US3878468A
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US
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Joint equalization and carrier recovery adaptation in data transmission systems
Assignee: AT&T Inc
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Filing: 1974-01-30
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Granted: 1975-04-15
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Expires: 1994-01-30
Abstract
Abstract An adaptive transversal equalizer acts jointly with a phasejitter compensator to achieve substantially jitter-free passband equalization of a suppressed-carrier coherent data signal without the use of transmitted pilot tones. The received signal is split into quadrature components for separate equalization. The equalized outputs are demodulated to baseband, quantized and remodulated to passband. The differences between the equalized and remodulated outputs constitute error signals for direct control of tap-gain attenuator adjustments and after further data-directed processing control signals for recovery of a jitter-compensating demodulating carrierwave are generated. In an alternative embodiment the received data signals, after splitting into quadrature components, are demodulated to baseband under the control of a first demodulating carrier-wave oscillator whose phase and frequency are determined by the intermodulation of respective quadrature-related equalizer outputs. The phase jitter is tracked in a second oscillator under the control of signals derived from the intermodulation of the inputs and outputs of a data signal decision circuit following the equalizers.
Inventors
- 👤 David Duncan Falconer
- 👤 Kurt Hugo Mueller
- 👤 Jack Salz
- 👤 David Adams Spaulding
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 15:27
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/01; H04L27/32; H04L27/34; H04L27/38; H04L27/3818; H04L27/3836
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
223 words
In a data receiver for data signals synchronously modulated onto quadrature phases of a common carrier wave including a transversal equalizer structure having a delay line with taps located at synchronous intervals therealong for each of the quadrature-related received signals, an adjustable attenuator connected to each tap on each delay line and a corresponding correlator jointly responsive to error and tap signals for determining the adjustment of each attenuator, and combining circuits for forming each of the in-phase and quadrature-phase equalizer outputs; and further including a demodulating carrierwave source, a demodulator for respective in-phase and quadrature-phase received-signal components, and a data recovery circuit operating on demodulated in-phase and quadrature-phase received signals to derive quantized baseband data signals: the improvement comprising means for forming in-phase and quadraturephase error signals from the differences between respective in-Phase and quadrature-phase outputs of said equalizer and said data recovery circuit, means responsive to said in-phase and quadrature-phase error signals for generating control signals for said adjustable attenuators on each of said delay lines, means for cross-multiplying respective in-phase and quadraturephase error signals from said generating means with the quadrature-phase and in-phase equalizer outputs to form crossproduct signals, and means responsive to the differences between said cross-product signals from said cross-multiplying means for deriving control signals for the frequency and phase of the output of said demodulating carrier-wave source.--.
Claim 2
Dependent Claim
223 words
In a data receiver for data signals synchronously modulated onto quadrature phases of a common carrier wave including a transversal equalizer structure having a delay line with taps located at synchronous intervals therealong for each of the quadrature-related received signals, an adjustable attenuator connected to each tap on each delay line and a corresponding correlator jointly responsive to error and tap signals for determining the adjustment of each attenuator, and combining circuits for forming each of the in-phase and quadrature-phase equalizer outputs; and further including a demodulating carrierwave source, a demodulator for respective in-phase and quadrature-phase received-signal components, and a data recovery circuit operating on demodulated in-phase and quadrature-phase received signals to derive quantized baseband data signals: the improvement comprising means for forming in-phase and quadraturephase error signals from the differences between respective in-Phase and quadrature-phase outputs of said equalizer and said data recovery circuit, means responsive to said in-phase and quadrature-phase error signals for generating control signals for said adjustable attenuators on each of said delay lines, means for cross-multiplying respective in-phase and quadraturephase error signals from said generating means with the quadrature-phase and in-phase equalizer outputs to form crossproduct signals, and means responsive to the differences between said cross-product signals from said cross-multiplying means for deriving control signals for the frequency and phase of the output of said demodulating carrier-wave source.--.
Claim 3
Dependent Claim
94 words
The data receiver defined in claim 1 further comprising means for applying said received signals directly to said equalizer in the passband frequency range, means for demodulating equalized passband received signals from said equalizer to the baseband frequency range, means for quantizing baseband signals from said demodulating means to preassigned discrete data-signal levels, and means for remodulating data-signal levels from said quantizing means to frequencies corresponding to the passband range effective at said equalizer, whereby said error differences are taken between passband signals respectively in the outputs of said equalizer and said remodulating means.--.
Claim 4
Dependent Claim
65 words
The data receiver defined in claim 1 further comprising means for demodulating quadrature-related received signals from a passband frequency range to a baseband frequency range before application to said equalizer, and means for quantizing baseband signals from said equalizer to preassigned discrete data-signal levels, whereby said error differences are taken between baseband signals respectively in the outputs of said demodulating means and said quantizing means.--.
Claim 5
Dependent Claim
72 words
The data receiver defined in claim 3 further comprising a jitter-compensating modulator interposed between said equalizer and said data recovery circuit, a local oscillator for providing a predetermined nominal frequency of expected phase jitter to said jitter-compensating modulator, and means for taking the difference between the cross-products of the quadrature-related outputs of said jitter-compensating modulator with quantized data signals from said quantizing means to form a control signal for said local oscillator.
