US3689844A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Digital filter receiver for frequency-shift data signals
Assignee: AT&T Inc
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Filing: 1969-12-11
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Granted: 1972-09-05
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Expires: 1989-12-11
Abstract
Abstract Sampled FSK data signals are converted to multibit numbers and processed by a digital filter receiver which includes a band-pass filter, a dual-resonator discriminator and a low-pass filter. The dc baseband data signal is reconstructed from the receiver output number by a ''''slicer'''' which detects the sign of the output numbers. The analog-to-number conversion is simplified by limiting the multibit numbers to be processed to two values, simulating the hard limiting of analog signals. Signal harmonics introduced by the nonlinearities of the analog-to-digital converter are substantially eliminated by fixing the sampling rate to a rate which interleaves, in the frequency spectrum, the filter aliases with the harmonies. The receiver is advantageously arranged to be time-shared by a plurality of channels.
Inventors
- 👤 Clair A Buzzard
- 👤 Burton R Saltzberg
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 19:52
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/10; H04L27/14; H04L27/156; H04L27/1566
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
132 words
A frequency-shift signal receiver including sampling means for producing signal samples defining instantaneous amplitudes of the frequency-shift signal; generator means for producing multibit digital signals representing numbers which designate amplitude link in response to said signal samples; and a digital filter for processing the multibit digital signals characterized in that the generator means comprises means arranged to gate to the digital filter the digital signal representing one of the numbers in response to the signal samples defining the instantaneous amplitudes above a midpoint level and the digital signal complement of the one number, with respect to a number designating the midpoint level, in response to the signal samples defining the instantaneous amplitudes below the midpoint level, whereby the gated digital signals are limited to the one number value and the complement thereof.
Claim 2
Dependent Claim
132 words
A frequency-shift signal receiver including sampling means for producing signal samples defining instantaneous amplitudes of the frequency-shift signal; generator means for producing multibit digital signals representing numbers which designate amplitude link in response to said signal samples; and a digital filter for processing the multibit digital signals characterized in that the generator means comprises means arranged to gate to the digital filter the digital signal representing one of the numbers in response to the signal samples defining the instantaneous amplitudes above a midpoint level and the digital signal complement of the one number, with respect to a number designating the midpoint level, in response to the signal samples defining the instantaneous amplitudes below the midpoint level, whereby the gated digital signals are limited to the one number value and the complement thereof.
Claim 3
Dependent Claim
24 words
A frequency-shift receiver in accordance with claim 1 wherein the one number and the complement thereof are equal in magnitude and opposite in sign.
Claim 4
Dependent Claim
37 words
converting the input signals by: sampling the frequency-shift signal input using the clock pulses and producing signal bits defining instantaneous amplitudes of the frequency-shift signals, operating on a signal bit to produce multibit digital signals representing numbers,
Claim 5
Dependent Claim
37 words
converting the input signals by: sampling the frequency-shift signal input using the clock pulses and producing signal bits defining instantaneous amplitudes of the frequency-shift signals, operating on a signal bit to produce multibit digital signals representing numbers,
Claim 6
Dependent Claim
14 words
digitally filtering the multibit digital signals using the clock pulses to operate the filter,
Claim 7
Dependent Claim
14 words
digitally filtering the multibit digital signals using the clock pulses to operate the filter,
Claim 8
Dependent Claim
59 words
A frequency-shift receiver in accordance with claim 2 wherein the generator means further includes means for repetitively generating identical groups of bits to form the digital signal representing the one number and means responsive to the signal samples for producing a sign bit and inserting the sign bit into the group of bits to produce positive and negative numbers.
Claim 9
Independent Claim
17 words
A method of suppressing signal harmonics in a receiver for a frequency-shift signal comprising the steps of,
Claim 10
Independent Claim
17 words
A method of suppressing signal harmonics in a receiver for a frequency-shift signal comprising the steps of,
Claim 11
Dependent Claim
30 words
Selecting a pulse rate for said train which interleaves, in the frequency spectrum, the filtering aliases generated during said filtering step with the signal harmonics introduced by said converting step.
Claim 12
Dependent Claim
30 words
Selecting a pulse rate for said train which interleaves, in the frequency spectrum, the filtering aliases generated during said filtering step with the signal harmonics introduced by said converting step.
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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) | 1975-09-05 | 1976-03-06 | 1976-09-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-09-05 | 1980-03-06 | 1980-09-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-09-05 | 1984-03-06 | 1984-09-05 | $7700.00 | Window Closed / Lapsed |