Browse Prior Art Database

Servo Channel Equalization Network

IP.com Disclosure Number: IPCOM000080405D
Original Publication Date: 1973-Dec-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 62K

Publishing Venue

IBM

Related People

Schwarz, TA: AUTHOR

Abstract

This apparatus eliminates an error in head-to-track registration, which is caused by additive tolerance differentials in electronic components of a head positioning servo system. This apparatus incorporates a special equalization sector in magnetic disk.

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Servo Channel Equalization Network

This apparatus eliminates an error in head-to-track registration, which is caused by additive tolerance differentials in electronic components of a head positioning servo system. This apparatus incorporates a special equalization sector in magnetic disk.

With reference to Fig. 2 and Fig. 3, the surface of disk 17 includes data track 11 in an upper layer and servo tracks 2, 3, 4 and 5 in a lower layer. Head 16 is to be positioned in line with the center of track 11 and midway between tracks 3 and 4 for exact registration with track 11. Head 16 is positioned radially over disk 17 by the servo system in such a way, as to minimize the difference between the servo signals, respectively, read from tracks 3 and 4. As schematically illustrated, track 3 is recorded with a servo signal of frequency F1 while track 4 is recorded with a frequency F2, which is twice as large as F1.

In Fig. 2 equalization sector 40 is shown provided between radials 42 and 44. Sector 40 consists of a F1 band between radials 42 and 43 wherein the servo signal is entirely recorded with frequency F1, and a F2 band between radials 43 and 44 wherein servo signal is entirely recorded with frequency F2. Gap 45 between radials 41 and 42 is provided for alerting the system that sector 40 is approaching. Gap 45 is not shown in Fig. 3 for simplicity.

In Fig. 1, signals from head 16 enter a preamplifier 20. A variable-gain amplifier 21 with an automatic gain control (AGC) circuit 22 keeps the envelope, which is common to all signals, constant for input to filters 23 and 24. The signals are sent through filters to separate the data signal out and to separate the F1 servo signal from the F2 servo signal. Peak detectors 25 and 26 convert the maximum amplitude of F1 and F2 signals to DC values, which are then compared in comparator 27 in order to provide a DC position error signal. The error signal is amplified and sent to an actuator to move head 16 in one direction or another, depending on the polarity and magnitude of the signal...