JP5965370B2 - Antenna device and reflector arrangement method - Google Patents

Description

  The present invention relates to an antenna device that transmits and receives electromagnetic waves having a plurality of frequencies, and a reflector arrangement method for the antenna device.

  In recent years, there has been proposed a technique (metamaterial technique) for artificially controlling the propagation characteristics of electromagnetic waves propagating through a structure having a periodic arrangement of dielectrics or conductors. Some metamaterials have a characteristic of reflecting (blocking) only electromagnetic waves belonging to a specific frequency band among incident electromagnetic waves according to the periodic arrangement structure. For example, using the above-mentioned metamaterial technology, the following Non-Patent Document 1 discloses that a conductor coating portion of a dielectric substrate (printed substrate) whose plate surface is coated with a conductor (metal) is arranged in a predetermined lattice-like periodic arrangement. A frequency selective surface (FSS) produced by patterning with a pattern is disclosed.

  Such a frequency selection plate realizes a negative dielectric constant by an artificial periodic arrangement structure, and has a band gap band corresponding to the period interval and shape of the lattice-like periodic arrangement structure. The band gap band is a frequency band of the electromagnetic wave when the electromagnetic wave incident on the metamaterial reflector is reflected at a predetermined ratio or more.

H. So, A. Ando, T. Seki, M. Kawashima, and T. Sugiyama, Directional Multi-Band Antenna Employing Frequency Selective Surfaces, Electron. Lett., Vol. 49, no. 4, pp. 243-245, Feb. 2013.

  By the way, an antenna device has been devised that can transmit and receive electromagnetic waves of a plurality of frequency bands by using a plurality of frequency selection plates having different band gap bands and an antenna element that radiates or absorbs electromagnetic waves of a plurality of frequencies. In this antenna device, for example, a plurality of frequency selection plates are arranged so that the directions of the normal vectors of the respective plate surfaces coincide with each other while being spaced apart from the antenna element by a predetermined distance, and the electromagnetic waves projected on each of them. Are configured to transmit electromagnetic waves in a frequency band other than the maximum frequency. Here, the frequency selection plate is arranged so that the conductor (metal foil) on the surface faces the antenna element.

  However, in such an antenna device, the impedance of the antenna element changes due to the influence of the conductor on the surface of the frequency selection plate, and the VSWR ( There has been a problem that the voltage standing wave ratio characteristic deteriorates.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to suppress deterioration of VSWR characteristics.

In order to achieve the above object, according to the present invention, as a first solving means related to an antenna device, an antenna element that transmits and receives electromagnetic waves in a plurality of frequency bands, and a metal foil on one plate surface of a dielectric substrate are periodically A plurality of frequency selection plates formed and arranged, and the plurality of frequency selection plates are spaced apart from the antenna element by a predetermined distance, and the directions of the normal vectors of the respective plate surfaces coincide with each other. And an antenna device that transmits electromagnetic waves in a frequency band other than the maximum frequency among the electromagnetic waves projected to each of the plurality of frequency selection plates, on the side where the metal foil is not disposed A means is adopted in which the plate surface is arranged facing the antenna element.

According to the present invention, as a second solving means relating to the antenna device, in the first solving means described above, further comprising a metal reflecting plate in which one whole plate surface of the dielectric substrate is coated with a metal foil, and the metal reflecting While the plate is further away from the antenna element than the plurality of frequency selection plates, the direction of the normal vector of the plate surface coincides with the direction of the normal vector of the plate surface of the plurality of frequency selection plates. At the same time , a means is adopted in which the plate surface on the side not coated with the metal foil is arranged facing the antenna element.

