JP5842731B2 - Metamaterial antenna - Google Patents

Description

  The present invention relates to a metamaterial antenna.

  Conventionally, patch antennas (microstrip line antennas) in which a conductive pattern is formed on one surface of a substrate and a ground pattern is formed on the opposite surface of the substrate have been widely used. In such a patch antenna, the phase rotates as it travels in the direction of propagation of radio waves.

  In addition, a conductive pattern is formed on one surface of the substrate, a ground pattern is formed on the opposite surface of the substrate, and the conductive pattern and the ground pattern are electrically connected by a through hole. A patch antenna called a metamaterial antenna has been put into practical use (for example, see Patent Document 1).

US7911386 B1 Publication

  A structure of a conventional metamaterial antenna is shown in FIG. As shown in this figure, the metamaterial antenna has a conductor plate 11a formed on one surface of the substrate 11, a ground plate 11b formed on the opposite surface of the substrate 11, and a through hole 11c between the conductor plate 11a and the ground plate 11b. It is configured to conduct.

  FIG. 12 shows an equivalent circuit of the metamaterial antenna shown in FIG. In the metamaterial antenna shown in this figure, if the inductance component due to the through hole 11c is L and the capacitance component between the conductor plate 11a and the ground 11b plate of the metamaterial antenna is C, the operating frequency of the metamaterial antenna is ω = 1. / √ (LC). Further, when the dielectric constant is ε, the area of the conductor plate 11a is S, and the thickness between the conductor plate 11a and the ground plate 11b is d, the capacitance component C formed between the conductor plate 11a and the ground plate 11b is C = It is expressed as ε · (S / d).

  In such a metamaterial antenna, there is a demand for reducing the area occupied by the antenna. However, if the area S of the conductor plate 11a is reduced in order to reduce the area occupied by the antenna, the capacitance C formed between the conductor plate 11a and the ground plate 11b is reduced, and the operating frequency ω is shifted to the high frequency side. The problem that it ends up occurs.

  The present invention has been made in view of the above problems, and an object thereof is to reduce the area occupied by a conductive pattern without changing the operating frequency.

In order to achieve the above object, according to the present invention, the conductive pattern (11a) is formed on one surface, the ground pattern (11b) is formed on the opposite surface, and the conductive pattern (11a) and the ground pattern (11b) are formed. An insulating layer (11) in which a through hole (11c) is formed to conduct electricity between the inductance component of the through hole (11c) and the conductive pattern (11a) according to the power supply to the power supply pattern (12). Due to the parallel resonance with the capacitance component between the ground patterns (11b), the electric field is perpendicular to the ground pattern (11b) formed in the insulating layer (11) and in the same direction at any position on the conductive pattern. A metamaterial antenna that generates a polarized wave that is directed to an inductance component of a through hole (11c) and a conductive pattern (1 The insulating layer (11) has a structure in which a plurality of blocks composed of a) and a capacitance component between the ground pattern (11b) are arranged in parallel, and through-holes (11c) are formed in each block. A configuration in which a second region in which the thickness between the conductive pattern (11a) and the ground pattern (11b) is thinner than the first region is formed around the first region to increase the capacitance component in the block. It has become . The thickness between the conductive pattern (11a) and the ground pattern (11b) changes from the first region to the second region so as to be inclined.

  According to such a configuration, the conductive pattern (11a) and the ground pattern (11b) are disposed around the first region of the insulating layer (11) in which the through hole (11c) is formed, rather than the first region. The second region having a small thickness is formed, and even though the area occupied by the conductive pattern is reduced to reduce the capacitance component between the conductive pattern (11a) and the ground pattern (11b), the through hole (11c) The capacitance component between the conductive pattern (11a) and the ground pattern (11b) can be increased by the second region while the inductance component due to is maintained, so that the conductive pattern can be changed without changing the operating frequency. The exclusive area can be reduced.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is a figure which shows the structure of the metamaterial antenna which concerns on one Embodiment of this invention. It is the figure which showed a mode that the metamaterial antenna was seen from the arrow A direction in FIG. It is the figure which showed a mode that the metamaterial antenna was seen from the arrow B direction in FIG. It is a figure for demonstrating the capacitance capacity | capacitance of this metamaterial antenna. (A) is the figure which showed the dimension of each part of the metamaterial antenna which concerns on this embodiment shown in FIG. 1, (b) is the figure which showed the dimension of each part of the conventional metamaterial antenna shown in FIG. It is. It is a figure which shows the frequency characteristic of the voltage standing wave ratio (VSWR) of the metamaterial antenna shown to Fig.5 (a), and the metamaterial antenna shown to FIG.5 (b). It is a figure which shows the frequency characteristic of the voltage standing wave ratio (VSWR) of a metamaterial antenna. It is a figure which shows the characteristic of an operating frequency at the time of changing thickness tt of the conductive pattern of the 2nd area | region of the metamaterial antenna shown to Fig.5 (a). It is a figure for demonstrating a modification. It is a figure which shows the frequency characteristic of the voltage standing wave ratio (VSWR) of each structure in FIG. It is a figure which shows the structure of the conventional metamaterial antenna. It is a figure which shows the equivalent circuit of the metamaterial antenna in FIG.

