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Erase base servo pattern writing Disclosure Number: IPCOM000016368D
Original Publication Date: 2002-Oct-02
Included in the Prior Art Database: 2003-Jun-21
Document File: 2 page(s) / 64K

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Disclosed is the method to write servo pattern which give us benefit below.

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Erase base servo pattern writing

Disclosed is the method to write servo pattern which give us benefit below.

1. Improve frozen-in RRO caused by REPEATABLE runout when servo writing.

2. Neither servo pattern detection nor servo control algorithm in product affect by this


HDD capacity grow every year by applying higher TPI and BPI. Consequently higher servo sampling rate is required which means more servo sector and higher servo pattern frequency. To take lower rotation speed when servowriting is the conventional way to write higher frequency servo pattern at product speed as well as minimize frozen-in RRO. However Fluid Bearing Motor (FDB) shows much higher REPEATABLE(harmonic) runout than ball bearing motor and its magnitude is varied at different rotation speed. Though NON-REPEATABLE runout of FDB motor is smaller than ball bearing motor.

By knowing FDB motor character above, it seems better to take same rotation speed as product when servowriting. But servowriter is limiting its clock generator frequency and phase alignment capability so that it is difficult to write higher pattern without bad phase alignment.

There are mainly two functions in servo pattern, one is ID field such as servo start mark, cylinder id etc, which need precise phase alignment between adjacent track, the other is position signals which provide radius location. Idea here is write ID field at much lower speed than product resulting better phase alignment and write position signal a...