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Recording Servo Information Below a Data Surface in a Homogeneous Medium

IP.com Disclosure Number: IPCOM000081690D
Original Publication Date: 1974-Jul-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 50K

Publishing Venue

IBM

Related People

Schwarz, TA: AUTHOR

Abstract

Servo information is recorded in a lower layer of a magnetic medium, sufficiently thick that a nonsignal region exists between this layer and data written in a surface layer.

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Recording Servo Information Below a Data Surface in a Homogeneous Medium

Servo information is recorded in a lower layer of a magnetic medium, sufficiently thick that a nonsignal region exists between this layer and data written in a surface layer.

The servo tracks are first written by a servo writer whose write head has sufficient ampere-turn capability, to record through the total thickness of the medium. After the servo signal has been recorded, a DC or AC biased erase signal of lower intensity is applied, creating a nonsignal region between the surface and a remnant lower layer of servo information. Data is written in the surface layer using baseband partial penetration or AC bias recording at significantly reduced field. Prior to the next write, the track is DC or AC erased with a magnetic field whose strength is less than the initial erase field, but larger than the data write field.

The significant design characteristics for this disk are:
1) The maximum frequency component of the recorded servo signal.

f(s)max, must be less than 1/10th the data frequency, f(d)

i.e., f(s)max 0'1 f(d).
2) The recording field, Hy, must be greater than 1.5 times the

Hc of the media at the lower edge of the recorded layer, i.e.,

Hy > 1.5 Hc(servo).
3) To assure the integrity of servo layer, the data recording

field, Hd, must be less than 0.5 Hc at the upper boundary of

the servo layer.

The recording field intensity, Hy, may be approximated: Hy = Ho tan/-1/(g/2y) (1) where Ho is the field intensity at the head plane.

The effective thickness of the data layer, t(1), is determined by the head and spacing geometry, the magnetic properties of the medium, and the required resolution and/or amplitude...