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Browse Prior Art Database

Signal Modulator Which Simulates Magnetic Media Defects

IP.com Disclosure Number: IPCOM000039684D
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 30K

Publishing Venue

IBM

Related People

Cunningham, EA: AUTHOR [+2]

Abstract

The described circuit accurately generates electronic signals analogous to those found during surface analysis testing of magnetic data storage media, specifically including modulated "defects" as might be found on non-ideal media. The following formula is duplicated to represent the complete mathematical model of the complex phenomenon involved in magnetic modulation. Vout = d(m(x) * M(x)) / dt = [M(x) * d(m(x)/dt] [M(x) * d(m(x)/dt] where m(x) = the envelope of available magnetization from the media, including the defect, and M(x) = the ideal magnetization of the media, which represents the information stored. The mathematical expansion shows the first term not present in standard amplitude modulators, which only simulates the second term.

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Signal Modulator Which Simulates Magnetic Media Defects

The described circuit accurately generates electronic signals analogous to those found during surface analysis testing of magnetic data storage media, specifically including modulated "defects" as might be found on non-ideal media. The following formula is duplicated to represent the complete mathematical model of the complex phenomenon involved in magnetic modulation. Vout = d(m(x) * M(x)) / dt = [M(x) * d(m(x)/dt] [M(x) * d(m(x)/dt] where m(x) = the envelope of available magnetization from the media, including the defect, and

M(x) = the ideal magnetization of the media, which represents

the information stored. The mathematical expansion shows the first term not present in standard amplitude modulators, which only simulates the second term. Simulating the terms by electronic signals results in the following formula: Vout = d(v(t) * V(t)) / dt The main phenomenon not represented in these formulas, but easily understood magnetically and implemented electronically, is a high-frequency roll-off resulting from the bandwidth limitations of the media and of the magnetic read/write head. The desired results are achieved using a pair of double-balanced mixers, one to handle each of the two basic modes of surface analysis testing. The input signal is modulated by pulses, generated externally and triggered to modulate the signal at the desired point. The resulting signal is differentiated by a bandpass filter, which also provides the desired high-frequency roll-off.

This approach accurately duplicates the desired magnetic modulation formula and allows for the simulation of defects even shorter than the length of a stored "bit", allowing the simulation of "bit-shift"-type defec...