Tag antenna

• US 20060208955A1
• Filed: 12/22/2005
• Published: 09/21/2006
• Est. Priority Date: 03/17/2005
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Kai, Manabu, Maniwa, Toru, Yamagajo, Takashi
• Granted Patent: US 7,659,863 B2
• Time in Patent Office: Days
• US Class Current: 343/795
• 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 9/24 Shunt feed arrangements to single active elements, e.g. for delta matching
• CPC Class Codes: H01Q 9/285 Planar dipole H01Q9/065 takes precedence; patch antenna H01Q9/0407

Abstract

A dipole part of a length shorter than half of an antenna resonance wavelength is placed so as to be rolled and enables a feeding part 11 to feed a chip. An inductance part 12 for adjusting the inductance of the antenna is provided so as to sandwich the feeding part 11. The inductance 12 is provided using an empty space of the inside of the rolled dipole part. By providing the inductance part 12, the inductance of the antenna can be adjusted so as to resonate at a predetermined frequency with the capacitance of the chip connected to the feeding part 11. At this time, although the radiation resistance of the antenna becomes extremely large according to calculations, it is actually almost the same as the resistance of the chip due to loss, and the power received by the antenna can be provided to the chip.

Claims

1. A tag antenna composed of a dipole antenna and a feeding part with a chip mounted thereto, comprising:

a dipole part of a length shorter than half of an antenna resonance wavelength;

a feeding part provided in the center of said dipole part; and

end parts provided with an area larger than the line width of said dipole part, on both ends thereof.

3. The tag antenna according to claim 1, wherein:

both ends of said dipole part are folded.

4. The tag antenna according to claim 1, wherein:

both ends of said dipole part are folded to become closer to each other.

5. The tag antenna according to claim 1, wherein:

said dipole part is shaped like the wings of a butterfly.

2. A tag antenna composed of a dipole antenna and a feeding part with a chip mounted thereto, comprising:

a dipole part of a length shorter than half of an antenna resonance wavelength;

a feeding part provided in the center of said dipole part;

an inductance part formed such as to surround said feeding part with said feeding part in the center and such that both ends are connected to said dipole part; and

end parts provided with an area larger than the line width of said dipole part, on both ends thereof.

14. The tag antenna according claim 2, wherein:

said dipole part and said inductance part are formed through the same procedure as printing, using a liquid including metal, of which the main constituent is copper, silver, or aluminum, on a sheet composed of paper, film, or PET.

6. A tag antenna which is connected to a chip and supplies signals and power to said chip, comprising:

a dipole part of a length shorter than half of an antenna resonance wavelength; and

an inductance part having a length which adjusts the admittance of said tag antenna such that an imaginary part of the admittance of said tag antenna has the same absolute value as the imaginary part of the admittance of said chip, in the dipole part;

wherein the radiation resistance of said dipole part becomes almost the same as the resistance of said chip due to loss, in said dipole part.

7. The tag antenna according claim 6, wherein:

said dipole part is formed by folding around the inside.

8. The tag antenna according to claim 7, wherein:

said inductance part is formed in an empty space on the inner side of said dipole part.

9. The tag antenna according to claim 8, wherein:

the length of said dipole part is longer than the inductance part.

10. The tag antenna according to claim 6, wherein:

the length of said inductance part is determined according to the specific dielectric constant and thickness of the object to which said tag antenna is adhered.

11. The tag antenna according to claim 6, wherein:

the line width of said dipole part is partially widened.

12. The tag antenna according to claim 11, wherein:

said dipole part is formed such that sections thereof which have a low current density are partially cut away.

13. The tag antenna according claim 12, wherein:

said dipole part is cut into slits.