US3789380A
Expired / Lapsed
US
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Digital recording at twice nyquist bandwidth
Assignee: International Business Machines Corp
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Filing: 1973-04-09
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Granted: 1974-01-29
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Expires: 1993-04-09
Abstract
Abstract A digital magnetic recorder uses up to twice the Nyquist bandwidth of a data signal, plus a clock signal at a frequency exactly equal to the bit rate for reliably exchanging data signals with a magnetic media. The frequency response of the recording system is greater than twice the Nyquist bandwidth of the data signals to be recorded. Optionally, additional control signals at frequencies above or below the clock frequency but within the available recorder bandwidth may be recorded. Preferably, in a multitrack magnetic recording system, a signal component is added at a frequency near the clock frequency such that the difference between this signal and the clock has a wavelength on the magnetic media greater than the maximum skew of the multi-track system. Such signal component is usable as a resynchronization pattern. Additionally, write errors are detected during recording with special control indicia recorded on the media indicating such errors. Various forms of indicia are described including special data patterns, special signal components, and the like.
Inventors
- 👤 M Cannon
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 07:37
CPC Classifications
G; G11; G11B; G11B20/00; G11B20/10; G11B20/18; G11B20/1883; G11B20/12; G11B20/1201; G11B20/1202; G11B20/14; G11B20/1403; G11B20/1407; G11B20/1419; G11B20/1816; G11B20/20; G11B5/00; G11B5/008; G11B5/00813; G11B5/00817; G11B5/02; G11B5/09; G11B2220/00; G11B2220/90; G11B5/48; G11B5/58; G11B5/584
Claims Analysis
Total Claims: 55
Claim 1
Independent Claim
93 words
A signal processing system for exchanging data indicating signals with a signal track on magnetic media, the improvement including the combination: means establishing data-representing signals having a given periodicity; means operatively associated with said establiShing means to supply a clock signal at approximately an integral multiple of said given periodicity; means for summing and exchanging said signals between said media track and said establishing and said supplying means; and means for correlating said data-representing signals and said clock signal to establish a fixed phase relationship therebetween for facilitating signal exchanges with said media.
Claim 2
Dependent Claim
93 words
A signal processing system for exchanging data indicating signals with a signal track on magnetic media, the improvement including the combination: means establishing data-representing signals having a given periodicity; means operatively associated with said establiShing means to supply a clock signal at approximately an integral multiple of said given periodicity; means for summing and exchanging said signals between said media track and said establishing and said supplying means; and means for correlating said data-representing signals and said clock signal to establish a fixed phase relationship therebetween for facilitating signal exchanges with said media.
Claim 3
Dependent Claim
72 words
The signal processing system set forth in claim 1 wherein said supplying means is further operative with respect to a predetermined number of said data signals in association with a predetermined number of cycles of said clock signal to establish a unique indicia in said signal track superposed with said clock and data-representing signals in said track for identifying that a given number of said data and clock signals has been exchanged.
Claim 4
Dependent Claim
35 words
The signal processing system set forth in claim 1 wherein said establishing means supplies said clock signal having an amplitude greater than said data-representing signal for linearizing the signal characteristics of said system and media.
Claim 5
Dependent Claim
59 words
The signal processing system set forth in claim 2 wherein exchanging signals include recording signals on said media; means for detecting that a recording error has occurred; and retry means responsive to said write error for establishing a signal indicia of a write error and causing said establishing means to re-record signals supposedly recorded during said write error detection.
Claim 6
Dependent Claim
28 words
The signal processing system set forth in claim 4 further including delay means in said retry means for delaying retry until one of said unique indicia is exchanged.
Claim 7
Dependent Claim
51 words
The signal processing system set forth in claim 4 wherein said exchanging means includes means for detecting signals recorded on said media; direction of motion indicating means; and said correlating means being responsive to said direction indicating means to either ignore or read signals in association with said error indicating indicia.
Claim 8
Dependent Claim
45 words
The signal processing system set forth in claim 2 wherein said supplying means supplies a control indicia in predetermined frequency association with said clock signal, and said establishing means is responsive to said control indicia to perform a function with respect to said data signals.
