JP2014217031A - Reflection plate and antenna apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection plate and an antenna apparatus with which a band gap band widens to a broad band.SOLUTION: A reflection plate 1 reflecting an electromagnetic wave belonging to a specific band gap band comprises: columnar state elements 10a-10d made of a columnar dielectric body, which have a plurality of reflection layers 1A-1D periodically arranged in parallel and at equal intervals on a same plane. The plurality of reflection layers 1A-1D respectively includes the columnar elements 10a-10d arranged orthogonal to each other and laminated, and size of bottom faces of each the columnar elements 10a-10d and intervals in the periodical arrangement (a periodical width a) of the columnar elements 10a-10d are set satisfying a condition in which a specific bandwidth indicating a ratio of the band gap bandwidth against a central frequency of the band gap bandwidth is 20% or more.

Description

  The present invention relates to a reflector that reflects an electromagnetic wave having a predetermined frequency and an antenna device using the same.

  In recent years, a technique (metamaterial technique) for artificially controlling the propagation characteristics of electromagnetic waves propagating through the structure by having a periodic array structure has been proposed. 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.

  Here, the literature discloses an antenna device including a reflector having a periodic arrangement structure as described above (for example, Patent Literature 1 and Non-Patent Literature 1). In the antenna device of Patent Document 1, a reflector (metamaterial reflector) formed by the periodic arrangement structure as described above is used. This periodic arrangement structure is a periodic arrangement structure in which fine columnar elements made of prismatic or cylindrical wire rods are combined in a lattice shape at equal intervals at a distance sufficiently smaller than the wavelength of the reflected electromagnetic wave. Such a metamaterial reflector has a negative dielectric constant due to an artificial periodic structure, and has a band gap band corresponding to the periodic interval of the lattice-like arrangement structure. Here, the band gap band is a frequency band of the electromagnetic wave when the electromagnetic wave incident on the metamaterial reflector reflects at a predetermined ratio or more.

JP 2011-244136 A

"Dipole antennas used with all-dielectric, woodpile photonic-bandgap reflectors: gain, field patterns, and input impedance" GSSmith, MPKesler, and JGMaloney, Microwave and Opt.Tech.Lett., Vol.21, no.3 , pp.191-196, May 1999.

  By the way, the frequency band which can be reflected in the metamaterial reflector described above is uniquely determined based on the periodic arrangement structure of the metamaterial reflector. In particular, it is possible to reflect a desired frequency band by selecting them while matching the ratio between the thickness of one columnar element forming the periodic array and the arrangement interval of the periodic array of the columnar elements. .

  However, Patent Document 1 and Non-Patent Document 1 do not clearly disclose a method for controlling the bandwidth of the band gap band described above. Therefore, in the case where an antenna device including a metamaterial reflector is applied to various electronic devices, a wider band gap band has been demanded.

  Accordingly, an object of the present invention is to provide a reflector and an antenna device that can solve the above-described problems.

  The present invention has been made to solve the above-described problems, and is a reflector having a characteristic of reflecting an electromagnetic wave belonging to a specific band gap band, and a columnar element made of a columnar dielectric is formed on the same plane. A plurality of reflective layers formed in parallel and periodically arranged at regular intervals, wherein the plurality of reflective layers are stacked while the columnar elements constituting each of them are arranged so as to be orthogonal to each other; The size of each bottom surface and the interval of the periodic arrangement of the columnar elements are configured such that the ratio band of the band gap band is equal to or greater than the ratio band of the frequency band of the electromagnetic wave used in a device including a reflector. It is the reflector characterized by being made.

  Further, according to the present invention, in the above-described reflector, the first columnar element made of a columnar dielectric is formed of a columnar dielectric and a first reflective layer in which the first columnar elements are periodically arranged in parallel and at equal intervals on the same plane. A plurality of second columnar elements are arranged in such a manner that they are periodically arranged on the same plane at the same intervals as the plurality of first columnar elements, and are arranged so as to be orthogonal to and in contact with the plurality of first columnar elements. The plurality of third columnar elements made of the reflective layer and the columnar dielectric are parallel to the plurality of first columnar elements and are shifted from these by a half cycle at the same interval as the plurality of first columnar elements. And a plurality of second reflection layers made of a columnar dielectric, and a third reflection layer that is periodically arranged on the same plane and that is arranged so as to sandwich the second reflection layer with the first reflection layer. A four-columnar element is parallel to the plurality of second columnar elements; Further, the plurality of second columnar elements are periodically arranged on the same plane so as to be shifted by a half cycle at the same interval, and the third reflective layer is sandwiched with the second reflective layer. And a fourth reflective layer.

  Further, the present invention provides the above reflector, wherein each of the first columnar element, the second columnar element, the third columnar element, and the fourth columnar element has a square columnar shape having a square bottom surface having an equal size. And the distance between the plurality of first columnar elements (a [mm]) and the length of one side of the square (w [mm]) satisfy the relationship of 3.4w ≦ a ≦ 4.9w. It is characterized by.

  Further, according to the present invention, in the above-described reflector, each of the first columnar element, the second columnar element, the third columnar element, and the fourth columnar element has a cylindrical shape having a circular bottom surface having an equal size. And the interval between the plurality of first columnar elements (a [mm]) and the circular diameter (r [mm]) satisfy the relationship of 2.9r ≦ a ≦ 4.6r. To do.

  Further, according to the present invention, in the above reflector, each of the first columnar element, the second columnar element, the third columnar element, and the fourth columnar element has a polygonal columnar shape having a polygonal bottom surface having an equal shape. And the interval between the plurality of first columnar elements (a [mm]) and the diameter of the circumscribed circle of the polygon (r [mm]) satisfy the relationship of 2.9r ≦ a ≦ 4.6r It is characterized by that.

