US4415872A
Expired / Lapsed
US
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Adaptive equalizer
Assignee: AT&T Inc
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Filing: 1981-08-17
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Granted: 1983-11-15
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Expires: 2001-08-17
Abstract
Abstract The dispersive effects of frequency selective fading in a digital, FM, or AM radio system are reduced by means of an adaptive equalizer (11) comprising a cascade of feed-forward stages (1,2, . . . N), each of which includes: a first parallel wavepath (1-1, 1-2, . . . 1-N) including a first adjustable attenuator (20-1, 20-2, . . . 20-N); a second parallel wavepath (2-1, 2-2, . . . 2-N) including a second adjustable attenuator (21-1, 21-2, . . . 21-N) and delay means (22-1, 22-2, . . . 22-N); and means (23-1, 23-2, . . . 23-N) for combining the signals in said wavepaths and for coupling said combined signal to the next stage. By a suitable selection of parameters, according to two unique relationships, a transfer function can be realized which can compensate for amplitude and delay distortions caused by minimum and nonminimum phase fades.
Inventors
- 👤 Peter D. Karabinis
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 03:32
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/04; H04B3/14; H04B3/143; H04B3/145; H04B7/00; H04B7/005
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
135 words
An equalizer (11) comprising a plurality of feed-forward stages (1, 2, . . . N) connected in cascade: each stage comprising: a first parallel wavepath (1-1, 1-2, . . . 1-N) including a first variable attenuator (20-1, 20-2, . . . 20-N); a second parallel wavepath (2-1, 2-2, . . . 2-N) including a second variable attenuator (21-1, 21-2, . . . 21-N), and delay means (22-1, 22-2, . . . 22-N); means (23-1, 23-2, . . . 23-(N-1)) for combining the signals in the parallel wavepaths of each of the first (N-1) stages and for coupling the combined signals to the next stage of said equalizer; and means (23-N) for combining the signals in the parallel wavepaths of the N th equalizer stage and for coupling the combined signals to the equalizer output terminal.
Claim 2
Dependent Claim
135 words
An equalizer (11) comprising a plurality of feed-forward stages (1, 2, . . . N) connected in cascade: each stage comprising: a first parallel wavepath (1-1, 1-2, . . . 1-N) including a first variable attenuator (20-1, 20-2, . . . 20-N); a second parallel wavepath (2-1, 2-2, . . . 2-N) including a second variable attenuator (21-1, 21-2, . . . 21-N), and delay means (22-1, 22-2, . . . 22-N); means (23-1, 23-2, . . . 23-(N-1)) for combining the signals in the parallel wavepaths of each of the first (N-1) stages and for coupling the combined signals to the next stage of said equalizer; and means (23-N) for combining the signals in the parallel wavepaths of the N th equalizer stage and for coupling the combined signals to the equalizer output terminal.
Claim 3
Dependent Claim
39 words
The equalizer according to claim 1 wherein: the combining means (23-1) of the first stage is a differencing circuit; and the combining means of each of the other (N-1) stages (23-2, . . . 23-N) is a summing circuit.
Claim 4
Dependent Claim
40 words
The equalizer according to claim 1 wherein the delay, T i of the delay means in each of said stages is a constant given by T.sub.i =2.sup.(i-1) T.sub.1 where 1≦i≦N and T 1 is the delay in the first stage.
Claim 5
Dependent Claim
59 words
The equalizer according to claim 3 wherein: the first attenuator in each of said stages has a gain factor b i ; the second attenuator in each of said stages has a gain factor a i ; and wherein a.sub.i /b.sub.i =(a.sub.1 /b.sub.1).sup.2.spsp.(i-1) where 1≦i≦N and a.sub.1 and b.sub.1 are the attenuator gain factor of the first equalizer stage.
Claim 6
Dependent Claim
81 words
An adaptive, frequency-selective fade equalizer arrangement comprising: an equalizer in accordance with claim 4: a phase analyzer (50) for determining the phase characteristic of the fade; means for determining the fade notch frequency and for shifting said fade notch into frequency coincidence with the equalizer gain bump frequency defined by the delay T 1 ; and means for adjusting the gain factors a i and b i of the equalizer stages to minimize the inband amplitude dispersion produced by said fade.
Claim 7
Dependent Claim
101 words
A transversal filter equalizer having a transfer function H(jω) given by ##EQU5## comprising: a delay line having 2 N taps with tap spacing T and tap weights C(-1) i K i , where: a 1 , a 2 . . . a n and b 1 , b 2 . . . b n are arbitrary functions of time; N is any integer; ≦ i≦2 N-1 ; T 1 , T 2 . . . T N are constants; C=b 1 b 2 . . . b n ; and K.sup.2.spsp.(i-1) =a.sub.i /b.sub.i ; and means for summing the tap outputs.
Claim 8
Dependent Claim
101 words
A transversal filter equalizer having a transfer function H(jω) given by ##EQU5## comprising: a delay line having 2 N taps with tap spacing T and tap weights C(-1) i K i , where: a 1 , a 2 . . . a n and b 1 , b 2 . . . b n are arbitrary functions of time; N is any integer; ≦ i≦2 N-1 ; T 1 , T 2 . . . T N are constants; C=b 1 b 2 . . . b n ; and K.sup.2.spsp.(i-1) =a.sub.i /b.sub.i ; and means for summing the tap outputs.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-11-14 | 1987-05-16 | 1987-11-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-11-14 | 1991-05-16 | 1991-11-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-11-14 | 1995-05-16 | 1995-11-15 | $7700.00 | Window Closed / Lapsed |