JP2015119363A - Antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna device that can be further small-sized in comparison with the prior arts, while maintaining an electromagnetic wave radiation property similar to the conventional antenna device.SOLUTION: The antenna device includes: an antenna radiation element that radiates an electromagnetic wave; and a frequency selection plate which is disposed at a position opposing the antenna radiation element, with which elements of conductors are periodically arrayed in a lattice shape on a surface of a dielectric substrate and on which a specific frequency of electromagnetic waves is reflected. The dielectric substrate is formed in such a size that the element arrayed in the outermost circumference becomes a partial element of a shape in which partial areas of the element remain in a predetermined ratio, and the predetermined ratio is a numerical value obtained by dividing a total value of areas of all the partial elements in the outermost circumference by a result of multiplying an area of elements in a perfect shape by the number of all partial elements in the outermost circumference.

Description

  The present invention relates to an antenna device using a frequency selection plate made of a periodic array of conductor patches and slits as a reflection plate.

Conventionally, in an antenna device, the directivity of electromagnetic waves radiated in a specific direction is enhanced by a basic structure using an antenna radiating element and a reflector that reflects radio waves radiated by the antenna radiating element.
There has been proposed an antenna device that applies a frequency selection plate to the reflection plate and controls the emission of electromagnetic waves having a specific frequency (see, for example, Non-Patent Document 1). A metamaterial reflector is used as the frequency selection plate.

The metamaterial is a structure in which dielectrics, metal patches, and the like are periodically arranged, and can control both the dielectric constant ε and the magnetic permeability μ. A metamaterial in which both the dielectric constant ε and the permeability μ are negative is called a left-handed metamaterial, and this material has a left-handed electromagnetic field vector. Have.
In the metamaterial reflector, for example, a conductor coating portion of a dielectric substrate (printed substrate) whose substrate surface is coated with a conductor (for example, metal) has a predetermined lattice shape as shown in Non-Patent Document 1. It is created by patterning into a pattern having a periodic array of

  The metamaterial reflector described above achieves a negative dielectric constant ε by the structure of the pattern periodically arranged in a lattice pattern, and has a band gap band corresponding to the period interval and shape of the pattern of the lattice pattern. have. Here, the band gap band indicates the frequency band of the electromagnetic wave when the electromagnetic wave incident on the metamaterial reflector is reflected at a predetermined ratio or more.

FIG. 8 is a diagram illustrating an example of an antenna device using a frequency selection plate having a conventional configuration. The antenna radiating element 100 and the frequency selection plate 101 are arranged to face each other. FIG. 8A is a perspective view showing a configuration example of an antenna device using a frequency selection plate 101 having a conventional configuration as a reflection plate. The antenna radiating element 100 and the frequency selection plate 101 are disposed to face each other with a distance s. The distance s is a distance that is ¼ of the wavelength λ of the electromagnetic wave in the band gap band of the frequency selection plate 101.
FIG. 8B is a side view illustrating a configuration example of an antenna device using the frequency selection plate 101 having a conventional configuration as a reflection plate.

  In the configuration shown in FIGS. 8A and 8B, an element (patch) is formed in which electromagnetic waves radiated from the antenna radiating element 100 are periodically arranged in a lattice pattern of the frequency selection plate 101. The electromagnetic wave reflected by the surface is radiated in the X-axis direction. The electromagnetic wave reflected by the frequency selection plate 101 has a frequency in the band gap band of the frequency selection plate 101. The frequency selection plate 101 is composed of an L × L square dielectric substrate.

However, since Non-Patent Document 1 does not describe arbitrarily changing the beam width of the antenna device, it is unclear how to control the beam width.
On the other hand, a beam width control method for controlling the beam width emitted by the antenna device by changing the number of periods in which the elements arranged on the frequency selection plate are arranged is conceivable.

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.

