EP0145022A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Method and apparatus for cancelling echo
Assignee: NEC Corp
•
Filing: 1984-12-13
•
Granted: —
•
Expires: 2004-12-13
Abstract
Abstract A method and apparatus cancels an echo by using an echo replica generated such that a tap coefficient of an adaptive filter is sequentially updated, the echo being received from a transmitting end to a four-wire side through a two'four wire converter and being obtained such that a pulse signal having positive and negative polarities is fed into a receiving end, wherein a difference signal (error signal) between the echo replica and a reception signal is calculated: a correlation value between a signal representing a polarity of the error signal and a signal representing a polarity of the echo replica is calculated: when the correlation value is smaller than a predetermined value, a first of two types of tap coefficients which belong to each of a plurality of taps is updated based on at least the error signal and is set as the tap coefficient of the adaptive filter during a period in which the pulse signal is set in the positive polarity, and a second type of tap coefficient is updated based on at least the error signal and is set as the tap coefficient of the adaptive filter during a period in which the pulse signal is set in the negative polarity; and when the correlation value is larger than the predetermined value, the first and second types of tap coefficients are updated irrespective of the polarity of the transmission pulse on the basis of the error signal.
Inventors
- 👤 Akira Kanemasa
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-25 15:47
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/20; H04B3/23; H04B3/238
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
240 words
A method for cancelling an echo by using an echo replica generated such that a tap coefficient of an adaptive filter is sequentially updated, the echo being received from a transmitting end to a four-wire side through a two/four wire converter and being obtained such that a pulse signal having positive and negative polarities is fed into a receiving end, comprising the steps of: calculating an error signal representing a difference between the echo replica and a reception signal; calculating a correlation value between a signal representing a polarity of the error signal and a signal representing a polarity of the echo replica; when the correlation value is smaller than a predetermined value, updating a first of two types of tap coefficients which belong to each of a plurality of taps in accordance with at least the error signal and setting the updated coefficient as the tap coefficient of the adaptive filter during a period in which the pulse signal has the positive polarity, and updating a second type of tap coefficient in accordance with at least the error signal and setting the updated coefficient as the tap coefficient of the adaptive filter during a period in which the pulse signal has the negative polarity; and when the correlation value is larger than the predetermined value, updating the first and second types of tap coefficients irrespective of the polarity of the transmission pulse on the basis of the error signal.
Claim 2
Independent Claim
240 words
A method for cancelling an echo by using an echo replica generated such that a tap coefficient of an adaptive filter is sequentially updated, the echo being received from a transmitting end to a four-wire side through a two/four wire converter and being obtained such that a pulse signal having positive and negative polarities is fed into a receiving end, comprising the steps of: calculating an error signal representing a difference between the echo replica and a reception signal; calculating a correlation value between a signal representing a polarity of the error signal and a signal representing a polarity of the echo replica; when the correlation value is smaller than a predetermined value, updating a first of two types of tap coefficients which belong to each of a plurality of taps in accordance with at least the error signal and setting the updated coefficient as the tap coefficient of the adaptive filter during a period in which the pulse signal has the positive polarity, and updating a second type of tap coefficient in accordance with at least the error signal and setting the updated coefficient as the tap coefficient of the adaptive filter during a period in which the pulse signal has the negative polarity; and when the correlation value is larger than the predetermined value, updating the first and second types of tap coefficients irrespective of the polarity of the transmission pulse on the basis of the error signal.
Claim 3
Dependent Claim
107 words
A method according to claim 1, wherein when the correlation value is smaller than a predetermined value, a correction coefficient is updated based on at least the error signal, and an updated correction coefficient is added to the first tap coefficient to generate a second tap coefficient as the tap coefficient of the adaptive filter during the period in which the pulse signal has the negative polarity; and when the correlation value is larger than the predetermined value, the first tap coefficient is updated irrespective of the polarity of the transmission pulse on the basis of the error signal and updating of the correction coefficient is discontinued.
