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EP0253583A2
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Adaptive digital filter
Assignee: Oki Electric Industry Co Ltd
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Filing: 1987-07-10
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Granted: —
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Expires: 2007-07-10
Abstract
Abstract In an adaptive digital filter, the inputs to the variable-coefficient scalers (26-m, 25-m) of an adaptive digital filter are mutually orthogonal and their mean square values are equal. As a result, the rate of convergence of the variable coefficients of the variable-coefficient scalers is rapid. The adaptive filter is suitable for use echo cancelers.
Inventors
- 👤 Masaki Oki Electric Industry Co Ltd. Kobayashi
- 👤 Yoshio Oki Electric Industry Co Ltd. Itoh
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 16:09
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/20; H04B3/23; H03; H03H; H03H21/00; H04B3/238
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
587 words
An adaptive digital filter comprising M basic sections (ADF-1 to ADF-M: where M is a positive integer) connected in series, in which the first M-1 basic sections (ADF-1 to ADF-(M-1)) include an input terminal (10-m), a first output terminal (11-m), and a second output terminal (10-(m+1)), the M-th basic section includes an input terminal (10-M) and a first output terminal (11-M), the input terminal (10-1) of the first basic section (ADF-1) is the signal input terminal of the adaptive digital filter as a whole, the input terminal (10-m) of each of the other basic sections (ADF-2 to ADF-M) is connected to the second output terminal of the immediately preceding basic section (ADF-(m-1)), and the output of the adaptive digital filter as a whole is the sum of the signals output from the first output terminals (11-m) of each of the basic sections, wherein: (a) in each of the M basic sections (ADF-m), the path from the input terminal (10-m) to the first output terminal (11-m) comprises a first scaler (12-m), a second-order recursive digital filter (E m -1), and a first-order nonrecursive digital filter (E m -2), which are connected in series, and the input of the first-order nonrecursive digital filter (E m -2) is connected to the 0th-order circuit in the second-order recursive digital filter (E m -1), (b) in each of the first through the M-1-th basic sections (ADF-m), the path from the input terminal (10-m) to the second output terminal (11-m) comprises: the above first scaler (12-m), the above second-order recursive digital filter (E m -1), and a second-order nonrecursive digital filter (E m -3), which are connected in series, (c) in the m-th basic section (1 ≦ m ≦ M), the first-order nonrecursive digital filter (Em-2) comprises a second scaler (22-m; 22ʹ-m) for multiplying a first one of the input signal u m (k) and the signal u m (k-1) delayed by one unit of time, by a coefficient R m , a first adder (23-m; 23ʹ-m) for adding the output of the second scaler (22-m; 22ʹ-m) to a second one of the signal u m (k) and the signal u m (k-1), a third scaler (24-m; 24ʹ-m) for multiplying the output of the first adder (23-m; 23ʹm) by a coefficient S m , a variable-coefficient scaler (26-m; 25ʹ-m) for multiplying the output û m (k) of the third scaler (24-m; 24ʹ-m) by a variable coefficient (d m (k);cʹ m (k))to form a product, a variable-coefficient scaler (25-m; 26ʹ-m) for multiplying the second one of the signal u m (k) and the signal u m (k-1) by a variable coefficient (c m (k);dʹ m (k)) to form a product, and a second adder (27-m) for adding these two products, (d) the coefficient Q m of the first scaler (12-m) is selected so that the mean square value of the signal at the point at which the second-order recursive digital filter (E m -1) and the second-order nonrecursive digital filter (E m -3) are connected in series in each basic section is equal to the mean square value of the signals at the corresponding series connection points in the other basic sections, (e) the coefficient R m of the second scaler (22-m; 22ʹ-m) is selected so that the signals u m (k) and û m (k) are orthogonal. (f) the coefficient S m of the third scaler is selected so that the mean square value of the signal u m (k) and the mean square value of the signal û m (k) are equal.