However, when trying to improve the directivity of electromagnetic waves radiated by the antenna device, that is, when trying to adjust the beam width to be narrow, it is necessary to increase the number of periods of the elements arranged on the frequency selection plate.
For this reason, when the number of element cycles is increased, it is necessary to increase the area of the frequency selection plate by the amount of increase in the number of element cycles. The size of the antenna device is determined by the area of the frequency selection plate 101 and the distance between the antenna radiating element 100 and the frequency selection plate 101. This distance is determined by the frequency of the electromagnetic wave to be radiated.
Therefore, when improving the directivity of the electromagnetic wave radiated from the antenna device, the area of the frequency selection plate 101 is increased, which causes a problem that the antenna device is enlarged.

  The present invention has been made in view of such circumstances, and an antenna device capable of reducing the size of an antenna device as compared with the conventional antenna device while maintaining the same electromagnetic wave radiation characteristics as a conventional antenna device. The purpose is to provide.

  The present invention has been made to solve the above-described problems. An antenna device according to the present invention includes an antenna radiating element that radiates electromagnetic waves, a position facing the antenna radiating element, and a dielectric body. Conductor elements are periodically arranged in a lattice pattern on the surface of the substrate, and a frequency selection plate that reflects a specific frequency of the electromagnetic wave is provided, and the dielectric substrate has the elements arranged on the outermost periphery. The partial area is formed in a size that becomes a partial element having a shape in which a predetermined ratio remains, and the predetermined ratio is a total value of the areas of all the partial elements on the outermost periphery. It is a numerical value obtained by dividing the area of the element having a simple shape by the result of multiplying the number of all the partial elements on the outermost periphery.

  In the antenna device of the present invention, the predetermined ratio is 20% or more.

  The antenna device according to the present invention is characterized in that when controlling the beam width when the electromagnetic wave is radiated, the number of periods of the arrangement of the patches is changed.

  The antenna device of the present invention is characterized in that a plurality of the frequency selection plates having different frequencies of reflected electromagnetic waves are provided so that the reflecting surfaces thereof are parallel to each other.

  According to the present invention, it is possible to provide an antenna device capable of reducing the size of the antenna device as compared with the conventional antenna device while maintaining the same electromagnetic wave radiation characteristic as that of the conventional antenna device.

It is a figure which shows the structural example of the antenna apparatus which used the frequency selection board by one Embodiment of this invention as a reflecting plate. It is a figure for demonstrating the residual metal ratio of the outermost periphery element used by this embodiment. It is a figure of the planar view which shows the shape of the basic block in which the element in this embodiment was formed. It is a top view which shows element shapes other than the cross shape used by this embodiment. 4 is a diagram showing the relationship between the beam width of an electromagnetic wave radiated from the antenna device 1 and the residual metal ratio of the outermost element formed on the dielectric substrate in the frequency selection plate 11. FIG. It is a figure which shows that the area of an antenna reduces by reducing the residual metal ratio of the outermost element. It is a figure which shows the radiation pattern in a horizontal surface which shows the azimuth of each beam radiation of the electromagnetic waves of the antenna device 1 in this embodiment, and the conventional antenna device. It is a figure which shows the example of the antenna device using the frequency selection board of the conventional structure.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a configuration example of an antenna device using a frequency selection plate according to an embodiment of the present invention as a reflection plate. In FIG. 1, the antenna radiating element 100 and a frequency selection plate 11 are included. In the antenna device 1, each of the antenna radiating element 100 and the frequency selection plate 11 is disposed at a position facing each other with a separation distance s. The electromagnetic wave radiated from the antenna radiating element 100 is affected by the reflection by the reflecting plate 1 according to the frequency thereof, so that the antenna device 1 has a mechanism for obtaining a desired directivity. The separation distance s between the antenna device 100 and the frequency selection plate 11 is selected according to the frequency of electromagnetic waves transmitted and received by the antenna device 1 so as to obtain desired directivity. Specifically, it is preferable to set to an integer (for example, 1/4) of the wavelength of the electromagnetic wave transmitted and received by the antenna device 1.
Here, the antenna radiating element 100 has the same configuration as that of the conventional example, and is a λ / 2 dipole antenna. Here, λ is the wavelength of the electromagnetic wave emitted by the antenna radiating element 100.