  The structure of a metamaterial antenna according to an embodiment of the present invention is shown in FIG. FIG. 2 shows a metamaterial antenna viewed from the direction of arrow A in FIG. FIG. 3 shows a metamaterial antenna viewed from the direction of arrow B in FIG.

  This metamaterial antenna is used in an infrastructure enhancement system such as inter-vehicle communication using a frequency in the UHF band where the antenna size is large. The metamaterial antenna is configured by using a so-called left-handed metamaterial technology.

  This metamaterial antenna has an insulating layer 11 made of a dielectric. A conductive pattern 11a is formed on one surface (upper surface in FIG. 2) of the insulating layer 11, and a ground pattern 11b is formed on the opposite surface (lower surface in FIG. 2) of the insulating layer 11. In addition, a through hole 11c is formed between the conductive pattern 11a and the ground pattern 11b to connect the conductive pattern 11a and the ground pattern 11b. In addition, a power supply pattern 12 for power supply is connected to the conductive pattern 11a.

  Further, as shown in FIG. 2, one surface of the insulating layer 11 protrudes in the direction perpendicular to the insulating layer 11 around the through hole 11 c. In other words, a second region having a smaller thickness between the conductive pattern 11a and the ground pattern 11b than the first region is formed around the first region where the through hole 11c is formed.

  In the present embodiment, as shown in the first, second, third, and fourth stages in FIG. 3, a region including one through hole 11c formed in the insulating layer 11 is described as one block. To do. That is, this metamaterial antenna has a four-stage configuration in which one block close to the feeding pattern 12 is the first stage.

  This metamaterial antenna has a ground pattern formed in the insulating layer 11 by parallel resonance of the inductance component of the through hole 11c and the capacitance component between the conductive pattern 11a and the ground pattern 11b in response to power feeding to the power feeding pattern 12. Polarization is generated such that the electric field is directed to the same direction at an arbitrary position on the conductive pattern and perpendicular to 11b.

  Here, a basic configuration of the conventional metamaterial antenna shown in FIG. 11 will be described. In the conventional metamaterial antenna shown in FIG. 11, the thickness of the insulating layer 11 is uniform in the entire region.

  In the equivalent circuit of the conventional metamaterial antenna shown in FIG. 12, an inductance component L11 in the figure is an inductance component of each through hole 11c, and a capacitance component C1 is a capacitance between the conductive pattern 11a and the ground pattern 11b. It is an ingredient. The inductance component L12 is an inductance component of the conductive pattern between the through holes 11c.

  When the inductance component due to the through hole 11c of the metamaterial antenna is L and the capacitance component between the conductive pattern 11a of the metamaterial antenna and the ground pattern 11b is C, the operating frequency of the metamaterial antenna is ω = 1 / √ (LC) Represented as: Further, when the dielectric constant is ε, the area of the conductive pattern 11a is S, and the thickness between the conductive pattern 11a and the ground pattern 11b is d, the capacitance component C formed between the conductive pattern 11a and the ground pattern 11b is C = It is expressed as ε · (S / d).

  In such a metamaterial antenna, if the area S of the conductive pattern 11a is reduced in order to reduce the area occupied by the antenna, the capacitance capacitance C formed between the conductive pattern 11a and the ground pattern 11b is reduced, and the operating frequency ω Shifts to the high frequency side.

  Further, when the overall thickness between the conductive pattern 11a and the ground pattern 11b is reduced, the operating frequency ω can be shifted to the low frequency side, but the inductance L formed by the through hole is also reduced, so that the antenna Performance will be degraded.

  Therefore, as shown in FIG. 4, in the metamaterial antenna, the thickness between the conductive pattern 11a and the ground pattern 11b is smaller than the first region around the first region where the through hole 11c is formed. By forming the second region, the area occupied by the antenna is reduced without changing the operating frequency.

  The capacitance capacitance C formed between the conductive pattern 11a and the ground pattern 11b of the metamaterial antenna shown in FIG. 4 is S for the exclusive area of the antenna, d for the thickness of the conductive pattern 11a in the first region, When the thickness of the conductive pattern 11a in this region is tt, it can be expressed as Equation 1 in FIG.

  Even if the capacitance component C formed between the conductive pattern 11a and the ground pattern 11b is reduced due to the reduction of the exclusive area of the antenna, that is, the exclusive area of the conductive pattern 11a, the convex portion (first portion) formed on one surface of the insulating layer 11 is reduced. The capacitance component C is increased by reducing the thickness d of the (second region) on both sides of the first region (1 region), thereby operating at substantially the same operating frequency.

  Next, referring to FIG. 5 and FIG. 6, the voltage standing wave ratio (VSWR) with respect to the frequency of the metamaterial antenna according to the present embodiment shown in FIG. 1 and the conventional type metamaterial antenna shown in FIG. The characteristics will be described.

