US3778787A
Expired / Lapsed
US
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Readback systems for digital recorders
Assignee: International Business Machines Corp
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Filing: 1973-04-09
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Granted: 1973-12-11
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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
2026-10-26 03:50
CPC Classifications
G; G11; G11B; G11B20/00; G11B20/20
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
82 words
A readback system for a magnetic record member including the combination: means establishing a readback signal based upon magnetization of said record member; first means responsive to a first frequency portion of said readback signal to detect data signals therefrom; and second means responsive to a second frequency portion of said readback signal to delete some Of said detected data signals and substitute other data signals therefor received from said media in a predetermined time relationship to said second frequency portion signal.
Claim 2
Dependent Claim
82 words
A readback system for a magnetic record member including the combination: means establishing a readback signal based upon magnetization of said record member; first means responsive to a first frequency portion of said readback signal to detect data signals therefrom; and second means responsive to a second frequency portion of said readback signal to delete some Of said detected data signals and substitute other data signals therefor received from said media in a predetermined time relationship to said second frequency portion signal.
Claim 3
Dependent Claim
68 words
The readback system set forth in claim 1 further including means responsive to a third frequency portion of said readback signal to identify groups or frames of said detected data signals and said third-mentioned means being responsive to a second portion of said readback signals only if said second portion has a signal state for the duration of a frame before deleting any of said detected data signals.
Claim 4
Dependent Claim
37 words
The system set forth in claim 2 wherein said third means deletes data signals in the frame said second frequency portion second state occurs and substituting data signals from the next subsequent frame for deleted data signals.
Claim 5
Dependent Claim
108 words
The system set forth in claim 3 having a plurality of tracks on a magnetic record and a like plurality of the apparatus set forth in claim 2 for the respective tracks on the media; buffering means for receiving said data signals from said second-mentioned means for storing a plurality of frames of said detected data signals; and means responsive to said third-mentioned means associated with any of said tracks for erasing detected data signals from all of said tracks in one of said buffer means and substituting data signals in all of said tracks in a subsequent received frame of data for such erased detected data signals.
Claim 6
Dependent Claim
65 words
The readback system set forth in claim 4 further including: transducing means in said establishing means; means relatively moving a record member with respect to said transducing means; direction of record member relative motion indicating means; and said second responsive means being responsive to said direction indicating means to either ignore or read signals having said predetermined time relationship to said second frequency portion signal.
Claim 7
Dependent Claim
53 words
The readback system set forth in claim 5 wherein said second responsive means supplies a control signal having a predetermined frequency association with said detected data signals, and said establishing means being responsive to said control signal to perform a readback adjusting function on said data signals in accordance with said control signal.
Claim 8
Dependent Claim
49 words
The readback system set forth in claim 6 including means in said establishing means for simultaneously receiving signals from a plurality of record tracks on said record, and said establishing means being responsive to said control signal to perform said readback readjusting function simultaneously on signals from all tracks.
Claim 9
Dependent Claim
45 words
The readback system set forth in claim 1 wherein said second frequency portion signal for each track has an effective frequency of exactly twice the data rate frequency of said first frequency portion and having a constant phase relationship with respect to said data signals.
Claim 10
Dependent Claim
70 words
The readback system set forth in claim 1 wherein said second means includes error correction and detection means, said error detection and correction means establishing a set of check bits on a set of detected data signals wholly confined within one wavelength of said signal in said second frequency portion and said one wavelength having a duration equal to the duration of an integral number of said detected data signals.
Claim 11
Dependent Claim
94 words
The readback system set forth in claim 1 for a multitrack magnetic record system and having one each of all of said means for each track; a signal establishing monitoring means for each said establishing means, each said monitoring means operating independent of every other of said monitoring means; and means in each of said second means responsive to the respective monitoring means to indicate an error condition and all said second means for all of said tracks respectively responsive to such error indication to delete said detected data signals from the respective tracks.
Claim 12
Dependent Claim
65 words
The readback system set forth in claim 10 wherein each said establishing means includes signal filter means passing said data signals in a base pass band of up to twice the Nyquist bandwidth of frequency of said data signals and a second filter means having a narrow pass band at twice said Nyquist frequency for selecting said second frequency portion signal for said second means.
Claim 13
Dependent Claim
68 words
The readback system of claim 11 further including means in each said establishing means supplying signals derived from said readback signal in addition to said first and second frequency portion signals; additional means for combining selected ones of said signals to generate additional control signals; and means in each said second means responsive to said additional control signals to perform additional readback functions on said detected data signals.
Claim 14
Dependent Claim
87 words
The readback system of claim 11 wherein each said establishing means includes third filter means having a narrow pass band at a frequency displaced from a frequency of said second frequency portion signal a predetermined submultiple frequency of said Nyquist band frequency; control means responsive to said readback signal for establishing signal components at said displaced frequency; and operating means in said second means responsive to said second frequency portion and displaced frequency signals to adjust operation of said establishing means in accordance with said error indications.
Claim 15
Dependent Claim
94 words
The readback system set forth in claim 13 including means controlling said control means to establish said displaced signal in a manner to establish said error indication in relatively identical timing relations to readback signals from all tracks on said media as a reference characteristic identifying signal groups on said media; and deskewing means in said second means receiving detected data signals from said first means for aligning detected data signals in signal groups, one signal from each track, and responsive to said reference characteristic to reset alignment of signals to said signal groups.