The antenna radiating element 100 is a functional unit that radiates electromagnetic waves in a specific frequency band to the atmosphere. A high-frequency power source (not shown) is connected to the antenna radiating element 100 and radiates a high-frequency signal in a specific frequency band input from the high-frequency power source to the atmosphere. The antenna radiating element 100 may function as a receiving element that absorbs and receives an electromagnetic wave signal in a specific frequency band that propagates in the atmosphere.
The antenna radiating element 100 of the antenna device 1 according to the present embodiment is a dipole antenna extending along the z-axis as shown in FIG. 1, but for the antenna device 100 according to other embodiments, It is not limited to this aspect. For example, the antenna radiating element 100 may be a monopole antenna, a patch antenna, a horn antenna, or the like.

Further, the frequency selection plate 11 is configured by patterning with a predetermined number of periods on the surface of the dielectric substrate so that the elements (patches) 50 of the conductive thin film are arranged in a lattice pattern. .
The antenna device 1 of FIG. 1 in the present embodiment is the same as the other components of the conventional antenna device except that the configuration of the frequency selection plate 11 is different from the configuration of the frequency selection plate 101 of FIG.

The frequency selection plate 11 in FIG. 1 has a square shape in plan view, and each side has a length of L-α. Since each side is L in the conventional example, the frequency selection plate 11 is reduced to an area of a ratio of (L−α) ² / L ² as compared with the conventional example.
In the present embodiment, the frequency selection plate 11 has a smaller area than the frequency selection plate 101 of the conventional example while maintaining the beam width which is the directivity characteristic of the electromagnetic wave radiated from the antenna device 1. .

  FIG. 2 is a plan view of a frequency selection plate for explaining the residual metal ratio of the outermost peripheral element (partial element 51) used in the present embodiment. In FIG. 2, patterns of elements 50 and partial elements 51 formed of a conductor (metal) on the surface of a dielectric substrate 12 are arranged in a lattice-like periodic arrangement. In FIG. 2, the elements 50 and the partial elements 51 are arranged in five cycles in the row direction (X-axis direction) and the column direction (Y-axis direction).

  The size of the outer periphery L (vertical) × L (horizontal) is the configuration of the conventional frequency selection plate 101. On the other hand, the inside of the frame including the element 50 and the partial element 51 having the area painted black is the size of the frequency selection plate 11 of the present embodiment. Here, the portion painted black is the remaining conductor portion. Therefore, the element included in the region 20 surrounded by the wavy line is the outermost partial element 51.

The frequency selection plate 11 in the present embodiment shrinks the outer peripheral portion of the dielectric substrate 12 in order to make the dielectric substrate 12 from (L × L) to (L−α) × (L−α) ( That is, the outer peripheral area of the dielectric substrate 12 is cut and deleted by the amount of α).
At this time, the shape of the outermost partial element 51 is only partially left as shown in FIG. 2, and is incomplete with respect to the complete element 50 in the central portion. Here, the incomplete shape means that the outer peripheral region of the dielectric substrate 12 is cut and deleted by α, and a part of the pattern of the outermost element is also lost due to the complete shape of the element 50 being cut. The pattern has a predetermined area and remains.

  Therefore, the remaining metal ratio (%) of the outermost peripheral element 51 is the total area (outermost peripheral area) of the outermost partial element 51 when the outermost element has a complete shape (that is, the element 50). This is a value obtained by dividing the total area of the remaining portions (the portions painted in black) of all the partial elements 51 by a numerical value obtained by multiplying the number of elements by the area of the elements 50). However, in the present embodiment, the outer peripheral region is cut and deleted so that the partial elements 51 remain in point symmetry with respect to the center of gravity of the frequency selection plate 11.

  FIG. 3 is a plan view showing the shape of the basic block in which the elements (element 50 and partial element 51) in this embodiment are formed. The basic block 800 is periodically arranged on the surface of the dielectric substrate 12 to form the frequency selection plate 11. In FIG. 3, the element 50 is formed as a cross-shaped conductor pattern in a square basic block 800. The thickness of the pattern forming the element 50 is 8.125 (mm), and the length of the pattern is 32.5 (mm). The length of the pattern is set to about λ / 2 with respect to the wavelength λ of the reflected electromagnetic wave. Each side of the basic block 800 is 35.5 (mm). Therefore, in the case of 5 cycles, since 35.5 × 5 =, L is 177.5 in the conventional case where the element has a complete shape, that is, all the basic blocks have a complete shape.