Claim 4
Independent Claim
220 words
An apparatus for cancelling an echo by using an echo replica generated such that a tap coefficient of an adaptive filter is sequentially updated, the echo being received from a transmitter to a four-wire side through a two/four wire converter and being obtained such that a pulse signal having positive and negative polarities is fed into a receiver, comprising: an adaptive filter for receiving a reception signal and generating the echo replica; error signal generating means for generating an error signal representing a difference between the reception signal supplied to the receiver and the echo replica; correlating means for generating a correlation value between a signal representing a polarity of the error signal and a signal representing a polarity of the echo replica; comparing means for comparing the correlation value and a predetermined value; first updating means for sequentially updating a first of two types of tap coefficients which belong to each of a plurality of taps, for a positive polarity of a pulse sent from the transmitter in accordance with at least the error signal; second updating means for updating a second type of tap coefficient; selecting means for selecting one of the first and second types of tap coefficients in accordance with the polarity of the pulse signal; and controlling means for generating first and second control signals.
Claim 5
Independent Claim
220 words
An apparatus for cancelling an echo by using an echo replica generated such that a tap coefficient of an adaptive filter is sequentially updated, the echo being received from a transmitter to a four-wire side through a two/four wire converter and being obtained such that a pulse signal having positive and negative polarities is fed into a receiver, comprising: an adaptive filter for receiving a reception signal and generating the echo replica; error signal generating means for generating an error signal representing a difference between the reception signal supplied to the receiver and the echo replica; correlating means for generating a correlation value between a signal representing a polarity of the error signal and a signal representing a polarity of the echo replica; comparing means for comparing the correlation value and a predetermined value; first updating means for sequentially updating a first of two types of tap coefficients which belong to each of a plurality of taps, for a positive polarity of a pulse sent from the transmitter in accordance with at least the error signal; second updating means for updating a second type of tap coefficient; selecting means for selecting one of the first and second types of tap coefficients in accordance with the polarity of the pulse signal; and controlling means for generating first and second control signals.
Claim 6
Dependent Claim
118 words
An apparatus according to claim 3, wherein said second updating means sequentially updates the second type of tap coefficient corresponding to the negative polarity in accordance with at least the error signal; and said controlling means generates the first control signal to operate said first updating means during a period in which the pulse signal has the positive polarity and said second updating means during a period in which the pulse signal has the negative polarity when the correlation value is smaller than a predetermined value, and generates the second control signal to operate said first and second updating means irrespective of the polarity of the pulse signal when the correlation value is larger than the predetermined value.
Claim 7
Dependent Claim
35 words
An apparatus according to claim 4, wherein said first updating means comprises an adder and a delay element which updates the first type of tap coefficient corresponding to the positive polarity of the pulse signal.
Claim 8
Dependent Claim
37 words
An apparatus according to claim 4 or 5, wherein said second updating means comprises an adder and a delay element which updates the second type of tap coefficient corresponding to the negative polarity of the pulse signal.
Claim 9
Independent Claim
146 words
An apparatus according to any of claims 3 to 6, wherein said second updating means generates the second type of tap coefficient obtained such that a correction coefficient is updated in accordance with at least the error signal and an updated correction coefficient is added to the first type of tap coefficient; and said controlling means generates the first control signal to operate said first updating means during a period in which the pulse signal has the positive polarity and said second updating means during a period in which the pulse signal has the negative polarity when the correlation value is smaller than a predetermined value, and generates the second control signal to operate said first updating means irrespective of the polarity'of the.pulse signal and discontinue updating of the correction coefficient in said second updating means when the correlation value is larger than the predetermined value.
Claim 10
Dependent Claim
34 words
An apparatus according to claim 7, wherein said first updating means comprises an adder and a delay circuit which updates the first type of tap coefficient irrespective of the polarity of the pulse signal.
Claim 11
Dependent Claim
69 words
An apparatus according to claim 7 or 8, wherein said second updating means comprises a first adder, a delay circuit and a second adder, said first adder and said delay circuit being arranged so as to update the correction coefficient, and said second adder being arranged so as to add the updated correction coefficient and the first type of tap coefficient to obtain the second type of tap coefficient.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.