EP0709958A1
Expired / Lapsed
EP
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Adaptive finite impulse response filtering method and apparatus
Assignee: AT&T Inc
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Filing: 1995-10-18
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Granted: —
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Expires: 2015-10-18
Abstract
Abstract The present invention provides a signal processing method and apparatus including a digital finite impulse response filter (53) wherein the error caused by slow asymptotic convergence of the filter's adaptive coefficients is reduced. According to one embodiment of the present invention, a first input signal (x(n)) is provided to an adaptive FIR filter (53) comprising a coefficient calculator (56), an FIR filter (54) and a summation device (62). The filter also receives a second input signal (y(n)), which may, for example, be the echo of the first input signal. The first input signal and the second input signal have a first bandwidth (by 50,58). The adaptive FIR filter provides an output signal to a filter (66), which filters the output signal to a second bandwidth which is less than the first bandwidth. The processed signal will have less error caused by the slow asymptotic convergence of the filter (53) than previously possible because the error-concentrated frequency components near the band edge of the first frequency band have been filtered or removed.
Inventors
- 👤 Phillip Louis De Leon Ii
- 👤 Dennis R. Morgan
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 03:08
CPC Classifications
H; H03; H03H; H03H21/00; H03H21/0012; H04; H04M; H04M9/00; H04M9/08; H04M9/082; H03H2021/007; H03H2021/0072; H03H2021/0074
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
175 words
A signal processing apparatus for use in a system having a predetermined frequency band of interest, the signal processing apparatus comprising: a) a first input operable to receive a first input signal and a second input operable to receive a second input signal, the first and second input signals having a first operating bandwidth that exceeds the predetermined frequency band of interest; b) an adaptive finite impulse response filter connected to the first input and the second input, said filter operable to produce coefficients defining an impulse response, said impulse response representative of a relationship between the first input signal and the second input signal, process the first input signal using the impulse response and produce an estimated signal therefrom, produce an error signal representative of the difference between the estimated signal and the second input signal, and generate an output signal corresponding to the first input signal; wherein said signal processing apparatus is operable to provide the output signal to the system, said output signal having reduced error in the frequency band of interest.
Claim 2
Dependent Claim
168 words
A signal processing apparatus comprising: a) a first input operable to receive a first input signal and a second input operable to receive a second input signal, the first and second input signals having a first operating bandwidth; b) an adaptive finite impulse response filter connected to the first input and the second input, said filter operable to produce coefficients defining an impulse response, said impulse response representative of a relationship between the first input signal and the second input signal, process the first input signal using the impulse response and produce an estimated signal therefrom, produce an error signal representative of the difference between the estimated signal and the second input signal, and generate an output signal corresponding to the first input signal; and c) a shaving device connected to receive the output signal from the adaptive finite impulse response filter, said shaving device operable to generate a processed signal therefrom, the processed signal having a second operating bandwidth which is less than said first operating bandwidth.
Claim 3
Dependent Claim
273 words
A signal processing apparatus comprising: a) a first low pass filter operable to receive a first input signal, the first low pass filter having a cutoff at a first frequency; b) a second low pass filter operable to receive a second input signal, the second low pass filter having a cutoff at the first frequency; c) an A/D converter connected to the first low pass filter; d) an A/D converter connected to the second low pass filter; e) an adaptive finite impulse response filter comprising a coefficient calculator connected to the first A/D converter operable to produce coefficients defining an impulse response, said impulse response representative of the relationship between the first input signal and the second input signal, said coefficients depending on the first input signal and an error signal; an FIR filter connected to the first A/D converter and further operably connected to receive the coefficients from the coefficient calculator, said FIR filter operable to process the first input signal using the impulse response and produce a simulated signal therefrom; a summation device connected to the second A/D converter and the FIR filter, the summation device operable to produce the error signal, said error signal representative of the difference between the simulated signal received from the FIR filter and the signal received from the second A/D converter, said summation device further operably connected to provide the error signal to the coefficient calculator; f) a shaving filter connected to receive an output signal from the adaptive finite impulse response filter and generate a processed signal therefrom, the filter having a cutoff at a second frequency which is lower than the first frequency.
Claim 4
Dependent Claim
200 words
An signal processing apparatus comprising: a) a first subband analyzer operable to receive a first input signal and produce a plurality of first subband input signals, each first subband signal having a frequency bandwidth that overlaps a frequency bandwidth of another first subband signal; b) a second subband analyzer operable to receive a second input signal and produce a plurality of second subband input signals, each second subband signal having a frequency bandwidth that overlaps a frequency bandwidth of another second subband signal; c) a plurality of adaptive finite impulse response filters, each filter comprising d) an adaptive finite impulse response filter connected to the first input and the second input, said filter operable to produce coefficients defining an impulse response, said impulse response representative of a relationship between the first input signal and the second input signal, process the first input signal using the impulse response and produce an estimated signal therefrom, and produce an error signal representative of the difference between the estimated signal and the second input signal; d) a subband synthesizer connected to receive the plurality of subband error signals, said subband synthesizer including a filter operable to reduce the bandwidth of each subband error signal.
Claim 5
Independent Claim
148 words
A method of reducing error in a signal for use in a communication system, said system having a predetermined frequency band of interest, the method comprising: a) providing a first input signal to an adaptive finite impulse response filter, the first input signal having an operation bandwidth exceeding the frequency band of interest; b) providing a second input signal to the adaptive finite impulse response filter, the second input signal having an operation bandwidth exceeding the frequency band of interest; c) iteratively generating an impulse response associated with the adaptive finite impulse response filter, said impulse response approximating the relationship between the first input signal and a second input signal; d) generating an output signal based upon the impulse response and providing said output signal to the system; and wherein the system only uses the portion of the output signal that is within the frequency band of interest.
Claim 6
Independent Claim
131 words
A method of processing a signal for use in a system, the system having a predetermined frequency band of interest, the method comprising: a) providing a first input signal to a first filter, the first filter having a first pass band; b) providing a second input signal to a second filter, the second filter having the first pass band; b) providing the first input signal to an adaptive finite impulse response filter, said filter having an impulse response that approximates the relationship between the first input signal and a second input signal; c) employing said filter to generate an output signal; and d) providing the output signal to a shaving filter, the shaving filter having a second pass band, the second pass band having less bandwidth than the first pass band.
References Cited (Backward Citations)
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