US4873700A
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Auto-threshold/adaptive equalizer
Assignee: National Semiconductor Corp
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Filing: 1987-10-14
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Granted: 1989-10-10
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Expires: 2007-10-14
Abstract
Abstract An auto-threshold circuit in accordance with the present invention comprises a full-wave peak sensor for accurately estimating slice levels for input signal detection. The peak sensor is qualified such that the auto-threshold circuit does not track an input signal with no modulation. The input signal is windowed with a phase-locked-loop so that the peak sensor is coherent to the input signal, causing the circuit to be insensitive to noise spikes or input distortion outside the window. The auto-threshold circuit includes a digital loop filter which receives the output from an auto-threshold controller and generates a corresponding binary signal which is converted by a digital Sigma/delta modulator to a single bit pulse density modulated signal having a predetermined sampling frequency. An adaptive equalizer in accordance with the present invention shares the auto-threshold slicing signal for generating its error feedback signal. The adaptive equalizer comprises a frequency selector which generates an output signal in response to the input signal and the feedback signal. As stated above, a threshold comparator slices the equalizer output at predetermined levels. A controller receives the comparator output and provides a controller output representative of the voltage level of the comparator output. A digital filter is then utilized to generate a corresponding binary signal as the feedback signal to the frequency selector. The adaptive equalizer is operable at more than one speed.
Inventors
- 👤 Hee Wong
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 18:09
CPC Classifications
H; H04; H04L; H04L25/00; H04L25/02; H04L25/06; H04L25/061; H04L25/063; H04L25/03; H04L25/03006; H04L25/03012; H04L25/03019; H04L25/03038
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
110 words
An auto-threshold circuit that allows a signal receiver to detect an input signal at different amplitude levels, the input signal comprising data and a carrier waveform, the auto-threshold circuit comprising window comparator means for slicing the input signal at predetermined levels; an auto-threshold controller which receives the sliced input signal and provides an output voltage representative of the sliced input signal; a digital loop filter which receives the output voltage of the auto-threshold controller and generates a corresponding binary signal; and converter means for converting the binary signal to a single-bit, pulse density modulated signal having a predetermined sampling frequency whereby the auto-threshold circuit provides selected data as an ouput.
Claim 2
Dependent Claim
110 words
An auto-threshold circuit that allows a signal receiver to detect an input signal at different amplitude levels, the input signal comprising data and a carrier waveform, the auto-threshold circuit comprising window comparator means for slicing the input signal at predetermined levels; an auto-threshold controller which receives the sliced input signal and provides an output voltage representative of the sliced input signal; a digital loop filter which receives the output voltage of the auto-threshold controller and generates a corresponding binary signal; and converter means for converting the binary signal to a single-bit, pulse density modulated signal having a predetermined sampling frequency whereby the auto-threshold circuit provides selected data as an ouput.
Claim 3
Dependent Claim
16 words
An auto-threshold circuit as in claim 1 wherein the converter means comprises a digital Sigma/delta modulator.
Claim 4
Dependent Claim
29 words
An auto-threshold circuit as in claim 2 wherein the auto-threshold control voltage generated form the digital Sigma/delta modulator is filtered by an RC circuit with a non-critical time constant.
Claim 5
Dependent Claim
22 words
An auto-threshold circuit as in claim 1 and further including means for operating the digital loop filter at more than one speed.
Claim 6
Dependent Claim
32 words
An auto-threshold circuit as in claim 1 and further including an adaptive equalizer that receives the auto-threshold slicing signal and generates an error feedback signal as an input to the adaptive equalizer.
Claim 7
Dependent Claim
22 words
An auto-threshold circuit as in claim 1 and including means for qualifying the auto-threshold controller to provide selected data as an output.
Claim 8
Dependent Claim
37 words
An auto-threshold circuit as in claim 6 wherein the means for qualifying comprises means for providing a first qualifier signal to the autothreshold controller, the first qualifier signal comprising a sliced output from 0+ and 0- filters.
Claim 9
Dependent Claim
105 words
In a receiver of the type that recovers data from input signals comprising data and a carrier waveform, an auto-threshold circuit that allows the receiver to detect input signals at different amplitude levels, the auto-threshold circuit comprising full-wave peak sensing means for estimating slice levels for input signal detection; means for qualifying the peak sensing means such that the auto-threshold circuit provides selected data as an output; and means for providing a window for the input signal such that the peak sensing means is coherent to the input signal, whereby the auto-threshold circuit is insensitive to noise spikes or input signal distribution outside the window.
Claim 10
Dependent Claim
105 words
In a receiver of the type that recovers data from input signals comprising data and a carrier waveform, an auto-threshold circuit that allows the receiver to detect input signals at different amplitude levels, the auto-threshold circuit comprising full-wave peak sensing means for estimating slice levels for input signal detection; means for qualifying the peak sensing means such that the auto-threshold circuit provides selected data as an output; and means for providing a window for the input signal such that the peak sensing means is coherent to the input signal, whereby the auto-threshold circuit is insensitive to noise spikes or input signal distribution outside the window.
Claim 11
Dependent Claim
168 words
An auto-threshold circuit that allows a signal receiver to detect an input signal at different amplitude levels, the auto-threshold circuit comprising window comparator means for slicing the input signal at predetermined levels; an auto-threshold controller which receives the sliced input signal and provides an output representative of the voltage level of the sliced input signal; means for qualifying the auto-threshold controller such that the auto-threshold circuit does not track an input signal with no modulation, wherein the means for qualifying provides first and second qualifier signals to the auto-threshold controller, the first qualifier signal being a sliced output from 0+ and 0- filters, the second qualifier signal enabling the auto-threshold circuit to operate on the same input signal segments as an adaptive equalizer included in the receiver; a digital loop filter which receives the output of the auto-threshold controller and generates a corresponding binary output signal; and converter means for converting the binary output signal to a single bit pulse density modulated signal having a predetermined sampling frequency.
Claim 12
Dependent Claim
168 words
An auto-threshold circuit that allows a signal receiver to detect an input signal at different amplitude levels, the auto-threshold circuit comprising window comparator means for slicing the input signal at predetermined levels; an auto-threshold controller which receives the sliced input signal and provides an output representative of the voltage level of the sliced input signal; means for qualifying the auto-threshold controller such that the auto-threshold circuit does not track an input signal with no modulation, wherein the means for qualifying provides first and second qualifier signals to the auto-threshold controller, the first qualifier signal being a sliced output from 0+ and 0- filters, the second qualifier signal enabling the auto-threshold circuit to operate on the same input signal segments as an adaptive equalizer included in the receiver; a digital loop filter which receives the output of the auto-threshold controller and generates a corresponding binary output signal; and converter means for converting the binary output signal to a single bit pulse density modulated signal having a predetermined sampling frequency.
Claim 13
Dependent Claim
43 words
An auto-threshold circuit as in claim 9 wherein the qualifying means further includes means for providing a third qualifier signal to the controller, the third qualifier signal preventing the auto-threshold circuit from responding to bits which may contain distortion due to bus contention.
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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) | 1992-10-09 | 1993-04-10 | 1993-10-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-10-09 | 1997-04-10 | 1997-10-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-10-09 | 2001-04-10 | 2001-10-10 | $7700.00 | Window Closed / Lapsed |