Browse Prior Art Database

Correcting Read Pulse Asymmetry

IP.com Disclosure Number: IPCOM000089383D
Original Publication Date: 1977-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Taub, DM: AUTHOR

Abstract

Read pulses from magnetic recording media, such as tapes and flexible discs, tend to be asymmetrical due to the component of magnetization perpendicular to the plane of the recording medium. This causes a peak shift in addition to that due to intersymbol interference. A circuit is disclosed which corrects this asymmetry.

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Correcting Read Pulse Asymmetry

Read pulses from magnetic recording media, such as tapes and flexible discs, tend to be asymmetrical due to the component of magnetization perpendicular to the plane of the recording medium. This causes a peak shift in addition to that due to intersymbol interference. A circuit is disclosed which corrects this asymmetry.

An asymmetrical pulse can be expressed as the sum of an even and an odd function. The correction circuit passes the even terms and suppresses the odd terms. The figure shows a correction circuit in which an asymmetric pulse source V(in) supplies an input signal through RO which correctly terminates the input end of the delay line of delay Tau d. transistors T3, T4 present a very low terminating impedance to the delay line and the collector current i(c3) of transistor T3 forms a first component of output current iout.

A second signal path in parallel with the delay line is provided by long tailed pair transistors T1, T2 each having an emitter resistor R1. The collector current i(c2) of transistor T2 supplies a second component of output current i(out).

For a particular case studied, proper correction was found to be obtained with R1 = 1.9 RO, and Tau d = Pi a over 3.4. where a = time taken for the even function to fall from its peak value to half its peak value.

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