Claim 16
Dependent Claim
148 words
A readback system for a multitrack digital signal recorder wherein record media is subjected to a predetermined maximum skew with respect to a readback transducer means; a plurality of record tracks on said media subject to said skew; a separate independent single-track readback system portion for each track consisting of the claim 1 subject matter; further including in combination: framing means operatively connected to all said second means of said single track systems for generating framing signals for all said tracks based upon said second frequency portion, which framing signals have certain unique wavelength characteristics repeated at intervals not less than said predetermined maximum skew; and each said establishing means being individually responsive to said framing signal to introduce control signals along with each said readback signal to independently indicate frames of signals in each track in a fixed relationship to frames in each and every other track.
Claim 17
Independent Claim
110 words
The method of operating a readback system for a magnetic recording system including the steps of: establishing digital data-indicating signals based upon recorded indicia and having a given periodicity and limiting the bandwidth of said data-indicating signals within the readback system to twice the Nyquist band of said data; establishing a control signal from said readback signal having a frequency equal to twice the Nyquist frequency of said data-indicating signals and establishing a pass band in said readback system greater than twice the Nyquist frequency of said data-indicating signals; and combining said control and data-indicating signals to supply output detected data signals with timing indications established by said control signal.
Claim 18
Independent Claim
110 words
The method of operating a readback system for a magnetic recording system including the steps of: establishing digital data-indicating signals based upon recorded indicia and having a given periodicity and limiting the bandwidth of said data-indicating signals within the readback system to twice the Nyquist band of said data; establishing a control signal from said readback signal having a frequency equal to twice the Nyquist frequency of said data-indicating signals and establishing a pass band in said readback system greater than twice the Nyquist frequency of said data-indicating signals; and combining said control and data-indicating signals to supply output detected data signals with timing indications established by said control signal.
Claim 19
Dependent Claim
58 words
The method set forth in claim 16 further including the steps of grouping said data-indicating signals into groups of signals having a small number of signals greater than one, and receiving another signal from said readback signal haviNg a wavelength characteristic encompassing one group of signals and re-establishing said grouping step at one extremity of said wavelength characteristic.
Claim 20
Dependent Claim
84 words
A multichannel readback circuit for a magnetic recording system, including the combination: transducing means operatively associated with each recording channel for sensing recorded signals and supplying corresponding readback signals; indicia means responsive to said readback signals to indicate a detected write error indicia received from a record channel; means for detecting said indicia; means for receiving said readback signals for detecting data errors in said readbck signals; and means combining said detected error indicia and said data error detection to correct said data error.
Claim 21
Dependent Claim
84 words
A multichannel readback circuit for a magnetic recording system, including the combination: transducing means operatively associated with each recording channel for sensing recorded signals and supplying corresponding readback signals; indicia means responsive to said readback signals to indicate a detected write error indicia received from a record channel; means for detecting said indicia; means for receiving said readback signals for detecting data errors in said readbck signals; and means combining said detected error indicia and said data error detection to correct said data error.
Claim 22
Dependent Claim
163 words
A magnetic recording readback system having means for effecting relative displacement between a record member and a transducer for enabling record sensing transducing operations along tracks in the media caused by relative scanning of said transducer with respect to said media, said readback system having a given frequency pass band; the improvement including in combination: data signal processing means associated with said transducer for effecting data signal processing and detecting operations within a frequency band substantially equal to twice the Nyquist bandwidth of data represented in signals received from said media via said transducer; control means operatively associated with said data signal processing means and said transducer establishing a substantially single-frequency control signal at one extremity of said frequency band and having a relatively fixed phase relationship to one signal frequency in said twice Nyquist band; and means in said data signal processing means responsive to said single-frequency control signal to adjust said readback signal processing operations in accordance with said control signal.
Claim 23
Dependent Claim
163 words
A magnetic recording readback system having means for effecting relative displacement between a record member and a transducer for enabling record sensing transducing operations along tracks in the media caused by relative scanning of said transducer with respect to said media, said readback system having a given frequency pass band; the improvement including in combination: data signal processing means associated with said transducer for effecting data signal processing and detecting operations within a frequency band substantially equal to twice the Nyquist bandwidth of data represented in signals received from said media via said transducer; control means operatively associated with said data signal processing means and said transducer establishing a substantially single-frequency control signal at one extremity of said frequency band and having a relatively fixed phase relationship to one signal frequency in said twice Nyquist band; and means in said data signal processing means responsive to said single-frequency control signal to adjust said readback signal processing operations in accordance with said control signal.
Claim 24
Dependent Claim
76 words
The system set forth in claim 19 further including additional control means jointly responsive to said signal processing means and to said control signal to establish signal components in frequency juxtaposition to said control signal outside said twice Nyquist bandwidth for establishing further identifying signals with respect to signals in said twice Nyquist bandwidth; and means in said signal processing means responsive to said identifying signals to adjust the timing of said readback signal processing operations.
Claim 25
Dependent Claim
114 words
A multitrack system for having a single record member with plural parallel signal tracks, a recording system as set forth in claim 19 for being operatively associated with each of said tracks; a multitrack readback system improvement including in combination: multitrack control means operative with each said claim 19 recited control means, said signal processing means and transducer means, means identifying groups of signals exchangeable with said media tracks in a substantially simultaneous manner and means processing another control signal having a wavelength characteristic in a constant predetermined relation to said first-mentioned control signal for retiming operations of selected ones of said signal processing means for realigning timing of signals received for all tracks.
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) | 1976-12-10 | 1977-06-11 | 1977-12-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-10 | 1981-06-11 | 1981-12-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-10 | 1985-06-11 | 1985-12-11 | $7700.00 | Window Closed / Lapsed |