Further, in the present invention, as a means for solving the reflector arrangement method, an antenna element that transmits and receives electromagnetic waves in a plurality of frequency bands and a metal foil is periodically arranged on one plate surface of the dielectric substrate. A plurality of frequency selection plates, and the plurality of frequency selection plates are arranged so that the directions of the normal vectors of the respective plate surfaces coincide with each other while being separated from the antenna element by a predetermined distance, The plurality of frequency selection plates of the antenna device that transmits electromagnetic waves in a frequency band other than the maximum frequency among the electromagnetic waves projected to each of the plurality of frequency selection plates so that the plate surface on the side where the metal foil is not disposed faces the antenna element. The means of arranging is adopted.

According to the present invention, the plurality of frequency selection plates are arranged with the plate surface on the side where the conductor (metal foil) is not disposed facing the antenna element, whereby the antenna element and the metal foil of the frequency selection plate are arranged. Since the antenna elements are separated from each other, a change in impedance of the antenna element is suppressed, and deterioration of VSWR characteristics can be suppressed.

It is a perspective view showing a schematic structure of antenna device A concerning one embodiment of the present invention. It is a side view (a) of the antenna device A which concerns on one Embodiment of this invention, and a figure (b) which shows the direction of the 1st reflecting plate M1, the 2nd reflecting plate M2, and the metal reflecting plate M3. It is a figure (a) which shows a periodic pattern of the 1st reflector M1 in one embodiment of the present invention, and a figure (b) which shows a periodic pattern of the 2nd reflector M2. It is a figure which shows the VSWR characteristic of the antenna apparatus A which concerns on one Embodiment of this invention. It is a figure which shows the VSWR characteristic according to the thickness of the 1st reflecting plate M1, the 2nd reflecting plate M2, and the metal reflecting plate M3 in one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the antenna device A according to this embodiment includes an antenna element E, a first reflector M1, a second reflector M2, and a metal reflector M3. In the following description, the directions of the x-axis, y-axis, and z-axis that are orthogonal to each other are defined as shown in the figure.

  The antenna element E radiates electromagnetic waves in a plurality of different frequency bands to the atmosphere. A feeding point E1 of the antenna element E is connected to a high frequency power source via a feeding line (not shown). The antenna element E radiates electromagnetic waves into the atmosphere based on the high frequency signal input from the high frequency power source. The antenna element E also functions as a receiving element that absorbs and receives electromagnetic waves in different frequency bands that propagate in the atmosphere.

  That is, the antenna element E transmits and receives electromagnetic waves in a plurality of different frequency bands. The antenna element E radiates, for example, electromagnetic waves in three different frequency bands of 800 MHz, 2 GHz, and 4 GHz to the atmosphere. Such an antenna element E is, for example, a frequency sharing antenna element shared by a plurality of frequency bands or a broadband antenna element that transmits and receives electromagnetic waves in a wide band including a plurality of frequency bands.

  Moreover, although the antenna element E is illustrated as a dipole antenna extending along the ± z axis as shown in FIG. 1, it is not limited to such a mode. For example, the antenna element E may be a monopole antenna, a patch antenna, a horn antenna, or the like as necessary.

  The first reflecting plate M1 and the second reflecting plate M2 are frequency selective surfaces (FSS) in which a grid-like periodic arrangement pattern of conductors is formed on the plate surface of the dielectric substrate. For example, the first reflecting plate M1 and the second reflecting plate M2 are formed by patterning a conductor coating portion of a dielectric substrate (printed substrate) whose plate surface is coated with a conductor (metal foil) with a predetermined lattice-shaped periodic arrangement pattern. Is produced. The first reflecting plate M1 and the second reflecting plate M2 transmit only electromagnetic waves belonging to a specific frequency band determined based on a lattice-like periodic arrangement pattern of conductors and dielectrics, and reflect electromagnetic waves in other frequency bands. have.

  The first reflecting plate M1 and the second reflecting plate M2 are formed with different periodic arrangement patterns. For this reason, the first reflector M1 and the second reflector M2 have different characteristics. That is, the first reflecting plate M1 and the second reflecting plate M2 are configured to reflect only electromagnetic waves in different frequency bands from among the electromagnetic waves radiated from the antenna element E.