Claim 9
Dependent Claim
50 words
The signal processing system set forth in claim 7 including means for simultaneously exchanging signals with a plurality of record tracks on said media, and said control indicia is placed in all tracks substantially simultaneously for effecting a similar control in all of said tracks on a substantial simultaneous basis.
Claim 10
Dependent Claim
48 words
The signal processing system set forth in claim 8 further including means modifying said control indicia in one of said tracks in accordance with detection of error signals in such one track for indicating a degraded write quality in such track in association with exchange of signals therewith.
Claim 11
Dependent Claim
42 words
The signal processing system set forth in claim 8 wherein said modifying means further effects rerecording the data in all said tracks associated with said error in one track in a predetermined relation to said modified control indicia in said one track.
Claim 12
Dependent Claim
57 words
The system set forth in claim 1 wherein said clock signal for each track has an effective frequency of exactly twice the data rate frequency and means in said clock means establishing a constant phase relationship with respect to said data-indicating signals and an amplitude during recording sufficient to effect a linearizing effect on the media recording.
Claim 13
Dependent Claim
53 words
The signal processing system set forth in claim 11 further including means limiting said data-indicating signals for each track to not greater than twice the Nyquist band of said data-indicating signals, and said clock means in each track establishing a clock frequency substantially at the upper frequency bounds of twice said Nyquist band.
Claim 14
Dependent Claim
32 words
The system set forth in claim 12 wherein said clock means supply a sine wave for reducing anY side band effects thereby limiting intermodulation of said clock signal to said data-indicating signal.
Claim 15
Dependent Claim
55 words
The signal processing system set forth in claim 13 further including additional means for selectively recording an additional control signal in each track at a frequency above twice the Nyquist band and establishing modulation signal components above said data frequency band for representing control functions associated with data signals to be exchanged with the media.
Claim 16
Dependent Claim
45 words
The signal processing system set forth in claim 14 wherein said additional means supplies said modulation signal components in a given relationship to data signals and recording same in a predetermined relationship in one track with respect to data signals in all of said tracks.
Claim 17
Dependent Claim
47 words
The signal processing system set forth in claim 15 wherein said additional means supplies said signal components to have a frequency relating to data signal representation on said media with an associated wavelength having a duration greater than the maximum skew between any of said record tracks.
Claim 18
Dependent Claim
40 words
The signal processing system set forth in claim 16 further including means selectively establishing additional signal components on each said additional control signal having an associative relationship with respect to the quality of the data-indicating signals recorded on the media.
Claim 19
Dependent Claim
57 words
The signal processing system set forth in claim 17 wherein said establishing means includes error correction and detection means, said error detection and correction means establishing a set of check bits on a set of data-indicating signals wholly confined within successive ones of said signal components having a wavelength greater than the maximum skew of said system.
Claim 20
Dependent Claim
65 words
The signal processing system set forth in claim 15 further including signal quality means in said exchanging means associated with each of said tracks on an independent basis for monitoring quality of recording in the respective tracks and generating signals indicative of a poor-quality recording in said respective tracks, and said exchanging means responsive to said generated signals for recording said indicia on the media.
Claim 21
Dependent Claim
34 words
The signal processing system set forth in claim 19 wherein said generated signals include a special code recordable in said data signal band and extending between successive ones of said skew spaced-apart signal components.
Claim 22
Dependent Claim
70 words
The signal processing system set forth in claim 19 wherein said signal quality means supplies said generated signal including additional signal components to be added to one of said control signals, and said establishing means repeating said data-indicating signals occurring during a write error detection in a space on said track at least separated by said skew indicating signal components and having a predetermined relationship with said additional signal components.
Claim 23
Dependent Claim
70 words
The signal processing system set forth in claim 1 further including means for monitoring quality of said signal exchange and responsive to a given deterioration of said exchange to magnetically record a signal in said signal track on said magnetic media at a frequency higher than any of said data-indicating signals on the same track containing such data-indicating signals in a manner so as to not destroy such data-indicating signals.
