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An algorithm of drive level Reader Insensitive Measurements of Eraseband , Total written track Width and ATI Erasure Profile for Ultra-Narrow Write Heads/High TPI applications

IP.com Disclosure Number: IPCOM000130134D
Publication Date: 2005-Oct-12
Document File: 3 page(s) / 39K

Publishing Venue

The IP.com Prior Art Database

Abstract

As the track width in HDD goes to narrower and narrower, correctly measurement of written magnetic track width, track edge noise, eraseband and total erase width becomes more and more difficult in the head/media design. The magnetic track width is currently measured by measuring offtrack profile which involve an integration of magnetic transition across the track. As a result, it highly depends on the reader's function. A poor reader can completely bring about big errors in the measurement. In addition, if the transition was not written uniformly across the track, the measurement will be incorrect even the reader 's function is uniform across the track. At high TPI, determining the eraseband is also important. Currently, track profile has to be used to determined the eraseband. This also is strongly depending on the reader. We developed the reader -insensitive method to determine the magnetic track width and the eraseband width so that the exact widths can be measurement no mater what kind of reader we have. These methods are critical for improve ATI and for High TPI Drives.

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  An algorithm of drive level Reader Insensitive Measurements of Eraseband , Total written track Width and ATI Erasure Profile for Ultra -Narrow Write Heads/High TPI applications

We determine the eraseband width as follow:

0.Write a track on the disk at frequency hf1, find the maximum amplitue Vmax of the signal by scaning the signal across the track;
1. Erase several track of the disk, then write a track on the disk at frequency Hf1. ;
2. Move the write elemenet off its written track by delta x;
3. using DC or at frequency hf2 to write on the disk, hf2 shall be very close to hf1 and shall be choosed in such a way that the hamonic of hf2 will not overlap those of hf1;
4. move the reader close to the center of the residual erased track, search for the maximum of the amplitude V(x) for hf1 using a narrow band filter; 5. repeat 1-4 at different offset locaton +x;
6. obtain moving average of normalized V(x) /Vmax and do a linear fitting on V(x)/Vmax, find the intercept point of from V(x)/Vmax. For the positive x-offset toward inner radii, this will be the outer eraseband. Only use the amplitude value from 0.05 to 0.25 to reduce the effect of the secondary writing on the measurement accuracy. It can also eliminated the effect of side reading for the readers.
7. For the inner eraseband, the offset x will be negative-toward the outer radii.

We determine the total erase width as follow:

1. Erase several tracks on the disk, then write a track on the disk at frequency Hf1;
2. Move the writer off its original track location by detla +x;
3. using DC or at frequency hf2 to write on the disk, hf2 shall be very close to hf1 and shall be choosed in such a way that the hamonic of hf2 will not overlap those of hf1;
4. Move the writer off its original track location by negative detla -x;
5. Repeat step 3;
6.. move the reader close to the center of the residual erased track, search for the maximum of the amplitude V(x) for hf1 or just move the reader to the center of the erased track using a narrow band filter;
7.. obtain moving average of normalized V(x) /Vmax and do a linear fitting on V(x)/Vmax, find the intercept point of from V(x)/Vmax. The total eraseband will be 2*intercept. Only use the amplitude value from 0.05 to 0.25 to reduce the effect of the secondary writing on the measurement accuracy. It can also eliminated the effect of side reading for the readers.

Determining the real magnetic track widt...