JP2009268040A - Loop antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a communication distance between a loop antenna such as an RFID, EAS system etc. and a transponder such as a noncontact IC card and tag etc. <P>SOLUTION: A soft magnetic substance is positioned near a center of the loop antenna, thereby, a flux of a large density is concentrically formed especially near the center to expand the magnetic field largely and extend the communication distance. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

    The present invention relates to a loop antenna device such as an RFID (wireless authentication) system or an EAS (electronic merchandise monitoring) system.

    The reading distance of the antenna in the RFID field is about 5 m in the case of UHF 860-960 MHz. On the other hand, in the case of the 13.56 MHz radio band of HF, the maximum length is about 70 cm. UHF is more advantageous when looking only at the communication distance. However, recently, it has become clear that the UHF radio wave band may adversely affect medical devices such as implantable cardiac pacemakers, and the UHF radio wave band has been restricted in the field where it is used.

    However, the communication distance of the HF radio band using a loop antenna is short. For example, in the case of a gate type antenna, the distance is only about 1 m. In an emergency, there is a problem with evacuation through the gate. There is a need to improve the communication distance between an antenna (reader / writer) and a transponder (responder) such as a non-contact IC card or tag.

In Patent Documents 1 and 2, a soft magnetic body having a different shape is attached to the reverse side of the loop antenna base, that is, opposite to the direction in which electromagnetic waves are radiated from the loop antenna toward the transponder. Because the position is too close to the antenna and the area of the soft magnetic body is too large, the magnetic lines of force that flow through the soft magnetic body are concentrated only in the vicinity of the antenna, and a strong magnetic flux density cannot be generated at the center of the loop antenna, The effective communication distance has not been improved.
JP 2005-210213 JP 2005-210223 PR

    It improves the communication distance between loop antennas such as RFID and EAS systems and transponders such as contactless IC cards and tags.

    By providing a soft magnetic material in the vicinity of the center of the loop antenna of the present invention, a magnetic flux having a large density is focused and generated only in the vicinity of the center of the loop antenna, and a large magnetic field is radiated.

    The loop antenna device of the present invention is characterized in that a strong magnetic flux is focused and generated near the center of the loop antenna 1 in particular. For this purpose, the soft magnetic body 2 is kept at a certain distance from the loop antenna 1 and the soft magnetic body 2 is attached only near the center of the loop.

    FIG. 1 is an example of the present invention, and is a schematic view seen from the upper front where a soft magnetic body 2 is attached near the center of a loop antenna 1.

    FIG. 2 is a schematic view of the apparatus shown in FIG. 1 as viewed from the side. The magnetic field lines 3 are focused on the soft magnetic body 2 at the center of the loop antenna 1 and a strong magnetic flux is generated at the center of the loop antenna. It is the schematic showing radiating | emitting.

    FIG. 3 is a schematic diagram in the case where the present apparatus is employed in a gate type loop antenna. The soft magnetic body 2 shown in FIGS. 1, 2 and 3 is assumed to be attached near the center of the loop by a support not shown.

    Although a soft magnetic material such as permalloy can be used in the loop antenna device of the present invention, a mixture of a soft magnetic material powder and a resin having magnetic permeability may be used.

    Alternatively, a mixture of soft magnetic powder and magnetically permeable ink paint may be used for printing.

The invention's effect

    In the RFID system and the EAS system, it is significant that the communication distance is extended. Communication errors can be reduced, workability can be improved, and new uses can be created. In the case of a gate-type loop antenna, the distance between the gates can be set large, or can be installed on the ceiling or floor, so that obstacles to entry and exit can be reduced.

  Schematic front view showing a soft magnetic body 2 attached near the center of the loop antenna 1   Schematic side view showing the flow of magnetic field lines and magnetic flux   Schematic diagram of gated loop antenna

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Loop antenna 2 Soft magnetic material 3 Flow of magnetic force line 4 Gate type loop antenna

Claims (3)

    A loop antenna such as an RFID (wireless authentication) system or an EAS (electronic merchandise monitoring) system, in which a soft magnetic material is provided near the center of the loop antenna, and a strong magnetic flux is focused and generated near the center of the loop antenna. A loop antenna device characterized by the above.     2. The loop antenna device according to claim 1, wherein a mixture of a soft magnetic powder and a permeable resin is used instead of the soft magnetic material.     2. The loop antenna device according to claim 1, wherein a mixture of a soft magnetic material powder and a permeable ink paint is used instead of the soft magnetic material and is applied by printing.

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