Claim 24
Dependent Claim
48 words
The signal processing system set forth in claim 22 for a multitrack magnetic record system and having one exchanging means for each track and one of said monitoring means for each said exchanging means, and each said monitoring means operating independent of every other of said monitoring means.
Claim 25
Dependent Claim
59 words
The signal processing system set forth in claim 23 wherein each said exchanging means includes filter means passing said data-indicating signal in a base pass band of up to twice the Nyquist bandwidth of frequency in said data-indicating signals and a second filter means having a narrow pass band at twice said Nyquist frequency for selecting said clock signal.
Claim 26
Dependent Claim
36 words
The signal proCessing system of claim 24 further including means in each said exchanging means establishing signal components associated with said clock signal and having additional means for combining said signal components with said clock signal.
Claim 27
Dependent Claim
78 words
The signal processing system of claim 24 wherein each said exchanging means includes a third filter means having a narrow pass band at a frequency displaced from a frequency of said clock signal a predetermined submultiple frequency of said Nyquist frequency, control means for establishing signal components at said displaced frequency, and operating means responsive to said clock and displaced frequency signals to adjust operation of said exchanging means in accordance with predetermined signal characteristics between said signals.
Claim 28
Dependent Claim
82 words
The signal processing system set forth in claim 26 including means controlling said control means to establish said displaced signal in a manner to establish said predetermined signal characteristics in relatively identical signal positions in all tracks on said media as a reference characteristic identifying signal groups on said media, and deskewing means receiving signals from said exchanging means for aligning signals in said byte signal group and responsive to said reference characteristic to reset alignment of signals to said signal groups.
Claim 29
Dependent Claim
59 words
The signal processing system of claim 1 wherein said establishing means supplies signals within twice the Nyquist bandwidth of data represented by such signals; and clocking means controlling the frequency of operation of said establishing means and supplying said clock signal at twice said Nyquist band upper frequency in a fixed phase relationship to operation of said establishing means.
Claim 30
Dependent Claim
65 words
The signal processing system of claim 1 wherein said supplying means further includes means determining a given number of data bits in said data-indicating signals and supplying signal components in association with said clock signal in a manner to identify groups of said data bits, and means determining the signal phase of said data-indicating signals and said clock signal to have a relatively fixed relationship.
Claim 31
Independent Claim
91 words
The method of operating a magnetic recording system including the steps of: establishing data-indicating signals to be recorded having a given periodicity and limiting the bandwidth of said signals within the recording system to twice the Nyquist band of said data; establishing a constant-frequency signal having a frequency equal to twice the Nyquist frequency of said data signal and establishing a pass band in said recording signals greater than twice the Nyquist frequency of said data signals; and exchanging said constant-frequency and data-indicating signals with a magnetic media as combined signals.
Claim 32
Independent Claim
91 words
The method of operating a magnetic recording system including the steps of: establishing data-indicating signals to be recorded having a given periodicity and limiting the bandwidth of said signals within the recording system to twice the Nyquist band of said data; establishing a constant-frequency signal having a frequency equal to twice the Nyquist frequency of said data signal and establishing a pass band in said recording signals greater than twice the Nyquist frequency of said data signals; and exchanging said constant-frequency and data-indicating signals with a magnetic media as combined signals.
Claim 33
Dependent Claim
32 words
The method set forth in claim 30 further including monitoring the exchange of said combined signals and recording an additional signal with said combined signal whenever said signal exchange exhibits predetermined characteristics.
Claim 34
Dependent Claim
36 words
The method set forth in claim 30 further including the steps of grouping said data signals and then adding signal components above said twice Nyquist bandwidth having predetermined repeated characteristics coextensively with said data signal groups.
Claim 35
Dependent Claim
50 words
The method set forth in claim 32 further establishing signals to be recorded in a plurality of parallel tracks on magnetic media; establishing said groups in general lateral alignment in said parallel tracks; and establishing said repeated characteristic in all tracks to establish groups of parallel signals in said media.
Claim 36
Dependent Claim
61 words
The method set forth in claim 33 further effecting relative motion between a media and a transducer and while effecting such relative motion, monitoring recording and effecting a re-recording of selected groups without altering said relative motion whenever predetermined recording characteristics are detected and further recording indicia in tracks giving rise to said recoRding characteristics upon such re-recording in all tracks.
