the feedback circuit further includes an emphasis filter.

5. The adaptive signal processing system of claim 1 further comprising a VAD for adjusting the sub-band processing circuit.

6. The adaptive signal processing system of claim 2 further comprising a VAD for adjusting the sub-band processing circuit.

7. The adaptive signal processing system of claim 3 further comprising a VAD for adjusting the sub-band processing circuit.

8. The adaptive signal processing system of claim 4 further comprising a VAD for adjusting the sub-band processing circuit.

9. The adaptive signal processing system of claim 1 wherein the sub-band processing circuit minimizes some error metric, which may include 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 weight of the filter, the “

E”

denotes the output of the summer and the “

*”

operator denotes complex conjugation.

10. The adaptive signal processing system of claim 1 wherein the primary information signal includes an audio signal and a first noise and the reference signal includes a second noise, and the first noise is correlated to the second noise.