ANTENNA DEVICE AND COMMUNICATION DEVICE

• US 20120019427A1
• Filed: 04/15/2011
• Published: 01/26/2012
• Est. Priority Date: 07/20/2010
• Status: Abandoned Application

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: ISHIKAWA, Shohei, NINOMIYA, Teruhisa
• Application Number:
  US13/087,524
• Publication Number:
  US 20120019427A1
• Time in Patent Office: Days
• US Class Current: 343/833
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 11/08 Helical antennas
• CPC Class Codes: H01Q 19/28 using a secondary device in the form of two or more substantially straight conductive elements log- periodic antennas H01Q11/10; constituting a reflecting surface H01Q19/10

Abstract

An antenna device includes a helical antenna that radiates a circularly polarized radio wave in a direction of an axis S, in which the helical antenna is formed with linear conducting bodies each helically winding around the predetermined axis and adjacent linear conducting bodies are spaced a distance P apart. The antenna device further includes a director that is on the axis S, along which a radio wave is radiated from the helical antenna, at a position a distance X away from the helical antenna, the distance X being substantially equal to the distance P.

Claims

1. An antenna device comprising:

an antenna that radiates a circularly polarized radio wave in a direction of a predetermined axis, wherein the antenna is formed with linear conducting bodies each helically winding around the predetermined axis, and adjacent linear conducting bodies are spaced a first distance apart; and

a director that is on the axis, along which a radio wave is radiated from the antenna, at a position a second distance away from the antenna, wherein the second distance is substantially equal to the first distance.

2. The antenna device according to claim 1, wherein

the director includes a plurality of conductive elements, each conductive element being on the axis along which a radio wave is radiated from the antenna, and

a distance between the antenna and a conductive element closest to the antenna and a distance between adjacent conductive elements are substantially equal to the second distance.

3. The antenna device according to claim 2, wherein the number of the conductive elements is an even number.

4. The antenna device according to claim 2, wherein the conductive elements are in a cross shape, viewed from a plate perpendicular to the axis along which a radio wave is radiated from the antenna.

5. The antenna device according to claim 2, wherein the conductive elements are in a hooked cross shape, viewed from a plate perpendicular to the axis along which a radio wave is radiated from the antenna.

6. The antenna device according to claim 1, wherein the first distance and the second distance are values not higher than 0.15λ

but not lower than 0.11λ

, where λ

is an equivalent wavelength of a radio wave radiated from the antenna.

7. The antenna device according to claim 6, wherein the number of the conductive elements is an even number.

8. The antenna device according to claim 6, wherein the conductive elements are in a cross shape, viewed from a plate perpendicular to the axis along which a radio wave is radiated from the antenna.

9. The antenna device according to claim 6, wherein the conductive elements are in a hooked cross shape, viewed from a plate perpendicular to the axis along which a radio wave is radiated from the antenna.

10. A communication device for radiating a radio wave toward a tag to make a communication with the tag, the communication device comprising:

an antenna that radiates a circularly polarized radio wave in a direction of a predetermined axis, wherein the antenna is formed with linear conducting bodies each helically winding around the predetermined axis, and adjacent linear conducting bodies are spaced a first distance apart; and

a director that is on the axis, along which a radio wave is radiated from the antenna, at a position a second distance away from the antenna, wherein the second distance is substantially equal to the first distance.