Loop antenna and contactless IC card read/write apparatus

• US 7,070,101 B2
• Filed: 07/08/2004
• Issued: 07/04/2006
• Est. Priority Date: 07/10/2003
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Yoshinaga, Hiroshi, Tanaka, Masahiko, Deguchi, Futoshi, Haruyama, Hiroaki
• Primary Examiner(s): Lee, Michael G.
• Assistant Examiner(s): Haupt, Kristy A.
• Application Number:
  US10/885,723
• Publication Number:
  US 20050006473A1
• Time in Patent Office: 726 Days
• Field of Search: 343/842, 343/742, 343/787, 343/788, 343/872, 235/449, 235/451
• US Class Current: 235/451
• CPC Class Codes: G06K 7/10316 using at least one antenna particularly designed for interrogating the wireless record carriers antennas in general H01Q1/22
• CPC Class Codes: G06K 7/10336 the antenna being of the near field type, inductive coil

Abstract

To provide a loop antenna capable of attenuating the distant electric field with the attenuation of the magnetic flux in the vicinity of an electromagnetic wave restrained, and a contactless IC card read/write apparatus.

A loop antenna 10 has an electromagnetic wave shield 1 over at least one side of the loop antenna, the electromagnetic wave shield 1 comprising a plurality of electric conductors 2, a ground contact 3 for grounding the plurality of electric conductors and a lead wire 4 for connecting the plurality of electric conductors 2 to the ground contact 3. The plurality of electric conductors 2 are electrically connected via the lead wire 4 to the ground contact 3 and the plurality of electric conductors 2 are arranged so that the paths of the respective electric conductors 2 from any of their given points to the ground contact 3 via the lead wire 4 are determined uniformly.

Claims

1. A loop antenna having an electromagnetic wave shield over at least one side of the loop antenna, the electromagnetic wave shield comprising:

a plurality of electric conductors;

a ground contact, grounding the plurality of electric conductors; and

a lead wire, connecting the plurality of electric conductors to the ground contact;

wherein;

the plurality of electric conductors are electrically connected via the lead wire to the ground contact and arranged so that the paths of the respective electric conductors from any of their given points to the ground contact via the lead wire are determined uniformly, and

a sheet of magnetic material is disposed at one side of the loop antenna and the electromagnetic wave shield is disposed at the other side of the loop antenna.

2. The loop antenna as claimed in claim 1, wherein the plurality of electric conductors, the ground contact and the lead wire of the electromagnetic wave shield are provided on a support plate.

3. The loop antenna as claimed in claim 1, wherein the plurality of electric conductors of the electromagnetic wave shield are covered with insulating material.

4. The loop antenna as claimed in claim 1, wherein the plurality of electric conductors of the electromagnetic wave shield are comb-shaped, reticulated or latticed.

5. The loop antenna as claimed in claim 1, wherein the electromagnetic wave shield is envelop-shaped.

6. The loop antenna as claimed in claim 1, wherein the electromagnetic wave shield is multi-layered.

7. The loop antenna as claimed in claim 1, wherein the plurality of electric conductors of the electromagnetic wave shield are so disposed as to wrap up the loop antenna.

12. The loop antenna as claimed in claim 1, wherein the ground contact of the electromagnetic wave shield is connected to the ground of the loop antenna.

13. A contactless IC card read/write apparatus comprising the loop antenna as claimed in claim 1 for supplying electric power and transmitting data to a contactless IC card by electromagnetic induction and receiving data from the contactless IC card through load changes, and a read/write apparatus connected to the loop antenna.

15. The contactless IC card read/write apparatus as claimed in claim 13, wherein the read/write apparatus and the loop antenna are disposed next to each other and housed in a casing.

8. A loop antenna having an electromagnetic wave shield over at least one side of the loop antenna, the electromagnetic wave shield comprising:

a plurality of electric conductors;

a ground contact, grounding the plurality of electric conductors; and

a lead wire, connecting the plurality of electric conductors to the ground contact, wherein;

the plurality of electric conductors are electrically connected via the lead wire to the ground contact and arranged so that the paths of the respective electric conductors from any of their given points to the ground contact via the lead wire are determined uniformly,

a sheet of magnetic material is disposed at the back of the loop antenna facing the electromagnetic wave shield, and

a side wall in a standing condition on the loop antenna side is provided to the sheet of magnetic material.

9. The loop antenna as claimed in claim 8, wherein a metal plate is disposed at the back of the sheet of magnetic material.

10. The loop antenna as claimed in claim 9, wherein a side wall in a standing condition on the loop antenna side is provided to the metal plate.

11. The loop antenna as claimed in claim 10, wherein a plurality of through-holes are provided in the metal plate.

14. A contactless IC card read/write apparatus comprising a loop antenna, having an electromagnetic wave shield over at least one side of the loop antenna, for supplying electric power and transmitting data to a contactless IC card by electromagnetic induction and receiving data from the contactless IC card through load changes and a read/write apparatus connected to the loop antenna, the electromagnetic wave shield comprising:

a plurality of electric conductors;

a ground contact, grounding the plurality of electric conductors; and

a lead wire, connecting the plurality of electric conductors to the ground contact;

wherein;

the plurality of electric conductors are electrically connected via the lead wire to the ground contact and arranged so that the paths of the respective electric conductors from any of their given points to the ground contact via the lead wire are determined uniformly, and

the read/write apparatus is disposed within the opening of the loop antenna and housed in a casing.