US4823382A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Echo canceller with dynamically positioned adaptive filter taps
Assignee: NEXTIRAONE LLC
•
Filing: 1986-10-01
•
Granted: 1989-04-18
•
Expires: 2006-10-01
Abstract
Abstract An echo canceller according to the present invention includes means for storing an impulse response in a memory, the impulse response being indicative of the characteristics of a transmission line. It also includes a detector for detecting ranges of samples within the impulse response having relatively large distribution of echo energy, these ranges of samples of relatively large distribution of echo energy being indicative of echoes on the transmission line. An echo canceller includes a digital filter having a plurality of weighted taps, each of the weighted taps having an associated tap weight value. A tap allocation circuit establishes the tap weight values in response to said detecting means so that only taps within the regions of relatively large distributions of echo energy are turned on. The ranges of echo energy are detected coarsely by detecting ranges of samples having relatively high estimated average echo power. The echo is more finely located by computing the terms analogous to the mechanical computation of the center of gravity type calculation referred to as a `center of echo` and radius of gyration type calculation referred to as `radius of echo` of the echo energy within the coarsely located ranges of samples.
Inventors
- 👤 Aldo A. Martinez
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 16:55
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/20; H04B3/23; H04B3/238
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
133 words
A method of allocating filter taps in an echo canceller for a transmission line comprising the steps of: storing a plurality of samples of a signal representative of said transmission line's impulse response in a memory; examining said plurality of stored samples to find variable sized ranges of samples of said impulse response having at least a predetermined amount of echo energy, said examining step including computing a center of echo of each of said ranges of said samples in order to find the approximate center of each of said ranges of samples of impulse response containing echo energy; and allocating a variable total number of filter taps of said echo canceller by turning on only those taps corresponding to said ranges of samples having at least said predetermined amount of echo energy.
Claim 2
Independent Claim
133 words
A method of allocating filter taps in an echo canceller for a transmission line comprising the steps of: storing a plurality of samples of a signal representative of said transmission line's impulse response in a memory; examining said plurality of stored samples to find variable sized ranges of samples of said impulse response having at least a predetermined amount of echo energy, said examining step including computing a center of echo of each of said ranges of said samples in order to find the approximate center of each of said ranges of samples of impulse response containing echo energy; and allocating a variable total number of filter taps of said echo canceller by turning on only those taps corresponding to said ranges of samples having at least said predetermined amount of echo energy.
Claim 3
Dependent Claim
67 words
The method of claim 1, wherein said examining step further includes the step of computing a radius of echo about each said center of echo for each of said ranges of samples; and wherein said allocating step includes the step of assigning nonzero values of tap weighting values to all tap weights within a predetermined multiple of said radii of echo about each said center of echo.
Claim 4
Dependent Claim
43 words
The method of claim 1, wherein said allocation step includes the step of assigning a predetermined maximum number of nonzero tap weight values and wherein said nonzero tap weight values are assigned to ranges of samples containing a maximum amount of echo energy.
Claim 5
Dependent Claim
45 words
The method of claim 1, wherein said stored plurality of samples is obtained by applying a pulse of energy to said transmission line and measuring a signal on said transmission line which is produced as a result of said application of said pulse of energy.
Claim 6
Dependent Claim
19 words
The method of claim 1, further including the step of modifying said allocated tap values with a window function.
Claim 7
Dependent Claim
29 words
The method of claim 1, wherein said examining step includes the step of comparing an estimate of the average power of ranges of said stored samples to a threshold.
Claim 8
Dependent Claim
110 words
The method of claim 1, wherein said examining step includes the steps of: comparing an estimate of the average power of ranges of said stored samples to a threshold as a coarse estimate of the location of said ranges of samples containing echo energy; computing the center of echo of samples within said coarse estimate and computing a radius of echo associated with and about each of the centers of echo; and determining which of the samples in said coarse estimate fall within a predetermined multiple of its associated radius of echo as a fine estimate of the location of said echo to be used as said range of samples.
Claim 9
Dependent Claim
42 words
The method of claim 1, wherein said examining step includes the step of computing a measure of distribution of echo energy about each said approximate center in order to locate a beginning and an end for each of said ranges of samples.
Claim 10
Dependent Claim
138 words
An echo canceller comprising in combination: means for storing an impulse response in a memory, said impulse response being indicative of the characteristics of a transmission line; means for detecting variable sized ranges of samples within said impulse response having echo energy, by locating a central sample of an echo and computing a radius of echo about said central sample in order to define said variable sized ranges; an echo canceller means including a digital filter having a plurality of weighted taps, each of said weighted taps having an associated tap weight value; and tap allocation means for activating and deactivating variable numbers of said taps in response to said detecting means so that only taps within said ranges of samples are turned on within said echo canceller and taps outside said ranges of samples are turned off.