  Further, the present invention includes the above-described reflector and a radiating element that radiates electromagnetic waves in a predetermined frequency band, and the interval between the plurality of first columnar elements is shorter than the wavelength of the electromagnetic waves. It is an antenna device.

  According to the present invention, the band gap band of the reflector can be widened.

It is a figure which shows the antenna apparatus which concerns on the 1st Embodiment of this invention. It is a perspective view of the reflecting plate which concerns on the 1st Embodiment of this invention. It is a top view of the reflecting plate concerning a 1st embodiment of the present invention. It is a figure explaining the characteristic of the reflecting plate which concerns on the 1st Embodiment of this invention. It is a 1st figure which shows the characteristic of the reflecting plate which concerns on the 1st Embodiment of this invention. It is a 2nd figure which shows the characteristic of the reflecting plate which concerns on the 1st Embodiment of this invention. It is the 1st figure which put together the characteristic of the reflecting plate concerning a 1st embodiment of the present invention. It is the 2nd figure which put together the characteristic of the reflecting plate concerning a 1st embodiment of the present invention. It is the graph which put together the characteristic of the reflector which concerns on the 1st Embodiment of this invention. It is a perspective view of the reflecting plate which concerns on the 2nd Embodiment of this invention. It is a top view of the reflecting plate concerning a 2nd embodiment of the present invention. It is a figure which shows the characteristic of the reflecting plate which concerns on the 2nd Embodiment of this invention. It is the figure which put together the characteristic of the reflecting plate which concerns on the 2nd Embodiment of this invention. It is a perspective view of the reflecting plate which concerns on the 3rd Embodiment of this invention. It is a top view of the reflecting plate concerning a 3rd embodiment of the present invention. It is a figure which shows the characteristic of the reflecting plate which concerns on the 3rd Embodiment of this invention. It is the figure which put together the characteristic of the reflecting plate which concerns on the 3rd Embodiment of this invention.

<First Embodiment>
Hereinafter, an antenna device according to a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating an antenna device according to a first embodiment of the present invention. In this figure, reference numeral 100 denotes an antenna device. In the drawings used for the following description, the directions of the x-axis, y-axis, and z-axis that are orthogonal to each other in the space illustrated in each figure will be described.

As shown in FIG. 1, the antenna device 100 according to this embodiment includes a reflector 1 and a radiating element 5.
The radiating element 5 is a functional unit that radiates electromagnetic waves in a specific frequency band to the atmosphere. The radiating element 5 is connected to a high frequency power source (not shown). The radiating element 5 radiates a high-frequency signal in a specific frequency band input from the high-frequency power source to the atmosphere. Here, the radiating element 5 may function as a receiving element that absorbs and receives an electromagnetic wave signal in a specific frequency band that propagates in the atmosphere. As shown in FIG. 1, the radiating element 5 is disposed so as to face a reflector 1 described later. The antenna device 100 has a mechanism for obtaining a desired directivity by the electromagnetic wave radiated from the radiating element 5 being affected by the reflection by the reflecting plate 1 according to the frequency. The radiating element 5 shown in FIG. 1 has a dipole antenna shape as an example, but the antenna device 100 according to the present embodiment is not limited to this mode. For example, the radiating element 5 may be a monopole antenna, a patch antenna, a horn antenna, or the like.

The reflecting plate 1 is a substrate having a periodic arrangement structure in which columnar elements made of columnar dielectrics are combined in a lattice shape at equal intervals at a distance sufficiently shorter than the wavelength of a reflected radio wave. The reflecting plate 1 has a characteristic of reflecting an electromagnetic wave belonging to a specific frequency band radiated from the radiating element 5 based on the periodic arrangement structure. Hereinafter, the frequency band of the electromagnetic wave when the electromagnetic wave incident on the reflector 1 is reflected at a predetermined ratio or more is defined as a “band gap band” (the “predetermined ratio” will be described later).
The reflecting plate 1 according to the present embodiment includes a plurality of reflecting layers in which columnar elements (described later) made of columnar dielectrics are arranged in parallel and at regular intervals on the same plane. The plurality of reflective layers are formed by being stacked while the columnar elements constituting each of them are arranged so as to be orthogonal to each other. As shown in FIG. 1, the reflecting plate 1 is arranged so that its plate surface is parallel to the xz plane. Further, all the columnar elements constituting the reflector 1 according to the present embodiment are formed of a dielectric having a relative dielectric constant εr of 9.6.

FIG. 2 is a perspective view of the reflector according to the first embodiment of the present invention. FIG. 3 is a plan view of the reflecting plate according to the first embodiment of the present invention. 3A is a plan view of the plate surface (surface parallel to the xz plane) of the reflecting plate 1, and FIG. 3B is a side view of the reflector plate 1 (surface parallel to the yz plane). It is a top view.
As shown in FIGS. 2, 3A, and 3B, the reflector 1 is a grid of prismatic elements made of prismatic dielectrics at regular intervals at a distance sufficiently shorter than the wavelength of the reflected electromagnetic wave. It is the board | substrate which makes the periodic arrangement structure which combined. The reflecting plate 1 has a structure in which four reflecting layers having a plane parallel to the xz plane are overlapped in the y-axis direction. Specifically, as shown in FIG. 2, the reflection plate 1 is formed by laminating four layers of a first reflection layer 1A, a second reflection layer 1B, a third reflection layer 1C, and a fourth reflection layer 1D. It has the structure formed.