FIG. 4 is a plan view showing an element shape other than the cross shape used in the present embodiment.
In FIG. 4A, an element 901 is configured by subelements 901a, 901b and 901c being arranged in parallel with a split perpendicular to the longitudinal direction of each subelement, each having a predetermined deviation width. Has been. Here, the length of each of the sub-elements 901a, 901b and 901c is about λ / 2 (in FIG. 4, “about” is indicated as “˜”).

  In FIG. 4B, the element 902 is configured such that each of the elongate sub-elements 902a, 902b, and 902c is connected at one end in common, and is arranged at an angle of 120 °. Here, the length of each of the sub-elements 902a, 902b, and 902c is approximately λ / 4. Thus, for example, the length to which the sub-elements 902b and 902c are connected is approximately λ / 2.

  In FIG. 4C, an element 903 is configured such that one end of each of the sub-elements 903a, 903b, and 903c each having an arrow shape is connected to each other in common and arranged at an angle of 120 °. Yes. Here, the length of each of the sub-elements 903a, 903b and 903c is about λ / 4. Therefore, for example, the length in which the sub-elements 903b and 903c are connected is approximately λ / 2.

  In FIG. 4 (d), an element 904 has T-shaped sub-elements 904a, 904b, 904c and 904d connected in common at the lower ends of the respective T-shaped Ts, each at an angle of 90 °. Arranged and configured. Here, the length of each of the sub-elements 904a, 904b, 904c and 904d is about λ / 4. Thus, for example, the length with which sub-elements 904a and 904c are connected is approximately λ / 2.

  In FIG. 4 (e), an element 905 has L-shaped sub-elements 905a, 905b, 905c, and 905d connected in common at the upper ends of the L-shaped L elements, each at an angle of 90 °. Arranged and configured. Here, the length of each of the sub-elements 905a, 905b, 905c and 905d is about λ / 4. Thus, for example, the length to which the sub-elements 905a and 905c are connected is approximately λ / 2.

  FIG. 5 is a diagram showing the relationship between the beam width of the electromagnetic wave radiated by the antenna device 1 and the residual metal ratio of the outermost partial element 51 formed on the dielectric substrate in the frequency selection plate 11. In FIG. 5, the vertical axis represents the beam width (deg), and the horizontal axis represents the residual metal ratio (%) of the outermost partial element 51. A curve L1 indicates the relationship between the remaining metal ratio of the outermost partial element 51 and the beam width until the element (element 50 and partial element 51) changes from one cycle to three cycles. A curve L2 shows the relationship between the remaining metal ratio of the outermost partial element 51 and the beam width until the elements (element 50 and partial element 51) are changed from 3 periods to 5 periods.

  A point A in the curve L1 indicates the beam width of the antenna device 1 on the frequency selection plate when the element 50 is one period, that is, when one element is a complete shape, that is, when the residual metal ratio is zero. The point B in the curve L1 is a case where the element 50 has one period and the partial element has two periods, that is, a total of three periods, that is, one element 50 and eight partial elements 51, and a total of nine elements. The beam width of the antenna device 1 in the frequency selection plate when the residual metal ratio in the partial element 51 is 20% is shown. The point C in the curve L1 is when the element 50 has three periods, that is, when the element 50 is nine, and when the outermost eight elements are the elements 50 and have a complete shape, the residual metal ratio is 100%. The beam width of the antenna device 1 in the frequency selection plate is shown. As can be seen from FIG. 5, when the elements (element 50 and partial element 51) are in the form of one to three periods, the beam width is almost the same when the remaining metal ratio of the outermost partial element 51 is 20% to 100%. It has become.

