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EP1075689A1 - Procede de detection de bord de rangee de bande dans une structure de positionneur a bande magnetique - Google Patents

Procede de detection de bord de rangee de bande dans une structure de positionneur a bande magnetique

Info

Publication number
EP1075689A1
EP1075689A1 EP98913304A EP98913304A EP1075689A1 EP 1075689 A1 EP1075689 A1 EP 1075689A1 EP 98913304 A EP98913304 A EP 98913304A EP 98913304 A EP98913304 A EP 98913304A EP 1075689 A1 EP1075689 A1 EP 1075689A1
Authority
EP
European Patent Office
Prior art keywords
signal
time period
clock pulses
frequency
frequency signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP98913304A
Other languages
German (de)
English (en)
Inventor
Ronald Dean Gillingham
Steven Gregory Trabert
John Paul Mantey
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Storage Technology Corp
Original Assignee
Storage Technology Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Storage Technology Corp filed Critical Storage Technology Corp
Publication of EP1075689A1 publication Critical patent/EP1075689A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B5/584—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on tapes
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
    • G11B27/10—Indexing; Addressing; Timing or synchronising; Measuring tape travel
    • G11B27/19—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier
    • G11B27/28—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier by using information signals recorded by the same method as the main recording
    • G11B27/30—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier by using information signals recorded by the same method as the main recording on the same track as the main recording
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B2220/00—Record carriers by type
    • G11B2220/90—Tape-like record carriers