Claim 6
Dependent Claim
245 words
A transversal equalizer for received signals modulating quadrature-related components of a common carrier wave transmitted at synchronous intervals comprising first and second delay lines each having a plurality of taps evenly spaced therealong at said synchronous intervals, a first and second attenuator connected to each tap on the respective first and second delay lines, first and second summation circuits for said quadrature-related received signals respectively traversing said first and second delay lines and the said attenuators connected thereto, first and second data decision circuits responsive to the outputs of said first and second summation circuits for quantizing the outputs thereof, means for generating respective in-phase and quadrature-phase error signals from the differences between the unquantized outputs of said first and second summation circuits and the corresponding quantized outputs of said first and second data decision circuits, means for multiplying the respective tap signals at synchronous intervals on each of said first and second delay lines with each of said in-phase and quadrature-phase error signals, first means for combining the direct products of the in-phase error and tap signals with those of the quadrature-phase error and tap signals to obtain a first attenuator adjustment signal, second means for combining the cross products of the respective in-phase and quadrature-phase error and tap signals to obtain a second attenuator adjustment signal, and switching means for applying the respective first and second attenuaTor adjustment signals in succession to each of said first and second attenuators during each synchronous interval.
Claim 7
Dependent Claim
245 words
A transversal equalizer for received signals modulating quadrature-related components of a common carrier wave transmitted at synchronous intervals comprising first and second delay lines each having a plurality of taps evenly spaced therealong at said synchronous intervals, a first and second attenuator connected to each tap on the respective first and second delay lines, first and second summation circuits for said quadrature-related received signals respectively traversing said first and second delay lines and the said attenuators connected thereto, first and second data decision circuits responsive to the outputs of said first and second summation circuits for quantizing the outputs thereof, means for generating respective in-phase and quadrature-phase error signals from the differences between the unquantized outputs of said first and second summation circuits and the corresponding quantized outputs of said first and second data decision circuits, means for multiplying the respective tap signals at synchronous intervals on each of said first and second delay lines with each of said in-phase and quadrature-phase error signals, first means for combining the direct products of the in-phase error and tap signals with those of the quadrature-phase error and tap signals to obtain a first attenuator adjustment signal, second means for combining the cross products of the respective in-phase and quadrature-phase error and tap signals to obtain a second attenuator adjustment signal, and switching means for applying the respective first and second attenuaTor adjustment signals in succession to each of said first and second attenuators during each synchronous interval.
Claim 8
Dependent Claim
55 words
The transversal equalizer defined in claim 5 in combination with third and fourth combining means for forming respective in-phase and quadrature-phase equalized output signals, and further switching means operating synchronously with said first-mentioned switching means for alternately connecting said first and second summation circuits to said third and fourth combining circuits during each synchronous interval.
Claim 9
Dependent Claim
229 words
In a data receiver for data signals synchronously modulated onto quadrature phases of a common carrier wave including a transversal equalizer structure having a delay line with taps located at synchronous intervals therealong for each of the quadraturerelated received signals, an adjustable attenuator connected to each tap on each delay line and a corresponding correlator jointly responsive to error and tap signals for determining the adjustment of each attenuator, and combining circuits for forming each of the in-phase and quadrature-phase equalizer outputs; and further including a demodulating carrier-wave source, a demodulator for respective in-phase and quadrature-phase received-signal components, and a data recovery circuit operating on demodulated in-phase and quadrature-phase received signals to derive quantized baseband data signals: the improvement comprising means for forming in-phase and quadraturephase error signals from the differences between respective in-phase and quadrature-phase outputs of said equalizer and said data recovery circuits, means responsive to said in-phase and quadrature-phase error signals for generating control signals for said adjustable attenuators on each of said delay lines, means for cross-multiplying respective inphase and quadrature-phase outputs of said equalizer with the quadrature-phase and in-phase quantized baseband data signals derived in said data recovery circuit to form cross-product signals, and means responsive to the differences between said cross-product signals from said cross-multiplying means for deriving control signals for the frequency and phase of the output of said demodulating carrier-wave source.--.
Claim 10
Dependent Claim
229 words
In a data receiver for data signals synchronously modulated onto quadrature phases of a common carrier wave including a transversal equalizer structure having a delay line with taps located at synchronous intervals therealong for each of the quadraturerelated received signals, an adjustable attenuator connected to each tap on each delay line and a corresponding correlator jointly responsive to error and tap signals for determining the adjustment of each attenuator, and combining circuits for forming each of the in-phase and quadrature-phase equalizer outputs; and further including a demodulating carrier-wave source, a demodulator for respective in-phase and quadrature-phase received-signal components, and a data recovery circuit operating on demodulated in-phase and quadrature-phase received signals to derive quantized baseband data signals: the improvement comprising means for forming in-phase and quadraturephase error signals from the differences between respective in-phase and quadrature-phase outputs of said equalizer and said data recovery circuits, means responsive to said in-phase and quadrature-phase error signals for generating control signals for said adjustable attenuators on each of said delay lines, means for cross-multiplying respective inphase and quadrature-phase outputs of said equalizer with the quadrature-phase and in-phase quantized baseband data signals derived in said data recovery circuit to form cross-product signals, and means responsive to the differences between said cross-product signals from said cross-multiplying means for deriving control signals for the frequency and phase of the output of said demodulating carrier-wave source.--.
Claim 11
Dependent Claim
92 words
The data receiver defined in claim 7 further comprising means for applying said received signals directly to said equalizer in the passband frequency range, means for demodulating equalized passband received signals from said equalizer to the baseband frequency range, means for quantizing baseband signals from said demodulating means to preassigned discrete datasignal levels, and means for remodulating data signals from said quantizing means to the passband frequency range effective at said equalizer, whereby said error differences are taken between passband signals respectively in the outputs of said equalizer and said remodulating means.
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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) | 1978-04-14 | 1978-10-14 | 1979-04-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-14 | 1982-10-14 | 1983-04-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-14 | 1986-10-14 | 1987-04-15 | $7700.00 | Window Closed / Lapsed |