  The point D in the curve L2 indicates the beam width of the antenna device 1 in the frequency selection plate when the element 50 is the three periods, that is, when the nine elements are the complete element 50, that is, when the residual metal ratio is zero. Show. The point E in the curve L2 is the case where the element 50 has 3 periods and the partial element 51 has 2 periods in total, that is, 5 elements in total, that is, 9 elements 50 and 16 partial elements 51 in total. The beam width of the antenna device 1 in the frequency selection plate when the residual metal ratio in the individual partial elements 51 is 20% is shown. The point F on the curve L2 is the case where the element 50 has 5 cycles, that is, the number of the element 50 is 25, and the 16 elements on the outermost periphery are the elements 50 having a complete shape and the residual metal ratio is 100%. The beam width of the antenna device 1 in the frequency selection plate is shown. As can be seen from FIG. 5, when the elements (element 50 and partial element 51) have a shape from 3 periods to 5 periods, the beam width is almost the same when the remaining metal ratio of the outermost element is 20% to 100%. ing.

As described above, each of the element (element 50 and partial element 51) has a shape from 1 cycle to 3 cycles and the element (element 50 and partial element 51) has a shape from 3 cycles to 5 cycles. When the ratio of the remaining metal of the outermost partial element 51 is 20% to 100%, the beam width is almost the same.
Further, as shown in FIG. 5, the frequency selection plate 11 in which elements are arranged in three cycles in the vertical and horizontal directions and the frequency selection plate 11 in which elements are arranged in five cycles in the vertical and horizontal directions are used. The beam width of the antenna device 1 has changed. Thereby, as the number of periods of the vertical and horizontal arrangements of the elements increases, the beam width of the emitted electromagnetic wave is narrow, that is, the directivity of the electromagnetic wave is improved. The directivity of electromagnetic waves can be adjusted by changing the number of periods of the vertical and horizontal arrangement of elements.

  Therefore, from FIG. 5, even in the period of any element (element 50 and partial element 51), even if the outermost partial element 51 has a partial shape, the characteristic of the beam width is a complete shape on the outermost periphery. It can be seen that a beam width characteristic equivalent to the case where the elements 50 are arranged can be obtained. That is, even if the area of the frequency selection plate 700 is reduced so that the area of the outermost partial element 51 is reduced so that any of the partial elements 51 remains, the beam width characteristic is the perfect element 50. The characteristics of the beam width equivalent to the case where are arranged on the outermost periphery can be obtained.

  FIG. 6 is a diagram showing that the area of the antenna is reduced by reducing the residual metal ratio of the outermost partial element 51. The frequency selection plate 600 has a configuration of a frequency selection plate in the prior art, and has a configuration in which elements 50 having a complete shape are arranged in 5 cycles of 5 rows and 5 columns. The frequency selection plate 700 is a frequency selection plate in the present embodiment, and the elements (elements 50 and partial elements 51) are arranged in 5 rows and 5 columns, but the remaining metal ratio of the outermost partial elements 51 is 20%. This is the configuration.

  When the antenna radiating element 100 radiates an electromagnetic wave having a frequency of 4 GHz, the distance between the antenna radiating element 100 and the frequency selection plate 11 in FIG. 1 is 18.8 (mm) which is a quarter of the wavelength of 4 GHz. In the present embodiment, the frequency selection plate 11 is designed to be a frequency band near 4 GHz as a band gap band (specific frequency band). The frequency selection plate 600 has L = 177.5 (mm), and the frequency selection plate 700 has L-α = 13.49 (mm). Therefore, each side of the frequency selection plate 700 becomes 0.76 L from 134.9 / 177.5 = 0.76. Accordingly, 0.76 × 0.76 = 0.58, and the area of the frequency selection plate 700 is 58% of the frequency selection plate 600, and the area of 42% is reduced with respect to the frequency selection plate 600.

Further, as can be seen from FIG. 1, the volume of the antenna device 1 is obtained by multiplying the area of the frequency selection plate 11 by the distance s between the antenna radiating element 100 and the frequency selection plate 11.
Here, since the distance s does not change in the conventional example and the present embodiment, the volume of the antenna device 1 of the present embodiment is also reduced by 42% as compared with the frequency selection plate 600 having the conventional configuration, similarly to the area. become.

  FIG. 7 is a diagram showing a horizontal plane radiation pattern indicating the azimuth angles of the electromagnetic wave beam radiation of the antenna device 1 according to the present embodiment and the conventional antenna device. In FIG. 7, the radiation pattern in the horizontal plane is shown by polar coordinates, the direction of the θ-axis is the azimuth angle, and the moving radius shows the power vector. In FIG. 7, the solid line pattern indicates the characteristic of the radiation pattern in the horizontal plane by the antenna device 1 using the frequency selection plate 700 according to the present embodiment. A broken line pattern indicates a radiation pattern in a horizontal plane by the antenna device using the conventional frequency selection plate 600.

