US4499508A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Digital magnetic recording
Assignee: Individual
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Filing: 1982-02-18
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Granted: 1985-02-12
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Expires: 2002-02-18
Abstract
Abstract In a system for retrieving data from a recording medium employing MFM or FM encoding forms, a decoding method and circuit employs the technique of delaying the third harmonic of the data signal relative to the fundamental of the data signal by 180 degrees. This delaying is effected by the use of two resonant networks each delaying the third harmonic relative to the fundamental by 90 degrees. The delaying technique enables a differentation stage to be eliminated.
Inventors
- 👤 Archibald M. Pettigrew
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 01:50
CPC Classifications
G; G11; G11B; G11B20/00; G11B20/10; G11B20/14; G11B20/1403; G11B20/1407; G11B20/1419; G11B20/1423
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
93 words
A method of data recovery in digital magnetic recording, comprising the steps of deriving an information-carrying data signal from a recording medium, delaying the third harmonic of said data signal with respect to the fundamental of said data signal by one half period of said third harmonic to produce a modified signal, and deriving a digital information-carrying pulse train from said modified signal wherein the delaying of said third harmonic is effected by passing the data signal through two resonant networks whose resonant frequencies are equal to the frequency of said third harmonic.
Claim 2
Independent Claim
93 words
A method of data recovery in digital magnetic recording, comprising the steps of deriving an information-carrying data signal from a recording medium, delaying the third harmonic of said data signal with respect to the fundamental of said data signal by one half period of said third harmonic to produce a modified signal, and deriving a digital information-carrying pulse train from said modified signal wherein the delaying of said third harmonic is effected by passing the data signal through two resonant networks whose resonant frequencies are equal to the frequency of said third harmonic.
Claim 3
Dependent Claim
16 words
A method as claimed in claim 1 wherein said resonant networks comprise resonant low pass filters.
Claim 4
Dependent Claim
28 words
A method as claimed in claim 1 wherein one of said resonant networks includes a magnetic reading head which derives said information-carrying data signal from said recording medium.
Claim 5
Dependent Claim
25 words
A method as claimed in claim 1 wherein one of said resonant networks is in the form of a second order low pass filter circuit.
Claim 6
Dependent Claim
18 words
A method as claimed in claim 1 and further including the step of decoding said information-carrying pulse train.
Claim 7
Dependent Claim
85 words
A circuit for data recovery in digital magnetic recording comprising means for deriving an information-carrying data signal from a recording medium, means for delaying the third harmonic of said data signal with respect to the fundamental of said data signal by one half period of said third harmonic to produce a modified signal, and means for deriving an information-carrying pulse train from said modified signal, wherein said delaying means comprises two resonant networks whose resonant frequencies are equal to the frequency of said third harmonic.
Claim 8
Dependent Claim
85 words
A circuit for data recovery in digital magnetic recording comprising means for deriving an information-carrying data signal from a recording medium, means for delaying the third harmonic of said data signal with respect to the fundamental of said data signal by one half period of said third harmonic to produce a modified signal, and means for deriving an information-carrying pulse train from said modified signal, wherein said delaying means comprises two resonant networks whose resonant frequencies are equal to the frequency of said third harmonic.
Claim 9
Dependent Claim
28 words
A circuit as claimed in claim 6 wherein said means for deriving data signal includes a magnetic reading head which forms part of one of said resonant networks.
Claim 10
Dependent Claim
25 words
A circuit as claimed in claim 6 wherein one of said resonant networks is in the form of a second order low pass filter circuit.
Claim 11
Dependent Claim
21 words
A circuit as claimed in claim 6 and further including means for decoding said information-carrying pulse train to obtain NRZ data.
References Cited (Backward Citations)
US4319288A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-02-12 | 1988-08-13 | 1989-02-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-02-12 | 1992-08-13 | 1993-02-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-02-12 | 1996-08-13 | 1997-02-12 | $7700.00 | Window Closed / Lapsed |