JP2024006723A - antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna device capable of increasing gain.

SOLUTION: An antenna device having an EBG (Electromagnetic Band Gap) structure includes: a reflector with a reflection plate; a partial reflection plate provided so as to be opposed to the reflection plate of the reflector; and a primary radiator that emits an electric wave into a space between the reflection plate and the partial reflection plate. The reflector further has an inclination part arranged on at least a part of an end part of the reflection plate so as to be extended toward the partial reflection plate while being inclined with respect to the reflection plate. A height of an upper end of the inclination part to the reflection plate is equal to or more than half of a height of the partial reflection plate with respect to the reflection plate.

SELECTED DRAWING: Figure 3

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present disclosure relates to an antenna device.

Conventionally, a main reflector for radiating microwaves and a support substrate disposed in the opening of the main reflector and on which a sub-reflection pattern made of a plurality of metal objects are formed are provided, and the sub-reflector is The pattern is such that the metal objects in the center in the direction of the magnetic field are arranged with a predetermined first gap, and the metal objects outside the center metal objects are arranged with a second gap smaller than the first gap. There is a microwave antenna designed to do this. An inclined portion is provided between the bottom surface and the inner surface of the main reflector (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 2012-147158

Incidentally, although an inclined portion is provided between the bottom surface and the inner surface of the main reflector (the bottom of the edge of the main reflector), there is no particular description regarding the height of the inclined portion. If the height of the inclined portion is not sufficiently high, a sufficient amount of reflected waves will not be obtained between the plurality of sub-reflection patterns of the support substrate, and a sufficient gain of the microwave antenna will not be obtained.

Therefore, it is an object of the present invention to provide an antenna device that can increase the gain.

An antenna device according to an embodiment of the present disclosure includes a reflector having a reflector, a partial reflector provided opposite to the reflector of the reflector, and a space between the reflector and the partial reflector. An antenna device having an EBG (Electromagnetic Band Gap) structure including a primary radiator that radiates radio waves, wherein the reflector is disposed at at least a part of an end of the reflector, It further includes an inclined part that is inclined with respect to the reflecting plate and extends toward the partial reflecting plate, and the height of the upper end of the inclined part with respect to the reflecting plate is equal to the height of the partial reflecting plate with respect to the reflecting plate. It is more than half the height of

An antenna device that can increase gain can be provided.

FIG. 1 is a perspective view showing an example of the configuration of an antenna device according to an embodiment. FIG. 2 is a plan view showing an example of the configuration of an antenna device. FIG. 3 is a diagram showing an example of the configuration of a cross section taken along the line AA in FIGS. 1 and 2. FIG. FIG. 2 is a perspective view showing an example of the configuration of a partial reflection plate. It is a figure which shows an example of the structure of the lower surface side of a partial reflection plate. It is a figure showing an example of EBG mode and propagation mode. It is a figure which shows an example of the position of an inclined surface. FIG. 3 is a diagram illustrating an example of simulation results of maximum gain frequency characteristics of the antenna device. It is a figure which shows an example of the simulation result of the directivity of an antenna apparatus. It is a figure which shows an example of the simulation result of the directivity of an antenna apparatus. FIG. 7 is a diagram illustrating an example of simulation results of maximum gain frequency characteristics of an antenna device for comparison. It is a figure which shows an example of the simulation result of the directivity of the antenna device for comparison. It is a figure which shows an example of the simulation result of the directivity of the antenna device for comparison. It is a figure which shows an example of the cross-sectional structure of the antenna device of the 1st modification of embodiment. It is a figure which shows an example of the cross-sectional structure of the antenna device of the 2nd modification of embodiment. It is a figure which shows an example of the planar structure of the antenna device of the 3rd modification of embodiment. It is a figure which shows an example of the planar structure of the antenna device of the 4th modification of embodiment. 16 is a diagram showing an example of the configuration of a cross section taken along the line BB in FIG. 15. FIG. FIG. 2 is a diagram showing an example of electric field distribution of EBG mode radio waves and propagation mode radio waves. It is a figure which shows an example of the simulation result of the frequency characteristic of the maximum gain of the antenna apparatus of the 4th modification of embodiment. It is a figure which shows an example of the simulation result of the directivity of the antenna apparatus of the 4th modification of embodiment. It is a figure which shows an example of the simulation result of the directivity of the antenna apparatus of the 4th modification of embodiment. It is a figure which shows an example of the planar structure of the antenna device of the 5th modification of embodiment. 21 is a diagram showing an example of the configuration of a cross section taken along line CC in FIG. 20. FIG. It is a figure showing an example of a cell. It is a figure showing an example of a cell.

Hereinafter, embodiments to which the antenna device of the present disclosure is applied will be described. Hereinafter, the same elements may be denoted by the same numbers, and redundant explanations may be omitted.

