JP2010279080A - Spiral antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spiral antenna which allows the reduction in the height of an antenna to be achieved while ensuring wide band properties. <P>SOLUTION: A spiral antenna includes: antenna elements 11 patterned in a spiral shape on a dielectric substrate; a cavity 13 formed by providing an air gap between the antenna elements 11; and a magnetic substance 15 located between the antenna elements 11 and the cavity 13. Further, the antenna is formed step-wise or tilted so that the sum of the distance between the antenna elements 11 and the magnetic substance 15, and the thickness of the magnetic substance increases from a spiral center toward the outer circumference. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a spiral antenna having broadband characteristics.

  In a spiral antenna that radiates electromagnetic waves only in the forward direction of the antenna, a gap corresponding to the operating frequency is provided between the antenna and the cavity. In this spiral antenna with a cavity, the gap between the antenna element and the cavity depends on the wavelength corresponding to the operating frequency, and thus becomes spatially large.

  Therefore, a microstrip spiral antenna that secures broadband characteristics by providing a radio wave absorber at the bottom of the cavity has been proposed (see Patent Document 1). However, by providing a radio wave absorber like this antenna, it is possible to ensure wideband characteristics, but the effect of lowering the height from the cavity to the antenna cannot be obtained, and it will be thick as an antenna There was a problem.

JP 2000-252738 A

  As described above, providing a radio wave absorber at the bottom of the cavity as in the above antenna makes it possible to ensure wideband characteristics, but the effect of reducing the height from the cavity to the antenna cannot be obtained. There was a problem that a certain installation space was required.

  The present invention has been made paying attention to the above circumstances, and an object of the present invention is to provide a spiral antenna capable of realizing a reduction in the height of the antenna while ensuring wideband characteristics.

  To achieve the above object, a spiral antenna according to the present invention comprises an antenna element patterned in a spiral shape on a dielectric substrate, a cavity formed by providing a gap between the antenna element, and the antenna A magnetic body disposed between the element and the cavity, and the sum of the distance between the antenna element and the cavity and the thickness of the magnetic body is from the center of the spiral toward the outer periphery. It is formed in a stepped or inclined shape so as to increase.

  Therefore, according to the present invention, it is possible to provide a spiral antenna that can realize a reduction in the height of the antenna while ensuring wideband characteristics.

The perspective view which shows the structure of the spiral antenna which concerns on one Embodiment of this invention. The figure which shows the cross section of A-A 'of the spiral antenna shown in FIG. The perspective view which shows the antenna structure when a spiral shape is made into a square. The perspective view which shows the antenna structure using the spiral antenna of one point electric power feeding.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a perspective view of an outer shape of an antenna showing an embodiment of a spiral antenna of the present invention. 2 is a cross-sectional view taken along the line AA ′ of the antenna shown in FIG.

  As shown in FIG. 1, this antenna has an antenna element 11 patterned in a spiral shape on a dielectric substrate, and is made of a metal that supports the dielectric substrate with a gap between the antenna element 11 and the antenna element 11. A structure having a cavity 13 is adopted. A magnetic body 15 is provided between the antenna element 11 and the cavity 13. As shown in FIG. 2, the cavity 13 and the magnetic body 15 are configured such that the sum of the distance between the antenna element 11 and the magnetic body 15 and the thickness of the magnetic body 15 corresponds to the spiral of the antenna element 11. It is formed in a stepped shape or an inclined shape so that the thickness increases from the outer periphery toward the outer periphery.

Next, the operation of the thus configured spiral antenna will be described.
This spiral antenna resonates at the outermost periphery of the antenna element at the lower limit frequency (corresponding to the element indicated by 14 in FIG. 2). Thereafter, as the frequency increases, the resonance point moves in the center direction of the antenna (the direction approaching the feeding point 12 in FIG. 2).

  When (d / λ × h / λ) is constant when the distance between the antenna element 11 and the magnetic body 15 is d, the thickness of the magnetic body 15 is h, and the wavelength at the resonance frequency of the spiral antenna is λ. The antenna has a good VSWR (Voltage Standing Wave Ratio) and a constant antenna gain. That is, when the resonance frequency is doubled, d and h are halved. Therefore, the sum (d + h) of the distance between the antenna element 11 and the magnetic body 15 and the thickness of the magnetic body 15 is as shown in FIG. It can be a stepped shape or a cross section that is inclined toward the outer peripheral direction and the interval is widened.

  As described above, in the above embodiment, the thickness (h) of the magnetic body and the distance (d) from the antenna to the magnetic body are changed in accordance with the resonance frequency of the spiral antenna, thereby wide frequency range. Thus, it is possible to realize an antenna element having a constant gain and a lower height than the conventional spiral antenna.

  In addition, this invention is not limited to the said embodiment as it is. For example, in the above-described embodiment, the circular spiral antenna is used, but this shape is not necessarily circular. For example, as shown in FIG. 3, the same effect can be obtained even when the spiral shape is a polygon such as a quadrangle. In addition, when a pair of spiral antennas is added and a structure having a total of two pairs of spiral antennas and two feed points is provided, the above-mentioned effect is obtained, and two orthogonally polarized waves (right-handed circularly polarized wave and left-handed circularly polarized wave) ).

  In the above embodiment, a circular antenna element having a feeding point at the center is used. However, as shown in FIG. 4, the antenna element may be constituted by a one-point feeding spiral antenna having a feeding point for only one of the antenna elements. Good. Furthermore, a plurality of combinations of these spiral antennas can be configured as a so-called array antenna device in which a plurality of combinations are regularly or irregularly arranged on a plane.

  In short, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

  DESCRIPTION OF SYMBOLS 11 ... Antenna element, 12 ... Feed point, 13 ... Cavity, 14 ... Element which resonates at a lower limit frequency, 15 ... Magnetic body.

Claims (2)

An antenna element patterned in a spiral pattern on a dielectric substrate;
A cavity formed by providing a gap between the antenna element;
A magnetic body disposed between the antenna element and the cavity;
The sum of the distance between the antenna element and the magnetic body and the thickness of the magnetic body is formed in a stepped shape or an inclined shape so as to increase from the center of the spiral toward the outer periphery. Spiral antenna.   The spiral antenna according to claim 1, wherein the antenna element has a circular or polygonal spiral shape.

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