Loop antenna unit and radio communication medium processor

• US 20070139285A1
• Filed: 09/22/2005
• Published: 06/21/2007
• Est. Priority Date: 09/22/2004
• Status: Active Grant

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Deguchi, Futoshi, Maruyama, Keisuke
• Granted Patent: US 7,446,729 B2
• Time in Patent Office: Days
• US Class Current: 343/741
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G06K 19/07771 the record carrier comprising means for minimising adverse effects on the data communication capability of the record carrier, e.g. minimising Eddy currents induced in a proximate metal or otherwise electromagnetically interfering object
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H01Q 19/10 using reflecting surfaces
• CPC Class Codes: H01Q 21/06 Arrays of individually energised antenna units similarly polarised and spaced apart
• CPC Class Codes: H01Q 21/08 the units being spaced along or adjacent to a rectilinear path waveguide fed H01Q21/0037
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop

Abstract

It is an object of the present invention to provide a radio communication medium processor having a stable performance that does not receive a limitation for an installed place, especially, the influence of a metallic structure, does not need to adjust the resonance frequency of an antenna or an impedance, is excellent in its convenience and extensibility upon installation and strong for unnecessary noise from a periphery. In electric current fed loop antenna units, non-electric current fed loop antenna are arranged in doughnut shapes outside the substantially same planes of electric current fed loop antennas so as to surround the electric current fed loop antennas. Thus, when non-electric current fed loop antenna units are installed linearly, in radial directions and in arrays adjacently to electric current fed loop antenna units, the influence of the non-electric current fed loop antenna units to the antenna characteristics of the electric current fed loop antenna units can be suppressed. When the non-electric current fed loop antenna units are extended and increased, the antennas of the electric current fed loop antenna units do not need to be adjusted.

Claims

1. A loop antenna unit having a plurality of loop antennas, said antenna unit comprising:

a first loop antenna to which an electric current is fed; and

a second loop antenna surrounding the first loop antenna to which the electric current is not fed.

2. A loop antenna unit according to claim 1, further comprising:

a grounded metal member, the first loop antenna and the second loop antenna being connected to the metal member.

3. A loop antenna unit according to claim 2, further comprising:

a single grounding cable for connecting the first loop antenna and the second loop antenna to the metal member.

4. A loop antenna unit according to claim 2, further comprising:

a magnetic member disposed between the first loop antenna and the second loop antenna and the metal member.

5. A loop antenna unit according to claim 1, further comprising:

a first circuit unit including a resonance circuit and a matching circuit connected to the first loop antenna and a second circuit unit including a resonance circuit, a matching circuit and a matched load connected to the second loop antenna.

6. A radio communication medium processor comprising:

the loop antenna unit according to claim 1;

and

a reading and writing part connected to the first loop antenna of the loop antenna unit to carry out at least one of processes of reading and writing information stored in a radio communication medium through the first loop antenna, a signal current from the reading and writing part being fed only to the first loop antenna.

7. A radio communication medium processor according to claim 6, further comprising:

a third loop antenna to which an electric current is not fed, the third loop being arranged adjacently to the loop antenna unit according to claim 1.

8. A loop antenna unit including a loop antenna communicating with a radio communication medium and having a pair of opening end parts at both ends and a metal member arranged closely to the loop antenna, wherein the metal member is electrically connected to one of the opening end parts of the loop antenna with a space about 1/200 to 1/4000 times as long as the wavelength of a communication frequency.

9. A loop antenna unit according to claim 8, wherein the loop antenna supplies an electric power and transmit data to the radio communication medium in accordance with an electromagnetic induction and obtains receive data from the radio communication medium in accordance with a load variation.

10. A loop antenna unit according to claim 8, wherein the metal member is arranged substantially in parallel with a main surface of the loop antenna.

11. A loop antenna unit according to claim 8, wherein a magnetic member is disposed between the loop antenna and the metal member.

12. A loop antenna unit according to claim 11, wherein the magnetic member is disposed substantially in parallel with the main surface of the loop antenna.

13. A loop antenna unit according to claim 11, wherein the magnetic member is disposed with a prescribed space from the loop antenna and from the metal member.

14. A loop antenna unit according to claim 8, wherein the area of the metal member is not smaller than about 1.1 times as large as the area of the opening part of the loop antenna.

15. A loop antenna unit according to claim 11, wherein the magnetic member has a flexibility.

16. A loop antenna unit according to claim 8, wherein one of the pair of the opening end parts is electrically connected to the metal member, an unbalanced type resonance circuit and a ground terminal of a matching circuit, and the other of the pair of the opening end parts is connected to the unbalanced type resonance circuit and a signal terminal of the matching circuit.

17. A loop antenna unit according to claim 8, wherein one of the pair of the opening end parts is connected to a ground terminal of a reading and writing part for reading, writing or reading and writing data of the radio communication medium, and the other of the pair of the opening end parts is connected to a signal terminal of the reading and writing part.

18. A loop antenna unit according to claim 8, wherein in the loop antenna unit, the loop antenna, the magnetic member, the metal member, a first isolating member disposed between the loop antenna and the magnetic member and a second isolating member disposed between the magnetic member and the metal member are laminated.

19. A loop antenna unit according to claim 18, wherein the loop antenna is formed with a pattern conductor provided on an electronic board and the electronic board is laminated as the loop antenna.

20. A loop antenna unit according to claim 19, wherein the resonance circuit and the matching circuit are formed on the electronic board.

21. A loop antenna unit according to claim 18, wherein the loop antenna unit is stored in an accommodating case.

22. A loop antenna unit according to claim 8, wherein the loop antenna unit is accomodated in a housing.

23. A loop antenna unit according to claim 8, wherein a plurality of the loop antenna units are arranged linearly, in radial directions or on arrays substantially on the same planes.

24. A loop antenna unit according to claim 23, wherein the plurality of the loop antenna units include electric current fed loop antenna units to which the signal current is fed and non-electric current fed loop antenna units to which the signal current is not fed.

25. A radio communication medium processor comprising:

the plurality of the loop antenna units according to claim 8 and the reading and writing part for reading, writing or reading and writing the data on the radio communication medium, wherein the plurality of the loop antenna units include the electric current fed loop antenna units to which the signal current is fed and the non-electric current fed loop antenna units to which the signal current is not fed.

26. A radio communication medium processor according to claim 25, wherein the reading and writing part is connected only to the electric current fed loop antenna units among the plurality of loop antenna units.

27. A loop antenna unit according to claim 14, wherein the magnetic member has a flexibility.