In the following, the XYZ coordinate system will be defined and explained. A direction parallel to the X axis (X direction), a direction parallel to the Y axis (Y direction), and a direction parallel to the Z axis (Z direction) are orthogonal to each other. Furthermore, hereinafter, for convenience of explanation, the −Z direction side may be referred to as the lower side or lower side, and the +Z direction side may be referred to as the upper side or upper side. In addition, "planar view" refers to viewing in the XY plane. Further, in the following, the length, thickness, thickness, etc. of each part may be exaggerated to make the configuration easier to understand. In addition, words such as parallel, right angle, orthogonal, horizontal, perpendicular, up and down, and the like allow deviations to the extent that the effects of the embodiments are not impaired.

Furthermore, in the following explanation, "radio wave" is a type of electromagnetic wave, and generally, electromagnetic waves of 3 THz or less are called radio waves. Hereinafter, electromagnetic waves emitted from outdoor base stations or relay stations will be referred to as "radio waves," and when referring to electromagnetic waves in general, they will be referred to as "electromagnetic waves." Further, in the following, the term "millimeter wave" or "millimeter wave band" includes not only the frequency band of 30 GHz to 300 GHz, but also the quasi-millimeter wave band of 24 GHz to 30 GHz.

The antenna device of the embodiment is, for example, a device that is fixedly attached to an outdoor structure or the like as a base station, and transmits and outputs radio waves of a predetermined frequency by adjusting the amount of radio wave transmission.

The radio waves emitted by the antenna device of the embodiment are preferably radio waves in the millimeter wave band of the fifth generation mobile communication system (5G) or the like, or in the frequency band of 1 GHz to 40 GHz including Sub-6. Further, the radio waves emitted by the antenna device of the embodiment may be LTE (Long Term Evolution), LTE-A (LTE-Advanced), or UMB (Ultra Mobile Broadband). Furthermore, the radio waves emitted by the antenna device of the embodiment include IEEE802.11 (Wi-Fi (registered trademark)), IEEE802.16 (WiMAX (registered trademark)), IEEE802.20, UWB (Ultra-Wideband), Bluetooth ( (registered trademark) or LPWA (Low Power Wide Area). As the frequency of radio waves increases, propagation loss due to reflection and diffraction increases, and an antenna device with high gain is required. Therefore, the antenna device of the embodiment is more suitable for communication that handles relatively high frequencies. In the following, unless otherwise specified, the description will be made using a millimeter wave band and Sub-6 radio waves as an example.

<Embodiment>
FIG. 1 is a perspective view showing an example of the configuration of an antenna device 100 according to an embodiment. FIG. 2 is a plan view showing an example of the configuration of the antenna device 100. FIG. 3 is a diagram showing an example of the configuration of a cross section taken along the line AA in FIGS. 1 and 2.

<Configuration of antenna device 100>
Antenna device 100 includes a reflector 110, a partial reflector 120, and a slot antenna 130. Slot antenna 130 is an example of a primary radiator. The following description will be made using FIGS. 4 and 5 in addition to FIGS. 1 to 3. FIG. 4 is a perspective view showing an example of the configuration of the partial reflection plate 120. FIG. 5 is a diagram showing an example of the configuration of the lower surface side of the partial reflection plate 120.

In the antenna device 100, the height h between the reflective surface 111A of the reflector 111 of the reflector 110 shown in FIG. The distance is set to approximately 1/2. Therefore, the reflector 110 and the partial reflector 120 act as resonators for the radio waves radiated from the slot antenna 130 and propagated in the Z direction between the reflector 111 and the partial reflector 120. Since the resonator has a cutoff frequency, the antenna device 100 is an antenna device with an EBG (Electromagnetic Band Gap) structure. Regarding the height h, an error of, for example, about ±5% to ±10% is allowed with respect to 1/2 of the wavelength λ of the radio waves used by the antenna device 100 for communication.

Further, a part of the radio waves radiated from the slot antenna 130 propagates in the ±X direction between the reflector 110 and the partial reflector 120 without resonating in the resonators of the reflector 110 and the partial reflector 120. is known from the simulation results. The antenna device 100 reflects radio waves propagating in the ±X direction between the reflector 110 and the partial reflector 120 in the +Z direction at the inclined portion 112 of the reflector 110, and radiates the waves in the +Z direction through the partial reflector 120. By doing so, the gain of the antenna device 100 is improved. Here, as an example, the slot antenna 130 is configured to radiate radio waves propagating within the XZ plane.

<Configuration of reflector 110>
The reflector 110 has a reflecting plate 111 and two inclined parts 112. The reflecting plate 111 is a plate-shaped portion provided at the center of the reflector 110 in a plan view, and its upper surface is a reflecting surface 111A. The reflective surface 111A is a flat surface parallel to the XY plane. The reflector 111 is provided to reflect radio waves emitted from the slot antenna 130 and reflected by the lower surface 120A of the partial reflector 120 in the +Z direction.