  For example, the first reflector M1 is configured to reflect only 4 GHz electromagnetic waves out of the electromagnetic waves (4 GHz, 2 GHz, 800 MHz) radiated from the antenna element E. The second reflector M2 is configured to reflect only 2 GHz electromagnetic waves among the electromagnetic waves radiated from the antenna element E. In addition, the periodic arrangement pattern of the 1st reflecting plate M1 and the 2nd reflecting plate M2 and the example of the characteristic are mentioned later.

  The metal reflector M3 is formed by coating the entire one surface of the dielectric substrate with a conductor (metal foil). Therefore, the metal reflector M3 does not have a characteristic of reflecting electromagnetic waves of all frequencies and transmitting only electromagnetic waves belonging to a predetermined frequency band. As will be described later, the metal reflector M3 is the lowest frequency (800 MHz) transmitted from the first reflector M1 and the second reflector M2 among the electromagnetic waves radiated by the antenna element E in the antenna device A. It is configured to reflect only the electromagnetic wave.

  The first reflecting plate M1, the second reflecting plate M2, and the metal reflecting plate M3 are installed in the same direction (−x direction) with respect to the antenna element E with a certain distance from the antenna element E. Yes. The first reflecting plate M1, the second reflecting plate M2, and the metal reflecting plate M3 are all disposed so that their plate surfaces are parallel to each other.

  Of the first reflector M1, the second reflector M2, and the metal reflector M3, the first reflector M1 that reflects electromagnetic waves of 4 GHz is only a distance s1 from the antenna element E, as shown in FIG. They are arranged at positions separated in the −x direction. The second reflecting plate M2 that reflects 2 GHz electromagnetic waves is disposed at a position separated from the antenna element E by a distance s2 larger than the distance s1 in the −x direction.

  As described above, the first reflecting plate M1 and the second reflecting plate M2 are spaced apart from the antenna element E by a predetermined distance, but the respective plate surfaces are parallel, and the direction of the normal vector of each plate surface is ± x. Arranged to match the direction.

  Due to the configuration of the antenna device A shown in FIG. 2A (how to dispose the first reflector M1 and the second reflector M2), the first reflector M1 has all the frequencies radiated from the antenna element E ( Electromagnetic waves including 4 GHz, 2 GHz, and 800 MHz) are projected. Therefore, the first reflecting plate M1 functions as a reflecting plate that reflects only 4 GHz of the electromagnetic waves radiated from the antenna element E based on transmission characteristics described later.

  On the other hand, as shown in FIG. 2A, the first reflector M1 exists between the antenna element E and the second reflector M2. Therefore, 4 GHz electromagnetic waves reflected by the first reflecting plate M1 are not projected on the second reflecting plate M2, and only 2 GHz and 800 MHz electromagnetic waves transmitted by the first reflecting plate M1 are not projected. Projected. Therefore, the second reflecting plate M2 functions as a reflecting plate that reflects only 2 GHz of the electromagnetic wave radiated from the antenna element E based on the reflection characteristics.

  Further, while the metal reflector M3 is separated by the distance s3 (> s2> s1) farthest from the antenna element E, the direction of the normal vector of the plate surface is the normal of the plate surface of the first reflector M1. They are arranged so as to coincide with the vector direction (−x direction).

  Due to such an arrangement order, 4 GHz and 2 GHz electromagnetic waves reflected by the first reflecting plate M1 and the second reflecting plate M2 are not projected onto the metal reflecting plate M3, and the first reflecting plate M1 and the second reflecting plate M2 are not projected. Only an electromagnetic wave of 800 MHz that passes through both is projected. Therefore, the metal reflector M3 functions as a reflector that reflects only 800 MHz, which is the lowest frequency, of the electromagnetic waves radiated from the antenna element E. In the present embodiment, the distance s1 is set to 18.8 mm, the distance s2 is set to 43.5 mm, and the distance s3 is set to 93.8 mm.

