US3764914A
Expired / Lapsed
US
⏱️ 0.0 years remaining
High speed line equalizer
Assignee: International Business Machines Corp
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Filing: 1971-12-27
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Granted: 1973-10-09
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Expires: 1991-12-27
Abstract
Abstract An extremely fast equalizer is disclosed which utilizes only channel response data to control the equalizer settings. The equalizer is adapted for operation in either the automatic or adaptive mode. A basic equalization module is developed which can be used either singly or in tandem wherein subsequent modules successively improve the equalization. The circuit differs markedly from prior art equalization circuits in that only line response data rather than equalizer outputs are utilized in determining equalizer tap settings. In one preferred embodiment, the equalizer design is based on an expansion in powers of F P/(1-T) which converges rapidly and wherein P represents precursor intersymbol interference terms, and T represents tail intersymbol interference terms. This expansion results in an iterative equalizer configuration.
Inventors
- 👤 M Karnaugh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 12:44
CPC Classifications
H; H04; H04L; H04L25/00; H04L25/02; H04L25/03; H04L25/03006; H04L25/03012; H04L25/03019; H04L25/03057; H04L25/03076; H04L25/03114; H04L25/03146
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
100 words
An equalizer for a transmission channel of limited bandwidth comprising: means for sampling the output of said channel; means for estimating and storing the sampled and normalized interference terms arising from the transmission of a data signal through said channel; modular means for equalizing the output of said channel wherein at least one module is connected in tandem to accomplish said equalization, each module including at least one delay element and time-domain filter; and means associated with said time-domain filters for determining the output tap gains of said time domain filter directly from said estimate of said normalized interference terms.
Claim 2
Dependent Claim
100 words
An equalizer for a transmission channel of limited bandwidth comprising: means for sampling the output of said channel; means for estimating and storing the sampled and normalized interference terms arising from the transmission of a data signal through said channel; modular means for equalizing the output of said channel wherein at least one module is connected in tandem to accomplish said equalization, each module including at least one delay element and time-domain filter; and means associated with said time-domain filters for determining the output tap gains of said time domain filter directly from said estimate of said normalized interference terms.
Claim 3
Independent Claim
121 words
A method for equalizing an electrical signal sequence received from a channel, said sequence being represented by the function 1-F where -F represents intersymbol interference terms caused by channel response characteristics, said method comprising the steps of: performing a series of iterative equalization operations on the received signal sequence, each operation being representable by a transfer function, said functions being derived by setting the desired equalizer function G equal to D/(1-F), wherein D is a delay, and selecting an iterative form of a polynomial expansion thereof with remainder terms truncated; each of said series of equalization operations including passing the received signal sequence through an equalizer module wherein each module performs one of the iterative terms of said desired function G.
Claim 4
Independent Claim
121 words
A method for equalizing an electrical signal sequence received from a channel, said sequence being represented by the function 1-F where -F represents intersymbol interference terms caused by channel response characteristics, said method comprising the steps of: performing a series of iterative equalization operations on the received signal sequence, each operation being representable by a transfer function, said functions being derived by setting the desired equalizer function G equal to D/(1-F), wherein D is a delay, and selecting an iterative form of a polynomial expansion thereof with remainder terms truncated; each of said series of equalization operations including passing the received signal sequence through an equalizer module wherein each module performs one of the iterative terms of said desired function G.
Claim 5
Dependent Claim
78 words
A method as set forth in claim 2 which includes the step of deriving tap settings for all of the adjustable tap means of an equalizer filter in each module by estimating the amplitudes of the intersymbol interference terms present in the as received signal from the channel and normalizing said amplitudes with respect to the main data pulse h0 and supplying these derived tap settings to the same respective tap of each equalizer filter in each module.
Claim 6
Dependent Claim
44 words
A method as set forth in claim 3 which includes passing said received signal sequence through as many iterative equalization modules as required by the particular form of the polynomial expansion of the equalizer transfer function to obtain satisfactory equalization for a particular application.
Claim 7
Dependent Claim
137 words
Apparatus for eqaulizing an electrical signal sequence received from a channel, said sequence being represented by the function 1-F wherein -F represents intersymbol interference terms in the as received signal due to the channel response characteristics, said apparatus comprising: a plurality of equalizing modules connected in tandem to the input of said channel, each module comprising an equalizer filter having at least as many taps as intersymbol interference terms to be equalized, means for deriving tap control settings for each tap directly from the as received signal from the channel; storage means for storing said desired tap control settings and supplying identical tap control signals to all modules; logic circuit means in each module whereby the module performs a transfer function derived from the polynomial expansion of the desired equalizer function rounded off to remove remainder terms.
Claim 8
Dependent Claim
137 words
Apparatus for eqaulizing an electrical signal sequence received from a channel, said sequence being represented by the function 1-F wherein -F represents intersymbol interference terms in the as received signal due to the channel response characteristics, said apparatus comprising: a plurality of equalizing modules connected in tandem to the input of said channel, each module comprising an equalizer filter having at least as many taps as intersymbol interference terms to be equalized, means for deriving tap control settings for each tap directly from the as received signal from the channel; storage means for storing said desired tap control settings and supplying identical tap control signals to all modules; logic circuit means in each module whereby the module performs a transfer function derived from the polynomial expansion of the desired equalizer function rounded off to remove remainder terms.
Claim 9
Dependent Claim
62 words
An equalization apparatus as set forth in claim 5 including means for operating said equalizer in the automatic mode including means for deriving the tap settings as the actual negatives of amplitudes of the respective intersymbol interference terms normalized with respect to the main data pulse h0 and means for applying the respective settings to the proper taps of the equalizer filters.
Claim 10
Dependent Claim
73 words
An equalization apparatus as set forth in claim 5 including means for operating said equalizer in the adaptive mode including further equalizer filter means in said adaptive control means wherein the received signal from the channel is compared with an estimate of said received signal to derive an error signal, and means for correlating said error signal with detected data magnitudes and for producing a corrective signal to the stored gain control settings.
Claim 11
Dependent Claim
82 words
An equalization apparatus as set forth in claim 5 wherein the iterative polynomial expansion performed by n modules takes the from Gn(1) ( ... (((DF) +D) (DF) + D2) ( DF) +...+ Dn 1, (DF) + Dn wherein DF is performed by a non-recursive time domain equalizer filter and D is performed by a delay of the signal sequence entering the module, and wherein in each module the signal represented as contained within each right parenthesis is the input to said filter.
Claim 12
Dependent Claim
77 words
An equalization apparatus as set forth in claim 5 wherein the polynomial expansion of the desired equalizer response is of the form Gn(2) ( ... ((D+(DF)) D+(DF)2) D +...+ (DF)n 1) D+(DF)n wherein DF is performed by a non-recursive time domain equalizer filter and D is performed by a delay of the signal sequence entering the module; and wherein each module the signal represented as contained within each right parenthesis is the input to the delay circuit.
Claim 13
Dependent Claim
22 words
An equalization apparatus as set forth in Claim 5 wherein the polynomial expansion of the deisred equalizer response is of the form
Claim 14
Dependent Claim
22 words
An equalization apparatus as set forth in claim 5 wherein the polynomial expansion of the desired equalizer response is of the form
References Cited (Backward Citations)
US3648171A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-10-08 | 1977-04-09 | 1977-10-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-08 | 1981-04-09 | 1981-10-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-08 | 1985-04-09 | 1985-10-09 | $7700.00 | Window Closed / Lapsed |