  FIG. 5A shows the dimensions of the metamaterial antenna according to the present embodiment shown in FIG. FIG. 5B shows the dimensions of the conventional metamaterial antenna shown in FIG. The size of the conductive pattern 11a of the metamaterial antenna shown in FIG. 5A is 100 mm × 50 mm, and the size of the conductive pattern 11a of the metamaterial antenna shown in FIG. It is 120 mm x 60 mm. That is, the exclusive area of the conductive pattern 11a of the metamaterial antenna shown in FIG. 5A is about 30 percent (%) less than that of the metamaterial antenna shown in FIG. Yes.

  FIG. 6 shows characteristics of the voltage standing wave ratio (VSWR) with respect to the frequency of the metamaterial antenna shown in FIG. 5A and the metamaterial antenna shown in FIG. The metamaterial antenna shown in FIG. 5A has a bandwidth of 7 megahertz (MHz) when VSWR = 3. Further, the metamaterial antenna shown in FIG. 5B has a bandwidth of 13 megahertz (MHz) when VSWR = 3.

  In addition, both the metamaterial antenna shown in FIG. 5A and the metamaterial antenna shown in FIG. 5B have an operating frequency of about 730 megahertz (MHz) to 755 megahertz (MHz). , Almost the same operating frequency can be realized.

  As a reference, the metamaterial antenna shown in FIG. 5 (a) while the thickness d (d = 6.4 mm) of the insulating layer 11 is kept constant over the entire area as in the conventional metamaterial antenna shown in FIG. Similarly to FIG. 7, the characteristic of the voltage standing wave ratio (VSWR) with respect to the frequency when the size of the conductive pattern 11a is reduced to 100 mm × 50 mm is shown in FIG.

  In this way, when the size of the conductive pattern 11a is simply reduced while the thickness of the insulating layer 11 is kept constant in the entire region as in the conventional metamaterial antenna, the conductive pattern 11a and the ground are reduced by reducing the occupied area. Since the capacitance component C between the patterns 11b decreases, as shown in FIG. 7, the operating frequency becomes a 1090 megahertz (MHz) band, and is greatly shifted to the high frequency side.

  FIG. 8 shows the characteristics of the operating frequency when the thickness tt of the conductive pattern 11a in the second region of the metamaterial antenna shown in FIG. 5A is changed. As shown in this figure, the operating frequency decreases as the thickness tt of the conductive pattern 11a in the second region decreases. Therefore, a desired operating frequency can be obtained by setting the thickness tt of the conductive pattern 11a in the second region to an optimum value.

  According to the configuration described above, the second region having a smaller thickness between the conductive pattern 11a and the ground pattern 11b than the first region around the first region of the insulating layer 11 in which the through hole 11c is formed. Even if the capacitance component C between the conductive pattern 11a and the ground pattern 11b is reduced by reducing the area occupied by the conductive pattern, the inductance component L due to the through hole 11c is maintained and the second component is maintained. Since the capacitance component C between the conductive pattern 11a and the ground pattern 11b can be increased depending on the region, the exclusive area of the conductive pattern can be reduced without changing the operating frequency.

  In addition, this invention is not limited to the said embodiment, Based on the meaning of this invention, it can implement with a various form.

  For example, in the embodiment, as shown in FIG. 2, the thickness between the conductive pattern 11a and the ground pattern 11b in the first region and the thickness between the conductive pattern 11a and the ground pattern 11b in the second region are divided into two stages. For example, a multi-stage structure as shown in FIG. 9A, a tapered structure as shown in FIG. 9B, a W-type structure as shown in FIG. it can.

  FIG. 10 shows the frequency characteristics of the voltage standing wave ratio (VSWR) of the metamaterial antenna having each structure shown in FIGS. As shown in FIG. 10, the frequency characteristic of the voltage standing wave ratio (VSWR) of the metamaterial antenna can be made different depending on the structure of the second region.

11 Insulating layer 11a Conductive pattern 11b Ground pattern 11c Through hole 12 Feed pattern

Claims (1)

Insulating layer in which a conductive pattern (11a) is formed on one surface, a ground pattern (11b) is formed on the opposite surface, and a through hole (11c) is formed between the conductive pattern (11a) and the ground pattern (11b). (11) and in parallel with the inductance component of the through hole (11c) and the capacitance component between the conductive pattern (11a) and the ground pattern (11b) according to the power supply to the power supply pattern (12). Due to resonance, a meta that generates a polarization that is perpendicular to the ground pattern (11b) formed in the insulating layer (11) and in which an electric field is directed in the same direction at an arbitrary position on the conductive pattern. A material antenna,
A plurality of blocks composed of an inductance component of the through hole (11c) and a capacitance component between the conductive pattern (11a) and the ground pattern (11b) are arranged in parallel.
In each of the blocks, the thickness between the conductive pattern (11a) and the ground pattern (11b) is around the first region of the insulating layer (11) where the through hole (11c) is formed. The second region thinner than the first region is formed to increase the capacitance component in the block ,
A metamaterial antenna , wherein a thickness between the conductive pattern (11a) and the ground pattern (11b) is inclined from the first region to the second region .

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