Method of processing electrical signals by means of Fourier transformations
First Claim
1. A method of cancelling echo in speech frequency electrical signals by a digital filtering arrangement, comprising the steps of applying at least one input signal u to a polyphase network to produce intermediate output signals Vv, subjecting the intermediate output signals to a discrete Fourier transformation to produce spectral partial signals Vv having separated real and imaginary components, processing the spectral partial signals Vv by an adaptive level control to produce at outputs of the digital filtering arrangement complex time signals Wv which meet the equation
wherein cv is a level factor determined during speech pausesas a function of momentary signal expectation values E1 and E2 and of the spectral partial signals Vv according to the equation ##EQU10## where Nv are interference components, and interpolating the processed signals Wv in an output signal S, the interpolation step including inverse, discrete Fourier transformation and inverse polyphase filtering in a polyphase network.
)=c.sub.v (ρ
)·
V.sub.v (ρ
),
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Abstract
In order to upgrade input signals for further processing, one or more of the input signals is split up by a decimating technique into spectral component signals which are processed according to the desired purpose and recombined by means of an interpolation technique into an output signal. In this manner a digital filtering device can be selectively employed for achieving an arbitrary combination of simultaneous filtering, signal improvement, echo or feedback compensation, or signal masking of the input signals.
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Citations
6 Claims
- 1. A method of cancelling echo in speech frequency electrical signals by a digital filtering arrangement, comprising the steps of applying at least one input signal u to a polyphase network to produce intermediate output signals Vv, subjecting the intermediate output signals to a discrete Fourier transformation to produce spectral partial signals Vv having separated real and imaginary components, processing the spectral partial signals Vv by an adaptive level control to produce at outputs of the digital filtering arrangement complex time signals Wv which meet the equation
- space="preserve" listing-type="equation">W.sub.v (ρ
)=c.sub.v (ρ
)·
V.sub.v (ρ
),
wherein cv is a level factor determined during speech pauses as a function of momentary signal expectation values E1 and E2 and of the spectral partial signals Vv according to the equation ##EQU10## where Nv are interference components, and interpolating the processed signals Wv in an output signal S, the interpolation step including inverse, discrete Fourier transformation and inverse polyphase filtering in a polyphase network. - View Dependent Claims (2, 3, 4, 5, 6)
- space="preserve" listing-type="equation">W.sub.v (ρ
Specification
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- Resources
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Current AssigneeTekade Felten & Guilleaume Fernmeldeanlagen GmbH
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Original AssigneeTekade Felten & Guilleaume Fernmeldeanlagen GmbH
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InventorsVary, Peter
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Primary Examiner(s)Smith, Jerry
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Assistant Examiner(s)Jablon, Clark A.
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Application NumberUS06/709,358Time in Patent Office620 DaysField of Search179/1.5 R, 179/1.5 FS, 179/170.2, 179/1.5 M, 364/723, 364/724US Class Current708/313CPC Class CodesG10L 21/02 Speech enhancement, e.g. no...G10L 25/18 the extracted parameters be...H03H 17/0288 Recursive, non-recursive, l...H04B 1/667 using a division in frequen...H04B 3/21 using a set of bandfiltersH04K 1/04 by frequency scrambling, i....
