Antenna

• US 20060290590A1
• Filed: 06/28/2006
• Published: 12/28/2006
• Est. Priority Date: 06/28/2005
• Status: Active Grant

• Current Assignee: DENSO Corporation, Nippon Soken, Inc.
• Original Assignee: DENSO Corporation, Nippon Soken, Inc.
• Inventors: Takaoka, Akira, Okada, Noriaki
• Granted Patent: US 7,545,340 B2
• Time in Patent Office: Days
• US Class Current: 343/895
• CPC Class Codes: H01Q 1/362 for broadside radiating helical antennas
• CPC Class Codes: H01Q 11/08 Helical antennas
• CPC Class Codes: H01Q 9/30 with feed to end of elongated active element, e.g. unipole H01Q9/44 takes precedence
• CPC Class Codes: H01Q 9/40 Element having extended radiating surface

Abstract

An antenna includes outer and inner elements, one of which is a signal line and the other of which is a ground line. Each of the outer and inner elements is a helical element having helical portions. The inner element is arranged inside the outer element such that the outer and inner elements are spaced from each other. An axis of the outer element is parallel to that of the inner element.

Claims

1. An antenna for transmitting and receiving a radio wave having a predetermined wavelength, the antenna comprising:

an outer element including a first plurality of helical portions, each of which having a first axis; and

an inner element including a second plurality of helical portions, each of which having a second axis parallel to the first axis, wherein

one of the outer and inner elements is a signal line and an other of the outer and inner elements is a ground line, and

the inner element is arranged inside the outer element such that the outer and inner elements are spaced from each other.

2. The antenna according to claim 1, wherein

a total electrical length of the outer and inner elements is approximately equal to half the wavelength of the radio wave.

3. The antenna according to claim 1, wherein

the outer element has a first height in a direction of the first axis,

the inner element has a second height in the direction of the second axis, and

the first height is approximately equal to the second height.

4. The antenna according to claim 1, wherein

the first axis of the outer element coincides with the second axis of the inner element.

5. The antenna according to claim 4, wherein

each of the first helical portions of the outer element has a first inner diameter,

each of the second helical portions of the inner element has a second inner diameter, and

a ratio of the second inner diameter to the first inner diameter is less than or equal to 0.6.

6. The antenna according to claim 5, wherein

the ratio of the second inner diameter to the first inner diameter is less than or equal to 0.3.

7. The antenna according to claim 4, wherein

a first spacing is provided between each of the first helical portions of the outer element,

a second spacing is provided between each of the second helical portions of the inner element, and

the second spacing is less than the first spacing.

8. The antenna according to claim 4, wherein

a spacing is provided between each of the first helical portions of the outer element to allow the antenna to have a self-resonant frequency closest to a predetermined resonant frequency, and

the self-resonant frequency is lower than or equal to the predetermined resonant frequency.

9. The antenna according to claim 1, further comprising:

a circuit board to which the outer and inner elements are fixed, wherein

each of the outer and inner elements has one end portion electrically connected to the circuit board.

10. The antenna according to claim 1, wherein

the antenna is included in a vehicular wireless device.