  First, the first reflective layer 1A is a layer in which first columnar elements 10a made of a prismatic dielectric are periodically arranged in parallel and at equal intervals (periodic width a) on the same plane (on the xz plane). is there. The direction in which the plurality of first columnar elements 10a periodically arranged extends is a direction parallel to the z-axis (FIGS. 2 and 3A). As shown in FIG. 2 and FIG. 3A, the first columnar elements 10a constituting the first reflective layer 1A are periodically arranged at regular intervals at intervals a. Each of the first columnar elements 10a has a prismatic shape whose bottom surface is a square with a side length of w (FIGS. 3A and 3B).

  Similarly, the second reflective layer 1B is formed by periodically arranging second columnar elements 10b made of a prismatic dielectric on the same plane (on the xz plane) in parallel and at equal intervals. Here, the plurality of second columnar elements 10b are periodically arrayed with the plurality of first columnar elements 10a at equal intervals, that is, with a period width a. In addition, the extending direction of the plurality of second columnar elements 10b arranged periodically is a direction parallel to the x-axis (FIGS. 2 and 3A). Therefore, the plurality of second columnar elements 10b are orthogonal to the plurality of first columnar elements 10a and have one side surface (the surface that each of the first columnar element 10a and the second columnar element 10b has in its extending direction). They are arranged so as to be in contact with each other and form a lattice shape together with the first columnar elements 10a. Similarly to the first columnar element 10a, the bottom surface of the second columnar element 10b according to the present embodiment has a prismatic shape formed of a square having a side length of w. (FIG. 3 (a), (b)).

  Similarly, the third reflective layer 1C is a layer in which third columnar elements 10c made of a prismatic dielectric are periodically arranged in parallel and at equal intervals on the same plane (on the xz plane). Here, the plurality of third columnar elements 10c are arranged so as to be parallel to the first columnar element 10a of the first reflective layer 1A (the extending direction of the third columnar element 10c is parallel to the z-axis). Is done. The interval (period width) between the third columnar elements 10c is the same period width a as that of the first columnar element 10a and the second columnar element 10b. However, as shown in FIGS. 2 and 3A, the plurality of third columnar elements 10c are arranged so as to be shifted from the first columnar element 10a by a half period (a / 2). That is, as shown in FIG. 3A, when the plate surface of the reflector 1 is viewed from the front (FIG. 3A), each third columnar element 10c and the first columnar element 10a are along the x-axis. Thus, they are arranged so that they appear alternately for each period width a / 2. Further, as shown in FIG. 3B, the third reflective layer 1C is arranged in contact with the second reflective layer 1B so as to sandwich the second reflective layer 1B together with the first reflective layer 1A. The Accordingly, the plurality of third columnar elements 10c are arranged such that one side surface thereof is in contact with each other orthogonal to the plurality of second columnar elements 10b. In addition, all the 3rd columnar elements 10c have comprised the square columnar shape which consists of a square whose one side length is w like the 1st columnar element 10a and the 2nd columnar element 10b (FIG. 3 ( a), (b)).

  The fourth reflective layer 1D is a layer in which the fourth columnar elements 10d made of a prismatic dielectric are periodically arranged in parallel and at equal intervals on the same plane (on the xz plane). Here, the plurality of fourth columnar elements 10d are arranged so as to be parallel to the second columnar element 10b of the second reflective layer 1B (the extending direction of the fourth columnar element 10d is a direction parallel to the x-axis). Is done. Further, the interval (period width) between the fourth columnar elements 10d is the same period width a as that of the first columnar element 10a, the second columnar element 10b, and the third columnar element 10c. However, as shown in FIGS. 2 and 3A, the plurality of fourth columnar elements 10d are arranged so as to be shifted from the second columnar element 10b by a half period (a / 2). That is, as shown in FIG. 3A, when the reflector 1 is viewed in the direction of the y-axis arrow, each of the fourth columnar elements 10d and the second columnar element 10b has a period width a / It will be arranged to appear alternately every two. Further, as shown in FIG. 3B, the fourth reflective layer 1D is disposed in contact with the third reflective layer 1C so as to sandwich the third reflective layer 1C together with the second reflective layer 1B. The Therefore, the plurality of fourth columnar elements 10d are arranged so as to be orthogonal to the plurality of third columnar elements 10c and so that one side surfaces thereof are in contact with each other. Note that all the fourth columnar elements 10d have a rectangular columnar shape whose bottom surface is a square with a side length of w, similarly to the first columnar element 10a, the second columnar element 10b, and the third columnar element 10c. (FIGS. 3A and 3B).

  Thus, the reflecting plate 1 according to the present embodiment is a plate-like layer having a thickness of 4w, in which the first reflecting layer 1A to the fourth reflecting layer 1D are stacked in the y-axis direction (FIG. 3 ( b)). 2 and 3 (a) and 3 (b) show only one region of the reflector 1 (only the width for two cycles), the reflector 1 is actually not shown in FIG. 2 and FIGS. 3A and 3B are structures that are repeatedly arranged in the x-axis direction and the z-axis direction and spread on the xz plane. Further, as described above, the first columnar element 10a to the fourth columnar element 10d constituting the reflector 1 according to the present embodiment are all formed of a dielectric having a relative dielectric constant εr of 9.6.

