Browse Prior Art Database

Automatic Bias Field Adjustment for Bubble Memory Devices

IP.com Disclosure Number: IPCOM000089701D
Original Publication Date: 1977-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Braun, RJ: AUTHOR

Abstract

It is well known that the bias field for a bubble memory device has to be held within a relatively controlled range, since above a certain field strength the bubbles collapse, and below a certain field strength the bubbles will spread out too far and their control becomes unreliable. Although this range may be fairly large for a single chip, it can become significantly more narrow for a cluster of chips over their entire operating range. It is proposed to adjust the bias field in the bubble memory device by applying a demagnetizing field across the magnet and the whole package in the form of steadily increasing pulses. In between the pulses, the actual magnetic field at the bubble chips is monitored, and once the desired field strength is reached, the demagnetizing process is stopped.

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Automatic Bias Field Adjustment for Bubble Memory Devices

It is well known that the bias field for a bubble memory device has to be held within a relatively controlled range, since above a certain field strength the bubbles collapse, and below a certain field strength the bubbles will spread out too far and their control becomes unreliable. Although this range may be fairly large for a single chip, it can become significantly more narrow for a cluster of chips over their entire operating range. It is proposed to adjust the bias field in the bubble memory device by applying a demagnetizing field across the magnet and the whole package in the form of steadily increasing pulses. In between the pulses, the actual magnetic field at the bubble chips is monitored, and once the desired field strength is reached, the demagnetizing process is stopped. The field measurement can be preferably monitored by operating the bubble chips and determining directly the proper field strength by the chips' operating characteristics.

In actual operation, the bias field magnets are initially over-magnetized at a field strength higher than the collapse field in a fully assembled package. Then a strong demagnetizing field is applied across the permanent magnets, the strength of this demagnetizing field being adjustable in small steps and applied in pulses of increasing field amplitudes. In between the application of the pulses, the bubble chips are operated and monitored in a test pattern...