  When the radiation patterns in the horizontal plane of the solid line pattern and the broken line pattern are compared, the solid line pattern and the broken line pattern have substantially the same characteristics. In particular, when looking at the main lobes of the solid line pattern (this embodiment) and the broken line pattern (conventional), the solid line pattern (this embodiment) is similar to the radiation pattern of the electromagnetic wave, That is, it can be seen that both beam widths are 105 deg and the beam power gain is the same. Further, the front-to-back ratio (FBR) is 2 dB lower than the broken line pattern (conventional) in the solid line pattern (this embodiment). As described above, in each side of the frequency selection plate used in the antenna device, the frequency selection plate of this embodiment is reduced by 24% compared to the conventional frequency selection plate. For this reason, the volume of the antenna device is reduced by 42% in the antenna device 1 of the present embodiment compared to the conventional antenna device.

As described above, this embodiment reduces the area of the outermost partial element 51 to such an extent that the radiation characteristics of electromagnetic waves do not deteriorate (the total area of the outermost partial element 51 is reduced to 20%), and the antenna device. The area of the frequency selection plate 11 used for 1 is reduced.
Thus, according to the present embodiment, the area of the frequency selection plate 11 can be reduced compared to the conventional antenna device while maintaining the same radiation characteristics as those of the electromagnetic wave in the conventional antenna device. Thus, the antenna device 1 with a reduced volume can be realized.

In the above-described embodiment, the antenna device has been described as having only one frequency selection plate 11 and performing transmission / reception corresponding to a single frequency.
However, as another configuration, a plurality of frequency selection plates 11 having bands in which the frequencies λ of the reflected electromagnetic waves are different from each other so that each reflecting surface faces the antenna radiating element 100 and each reflecting surface is parallel to each other. You may comprise so that it may overlap and provide. In this case, each of the plurality of frequency selection plates 11 is stacked, for example, in the order closer to the antenna radiating element 100 in order from the highest frequency to the lower frequency to be reflected.

As described above, by superimposing a plurality of frequency selection plates 11 having different reflection frequencies, it is possible to configure a multi-frequency antenna device that transmits and receives electromagnetic waves having a plurality of frequencies.
At this time, the antenna radiating element 100 is a multiband antenna radiating element capable of radiating or receiving electromagnetic waves having different frequencies. That is, the antenna radiating element 100 radiates or receives an electromagnetic wave having a frequency reflected by each of the frequency selection plates 11 in the above-described multi-frequency antenna device.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design and the like within a scope not departing from the gist of the present invention. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

DESCRIPTION OF SYMBOLS 1 ... Antenna apparatus 11,600 ... Frequency selection board 12 ... Dielectric substrate 20 ... Area | region 50 ... Element 51 ... Partial element 100 ... Antenna radiation | emission element

Claims (4)

An antenna radiating element that radiates electromagnetic waves;
A frequency selection plate disposed at a position facing the antenna radiating element, wherein conductive elements are periodically arranged in a lattice shape on the surface of the dielectric substrate, and reflect a specific frequency of the electromagnetic wave. ,
The dielectric substrate is formed in such a size that the elements arranged on the outermost periphery become partial elements having a shape in which a partial region of the element remains at a predetermined ratio,
The predetermined ratio is a numerical value obtained by dividing the total value of the areas of all the partial elements on the outermost periphery by the result of multiplying the area of the complete element by the number of all the partial elements on the outermost periphery. There is an antenna device.   The antenna device according to claim 1, wherein the predetermined ratio is 20% or more. 3. The antenna device according to claim 1, wherein the number of periods of the arrangement of the patches is changed when controlling a beam width when the electromagnetic waves are radiated.   4. A plurality of the frequency selection plates having different frequencies of electromagnetic waves to be reflected are provided so as to be overlapped so that their reflecting surfaces are parallel to each other. The antenna device according to item.

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