  By the way, the reflector 1 (antenna device 100) according to the present embodiment is provided in a predetermined device (for example, a communication device of a mobile phone wireless base station) for performing wireless communication. In this case, the reflector 1 is required to have equivalent reflection characteristics over the entire frequency band of the electromagnetic wave used in the device. Therefore, the reflecting plate 1 according to the present embodiment is configured such that the band gap band ratio band is equal to or higher than the electromagnetic wave frequency band band band used in the device including the reflecting plate 1. The “specific band (of frequency band)” refers to the ratio (Δf / f0) of the frequency bandwidth Δf to the center frequency f0 of the frequency band. Here, since the specific band of the frequency band allocated for mobile phones by law is about 20%, the reflector 1 according to the present embodiment has a condition that the specific band of the band gap band is 20% or more. Configured to meet. That is, the reflector 1 according to the present embodiment has a size of the bottom surface of each of the first columnar element 10a, the second columnar element 10b, the third columnar element 10c, and the fourth columnar element 10d (the length w of one side of the square). And the interval (period width a) between the plurality of first columnar elements 10a to fourth columnar elements 10d is determined so as to satisfy the condition that the band width of the band gap band is 20% or more. Hereinafter, the value specifically determined about w and a about the reflector 1 which concerns on this embodiment is demonstrated.

FIG. 4 is a diagram for explaining the characteristics of the reflector according to the first embodiment of the present invention. FIG. 5 is a first diagram showing the characteristics of the reflector according to the first embodiment of the present invention. FIG. 6 is a second diagram showing the characteristics of the reflector according to the first embodiment of the present invention.
Next, the characteristics of the reflector 1 according to this embodiment will be described. 5 and 6 show how much electromagnetic wave has a specific intensity when it is incident on the reflector 1 having the above-described structure (FIG. 2, FIG. 3 (a), (b)). Whether the light passes through the reflecting plate 1 (transmission characteristic S21 of the reflecting plate 1) is shown. The graphs shown in FIGS. 5 and 6 show the frequency f (GHz) of the electromagnetic wave on the horizontal axis and the transmission characteristic S21 (dB) on the vertical axis. The graphs shown in FIGS. 5 and 6 are the simulation results obtained by the electromagnetic field simulator calculated based on the simulation model as shown in FIG. That is, the transmission characteristic S21 shown on the vertical axis of the graphs shown in FIGS. 5 and 6 is a plane wave (incident incident) with a frequency f transmitted in a direction perpendicular to the plate surface of the reflector 1 (surface parallel to the xz plane). The intensity ratio of the electromagnetic wave (transmitted wave) transmitted through the reflector 1 out of the incident wave with respect to the wave) is expressed. Note that the reflector 1 in the simulation model of FIG. 4 actually extends to infinity on the xz plane.
In the following description, the frequency band of the electromagnetic wave when the transmission characteristic S21 of the reflecting plate 1 is 1/10 or less (−10 dB or less) is defined as a “band gap band”.
Here, the frequency band where the transmission characteristic S21 is 1/10 or less means that the ratio of the electromagnetic wave reflected by the reflector 1 in the incident wave is 9/10 or more, and the electromagnetic wave of the transmitted wave transmitted through the reflector 1 This is a frequency band in which the intensity is 1/10 or less of the incident wave. Further, the ratio of the band gap bandwidth to the center frequency of the band gap bandwidth is expressed as a specific band [%], which is an index indicating the effective size of the band gap bandwidth.

  5 and 6 show the transmission characteristics S21 when A1 to D1 (FIG. 5) and A2 to D2 (FIG. 6) when different values are set for the parameter of the period width a during the simulation. It is shown. Here, the reflector 1 according to the present embodiment is fixed at w = 9.4 mm. Among the plurality of graphs shown in FIG. 5, for example, a graph indicated by a solid line A is a transmission characteristic of the reflector 1 when the period width a is set to a = 3.4w (= 32 mm). According to this graph, since the frequency at which the transmission characteristic S21 is −10 dB or less is between about 4.2 GHz and 5.3 GHz, the band gap bandwidth is 1.1 GHz. Since the center frequency of the band gap bandwidth is 4.75 GHz, the specific band is 1.1 / 4.75≈0.23 (23%).

FIG. 7 is a first diagram summarizing the characteristics of the reflector according to the first embodiment of the present invention. FIG. 8 is a second diagram summarizing the characteristics of the reflector according to the first embodiment of the present invention.
FIG. 7 and FIG. 8 summarize the band gap bandwidth and the ratio band for the reflector 1 for each period width a. 7 corresponds to the graphs A1 to D1 shown in FIG. 5, and the numerical values shown in the rows of FIG. 8 are shown in the graphs A2 to D2 of FIG. It corresponds. The reflecting plate 1 for each periodic width a shown in FIG. 7 has a specific bandwidth of 23% when a = 3.4w (= 32.0 mm), a specific bandwidth of 32% when a = 3.8w (= 35.7 mm), and a = A specific bandwidth of 20% or more is realized with a bandwidth of 28% at 4.2w (= 39.5 mm) and a bandwidth of 21% at a = 4.9w (= 46.1 mm). On the other hand, the reflector 1 for each periodic width a shown in FIG. 8 has a specific bandwidth of 23% at a = 3.2w (= 30.0 mm), a specific bandwidth of 32% at a = 4.0w (= 37.5 mm), The bandwidth is 21% at a = 4.8w (= 45.0 mm), but 15% at a = 5.6w (= 52.5 mm), which is below 20%. Further, when a = 2.4w (= 22.5 mm), no band gap band appears.

FIG. 9 is a graph summarizing the characteristics of the reflector according to the first embodiment of the present invention.
The graph shown in FIG. 9 shows the relationship between the period width a of the reflector 1 and the ratio band in that case, with the period width a [mm] on the horizontal axis and the ratio band [%] on the vertical axis. Each plot of the graph shown in FIG. 9 corresponds to each period width a [mm] and specific band [%] shown in FIGS. 7 and 8. Here, 20% is selected as the predetermined value of the above-mentioned ratio band. Then, according to the graph shown in FIG. 9, the region where the specific band is 20% or more is a case where the condition of 32.0 mm ≦ a ≦ 46.1 mm, that is, 3.4 w ≦ a ≦ 4.9 w is satisfied. Can be read. Accordingly, the reflecting plate 1 according to the present embodiment satisfies the condition of 3.4 w ≦ a ≦ 4.9 w, so that the specific band becomes 20% or more, and a wide band gap can be realized.
As described above, according to the first embodiment of the present invention, it is possible to provide a reflector and an antenna device in which the band gap band is widened to a specific band of 20% or more. In addition to the reflector and the antenna device according to the first embodiment, the reflector and the antenna device according to the following embodiments can obtain the same effect.