Claim 11
Dependent Claim
138 words
An echo canceller comprising in combination: means for storing an impulse response in a memory, said impulse response being indicative of the characteristics of a transmission line; means for detecting variable sized ranges of samples within said impulse response having echo energy, by locating a central sample of an echo and computing a radius of echo about said central sample in order to define said variable sized ranges; an echo canceller means including a digital filter having a plurality of weighted taps, each of said weighted taps having an associated tap weight value; and tap allocation means for activating and deactivating variable numbers of said taps in response to said detecting means so that only taps within said ranges of samples are turned on within said echo canceller and taps outside said ranges of samples are turned off.
Claim 12
Dependent Claim
20 words
The echo canceller of claim 9, further including windowing means for adjusting said tap weight values with a windowing function.
Claim 13
Dependent Claim
32 words
The echo canceller of claim 9, wherein said detecting means includes means for computing a center of echo of each of said ranges of samples within said impulse response having echo energy.
Claim 14
Dependent Claim
39 words
The echo canceller of claim 11, wherein said tap allocation means includes means for activating a plurality of taps within a predetermined multiple of radii of echo about each of said centers of echo of said ranges of samples.
Claim 15
Dependent Claim
15 words
The echo canceller of claim 9, wherein said digital filter includes a transversal digital filter.
Claim 16
Dependent Claim
39 words
The echo canceller of claim 12, wherein said tap allocation means includes means for activating taps within 2.5 to 3.5 times the radius of echo about each of said centers of echo of each of said ranges of samples.
Claim 17
Dependent Claim
36 words
The echo canceller of claim 12, wherein said tap allocation means includes means for activating taps within approximately 3.0 times the radius of echo about each of said centers of echo of said ranges of samples.
Claim 18
Dependent Claim
37 words
The echo canceller of claim 9, wherein said echo canceller means includes a plurality of multipliers and wherein said tap allocation means includes means for bypassing multiplication by said multipliers in order to turn off said taps.
Claim 19
Dependent Claim
82 words
The echo canceller of claim 9, wherein said tap allocation means includes: means for estimating average power of ranges of samples; means for comparing said estimated average power with a predetermined threshold to coarsely locate said ranges of samples containing echo energy; means for computing a center of echo of each of said coarsely located ranges of samples; and means for turning on echo canceller taps within a predetermined number times the radius of echo about each of said centers of echo.
Claim 20
Independent Claim
94 words
A method of locating taps for allocation to an echo canceller, comprising the steps of: storing a plurality of samples representative of a transmission line's impulse response; estimating the average power in said stored samples; comparing said estimated average power to a predetermined threshold in order to coarsely locate samples containing echo energy; computing the center of echo of said coarsely located samples in order to estimate the center of the echo energy; and computing a radius of echo about said center of echo in order to estimate the spread of the echo energy.
Claim 21
Independent Claim
94 words
A method of locating taps for allocation to an echo canceller, comprising the steps of: storing a plurality of samples representative of a transmission line's impulse response; estimating the average power in said stored samples; comparing said estimated average power to a predetermined threshold in order to coarsely locate samples containing echo energy; computing the center of echo of said coarsely located samples in order to estimate the center of the echo energy; and computing a radius of echo about said center of echo in order to estimate the spread of the echo energy.
Claim 22
Dependent Claim
147 words
An echo canceller comprising in combination: means for storing an impulse response in a memory, said impulse response being indicative of the characteristics of a transmission line; an echo canceller means including a digital filter having a plurality of weighted taps, each of said weighted taps having an associated tap weight value; means for estimating the average power of ranges of samples of said impulse response; means for comparing said estimated average power with a predetermined threshold to coarsely locate ranges of samples containing echo energy; means for computing a center of echo of each of said ranges of samples of said impulse response; means for computing a radius of echo about each said center of echo; tap allocation means for activating a variable number of echo canceller taps within a range of 2.5 to 3.5 times the radius of echo about each said center of echo.
Claim 23
Dependent Claim
147 words
An echo canceller comprising in combination: means for storing an impulse response in a memory, said impulse response being indicative of the characteristics of a transmission line; an echo canceller means including a digital filter having a plurality of weighted taps, each of said weighted taps having an associated tap weight value; means for estimating the average power of ranges of samples of said impulse response; means for comparing said estimated average power with a predetermined threshold to coarsely locate ranges of samples containing echo energy; means for computing a center of echo of each of said ranges of samples of said impulse response; means for computing a radius of echo about each said center of echo; tap allocation means for activating a variable number of echo canceller taps within a range of 2.5 to 3.5 times the radius of echo about each said center of echo.
References Cited (Backward Citations)
US3465106A
Cited
US3535473A
Cited
US3578544A
Cited
US3732410A
Cited
US3723911A
Cited
US3735055A
Cited
US3721777A
Cited
US4024357A
Cited
US4087654A
Cited
US4464545A
Cited
US4602133A
Cited
US4582963A
Cited
US4593161A
Cited
US4677668A
Cited
JPH107928A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-04-17 | 1992-10-17 | 1993-04-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-04-17 | 1996-10-17 | 1997-04-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-04-17 | 2000-10-17 | 2001-04-18 | $7700.00 | Window Closed / Lapsed |