Patent EP0269381A2 successfully refreshed from Google Patents.
EP0269381A2
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EP
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Sampled servo code format and system for a disc drive
Assignee: HP Inc
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Filing: 1987-11-20
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Granted: —
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Expires: 2007-11-20
Abstract
Abstract The system and method for normalizing the amplitude of servo code derived signals in a disc drive, includes an improved embedded servo code format of separate magnetic dibit fields, recorded in half track steps. One magnetic dibit field is an automatic gain control field (27) in which the magnetic head (5) sees the same amount of magnetic dibit regardless of its position with respect to the track (21). A fast settling AGC loop responding to signals (27a) from the AGC field (27), produces a gain adjust signal while the magnetic head (5) is still in the AGC field (2), which is used to normalize the amplitude of all following servo code and data code signals in that sector (17). The cycle of automatic gain control is repeated for each track (21) in each sector (17). A sector mark (29) following the AGC field (27) has a magnetic dibit pattern which is fault tolerant. It is transduced in three parts to minimize error in its detection and identification and provides a timing reference for servo signals which follow. A defect dibit (D) is recorded if the following servo gap (19) is found to be defective during manufacture so that the next gap (19) may be ignored. A track position servo code field (23) provides signals for track (21) following.
Inventors
- 👤 Vernon L. Knowles
- 👤 Robert E. Kier
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 15:15
CPC Classifications
G; G11; G11B; G11B20/00; G11B20/10; G11B20/12; G11B20/1217; G11B27/00; G11B27/10; G11B27/19; G11B27/28; G11B27/30; G11B27/3027; G11B5/00; G11B5/48; G11B5/58; G11B5/596; G11B5/59633; G11B5/59655; G11B2020/1264; G11B2020/1265; G11B2020/1281; G11B2020/1282; G11B2220/00; G11B2220/20
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
172 words
In a magnetic disc drive, an improvement comprising: a rotatable memory disc (1) having a plurality or concentric circular tracks (21) which are each divided into sectors (17), each sector (17) being radially aligned with sectors (17) in adjacent tracks (21), each sector (17) having a servo gap (19) which is radially aligned with servo gaps (19) in adjacent tracks (21); characterized by an automatic gain control field (27) adjacent the beginning of each servo gap (19), having magnetic dibits disposed in radial alignment with each other in half-track positions on each side of the center of the track (21) thereat and in radial alignment with magnetic dibits in adjacent tracks (21); equally circumferentially spaced sector marks (29) in the track in each servo gap (19) following said automatic gain control field (29), each sector mark (29) being radially aligned with the sector mark (29) in an adjacent track; and magnetic dibits in each sector mark (29) disposed in half-track positions on each side of the center of the track (21) thereat.
Claim 2
Dependent Claim
172 words
In a magnetic disc drive, an improvement comprising: a rotatable memory disc (1) having a plurality or concentric circular tracks (21) which are each divided into sectors (17), each sector (17) being radially aligned with sectors (17) in adjacent tracks (21), each sector (17) having a servo gap (19) which is radially aligned with servo gaps (19) in adjacent tracks (21); characterized by an automatic gain control field (27) adjacent the beginning of each servo gap (19), having magnetic dibits disposed in radial alignment with each other in half-track positions on each side of the center of the track (21) thereat and in radial alignment with magnetic dibits in adjacent tracks (21); equally circumferentially spaced sector marks (29) in the track in each servo gap (19) following said automatic gain control field (29), each sector mark (29) being radially aligned with the sector mark (29) in an adjacent track; and magnetic dibits in each sector mark (29) disposed in half-track positions on each side of the center of the track (21) thereat.
Claim 3
Dependent Claim
53 words
The improvement as in Claim 1, characterized by a track identification code (25) for each track (21) in each servo gap (19) having radially aligned magnetic dibits disposed in half-track positions on each side of the center of the track (21) thereat and radially aligned with magnetic dibits present in adjacent tracks (21).
Claim 4
Dependent Claim
41 words
The improvement as in Claim 1 or 2, characterized by a track position code (23) in each servo gap (19) having magnetic dibits (A,B) disposed in half-track alternate, circumferentially spaced positions on each side of the center of the track (21).