  The plate surfaces of the first reflecting plate M1, the second reflecting plate M2, and the metal reflecting plate M3 are squares whose sides are L1, L2, and L3, respectively (see FIG. 2). The size of the plate surface (length of L1, L2, L3) is determined based on the radiation characteristics (beam width) of the electromagnetic wave handled by the antenna device A. Here, the beam width is a half-value beam width (angle between directions at which the intensity distribution in the horizontal plane becomes a half value) with respect to the horizontal plane (xy plane) of the antenna device A.

  According to the antenna device A having the above-described configuration, electromagnetic waves of a plurality of frequency bands radiated from the antenna element E are generated by the first reflector M1, the second reflector M2, and the metal reflector M3 according to the frequency bands. Under the influence of reflection by either of them, each has a mechanism for obtaining a desired directivity.

Next, the operation of the antenna device A configured as described above will be described.
For example, the periodic arrangement pattern of the first reflector M1 and the second reflector M2 is formed as shown in FIGS. 3 (a) and 3 (b). In FIGS. 3A and 3B, the shaded area indicates a conductor portion, and the other area indicates a dielectric portion.

  In the periodic arrangement pattern of the first reflector M1, the parameters are set as d1 = 115.0 mm, a11 = 40.1 mm, a12 = 105.0 mm, w11 = 2.6 mm, and w12 = 11.3 mm.

  Such a first reflector M1 has high reflection characteristics in a frequency band centered on 4 GHz, and has low reflection characteristics in frequency bands centered on 2 GHz and 800 MHz. That is, only the maximum electromagnetic wave of 4 GHz among the electromagnetic waves (4 GHz, 2 GHz, 800 MHz) radiated from the antenna element E can be reflected on the first reflecting plate M1, and the electromagnetic waves of 2 GHz and 800 MHz, which are other frequencies, can be reflected. The periodic array pattern is formed so as to have a characteristic of transmitting the light.

  Here, “transmitting” does not mean that the first reflecting plate M1 and the second reflecting plate M2 completely transmit electromagnetic waves having a frequency belonging to a specific frequency band, but the first reflecting plate M1 and the second reflecting plate. It represents that the reflection characteristic of the plate M2 is a predetermined value or less (for example, −10 dB or less).

  On the other hand, in the periodic arrangement pattern of the second reflector M2, the parameters are set as d2 = 15.3 mm, a2 = 105.3 mm, and w2 = 11.5 mm. Both the first reflector M1 and the second reflector M2 are printed boards having a substrate thickness of 1.6 mm and a relative dielectric constant of 2.6 (dielectric loss tangent tan δ at 12 GHz).

  Such a second reflector M2 has high reflection characteristics in the frequency band centered on 2 GHz, and has low reflection characteristics in the frequency band centered on 800 MHz. In other words, the second reflector M2 has a characteristic that only the electromagnetic wave of 2 GHz among the frequencies (2 GHz, 800 MHz) projected from the antenna element E to itself can be reflected, and transmits the electromagnetic wave of 800 MHz that is other frequency. A periodic array pattern is formed to have.

The first reflecting plate M1 and the second reflecting plate M2 thus configured, and the metal reflecting plate M3 are arranged with the plate surface on the side where no conductor (metal foil) is arranged facing the antenna element E. Yes. That is, conventionally, the reflector is arranged so that the conductor faces the antenna element E. However, in the present embodiment, the first reflector M1, the second reflector M2, and the metal reflector M3 are shown in FIG. ), The conductor (metal foil) side is arranged to face the direction opposite to the antenna element E. This is to prevent the impedance of the antenna element E from changing due to the proximity of the antenna element E and the conductor of the reflector, thereby degrading the VSWR characteristics.

  FIG. 4 shows a conventional configuration (where the conductors of the first reflector M1, the second reflector M2, and the metal reflector M3 are arranged so as to face the antenna element E) and the VSWR corresponding to the frequency of this embodiment. It shows the characteristics. 4A shows the VSWR characteristic at a low frequency, and FIG. 4B shows the VSWR characteristic at a high frequency. As shown in FIG. 4, the VSWR characteristic of the present embodiment is lower, that is, improved than the conventional configuration.