<Second Embodiment>
Hereinafter, an antenna device according to a second embodiment of the present invention will be described with reference to the drawings.
The antenna device 100 according to the second embodiment includes a reflector 2 described below instead of the reflector 1 according to the first embodiment. The antenna device 100 according to the present embodiment has the same configuration (FIG. 1) as the antenna device 100 according to the first embodiment.
FIG. 10 is a perspective view of a reflector plate according to the second embodiment of the present invention. FIG. 11 is a plan view of a reflector according to the second embodiment of the present invention. Here, FIG. 11A is a plan view when the reflector 2 is viewed from the arrow direction of the y axis, and FIG. 11B is a diagram of the reflector 2 viewed from the direction opposite to the arrow of the x axis. FIG.
As shown in FIGS. 10, 11 (a) and 11 (b), the reflecting plate 2 is made of a columnar element made of a cylindrical dielectric in a lattice shape at equal intervals at a distance sufficiently shorter than the wavelength of the reflected radio wave. It is the board | substrate which makes the periodic arrangement structure which combined. Similar to the reflecting plate 1 according to the first embodiment, the reflecting plate 2 has a structure in which reflecting layers having a plane parallel to the xz plane are overlapped in four layers in the y-axis direction. Specifically, as shown in FIG. 10, the reflection plate 2 is formed by laminating four layers, ie, a first reflection layer 2A, a second reflection layer 2B, a third reflection layer 2C, and a fourth reflection layer 2D. It has the structure formed.

  First, the first reflective layer 2A is a layer in which first columnar elements 20a made of a cylindrical dielectric are periodically arranged in parallel and at equal intervals (periodic width a) on the same plane (on the xz plane). is there. In addition, the extending direction of the plurality of first columnar elements 20a arranged periodically is a direction parallel to the z-axis (FIGS. 10 and 11A). As shown in FIGS. 10 and 11A, the first columnar elements 20a constituting the first reflective layer 2A are periodically arranged at regular intervals at intervals a. Each of the first columnar elements 20a has a cylindrical shape whose bottom surface is a circular shape having a diameter r (FIGS. 11A and 11B).

  Similarly, the second reflective layer 2B is formed by periodically arranging second columnar elements 20b made of a cylindrical dielectric in parallel and at equal intervals on the same plane (on the xz plane). Here, the plurality of second columnar elements 20b are periodically arrayed with the plurality of first columnar elements 20a at equal intervals, that is, with a period width a. Further, the extending direction of the plurality of second columnar elements 20b arranged periodically is a direction parallel to the x-axis (FIGS. 10 and 11A). Therefore, the plurality of second columnar elements 20b are arranged so as to be orthogonal to the plurality of first columnar elements 20a so that their side surfaces (curved surfaces) are in contact with each other at one point, and form a lattice shape together with the first columnar elements 20a. doing. Similarly to the first columnar element 20a, the bottom surface of the second columnar element 20b according to the present embodiment has a cylindrical shape having a circular shape with a diameter r. (FIG. 11 (a), (b)).

  Similarly, the third reflective layer 2C is a layer in which third columnar elements 20c made of a cylindrical dielectric are periodically arranged in parallel and at equal intervals on the same plane (on the xz plane). Here, the plurality of third columnar elements 20c are arranged so as to be parallel to the first columnar element 20a of the first reflective layer 2A (the extending direction of the third columnar element 20c is parallel to the z-axis). Is done. The interval (period width) between the third columnar elements 20c is the same period width a as that of the first columnar element 20a and the second columnar element 20b. However, as shown in FIGS. 10 and 11A, the plurality of third columnar elements 20c are arranged so as to be shifted from the first columnar element 20a by a half period (a / 2). Furthermore, as shown in FIG. 11B, the third reflective layer 2C is disposed in contact with the second reflective layer 2B so as to sandwich the second reflective layer 2B together with the first reflective layer 2A. The Therefore, the plurality of third columnar elements 20c are arranged orthogonal to the plurality of second columnar elements 20b so that their side surfaces (curved surfaces) are in contact with each other at one point. In addition, all the 3rd columnar elements 10c form the column shape which the bottom face becomes circular with the diameter r similarly to the 1st columnar element 20a and the 2nd columnar element 20b (FIG. 11 (a), ( b)).

  The fourth reflective layer 2D is a layer in which the fourth columnar elements 20d made of a cylindrical dielectric are periodically arranged in parallel and at equal intervals on the same plane (on the xz plane). Here, the plurality of fourth columnar elements 20d are arranged so as to be parallel to the second columnar elements 20b of the second reflective layer 2B (the extending direction of the fourth columnar elements 20d is parallel to the x-axis). Is done. Further, the interval (period width) between the fourth columnar elements 20d is the same period width a as that of the first columnar element 20a, the second columnar element 20b, and the third columnar element 20c. However, as shown in FIGS. 10 and 11A, the plurality of fourth columnar elements 20d are arranged so as to be shifted from the second columnar element 20b by a half period (a / 2). Further, as shown in FIG. 11B, the fourth reflective layer 2D is disposed in contact with the third reflective layer 2C so as to sandwich the third reflective layer 2C together with the second reflective layer 2B. The Accordingly, the plurality of fourth columnar elements 20d are arranged orthogonal to the plurality of third columnar elements 20c so that their side surfaces (curved surfaces) contact each other at one point. Note that all the fourth columnar elements 20d have a cylindrical shape whose bottom surface is a circle having a diameter r, similarly to the first columnar element 20a, the second columnar element 20b, and the third columnar element 20c (see FIG. 11 (a), (b)).