Claim 37
Dependent Claim
34 words
The method set forth in claim 30 further supplying said constant-frequency signal at an amplitude substantially greater than the amplitude of said data-indicating signals for linearizing the recording system with a synchronous control signal.
Claim 38
Dependent Claim
133 words
A magnetic recording system having means for effecting relative displacement between a record member and a transducer for enabling transducing operations along tracks in the media caused by relative scanning of said transducer with respect to said media, said system having a given frequency pass band; the improvement including in combination: signal processing means associated with said transducer for effecting signal processing operations within a given frequency band fixedly related to the bandwidth of data represented in signals exchanged with said media via said transducer; and control means operatively associated with said signal processing means and said transducer establishing a substantially single-frequency signal exchangeable with said media via said transducer at one extremity of said frequency band and having a relatively fixed phase relationship to one signal frequency in said given frequency band.
Claim 39
Dependent Claim
133 words
A magnetic recording system having means for effecting relative displacement between a record member and a transducer for enabling transducing operations along tracks in the media caused by relative scanning of said transducer with respect to said media, said system having a given frequency pass band; the improvement including in combination: signal processing means associated with said transducer for effecting signal processing operations within a given frequency band fixedly related to the bandwidth of data represented in signals exchanged with said media via said transducer; and control means operatively associated with said signal processing means and said transducer establishing a substantially single-frequency signal exchangeable with said media via said transducer at one extremity of said frequency band and having a relatively fixed phase relationship to one signal frequency in said given frequency band.
Claim 40
Dependent Claim
47 words
The system set forth in claim 36 wherein said control means establishes said single-frequency signal independent of said signal processing means and supplies said single-frequency signal to said signal processing means such that said signal processing means adjusts its signal processing in accordance with said single-frequency signal.
Claim 41
Dependent Claim
54 words
The system set forth in claim 37 further including additional control means jointly responsive to said signal processing means and to said single-frequency signal to establish signal components in frequency juxtaposition to said single-frequency signal outside said twice Nyquist bandwidth for establishing further identifying signals with respect to signals in said twice Nyquist bandwidth.
Claim 42
Dependent Claim
99 words
A multitrack digital signal magnetic record system for having a single record member with plural parallel signal tracks, a recording system as set forth in claim 36 for being operatively associated with each of said tracks; the multitrack improvement including in combination: multitrack control means operative with each said claim 36 recited control means, said signal processing means and transducer means, and identifying groups of signals exchangeable with said media tracks in a substantially simultaneous manner and processing another single-frequency signal having a beat frequency and phase relation to said claim 36 recited single-frequency signal indicative of said groups.
Claim 43
Dependent Claim
45 words
The multitrack system set forth in claim 39 further including deskewing means capable of deskewing a set of parallel recorded groups and responsive to said beat frequency having a predetermined phase relationship to said control signal to reset said deskewing apparatus to a reference position.
Claim 44
Independent Claim
87 words
The method of operating a digital signal recorder, including the steps of: selecting a recording channel for the recorder having a given bandwidth; selecting data-indicating signals to be recorded to have recurrent bit periods of a given periodicity while simultaneously limiting such data-indicating signals to a data pass band substantially less than said given bandwidth; generating a sine-wave type signal having a fixed phase and frequency relationship to said bit periods; and linearly summing said signals and recording same on a record media as base band signals.
Claim 45
Independent Claim
87 words
The method of operating a digital signal recorder, including the steps of: selecting a recording channel for the recorder having a given bandwidth; selecting data-indicating signals to be recorded to have recurrent bit periods of a given periodicity while simultaneously limiting such data-indicating signals to a data pass band substantially less than said given bandwidth; generating a sine-wave type signal having a fixed phase and frequency relationship to said bit periods; and linearly summing said signals and recording same on a record media as base band signals.
Claim 46
Dependent Claim
44 words
The method set forth in claim 41 further including generating said sine-wave type signal to have a frequency equal to an integral multiple of said periodicity and supplying such sine-wave type signal with an amplitude substantially greater than the amplitude of the data-indicating signals.
