JPS5816551B2 - magnetic bubble drive magnetic circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive magnetic circuit for magnetic bubbles.

When driving a magnetic bubble, it is generally necessary to apply a rotating magnetic field to the magnetic bubble chip.

FIG. 1 shows a typical drive coil for this purpose.

Reference numerals 1 and 2 denote rectangular solenoid coils that are orthogonal to each other, and currents having a phase different by 90 degrees are passed through each solenoid coil to obtain a rotating magnetic field therein.

FIG. 2 shows a cross section of the coil, and the magnetic bubble chip 4 is placed on a substrate 3 made of ceramic or the like, and is set in a uniform area of the magnetic field generated by the coil.

In this configuration, since high frequency current flows through the coils 1 and 2, a fairly large voltage is generated across the coils.

This voltage is induced by electrostatic coupling to the wiring on the substrate 3, and becomes noise with respect to the small bubble detection signal.

On the other hand, as shown in FIG. 2, the electrostatic coupling can be reduced by inserting a shield plate made of a copper plate or the like between the coil and the board and grounding it.

By the way, as shown in the cross-sectional view of FIG. 3, the actual wiring board 3 is larger than the chip area, and the wiring is drawn out from between the coils 1 and 2.

In this case, coil 1 only partially overlaps coil 2, and coil 2 is larger than coil 1 in the cross section of FIG.

At this time, the shield plate 5 needs to match the larger coil.

Therefore, the shield plate 5 is larger than the coil 1.

At this time, the magnetic field distribution in the length direction of the coil 1 becomes worse as shown in FIG. 4, from the solid line (in the case where there is no shield plate) to the dotted line.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a magnetic bubble drive magnetic circuit that enables electrostatic shielding without impairing the uniformity of the magnetic field.

In order to achieve the above object, the present invention provides slits or the like in the shield plate 5 to prevent the flow of eddy currents that impair the magnetic field distribution.

Embodiments of the magnetic bubble drive magnetic circuit according to the present invention will be described below with reference to the drawings.

Generally, as shown in FIG. 2, if a uniform conductor thin plate shorter than the coil length is inserted in the axial direction of the coil, the magnetic field distribution will be improved compared to the case where no magnetic field distribution is provided.

However, as shown in FIG. 3, when the conductor thin plate is longer, the magnetic field distribution becomes worse.

Both are caused by eddy currents generated in the thin conductor plates.

5 and 6 are examples of shield plates used in the magnetic circuit of the present invention.

52 is a uniform conductive surface in order to improve the uniformity of the magnetic field in a portion where the coils 1 and 2 overlap and are located above the chip 4.

51 blocks the path of eddy current by providing a slit in the outside of the coil 1.

53 is a terminal for grounding the shield plate from inside the coil to the outside.

By using the above shield plate, the magnetic field distribution becomes as shown by the solid line in FIG. 4, and the shielding effect does not deteriorate.

Note that the thickness of the shield plate is preferably thinner than the skin depth of the material used for the driving frequency.

As explained above, in the magnetic circuit of the present invention, the uniformity of the magnetic field distribution is impaired and a shielding effect can be obtained.

In the future, as the speed of bubble memory increases, the drive frequency will increase and the voltage across the coil will also increase, making shielding effects even more important.

Therefore, it can be said that the present invention will greatly contribute to increasing the speed of bubble memories in the future.

[Brief explanation of the drawing]

Figure 1 shows the conventional bubble magnetic circuit, Figure 2, Figure 3,
Its cross-sectional view, FIG. 4, shows an example of the magnetic field distribution. Moreover, FIGS. 5 and 6 show shield plates used in the magnetic circuit of the present invention. 1.2...Bubble drive coil, 3...
Wiring board, 4... Bubble chip, 5...
・Shield plate.

Claims (1)

[Claims] 1. A substrate on which a magnetic bubble chip is mounted, and magnetic fields that are orthogonal to each other are generated to apply a rotating magnetic field to the magnetic bubble chip, one coil encloses the other coil, and both coils enclose the magnetic bubble chip. a pair of magnetic bubble drive coils arranged as shown in FIG. In a magnetic bubble drive magnetic circuit comprising a conductive thin plate that provides a magnetic field, the thin plate extends to correspond to the width of the substrate, and except for the portion facing the chip area that provides a uniform magnetic field, the thin plate is configured to prevent eddy current from forming. A magnetic bubble drive magnetic circuit characterized by having a slit to prevent flow.