  As described above, the reflecting plate 2 according to the present embodiment is a plate-like layer having a thickness of 4r in which the first reflecting layer 2A to the fourth reflecting layer 2D are stacked in the y-axis direction (FIG. 11 ( b)). 10 and 11 (a) and 11 (b) show only one region of the reflector 2 (only the width corresponding to two cycles), the reflector 2 is actually not shown in FIG. The structure shown in FIG. 10 and FIGS. 11A and 11B is a structure that is repeatedly arranged in the x-axis direction and the z-axis direction and spreads on the xz plane. As described above, the first columnar element 20a to the fourth columnar element 20d constituting the reflector 2 according to this embodiment are all formed of a dielectric having a relative dielectric constant ε0 of 9.6.

  The reflector 2 according to the present embodiment includes a plurality of first columnar elements 20a, second columnar elements 20b, third columnar elements 20c, and fourth columnar elements 20d. The interval (period width a) between the one columnar element 20a to the fourth columnar element 20d is determined so as to satisfy the condition that the “specific bandwidth” is 20% or more.

FIG. 12 is a diagram showing the characteristics of the reflector according to the second embodiment of the present invention.
FIG. 12 shows the transmission characteristics S21 as A3 to D3 when different values are set for the parameters of the period width a during the simulation. Here, the graph shown in FIG. 12 is a simulation result based on an electromagnetic field simulator, similar to the graphs of FIGS. 5 and 6 showing the transmission characteristic S21 of the reflector 1 according to the first embodiment. Further, the simulation result is calculated using a simulation model (FIG. 4) equivalent to the calculation of the graphs of FIGS. 5 and 6 showing the characteristics of the reflector 1 according to the first embodiment. . The reflector 2 according to the present embodiment is fixed at r = 9.4 mm. Among the plurality of graphs shown in FIG. 12, for example, the graph indicated by the solid line A3 is the transmission characteristic of the reflector 2 when the period width a is set to a = 4.0r (37.5 mm). According to this graph, since the frequency band in which the transmission characteristic S21 is −10 dB or less is between about 4.0 GHz to 5.4 GHz, the band gap bandwidth is 1.4 GHz. Further, since the center frequency of the band gap bandwidth is 4.7 GHz, the ratio band is 1.4 / 4.7≈0.30 (30%).

FIG. 13 is a diagram summarizing the characteristics of the reflector according to the second embodiment of the present invention.
FIG. 13 summarizes the band gap bandwidth and the ratio band for the reflector 2 for each period width a. The period width a and the ratio band shown in each row of FIG. 13 correspond to the graphs A3 to D3 shown in FIG. The reflecting plate 2 for each periodic width a shown in FIG. 13 has a specific band of 23% at a = 2.9r (= 27.3 mm), a specific band of 30% at a = 4.0r (= 37.5 mm), and a = At 4.6r (= 43.1 mm), a specific bandwidth of 21% and a specific bandwidth of 20% or more are realized.

From FIG. 13, it can be read that the ratio band is 20% or more in the reflector 2 according to this embodiment when the condition of 2.9r ≦ a ≦ 4.6r is satisfied. Therefore, the reflecting plate 2 according to the present embodiment satisfies the condition of 2.9r ≦ a ≦ 4.6r, so that the specific band becomes 20% or more, and the band gap can be widened.
As described above, according to the second embodiment of the present invention, it is possible to provide a reflector and an antenna device in which the band gap band is widened to a specific band of 20% or more.

<Third Embodiment>
Hereinafter, an antenna device according to a third embodiment of the present invention will be described with reference to the drawings.
The antenna device 100 according to the third embodiment includes a reflector 3 described below instead of the reflector 1 according to the first embodiment. The antenna device 100 according to the present embodiment has the same configuration (FIG. 1) as the antenna device 100 according to the first embodiment.
FIG. 15 is a perspective view of a reflector plate according to the third embodiment of the present invention. FIG. 16 is a plan view of a reflecting plate according to the third embodiment of the present invention. Here, FIG. 16A is a plan view when the reflecting plate 3 is viewed from the direction of the y-axis arrow, and FIG. 16B is a view of the reflecting plate 3 viewed from the direction opposite to the arrow of the x-axis. FIG.
As shown in FIGS. 15, 16A, and 16B, the reflector 3 is a grid of hexagonal columnar elements made of a hexagonal columnar dielectric at equal intervals at a distance sufficiently shorter than the wavelength of the reflected radio wave. It is the board | substrate which makes the periodic arrangement structure which combined. Similar to the reflectors 1 and 2 according to the first embodiment or the second embodiment, the reflector 3 has a structure in which a reflective layer having a plane parallel to the xz plane is overlapped in four layers in the y-axis direction. doing. Specifically, as shown in FIG. 15, the reflecting plate 3 is formed by laminating four layers of a first reflecting layer 3A, a second reflecting layer 3B, a third reflecting layer 3C, and a fourth reflecting layer 3D. It has the structure formed.

  First, the first reflective layer 3A is a layer in which first columnar elements 30a made of a hexagonal columnar dielectric are periodically arranged in parallel and at equal intervals (periodic width a) on the same plane (on the xz plane). is there. In addition, the extending direction of the plurality of first columnar elements 30a arranged periodically is a direction parallel to the z-axis (FIGS. 15 and 16A). As shown in FIG. 15 and FIG. 16A, the first columnar elements 30a constituting the first reflective layer 3A are periodically arranged at regular intervals at intervals a. Each of the first columnar elements 30a has a hexagonal columnar shape whose bottom surface is a regular hexagon inscribed in a circle having a diameter r (FIGS. 16A and 16B).

