Analysis of a biphase-based servo format for hard-disk drives

Author

Makinwa, K.A.A. ; Bergmans, J.W.M. ; Voorman, J.O.

Author_Institution

Fac. of Inf. Technol. & Syst., Delft Univ. of Technol., Netherlands

Volume

36

Issue

6

fYear

2000

fDate

11/1/2000 12:00:00 AM

Firstpage

4019

Lastpage

4027

Abstract

Biphase modulation in an embedded-servo format for hard-disk drives is investigated. It is shown that for biphase, at the low linear densities typical of servo information, near-maximum-likelihood performance can be attained by a simple bit detector consisting of a full-response linear equalizer and a binary slicer. Compared to the commonly used method of dibit coding, a signal-to-noise ratio gain of some 4 dB is achieved. The same equalizer may be used as the basis for near-maximum-likelihood position error signal amplitude estimation and timing recovery. Simulations of a practical servo demodulator based on a fifth-order analog filter show that at typical linear densities, this ideal performance is closely approached. The equalizer has a band-pass character and yields excellent suppression of the effects of thermal asperities and magneto-resistive head asymmetry

Keywords

disc drives; embedded systems; hard discs; phase modulation; servomechanisms; analog filter; band-pass equalizer; binary slicer; biphase modulation; dibit coding; embedded servo demodulator; full-response linear equalizer; hard disk drive; linear density; magnetic recording; magnetoresistive head; near-maximum-likelihood bit detection; position error signal amplitude estimation; signal-to-noise ratio; thermal asperity; timing recovery; Amplitude estimation; Band pass filters; Demodulation; Detectors; Equalizers; Hard disks; Magnetic separation; Servomechanisms; Signal to noise ratio; Timing;

fLanguage

English

Journal_Title

Magnetics, IEEE Transactions on

Publisher

ieee

ISSN

0018-9464

Type

jour

DOI

10.1109/20.914356

Filename

914356