Definitions

  • the invention relates to the field of dynamic magnetic information storage or retrieval.
  • the invention relates to the field of automatic control of a recorder mechanism.
  • the invention relates to track centering using a servo pattern.
  • the invention is a method for detecting a frame edge by generating a digital signal in response to a change in signal frequency.
  • Magnetic tape recording has been utilized for many years to record voice and data information.
  • magnetic tape has proven especially reliable, cost efficient and easy to use.
  • In an effort to make magnetic tape even more useful and cost effective there have been attempts to store more information per given width and length of tape. This has generally been accomplished by including more data tracks on a given width of tape. While allowing more data to be stored, this increase in the number of data tracks results in those tracks being more densely packed onto the tape. As the data tracks are more closely spaced, precise positioning of the tape with respect to the tape head -2-
  • the tape - tape head positioning may be affected by variations in the tape or tape head, tape movement caused by air flow, temperature, humidity, tape shrinkage, and other factors, especially at the outside edges of the tape.
  • servo stripes have been employed to provide a reference point to maintain correct positioning of the tape with respect to the tape head.
  • One or more servo stripes may be used depending upon the number of data tracks which are placed upon the tape.
  • the sensed signal from the servo stripe is fed to a control system which moves the head and keeps the servo signal at nominal magnitude.
  • the nominal signal occurs when the servo read gap is located in a certain position relative to the servo stripe.
  • a one-half inch wide length of magnetic tape 11 may contain up to 288 or more data tracks on multiple data bands 12. With such a large number of data tracks it may be desirable to include up to five or more servo bands 13 to improve data read and write function performance.
  • Servo bands 13 may utilize various patterns or frequency regions to allow precise tape to tape head positioning thus allowing a data read head to more accurately read data from data bands 12.
  • a portion of a conventional servo stripe 13 is shown having two -3-
  • a first frequency signal 16 is written across the width of servo stripe 13.
  • An erase frequency is written over first frequency signal 16 in a predetermined pattern such as five rectangles 17 in each of frames 14 and 15.
  • the five rectangles 17 in each frame result in nine horizontal interfaces 18 between frequency signal 16 and erase patterns 17 as the tenth edge 19 along the bottom is ignored.
  • a dashed line 21 illustrates the alignment of a read gap 22 in a tape read head 23.
  • dotted line 21 passes along one of edges 18 and through the center of gap 22. If the servo pattern on the tape is passed right to left over gap 22, then read gap 22 will alternate between reading frequency 16 across the full width 24 of gap 22 in areas 25 and frequency 16 across one half of read gap 22 and an erase frequency from patterns 17 across the other half of width 24 in areas 26.
  • Fig. 3 shows the read frequency signals from one frame 14 or 15 as read by head gap 22 in Fig. 2.
  • the amplitude of the signal is larger in areas 25 where frequency area 16 passes over the full width 24 of head gap 22.
  • the amplitude of the signal is about half as large in area 26 when one half of width 24 reads frequency area 16 and the other half reads erase patterns 17.
  • the servo control system in a tape drive uses the ratio of the full signal amplitude in field 25 to the half signal amplitude in field 26 to stay on -4 -
  • the tape controller can sense the position of the tape 11 with respect to the read gap 22 and move head 23 to keep the head gap 22 aligned with the servo stripe along line 21.
  • This alignment ensures precise reading of a data track in data bands 12 by the data read head (not shown) . While this system can result in more precise positioning of the tape head 23 with respect to tape 11, a difficulty can arise in that the controller must be able to determine in which field, 25 or 26, it is in at the time the signal is read. That is, there must be synchronization between the time the signal in field 25 is sampled and the time the signal in field 26 is sampled. -5-
  • the change in signal amplitude in moving to or from field 25 to or from field 26 could be used to determine in which field/area on the servo stripe read gap 22 is located. That is, if the signal drops to about one-half amplitude, it can be assumed that gap 22 is sensing movement of the servo pattern on the tape from field 25 into field 26. Conversely, if the signal amplitude approximately doubles, it can be assumed that gap 22 is sensing tape movement to field 25 from field 26.
  • the invention is a novel method for detecting a frame edge in a servo stripe pattern by generating a digital signal in response to a change in - 6-
  • the sensed analog signal from the frame is converted to a digital signal and the number of clock pulses sensed in a predetermined signal period are counted and compared. A lower number of counted pulses in given period represents a higher frequency and indicates the beginning of the frame.
  • a digital detection signal is generated in response to the change in pulse count.
  • the frequency difference is used as the criterion to improve frame edge detection.
  • Fig. 1 is an illustration of multiple servo stripes and data bands on magnetic tape
  • Fig. 2 is an illustration of a servo pattern including multiple erase bands
  • Fig. 3 is a graph of the analog signal generated from the servo pattern of Fig. 2;
  • Fig. 4 is an illustration of a servo pattern including a synchronization frequency area
  • Fig. 5 is a graph of the analog signal generated from the servo pattern of Fig. 4 converted to a digital signal along with the clock pulses and the detection signal; and -7-
  • Fig. 6 is a block diagram of signal conversion and detection circuitry.
  • Fig. 1 illustrates multiple servo stripes 13 written onto a given tape portion 11 to allow precise positioning of data bands 12 with respect to a data read tape head (not shown) .
  • Fig. 4 illustrates a servo pattern to be written as servo stripe 13 onto tape 11.
  • a synchronization frequency signal is written on a first area 27 across the width of servo stripe 13.
  • a different frequency signal is written on a second area 28 across the width of servo stripe 13.
  • First area 27 and second area 28 together comprise one frame 14.
  • Synchronization frequency region 27 and servo modulation frequency area 28 are then alternately written onto servo stripe 13 in successive frames 15, etc.
  • a third frequency signal which may be, for example, an erase frequency signal, is written in a predetermined band pattern in each frame over second area 28.
  • the erase frequency pattern is written in the form of parallelograms 17 which may take the form of a square or rectangle.
  • fields 25 and 26 in frames 14 and 15 may be identical to those in Fig. 2.
  • the signal frequency in area 27 is approximately double that of second frequency area 28.
  • the frequency in field 29 of an analog signal 30 sensed by the read gap 22 is approximately double the sensed frequency in adjacent fields 25/26/25.
  • This frequency difference allows use of a criterion other than change in amplitude to detect the transition to or from a frame (e.g. frame 14 to frame 15 in Fig 4) . That is, the frequency change from field 29 to fields 25/26 and vice versa enables frame edge detection which is less subject to noise and errors than a system such as shown in Figs. 2 and 3 which relies on detecting the amplitude change in moving to or from fields 25 and 26.
  • the analog signal from Fig. 5 is converted into a digital signal 31 by a data qualifier 32.
  • Data qualifier 32 may also be referred to as a zero crossing detector as used in data read channels as is known in the art.
  • the half period defined by each high and low pulse of digital signal 31 is proportional to the frequency period of the analog signal.
  • the frequency of digital signal 31 in fields 29 of Fig. 5 is different than the frequency of digital signal in fields 25, 26, 25 of Fig. 5.
  • the frequency of the signals in fields 25 and 26 is substantially identical. Because it is a digital signal, the amplitude differences between fields 25 and 26 of Fig. 5 are no longer significant.
  • a clock signal 33 from a crystal oscillator 34 is supplied to a counter 35 along with digital signal 31.
  • Clock signal 33 is a very accurate high frequency signal.
  • Counter 35 counts the number 36 of clock pulses 33 during a given half period of digital signal 31. Because the period of the signal in field 29 is about half of the period of the signals in fields 25 and 26, the counter will count half as many clock pulses 33 during a given half period of signal 31 in field 29 as compared to the number of clock pulses 33 during a given half period of signal 31 in fields 25 and 26. For example, referring to Fig.
  • Counter comparator logic 35 will generate a detection signal 37 in response to a change in count of clock pulses in 33 in successive half periods of digital signal 31. That is, compare logic circuitry in counter 35 is used to compare the number 36 of clock pulses 33 which are counted during each half period defined by a high or low pulse in digital signal 31. For example, upon detecting the decrease in the number 36 of clock pulses 33 during each half - 10 -
  • the transition in the number 36 of clock pulses 33 may not change from, for example, precisely 8 to 4 and back to 8 again. Uncertainty in these transition counts may be accounted for by delaying the detection signal one or more half periods of signal 31.
  • detection signal 37 changes state (high to low or vice versa) after two half periods of predetermined change in clock pulse counts 36 are detected.
  • the predetermined change in count may be, for example, from two successive half cycles with 6 or more counts to two half cycles with 5 or less counts (at 38) .
  • a change in count from two successive half cycles to a count of 5 or less to two half cycles with counts of 6 or more results in an output signal at 39.
  • the count frequency and the required number of counts to define a transition may be varied according to engineering design considerations as is known to one skilled in the art. While two half periods of frequency change are used in the preferred embodiment for redundancy/ accuracy purposes, any number of half periods of change may be used in accordance with the invention.