Claim 5
Dependent Claim
77 words
The improvement as in Claim 2 or 3, characterized by at least one index code (I1) in the track (21) in each servo gap (19) in each sector (17), of only one group of radially aligned sectors (17) in each sector gap (19) in said only one group of radially aligned sectors (17) having magnetic dibits disposed in half-track positions on opposite sides of the center of the track (21) thereat, for identifying the associated sector (17).
Claim 6
Dependent Claim
26 words
The improvement as in Claim 2, 3 or 4, characterized in that said track identification code (25) follows said sector mark (29) in each track (21).
Claim 7
Dependent Claim
51 words
The improvement as in any one of the preceding claims, characterized by a defect identifying code (D) in the track (21) in a servo gap (19) of a sector (17) which is followed by a servo gap (19) in the next sector (17) having a defect in the same track (21).
Claim 8
Dependent Claim
32 words
The improvement as in any one of the preceding claims, characterized in that each sector mark (29) comprises three sequential circumferential spaces (1,2,3) of magnetic dibit patterns which are detected in sequence.
Claim 9
Dependent Claim
85 words
The improvement as in any one of Claims 4, 5, 6 or 7 characterized by: means including a magnetic head (5) for scanning said track position code (23) and producing separate signals (23a) resulting from said magnetic dibits (A,B) on opposite sides of said track (21), respectively; means (33,35,37,39,41,43,45) including an automatic gain control circuit (33,35,37,39,41,43) responsive to said separate signals (23a) for producing separate output signals which are amplitude controlled; and means (45) responsive to said separate output signals for producing position error signals.
Claim 10
Dependent Claim
87 words
The improvement as in any one of the preceding claims, characterized by: means including a magnetic head (5) for scanning the magnetic dibits of said servo gap (19) and producing signals; means (37,39,43) for producing a gain adjustment signal in response only to signals from said magnetic head (5) as it scans said automatic gain control field (27); and means (33,35,37,38,45) for applying said gain adjustment signal to all other signals from said magnetic head (5) as it scans said sector (17) for producing amplitude normalized signals.
Claim 11
Dependent Claim
92 words
In a magnetic disc drive having a magnetic memory disc (1) provided with a plurality of concentric circular tracks (21) which are divided into sectors (17), the method for magnetic dibit recording of separate magnetic dibit fields for forming a servo gap (19) in each sector (17), comprising: providing a magnetic head (5) having a width corresponding to the width of a track (21); characterized by recording with said magnetic head (5) separate magnetic dibit fields in half-track steps, placing said magnetic dibits in selected circumferentially spaced positions, in radial half-track alignment.
Claim 12
Dependent Claim
92 words
In a magnetic disc drive having a magnetic memory disc (1) provided with a plurality of concentric circular tracks (21) which are divided into sectors (17), the method for magnetic dibit recording of separate magnetic dibit fields for forming a servo gap (19) in each sector (17), comprising: providing a magnetic head (5) having a width corresponding to the width of a track (21); characterized by recording with said magnetic head (5) separate magnetic dibit fields in half-track steps, placing said magnetic dibits in selected circumferentially spaced positions, in radial half-track alignment.
Claim 13
Dependent Claim
67 words
The method as in Claim 10, characterized by: recording a first one of said separate magnetic dibit fields as an automatic gain control field (27) at the beginning of said servo gap (19); and recording a second one of said separate magnetic dibit fields as a servo mark (29) of identical dibit patterns in each track (21) adjacent to and following said automatic gain control field (27).
Claim 14
Dependent Claim
30 words
The method as in Claim 11, characterized by deriving automatic gain control signals from said magnetic dibits of said automatic gain control field (27) which have substantially uniform peak amplitudes.
Claim 15
Dependent Claim
94 words
The method as in Claim 10, 11 or 12, characterized by: recording a separate track number field (25) of magnetic dibits in half-track position in the track (21) or each servo gap (19), each track number field (25) having a pattern defining a track number; deriving track number signals (25a) from one of said patterns (25), having peak amplitudes substantially the same as the peak amplitudes of said automatic gain control signals; and detecting said track number signals (25a) at a threshold which is half the peak amplitude of the automatic gain control signals.
References Cited (Backward Citations)
No citation records indexed.
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