Patent EP0528039A1 successfully refreshed from Google Patents.
US3715670A
Expired / Lapsed
US
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Adaptive dc restoration in single-sideband data systems
Assignee: AT&T Inc
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Filing: 1971-12-20
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Granted: 1973-02-06
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Expires: 1991-12-20
Abstract
Abstract Single-sideband, as well as vestigial-sideband, transmission of synchronous digital data over channels of limited bandwidth, such as voice telephone channels, is facilitated by removing lowfrequency signal energy at the transmitter to provide frequency space for a demodulating carrier component and by adaptively restoring such energy at the receiver after demodulation. A first transversal filter in series with, and a second transversal filter in parallel feedback relationship with a data detection circuit at the receiver are made jointly responsive to a common error component to both equalize and restore dc components adaptively to a received signal. More efficient bandwidth utilization than that achieved in systems using bandedge pilot ones is thereby attained.
Inventors
- 👤 D Hirsch
- 👤 D Spaulding
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:08
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/02; H04L27/06; H04L25/00; H04L25/02; H04L25/06; H04L25/061
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
155 words
An adaptive dc restoration circuit for digital data signals from which low-frequency energy has been removed for bandwidth conservation purposes comprising data detection means having an input and an output for transforming input signal samples of arbitrary amplitude into output signals of the most probable of preselected discrete amplitudes, error means responsive to the difference between the input and output of said data detection means for generating an error signal, transversal filter means having a plurality of adjustable attenuating means, and associated correlating means responsive to said error signal for controlling said attenuating means at synchronously spaced taps thereon and a summation circuit for combining selectively attenuated tap signal samples, means for applying output signals from said detector means to said transversal filter means, and means for combining signals from the summation circuit of said transversal filter means with received data signals to form an input signal with low-frequency energy restored for said detection means.
Claim 2
Dependent Claim
155 words
An adaptive dc restoration circuit for digital data signals from which low-frequency energy has been removed for bandwidth conservation purposes comprising data detection means having an input and an output for transforming input signal samples of arbitrary amplitude into output signals of the most probable of preselected discrete amplitudes, error means responsive to the difference between the input and output of said data detection means for generating an error signal, transversal filter means having a plurality of adjustable attenuating means, and associated correlating means responsive to said error signal for controlling said attenuating means at synchronously spaced taps thereon and a summation circuit for combining selectively attenuated tap signal samples, means for applying output signals from said detector means to said transversal filter means, and means for combining signals from the summation circuit of said transversal filter means with received data signals to form an input signal with low-frequency energy restored for said detection means.
Claim 3
Dependent Claim
155 words
An adaptive dc restoration circuit for digital data signals from which low-frequency energy has been removed for bandwidth conservation purposes comprising data detection means having an input and an output for transforming input signal samples of arbitrary amplitude into output signals of the most probable of preselected discrete amplitudes, error means responsive to the difference between the input and output of said data detection means for generating an error signal, transversal filter means having a plurality of adjustable attenuating means, and associated correlating means responsive to said error signal for controlling said attenuating means at synchronously spaced taps thereon and a summation circuit for combining selectively attenuated tap signal samples, means for applying output signals from said detector means to said transversal filter means, and means for combining signals from the summation circuit of said transversal filter means with received data signals to form an input signal with low-frequency energy restored for said detection means.
Claim 4
Dependent Claim
155 words
An adaptive dc restoration circuit for digital data signals from which low-frequency energy has been removed for bandwidth conservation purposes comprising data detection means having an input and an output for transforming input signal samples of arbitrary amplitude into output signals of the most probable of preselected discrete amplitudes, error means responsive to the difference between the input and output of said data detection means for generating an error signal, transversal filter means having a plurality of adjustable attenuating means, and associated correlating means responsive to said error signal for controlling said attenuating means at synchronously spaced taps thereon and a summation circuit for combining selectively attenuated tap signal samples, means for applying output signals from said detector means to said transversal filter means, and means for combining signals from the summation circuit of said transversal filter means with received data signals to form an input signal with low-frequency energy restored for said detection means.
Claim 5
Dependent Claim
52 words
The combination defined in claim 1 in which said transversal filter includes a summation circuit for selectively attenuated outputs of all taps and in which the output of said summation circuit is combined with a received data signal deficient in low-frequency energy to provide an input signal for said data detection circuit.
Claim 6
Dependent Claim
53 words
The combination defined in claim 1 in which a further transversal filter having adjustable attenuators at synchronously spaced taps thereon is connected in series with said data decision circuit to equalize received data signals and further means to correlate said error signal with signal samples at each tap on said further transversal filter.
Claim 7
Dependent Claim
117 words
In combination with a receiver for an asymmetric-sideband amplitude-modulated synchronous data signal from which low-frequency energy has been removed to allow frequency space for transmission of a separable carrier component susceptible of recovery without interference with data-signal components: a data detection circuit, a transversal filter having adjustable attenuators at synchronously spaced taps thereon in parallel feedback relationship with said detection circuit, means for deriving an error signal from the difference between the input and output of said detection circuit, and means for correlating said error signal with the signal samples at each tap on said transversal filter to generate control signals for adjusting associated attenuators and thereby to restore said low-frequency energy to a received data signal.
Claim 8
Dependent Claim
117 words
In combination with a receiver for an asymmetric-sideband amplitude-modulated synchronous data signal from which low-frequency energy has been removed to allow frequency space for transmission of a separable carrier component susceptible of recovery without interference with data-signal components: a data detection circuit, a transversal filter having adjustable attenuators at synchronously spaced taps thereon in parallel feedback relationship with said detection circuit, means for deriving an error signal from the difference between the input and output of said detection circuit, and means for correlating said error signal with the signal samples at each tap on said transversal filter to generate control signals for adjusting associated attenuators and thereby to restore said low-frequency energy to a received data signal.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-02-06 | 1976-08-07 | 1977-02-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-02-06 | 1980-08-07 | 1981-02-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-02-06 | 1984-08-07 | 1985-02-06 | $7700.00 | Window Closed / Lapsed |