  Similarly, the second reflective layer 3B is formed by periodically arranging second columnar elements 30b made of a hexagonal columnar dielectric in parallel and at equal intervals on the same plane (on the xz plane). Here, the plurality of second columnar elements 30b are periodically arranged with a plurality of first columnar elements 30a at equal intervals, that is, with a period width a. Further, the extending direction of the plurality of second columnar elements 30b arranged periodically is a direction parallel to the x-axis (FIGS. 15 and 16A). Accordingly, the plurality of second columnar elements 30b are arranged so as to be orthogonal to the plurality of first columnar elements 30a so that the sides of each side are in contact with each other at one point, and form a lattice shape together with the first columnar elements 30a. ing. Similarly to the first columnar element 30a, the bottom surface of the second columnar element 30b according to the present embodiment has a hexagonal columnar shape formed of a regular hexagon inscribed in a circle having a diameter r. (FIG. 16 (a), (b)).

  Similarly, the third reflective layer 3C is a layer in which third columnar elements 30c made of a hexagonal columnar dielectric are periodically arranged in parallel and at equal intervals on the same plane (on the xz plane). Here, the plurality of third columnar elements 30c are arranged so as to be parallel to the first columnar elements 30a of the first reflective layer 3A (the extending direction of the third columnar elements 30c is a direction parallel to the z-axis). Is done. The interval (period width) between the third columnar elements 30c is the same period width a as that of the first columnar element 30a and the second columnar element 30b. However, as shown in FIGS. 15 and 16A, the plurality of third columnar elements 30c are arranged so as to be shifted from the first columnar element 30a by a half period (a / 2). Further, as shown in FIG. 16B, the third reflective layer 3C is arranged in contact with the second reflective layer 3B so as to sandwich the second reflective layer 3B together with the first reflective layer 3A. The Accordingly, the plurality of third columnar elements 30c are arranged orthogonal to the plurality of second columnar elements 30b so that one side of each side surface contacts at one point. Note that all the third columnar elements 30c have a hexagonal columnar shape formed of regular hexagons whose bottom surfaces are inscribed in a circle having a diameter r, as in the first columnar element 30a and the second columnar element 30b (FIG. 16). (A), (b)).

  The fourth reflective layer 3D is a layer in which the fourth columnar elements 30d made of hexagonal columnar dielectrics are periodically arranged in parallel and at equal intervals on the same plane (on the xz plane). Here, the plurality of fourth columnar elements 30d are arranged so as to be parallel to the second columnar elements 30b of the second reflective layer 3B (the extending direction of the fourth columnar elements 30d is a direction parallel to the x-axis). Is done. Further, the interval (period width) between the fourth columnar elements 30d is the same period width a as that of the first columnar element 30a, the second columnar element 30b, and the third columnar element 30c. However, as shown in FIGS. 15 and 16A, the plurality of fourth columnar elements 30d are arranged so as to be shifted from the second columnar element 30b by a half period (a / 2). Further, as shown in FIG. 16B, the fourth reflective layer 3D is disposed in contact with the third reflective layer 3C so as to sandwich the third reflective layer 3C together with the second reflective layer 3B. The Therefore, the plurality of fourth columnar elements 30d are arranged orthogonal to the plurality of third columnar elements 30c so that the sides of each side face at one point. Note that all the fourth columnar elements 30d have a hexagonal columnar shape whose bottom surface is inscribed in a circle having a diameter r, similarly to the first columnar element 30a, the second columnar element 30b, and the third columnar element 30c. (FIGS. 16A and 16B).

  As described above, the reflecting plate 3 according to the present embodiment is a plate-like layer having a thickness of 4r in which the first reflecting layer 3A to the fourth reflecting layer 3D are stacked in the y-axis direction (FIG. 16 ( b)). 15 and 16 (a) and 16 (b) show only one region of the reflector 3 (only the width corresponding to two cycles), the reflector 3 is actually not shown in FIG. 15 and the structure shown in FIGS. 16A and 16B are repeatedly arranged in the x-axis direction and the z-axis direction and spread on the xz plane. Further, as described above, the first columnar element 30a to the fourth columnar element 30d constituting the reflector 3 according to the present embodiment are all formed of a dielectric having a relative dielectric constant ε0 of 9.6.

  The reflector 3 according to the present embodiment has a size of the bottom surface of each of the first columnar element 30a, the second columnar element 30b, the third columnar element 30c, and the fourth columnar element 30d (diameter r of a regular hexagonal circumscribed circle). ) And the interval (period width a) between the plurality of first columnar elements 30a to 4d columnar elements 30d are determined so as to satisfy the condition that the “ratio band” is 20% or more.

FIG. 16 is a diagram showing the characteristics of the reflector according to the third embodiment of the present invention.
In FIG. 16, the transmission characteristics S <b> 21 are indicated by A <b> 4 to D <b> 4 when different values are set for the parameters of the period width a during the simulation. Here, the graph shown in FIG. 16 is a simulation result based on an electromagnetic field simulator, similar to the graphs of FIGS. 5 and 6 showing the characteristics of the reflector 1 according to the first embodiment. Further, the simulation result is calculated using a simulation model (FIG. 4) equivalent to the calculation of the graphs of FIGS. 5 and 6 showing the characteristics of the reflector 1 according to the first embodiment. . The reflector 3 according to this embodiment is fixed at r = 9.4 mm. Among the plurality of graphs shown in FIG. 16, for example, a graph indicated by a solid line A <b> 4 is a transmission characteristic of the reflecting plate 3 when the period width a is set to a = 4.0r (37.5 mm). According to this graph, since the frequency band in which the transmission characteristic S21 is −10 dB or less is between about 4.0 GHz to 5.4 GHz, the band gap bandwidth is 1.4 GHz. Further, since the center frequency of the band gap bandwidth is 4.7 GHz, the ratio band is 1.4 / 4.7≈0.30 (30%).

