Patent US3611209A successfully refreshed from Google Patents.
US3611209A
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Digital filter frequency shift modulator
Assignee: AT&T Inc
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Filing: 1969-12-11
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Granted: 1971-10-05
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Expires: 1989-12-11
Abstract
Abstract Feedback circuitry is designed to place a digital filter on the borderline of stability. The filter, therefore, oscillates in a numerical sense. Other feedback circuitry includes two independent multipliers, each capable of determining different central coefficients, and thus different oscillation frequencies. Switch means operated by DC baseband data signals alternatively insert one or the other of the multipliers in the feedback path whereby the output frequency of the filter is shifted in accordance with the input data. Amplitude variations due principally to quantizing noise are stabilized by a correction generator which checks the amplitude of the filter output number and modifies the multiplied feedback number when the output number varies from a predetermined limit. The modulator is advantageously arranged to be time shared by a plurality of channels.
Inventors
- 👤 Burton R Saltzberg
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 16:33
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/10; H04L27/12
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
77 words
A frequency-shift signal modulator including a digital filter for processing multibit numbers to simulate continuous analog filter functions, means for placing the filter on the borderline of stability whereby the filter oscillates in a numerical sense a feedback path, a first and a second feedback means for determining the central coefficient of the filter, and switch means responsive to the application of data signals for alternatively inserting the first and second feedback means in the feedback path.
Claim 2
Dependent Claim
77 words
A frequency-shift signal modulator including a digital filter for processing multibit numbers to simulate continuous analog filter functions, means for placing the filter on the borderline of stability whereby the filter oscillates in a numerical sense a feedback path, a first and a second feedback means for determining the central coefficient of the filter, and switch means responsive to the application of data signals for alternatively inserting the first and second feedback means in the feedback path.
Claim 3
Dependent Claim
20 words
A frequency-shift modulator in accordance with claim 1 wherein the arranged means comprises a further feedback path having unity gain.
Claim 4
Dependent Claim
24 words
A frequency-shift signal modulator in accordance with claim 1 wherein each feedback means comprises means for multiplying the filter output number with a constant.
Claim 5
Dependent Claim
37 words
A frequency-shift signal modulator in accordance with claim 3 wherein there is further included means responsive to the amplitude of the filter output numbers for modifying the multiplied feEdback number whereby the filter output amplitude is stabilized.
Claim 6
Dependent Claim
71 words
An oscillator including a digital filter for processing multibit numbers to simulate continuous analog filter functions, the filter including first feedback means for multiplying the filter output number with a constant and further feedback means for placing the filter on the borderline of stability whereby the filter oscillates in a numerical sense, CHARACTERIZED IN THAT modifying means responsive to the amplitude of the filter output numbers feeds back modified output numbers.
Claim 7
Dependent Claim
71 words
An oscillator including a digital filter for processing multibit numbers to simulate continuous analog filter functions, the filter including first feedback means for multiplying the filter output number with a constant and further feedback means for placing the filter on the borderline of stability whereby the filter oscillates in a numerical sense, CHARACTERIZED IN THAT modifying means responsive to the amplitude of the filter output numbers feeds back modified output numbers.
Claim 8
Dependent Claim
16 words
An oscillator in accordance with claim 5 wherein the modifying means modifies the multiplied feedback number.
Claim 9
Dependent Claim
29 words
An oscillator in accordance with claim 5 wherein the modifying means decreases the value of a feedback number if the amplitude of an output number exceeds a predetermined limit.
Claim 10
Dependent Claim
42 words
An oscillator in accordance with claim 7 wherein the modifying means decreases the value of the feedback number by adding a correction number to the feedback number which is one-half a signal cycle after the output number that exceeds the predetermined limit.
Claim 11
Dependent Claim
32 words
An oscillator in accordance with claim 5 wherein the modifying means increases the value of the feedback number if the amplitudes of the filter output numbers do not exceed a predetermined limit.
Claim 12
Dependent Claim
37 words
An oscillator in accordance with claim 9 wherein the modifying means operates to increase the value of the feedback number when the amplitudes of a full signal cycle of output numbers do not exceed the predetermined limit.
Claim 13
Dependent Claim
50 words
A signal modulator including a digital filter for processing multibit numbers to simulate continuous analog filter functions, means for placing the filter on the borderline of stability whereby the filter oscillates in a numerical sense and means responsive to incoming baseband signals for determining the central coefficient of the filter.
Claim 14
Dependent Claim
50 words
A signal modulator including a digital filter for processing multibit numbers to simulate continuous analog filter functions, means for placing the filter on the borderline of stability whereby the filter oscillates in a numerical sense and means responsive to incoming baseband signals for determining the central coefficient of the filter.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-10-04 | 1975-04-05 | 1975-10-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-10-04 | 1979-04-05 | 1979-10-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-10-04 | 1983-04-05 | 1983-10-05 | $7700.00 | Window Closed / Lapsed |