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Browse Prior Art Database

High Density DC Balanced Write Current

IP.com Disclosure Number: IPCOM000082578D
Original Publication Date: 1975-Jan-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Ernisse, DJ: AUTHOR [+2]

Abstract

Write current for magnetic recording contains density compensating filler pulses which, nevertheless, maintain the zero-average current of the original pulse write method.

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High Density DC Balanced Write Current

Write current for magnetic recording contains density compensating filler pulses which, nevertheless, maintain the zero-average current of the original pulse write method.

The effectiveness of the write process is reduced by any DC component in the write process. This problem is increased by any inductive components used in the write circuit. Given an NRZI data code input, a write pulse is normally reversed for each sequential data 1-bit input when using the pulse write method. Additional filler pulses may be necessary between data pulses to present loss in field density between transitions. However, the filler pulses introduce an undesirable average DC level.

Here, each filler is a pair of positive and negative pulses with an average balanced DC level (of zero). In the figures, NRZI input data and clock signals are ANDed to give positive long pulses for 0-bit data levels. These are converted to negative short pulses by a pair of single-shots. A second AND circuit, in effect, cuts the short pulses corresponding to 0-bits out of the clock signals and then reverses a flip-flop for each transition. A differentiator then generates a spike for each reversal. The spikes alternate in polarity and represent the original NRZI data interspersed with filler pairs.

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