Landscapes

  • Adjustment Of The Magnetic Head Position Track Following On Tapes (AREA)

Abstract

L'invention concerne un procédé de détection d'un bord de rangée de bande dans une piste de positionneur sur la longueur d'une bande magnétique. Le procédé consiste à convertir un signal analogique en un signal numérique et à détecter une variation de fréquence du signal numérique au niveau d'un bord de rangée de bande. Un signal de détection est généré en réaction à une variation de fréquence détectée.
EP98913304A 1998-03-30 1998-03-30 Procede de detection de bord de rangee de bande dans une structure de positionneur a bande magnetique Withdrawn EP1075689A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1998/006260 WO1999050835A1 (fr) 1998-03-30 1998-03-30 Procede de detection de bord de rangee de bande dans une structure de positionneur a bande magnetique

Publications (1)

Publication Number Publication Date
EP1075689A1 true EP1075689A1 (fr) 2001-02-14

Family

ID=22266716

Family Applications (1)

Application Number Title Priority Date Filing Date
EP98913304A Withdrawn EP1075689A1 (fr) 1998-03-30 1998-03-30 Procede de detection de bord de rangee de bande dans une structure de positionneur a bande magnetique

Country Status (3)

Country Link
EP (1) EP1075689A1 (fr)
JP (1) JP2002510110A (fr)
WO (1) WO1999050835A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8947821B1 (en) 2014-07-17 2015-02-03 International Business Machines Corporation Detecting a servo pattern using a data channel in a magnetic tape drive

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5477103A (en) * 1993-06-04 1995-12-19 Cirrus Logic, Inc. Sequence, timing and synchronization technique for servo system controller of a computer disk mass storage device

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9950835A1 *

Also Published As

Publication number Publication date
WO1999050835A1 (fr) 1999-10-07
JP2002510110A (ja) 2002-04-02

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