Loop antenna device

• US 20050134519A1
• Filed: 08/30/2004
• Published: 06/23/2005
• Est. Priority Date: 08/29/2003
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group), Yoshikawa RF Systems Company Limited
• Original Assignee: Seiko Epson Corporation (Seiko Group), Yoshikawa RF Systems Company Limited
• Inventors: Asauchi, Noboru, Ishii, Eiichi, Kosugi, Yasuhiko, Fukano, Takakazu
• Granted Patent: US 7,142,163 B2
• Time in Patent Office: Days
• US Class Current: 343/867
• CPC Class Codes: G06K 7/10336 the antenna being of the near field type, inductive coil
• CPC Class Codes: G08B 13/2474 Antenna or antenna activator geometry, arrangement or layout loop antennae H01Q1/22
• CPC Class Codes: H01Q 7/04 Screened antennas H01Q7/02, H01Q7/06 take precedence

Abstract

A plurality of small loop antenna cells 61, 62 and 63 are magnetically coupled to an antenna coil 8 of a non-contact type data carrier 3. In the plurality of small loop antenna cells, the directions of the magnetic moments of the signals transmitted to the non-contact type data carrier 3 are opposite to each other, the sum of the magnetic moments generated from all the small loop antenna cells 61 to 63 is zero and a conductor forming a short ring pattern 67 is provided collectively for the plurality of small loop antenna cells. Thus, imbalance caused between the small loop antenna cells 61 to 63 can be compensated for by the short ring pattern 67.

Claims

1. A loop antenna device comprising a plurality of small loop antenna cells magnetically coupled to an antenna coil of a non-contact type data carrier to transmit signals to the non-contact type data carrier, wherein:

the small loop antenna cells generate magnetic moments in directions opposite to one another to transmit the signals to the non-contact type data carrier;

the sum of the magnetic moments generated from all the small loop antenna cells is zero; and

the loop antenna device further comprises a conductor that forms a short ring collectively for all the small loop antenna cells.

2. A loop antenna device according to claim 1, wherein conductors forming the small loop antenna cells and the conductor forming the short ring are laminated on a base.

3. A loop antenna device according to claim 1 or 2, further comprising electric field shielding conductors respectively provided for the small loop antenna cells to reduce electric field components emitted from the small loop antenna cells, each of the electric field shielding conductors having a gap for preventing formation of a short ring.

4. A loop antenna device comprising:

a base;

a first conductor forming a plurality of loop antenna cells, the first conductor being provided to a first surface of the base; and

a second conductor being provided to the first surface of the base, and having;

an outer continuous ring portion overlaid above an outer peripheral portion of the first conductor; and

an inner discontinuous portion defining a gap or gaps by which the second conductor is discontinuous above each of the loop antenna cells.

5. A loop antenna device according to claim 4, further comprising:

a third conductor forming electric shields and being disposed between the first and second conductors, each of the electric shield being substantially overlaid above but discontinuous above a corresponding one of the loop antenna cells.

6. A loop antenna device according to claim 4 or 5, further comprising:

a fourth conductor having;

an outer continuous ring portion overlaid above an outer peripheral portion of the first conductor; and

an inner discontinuous portion defining a gap or gaps by which the fourth conductor is discontinuous above each of the loop antenna cells,

the first conductor being interposed between the second conductor and the fourth conductor.

7. A loop antenna device according to claim 6, wherein the fourth conductor is provided to a second surface of the base opposite from the first surface of the base.