  Further, FIG. 5 shows the VSWR corresponding to the frequency of each substrate thickness (1.6 mm and 5.0 mm) of the conventional reflector and the first reflector M1, the second reflector M2, and the metal reflector M3 in the present embodiment. It shows the characteristics. 5A shows the VSWR characteristics in the conventional configuration, and FIG. 5B shows the VSWR characteristics in the present embodiment. As can be seen from comparison with FIGS. 5A and 5B, the VSWR characteristics of the present embodiment are lower than that of the conventional configuration, that is, improved in both cases where the substrate thickness is 1.6 mm and 5.0 mm. Yes.

According to this embodiment, the first reflector M1, the second reflector M2, and the metal reflector M3 are arranged with the plate surface on the side where no conductor (metal foil) is arranged facing the antenna element. As a result, the antenna element and the metal foil of the first reflector M1, the second reflector M2, and the metal reflector M3 are separated from each other, so that a change in impedance of the antenna element is suppressed, and deterioration of the VSWR characteristic can be suppressed.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, For example, the following modifications can be considered.
(1) Although the above embodiment includes two frequency selection plates, that is, the first reflection plate M1 and the second reflection plate M2, the present invention is not limited to this. For example, the antenna device A may be provided with three or more frequency selection plates. In this case, the antenna device A can radiate electromagnetic waves having four or more different frequencies, and each frequency selection plate is configured to reflect only one different frequency among the electromagnetic waves radiated by the antenna element E. The Also in this case, the metal reflector M3 is disposed farthest away from the antenna element E and reflects the electromagnetic wave having the lowest frequency.

(2) Although the said embodiment is provided with the metal reflecting plate M3, this invention is not limited to this. For example, the above embodiment may be configured by only the first reflector M1, the second reflector M, and the antenna element E without the metal reflector M3. That is, in the present invention, the metal reflector is not an essential requirement.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof, as long as they are included in the scope and gist of the invention.

  A ... Antenna device, E ... Antenna element, M1 ... First reflector, M2 ... Second reflector, M3 ... Metal reflector, E1 ... Feed point

Claims (3)

An antenna element for transmitting and receiving electromagnetic waves in a plurality of frequency bands; and a plurality of frequency selection plates formed by periodically disposing metal foils on one plate surface of the dielectric substrate. The plates are arranged so that the directions of the normal vectors of the respective plate surfaces coincide with each other while being spaced apart from the antenna element by a predetermined distance, and in the frequency band other than the maximum frequency among the electromagnetic waves projected to each. An antenna device that transmits electromagnetic waves,
The antenna device, wherein the plurality of frequency selection plates are arranged with a plate surface on which the metal foil is not disposed facing an antenna element. Further comprising a metal reflector coated with a metal foil on one entire plate surface of the dielectric substrate;
While the metal reflector is further away from the antenna element than the plurality of frequency selection plates, the direction of the normal vector of the plate surface is the direction of the normal vector of the plate surfaces of the plurality of frequency selection plates. The antenna device according to claim 1, wherein the antenna device is arranged so that a plate surface on the side not coated with the metal foil faces the antenna element. An antenna element for transmitting and receiving electromagnetic waves in a plurality of frequency bands; and a plurality of frequency selection plates formed by periodically disposing metal foils on one plate surface of the dielectric substrate. The plates are arranged so that the directions of the normal vectors of the respective plate surfaces coincide with each other while being spaced apart from the antenna element by a predetermined distance, and in the frequency band other than the maximum frequency among the electromagnetic waves projected to each. A reflector arrangement method, wherein the plurality of frequency selection plates of an antenna device that transmits electromagnetic waves are arranged such that a plate surface on which the metal foil is not disposed faces an antenna element.

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