Claim 47
Dependent Claim
107 words
A signal processing circuit having first and second portions; said first portion having a pass band equal to about twiCe the Nyquist bandwidth of a given set of data-representing signals for processing such signals; said second portion having a relatively narrow pass band at the upper frequency limits of said first portion pass band for processing a second signal; and other means for processing signals with respect to both said portions including synchronizing means for establishing a fixed phase relationship between signals processed in said portions whereby informational content of said first portion signals is indicated in said other means jointly by said first and second portion.
Claim 48
Dependent Claim
107 words
A signal processing circuit having first and second portions; said first portion having a pass band equal to about twiCe the Nyquist bandwidth of a given set of data-representing signals for processing such signals; said second portion having a relatively narrow pass band at the upper frequency limits of said first portion pass band for processing a second signal; and other means for processing signals with respect to both said portions including synchronizing means for establishing a fixed phase relationship between signals processed in said portions whereby informational content of said first portion signals is indicated in said other means jointly by said first and second portion.
Claim 49
Dependent Claim
37 words
The circuit set forth in claim 43 wherein said second signal is a sine wave at a frequency precisely at the upper limit of said twice Nyquist bandwidth and said second portion processing only said sine wave.
Claim 50
Dependent Claim
109 words
A magnetic digital signal recording system for exchanging signals with a magnetic media relatively movable with respect to transducing means and having a given frequency response characteristic; the improvement including in combination: data-signal processing means having a pass band signal frequency characteristic determined by twice the Nyquist pass band of signals to be processed; and auxiliary signal means having a frequency of operation outside said twice Nyquist pass band, but within said frequency characteristic of said recorder, and establishing predetermined frequency and phase relationships of selected control signals to data signals within said pass band for facilitating signal processing of such signals within said limited twice Nyquist pass band.
Claim 51
Dependent Claim
109 words
A magnetic digital signal recording system for exchanging signals with a magnetic media relatively movable with respect to transducing means and having a given frequency response characteristic; the improvement including in combination: data-signal processing means having a pass band signal frequency characteristic determined by twice the Nyquist pass band of signals to be processed; and auxiliary signal means having a frequency of operation outside said twice Nyquist pass band, but within said frequency characteristic of said recorder, and establishing predetermined frequency and phase relationships of selected control signals to data signals within said pass band for facilitating signal processing of such signals within said limited twice Nyquist pass band.
Claim 52
Dependent Claim
49 words
The magnetic recording system set forth in claim 45 wherein said auxiliary signal means includes substantially single-frequency passing means at the upper frequency of said twice Nyquist pass band and means establishing fixed phase relationship between such single frequency and a median frequency in said twice Nyquist pass band.
Claim 53
Independent Claim
84 words
The method of recording digital signals on a magnetic recording media including the steps of: establishing data-indicating signals in NRZ mode and limiting the bandwidth of such NRZ signals to approximately twice the Nyquist pass band thereof; establishing a control signal at twice the median frequency of said twice Nyquist pass band and supplying such signal for recording with said data signals at a constant energy level; and linearly combining and recording such combined signals on a magnetic media as base band record signals.
Claim 54
Independent Claim
84 words
The method of recording digital signals on a magnetic recording media including the steps of: establishing data-indicating signals in NRZ mode and limiting the bandwidth of such NRZ signals to approximately twice the Nyquist pass band thereof; establishing a control signal at twice the median frequency of said twice Nyquist pass band and supplying such signal for recording with said data signals at a constant energy level; and linearly combining and recording such combined signals on a magnetic media as base band record signals.
Claim 55
Dependent Claim
44 words
The method set forth in claim 47 further including the steps of sensing a recorded signal on said magnetic media and processing said readback signal as a combined signal and establishing a clocking relationship of said NRZ signals in accordance with said control signal.
References Cited (Backward Citations)
US3588836A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-01-28 | 1977-07-30 | 1978-01-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-28 | 1981-07-30 | 1982-01-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-28 | 1985-07-30 | 1986-01-29 | $7700.00 | Window Closed / Lapsed |