Claim 2
Dependent Claim
587 words
An adaptive digital filter comprising M basic sections (ADF-1 to ADF-M: where M is a positive integer) connected in series, in which the first M-1 basic sections (ADF-1 to ADF-(M-1)) include an input terminal (10-m), a first output terminal (11-m), and a second output terminal (10-(m+1)), the M-th basic section includes an input terminal (10-M) and a first output terminal (11-M), the input terminal (10-1) of the first basic section (ADF-1) is the signal input terminal of the adaptive digital filter as a whole, the input terminal (10-m) of each of the other basic sections (ADF-2 to ADF-M) is connected to the second output terminal of the immediately preceding basic section (ADF-(m-1)), and the output of the adaptive digital filter as a whole is the sum of the signals output from the first output terminals (11-m) of each of the basic sections, wherein: (a) in each of the M basic sections (ADF-m), the path from the input terminal (10-m) to the first output terminal (11-m) comprises a first scaler (12-m), a second-order recursive digital filter (E m -1), and a first-order nonrecursive digital filter (E m -2), which are connected in series, and the input of the first-order nonrecursive digital filter (E m -2) is connected to the 0th-order circuit in the second-order recursive digital filter (E m -1), (b) in each of the first through the M-1-th basic sections (ADF-m), the path from the input terminal (10-m) to the second output terminal (11-m) comprises: the above first scaler (12-m), the above second-order recursive digital filter (E m -1), and a second-order nonrecursive digital filter (E m -3), which are connected in series, (c) in the m-th basic section (1 ≦ m ≦ M), the first-order nonrecursive digital filter (Em-2) comprises a second scaler (22-m; 22ʹ-m) for multiplying a first one of the input signal u m (k) and the signal u m (k-1) delayed by one unit of time, by a coefficient R m , a first adder (23-m; 23ʹ-m) for adding the output of the second scaler (22-m; 22ʹ-m) to a second one of the signal u m (k) and the signal u m (k-1), a third scaler (24-m; 24ʹ-m) for multiplying the output of the first adder (23-m; 23ʹm) by a coefficient S m , a variable-coefficient scaler (26-m; 25ʹ-m) for multiplying the output û m (k) of the third scaler (24-m; 24ʹ-m) by a variable coefficient (d m (k);cʹ m (k))to form a product, a variable-coefficient scaler (25-m; 26ʹ-m) for multiplying the second one of the signal u m (k) and the signal u m (k-1) by a variable coefficient (c m (k);dʹ m (k)) to form a product, and a second adder (27-m) for adding these two products, (d) the coefficient Q m of the first scaler (12-m) is selected so that the mean square value of the signal at the point at which the second-order recursive digital filter (E m -1) and the second-order nonrecursive digital filter (E m -3) are connected in series in each basic section is equal to the mean square value of the signals at the corresponding series connection points in the other basic sections, (e) the coefficient R m of the second scaler (22-m; 22ʹ-m) is selected so that the signals u m (k) and û m (k) are orthogonal. (f) the coefficient S m of the third scaler is selected so that the mean square value of the signal u m (k) and the mean square value of the signal û m (k) are equal.
Claim 3
Dependent Claim
155 words
An adaptive digital filter according to claim 1, wherein (c) in the m-th basic section (1<m<M), the first-order nonrecursive digital filter (E m -2) comprises a second scaler (22-m) for multiplyuing the input signal u m (k) by a coefficient R m , a first adder (23-m) for adding the output of the second scaler (22-m) to the signal u m (k-1) delayed by one unit of time, a third scaler (24-m) for multiplying the output of the first adder (23-m) by a coefficient S m , a variable-coefficient scaler (26-m) for multiplying the output û m (k) of the third scaler (24-m) by a variable coefficient d m (k) to form a product d m (k)û m (k), a variable-coefficient scaler (25-m) for multiplying the signal u m (k) by a variable coefficient c m (k) to form product c m (k)u m (k), and a second adder (27-m) for adding these two products.
Claim 4
Dependent Claim
152 words
An adaptive digital filter according to claim 1, wherein (cʺ) the m-th basic section (1 < m < M), the first-order nonrecursive digital filter (E m -2) comprises a second scaler ((22ʹ-m) for multiplyuing the signal u m (k-1) by a coefficient R m , a first adder (23ʹ-m) for adding the output of the second scaler (22ʹ-m) to the input signal u m (k), a third scaler (24ʹ-m) for multiplying the output of the first adder (23ʹ-m) by a coefficient S m , a variable-coefficient scaler (25ʹ-m) for multiplying the output û m (k) of the third scaler (24ʹ-m) by a variable coefficient cʹ m (k) to form a product cʹ m (k)u m (k), a variable-coefficient scaler (26ʹ-m) for miltiplying the signal u m (k-1) by a variable coefficient dʹ m (k) to form product dʹ m (k)u m (k-1), and a second adder (27ʹ-m) for adding these two products.
Claim 5
Dependent Claim
83 words
A section for an adaptive digital filter having in series an input (10-m), a first scaling means (12-m), a second order recursive digital filter (E m -1) and a first order non-recursive digital filter (E m -2) with variable coefficient scalers (25-m; 26-m) contributing to a summed output (11-m) characterised in that a scaling means (22-m; 22ʹ-m) is provided in the filter (E m -2) for multiplication of a first input signal and a delayed input signal by a coefficient (R m ).
Claim 6
Dependent Claim
83 words
A section for an adaptive digital filter having in series an input (10-m), a first scaling means (12-m), a second order recursive digital filter (E m -1) and a first order non-recursive digital filter (E m -2) with variable coefficient scalers (25-m; 26-m) contributing to a summed output (11-m) characterised in that a scaling means (22-m; 22ʹ-m) is provided in the filter (E m -2) for multiplication of a first input signal and a delayed input signal by a coefficient (R m ).
Claim 7
Dependent Claim
46 words
A section according to claim 1 further characterised in that a further scaling means (24-m; 24ʹ-m) is provided for multiplying the output of an adder (23-m; 23ʹ-m) of the input signal and the output of the scaling means (22-m; 22ʹ-m) by a coefficient (S m ).
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