EP0464500A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Echo canceler having adaptive digital filter unit associated with delta-sigma modulation circuit
Assignee: NEC Corp
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Filing: 1991-06-20
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Granted: —
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Expires: 2011-06-20
Abstract
Abstract An echo canceler comprises an adaptive digital filter circuit (42) for producing an echo replica signal on the basis of a transmit digital signal (TD) and a first digital signal indicative of a far-end signal, and an adder (45) for eliminating the echo signal from a received signal with reference to the echo replica signal, wherein the echo replica signal is modulated by a delta-sigma modulation circuit (43) and, thereafter, converted into an analog signal for allowing the adder to operate on the echo replica signal and the received signal both in an analog form so that the adder with a narrow dynamic range can be available.
Inventors
- 👤 Yutaka Takahashi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 20:28
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/20; H04B3/23; H04B3/238
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
220 words
An echo canceler associated with a signal transmission unit (TM) for transmitting a transmit digital signal (TD) and operative to eliminate an echo signal from a received signal containing at least said echo signal and a far-end signal, comprising: a) an adaptive digital filter circuit (42) supplied with said transmit digital signal and a first digital signal without said echo signal so as to see a correlation therebetween, and operative to produce an echo replica signal; and b) a first adder (45) for eliminating said echo signal from said received signal with reference to said echo replica signal, characterized by c) a delta-sigma modulation circuit (43;98) operative to carry out a delta-sigma modulation on said echo replica signal in a digital form and producing a second digital signal representative of said echo replica signal; d) a digital-to-analog converting circuit (44) for converting said second digital signal to a first analog signal indicative of said echo replica signal, said first analog signal being fed to said adder for allowing said adder to operate on said received signal in an analog form; and e) means (46/47) supplied with said received signal without said echo signal from said adder, and operative to carry out a delta-sigma analog-to-digital converting operation on said received signal without said echo signal, and producing said first digital signal.
Claim 2
Dependent Claim
54 words
An echo canceler as set forth in claim 1, in which said delta-sigma modulation circuit (42) is of a second order type, and in which said digital echo replica signal is sampled at an over-sampling frequency n times larger than a baud rate frequency of said transmit digital signal where n is an integer.
Claim 3
Dependent Claim
63 words
An echo canceler as set forth in claim 2, in which said means comprise e-1) a second order delta-sigma analog-to-digital converting circuit (46) supplied with said received signal and producing a third digital signal, and e-2) a digital low pass filter circuit (47) for eliminating noises and decimating from said over-sampling frequency to said baud rate frequency for producing said first digital signal.
Claim 4
Dependent Claim
65 words
An echo canceler as set forth in claim 3, in which said echo canceler further comprises f) an equalizer coupled to said digital low pass filer circuit and eliminating a distortion therefrom for producing a received digital signal representative of said far-end signal, and g) a switching circuit selectively coupling said digital low pass filter circuit and said equalizer to said adaptive digital filter circuit.
Claim 5
Dependent Claim
55 words
An echo canceler as set forth in claim 4, in which said transmission unit drives a transformer (35) coupled to a two-wire signal path (L11/L12), and in which a balancing circuit ( BL) is coupled to said transformer for supplying said received analog signal through a low pass filter circuit (36) to said first adder.
Claim 6
Dependent Claim
63 words
An echo canceler as set forth in claim 1, in which said delta-sigma modulation circuit (98) comprises a digital low pass filter (98a) for carrying out an interpolation on said echo replica signal, and a delta-sigma modulator (98b) coupled to said digital low pass filter and carrying out a delta-sigma modulation on an echo replica signal fed from said digital low pass filter.
References Cited (Backward Citations)
No citation records indexed.
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