FIG. 17 is a diagram summarizing the characteristics of the reflector according to the third embodiment of the present invention.
FIG. 17 summarizes the band gap bandwidth and the ratio band for the reflector 3 for each period width a. The numerical values shown in each row in FIG. 17 correspond to the respective graphs shown in FIG. The reflector 3 for each period width a shown in FIG. 17 has a specific band of 23% at a = 2.9r (= 27.3 mm), a specific band of 30% at a = 4.0r (= 37.5 mm), and a = At 4.6r (= 43.1 mm), a specific bandwidth of 21% and a specific bandwidth of 20% or more are realized.

Therefore, it can be read that the ratio band is 20% or more in the reflector 3 according to this embodiment when the condition of 2.9r ≦ a ≦ 4.6r is satisfied. Therefore, even if the reflecting plate 3 according to the present embodiment is a hexagonal cross section of the columnar element, 2.9r ≦ a ≦ 4.6r as in the case of a cylinder (second embodiment). By satisfying the above condition, the specific band becomes 20% or more, and a wide band gap can be realized.
As described above, according to the third embodiment of the present invention, it is possible to provide a reflector and an antenna device in which the band gap band is widened to a specific band of 20% or more.

  In the present embodiment, the bottom surfaces of the columnar elements 30a to 30d are regular hexagons inscribed in a circle having a diameter r. However, in other embodiments of the present invention, the present invention is not limited to this aspect. That is, the reflecting plate according to the other embodiment may be configured such that the bottom surface of the columnar element is a polygon of hexagon or more inscribed in a circle having a diameter r, and all the columnar elements 30a to 30d are polygonal columnar. Good. Even in such a case, characteristics equivalent to those of the reflector 2 described in the second embodiment can be obtained.

100 ... Antenna devices 1, 2, 3, 4 ... Reflectors 1A, 2A, 3A, 4A ... First reflective layer 1B, 2B, 3B, 4B ... Second reflective layer 1C, 2C, 3C, 4C ... 3rd reflective layer 1D, 2D, 3D, 4D ... 4th reflective layer 10a, 20a, 30a, 40a ... 1st columnar element 10b, 20b, 30b, 40b. ..Second columnar elements 10c, 20c, 30c, 40c... Third columnar elements 10d, 20d, 30d, 40d... Fourth columnar element 5.

Claims (6)

A reflector having a characteristic of reflecting electromagnetic waves belonging to a specific band gap band,
A columnar element made of a columnar dielectric is provided with a plurality of reflective layers that are periodically arranged in parallel and at equal intervals on the same plane,
The plurality of reflective layers are stacked while the columnar elements constituting each are arranged so as to be orthogonal to each other, and the size of the bottom surface of each of the columnar elements and the periodic arrangement of the columnar elements are arranged. The reflecting plate is configured such that a specific band of the band gap band is equal to or larger than a specific band of a frequency band of an electromagnetic wave used in a device including the reflecting plate. A first reflective layer in which first columnar elements made of a columnar dielectric are periodically arranged in parallel and at equal intervals on the same plane;
A plurality of second columnar elements made of columnar dielectrics are periodically arranged on the same plane at the same interval as the plurality of first columnar elements, and are in contact with the plurality of first columnar elements at right angles. A second reflective layer arranged,
A plurality of third columnar elements made of columnar dielectrics are parallel to the plurality of first columnar elements and on the same plane so as to be shifted by a half period from them at the same interval as the plurality of first columnar elements. And a third reflective layer that is arranged so as to sandwich the second reflective layer with the first reflective layer, and
A plurality of fourth columnar elements made of a columnar dielectric are parallel to the plurality of second columnar elements and on the same plane so as to be shifted by a half cycle at the same interval as the plurality of second columnar elements. And a fourth reflective layer that is arranged so as to sandwich the third reflective layer with the second reflective layer, and
The reflector according to claim 1, comprising: Each of the first columnar element, the second columnar element, the third columnar element, and the fourth columnar element has a square columnar shape having a square bottom surface of the same size, and a plurality of the first columnar elements The space | interval (a [mm]) of this and the length (w [mm]) of one side of the said square satisfy | fill the relationship of 3.4w <= a <= 4.9w. The reflection of Claim 2 characterized by the above-mentioned. Board. Each of the first columnar element, the second columnar element, the third columnar element, and the fourth columnar element forms a columnar shape having a circular bottom surface of the same size, and a plurality of the first columnar elements 3. The reflector according to claim 2, wherein the distance (a [mm]) of the circular arc and the circular diameter (r [mm]) satisfy a relationship of 2.9r ≦ a ≦ 4.6r. Each of the first columnar element, the second columnar element, the third columnar element, and the fourth columnar element forms a polygonal columnar shape having a polygonal bottom surface of the same shape, and a plurality of the first columnar elements The distance (a [mm]) of the polygon and the diameter (r [mm]) of the circumscribed circle of the polygon satisfy a relationship of 2.9r ≦ a ≦ 4.6r. reflector. The reflector according to any one of claims 1 to 5,
A radiating element that radiates electromagnetic waves in a predetermined frequency band;
With
The interval between the plurality of columnar elements is shorter than the wavelength of the electromagnetic wave.

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