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Thermal Adaptive Equalization of HDD Data Read/Write Channel

IP.com Disclosure Number: IPCOM000014383D
Original Publication Date: 2001-Mar-01
Included in the Prior Art Database: 2003-Jun-19
Document File: 3 page(s) / 31K

Publishing Venue

IBM

Abstract

Disclosed is a method of HDD(Hard Disk Drive) performance and reliabi improvement. This invention aimed at improvement of·Error Rate of HDD in various temperature conditions. The improvement was accomplished by optimizing tap weight in channel each temperature conditions. First, I explained what is the Equalization, and what is the Tap Weig Then, I described a present problem and a solution to the problem.

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Thermal Adaptive Equalization of HDD Data Read/Write Channel

Disclosed is a method of HDD(Hard Disk Drive) performance and reliabi
improvement.

This invention aimed at improvement of·Error Rate of HDD in various
temperature conditions.

The improvement was accomplished by optimizing tap weight in channel
each temperature conditions.

First, I explained what is the Equalization, and what is the Tap Weig
Then, I described a present problem and a solution to the problem.

What is Equalization, What is Tap Weight ---------------------------

In HDD technology, we write down a digital signal on a disk as a chan
the direction of a magnetic field.

But, to some extent, the wave form of the data read from the disk is
from an optimum frequency characteristic to the method of signal proc
in the machines.

That was why we need to arrange the wave form to bring it to be close
optimum one for the method of signal processing. We call this "Equali

We have used DEQ(Direct EQualization) as one method of equalization.
In DEQ, we use FIR(Finite Impulse Response) filter to equalize, and c
some coefficients of filter (we call this "Tap Weight".) and sampling

A present problem --------------------------------------------------

Even for the same HDD, an impulse response varies with the temperatur
conditions in which HDD be placed.

Because, the signal read by the head from disk changes with change of
coercivity(coercivity:the volume of external magnetic field to make
magnetization zero) and flying height(flying height:an aperture betwe
head and disk surface when disk revolves) depending on temperature co

A change of an impulse response depending on a temperature means a ch
of tap weight value.

Therefore, if a temperature changed, we cannot equalize optimally alt
use a tap weight which is optimized for a certain temperature conditi
As a r...