The two inclined portions 112 are provided at the ends of the rectangular reflecting plate 111 on the ±X direction side in plan view, and have inclined surfaces 112A. That is, the two inclined portions 112 are provided on two opposing sides of the outer edge of the reflective plate 111 in plan view. The two inclined parts 112 are arranged so that the inclined surfaces 112A face each other in the X direction, but as an example, the shapes of the two inclined parts 112 are the same.

The inclined surface 112A extends from a position at the same height as the reflecting surface 111A on the lower end side of the inclined portion 112 to the upper end, and functions as a reflecting surface that reflects radio waves. The sloped surfaces 112A of the two sloped parts 112 are provided to reflect in the +Z direction radio waves radiated from the slot antenna 130 and propagated between the reflection plate 111 and the partial reflection plate 120 in the +X direction and the -X direction. It is being The inclined portion 112 is a columnar portion having a triangular XZ cross section and extending in the Y direction. The upper end of the inclined portion 112 is in contact with the lower surface 120A of the partial reflector 120, and supports the partial reflector 120.

Such an inclined portion 112 may be disposed on at least a portion of the end portion of the reflecting plate 111 and may extend toward the partial reflecting plate 120 while being inclined with respect to the reflecting plate 111 . By arranging the inclined portion 112 on at least part of the end of the reflector 111, the radio waves propagating in the ±X direction between the reflector 111 and the partial reflector 120 can be reflected in the +Z direction. be. Note that an opening may be provided at the end of the reflection plate 111 on the ±Y direction side, or a wall portion may be provided that covers at least a part of the end of the reflection plate 111 on the ±Y direction side. You can.

Here, as an example, a configuration in which the reflecting plate 111 and two inclined parts 112 are integrally formed will be described. The reflector 110 only needs to have at least the reflective surface 111A and the inclined surface 112A made of metal, but here, an embodiment in which the entire reflector 110 is made of metal will be described. However, the reflector 110 may be made of an insulator such as resin, and may have a configuration in which metal foil or the like is formed on the reflective surface 111A and the inclined surface 112A. Further, the reflector 110 may be made of a metal plate formed by bending a sheet metal to have a reflective surface 111A and an inclined surface 112A. When the reflector 110 is made of metal, for example, aluminum, iron, copper, stainless steel, brass, or the like can be used.

In addition, in order to make it possible to efficiently reflect radio waves emitted from the slot antenna 130 and propagating between the reflector 111 and the partial reflector 120 in the +X direction and the -X direction in the +Z direction, the inclined portion 112 is The height of the upper end relative to the reflecting plate 111 may be at least half the height h of the partial reflecting plate 120 relative to the reflecting plate 111. More specifically, the height of the upper end of the inclined portion 112 with respect to the reflective surface 111A of the reflective plate 111 is more than half the height h of the lower surface 120A of the partial reflective plate 120 with respect to the reflective surface 111A of the reflective plate 111. Good to have.

By setting the height of the upper end of the inclined portion 112 relative to the reflector 111 to be h/2 or more, the radiation is radiated from the slot antenna 130 and propagates between the reflector 111 and the partial reflector 120 in the +X direction and the -X direction. Radio waves can be efficiently reflected in the +Z direction by the inclined surface 112A, and the gain of the antenna device 100 can be improved. Note that, here, a configuration in which the inclined surface 112A extends from a position at the same height as the reflective surface 111A on the lower end side of the inclined portion 112 to the lower surface 120A of the partial reflector 120 will be described. As long as it extends to a height equal to or more than half of the height h of the partial reflector 120 with respect to the plate 111, it may be lower than the lower surface 120A of the partial reflector 120. In this case, a wall portion parallel to the YZ plane, for example, may be provided outside the inclined portion 112 in the X direction.

The inclination angle α of the inclined surface 112A is, for example, 45 degrees, but may be any angle within the range of 30 degrees to 60 degrees. The inclination angle α is the angle of the inclined surface 112A in the XZ plane with respect to the reflective surface 111A parallel to the XY plane. By setting the angle α within such a range, radio waves propagating in the +X direction and −X direction between the reflection plate 111 and the partial reflection plate 120 can be efficiently reflected in the +Z direction.

Furthermore, although a mode in which the partial reflector 120 is supported at the upper end of the inclined portion 112 will be described here, the partial reflector 120 may be supported by a support or the like provided separately from the inclined portion 112. Further, the reflecting plate 111 and the two inclined portions 112 may be provided as separate bodies, and their relative positions may be fixed.

<Partial reflector 120>
The partial reflector 120 includes a substrate 121 and a Frequency Selective Surface (FSS) structure 122 . The FSS structure section 122 is an example of a first FSS structure section.

The substrate 121 is a substrate made of an insulator, and an FSS structure portion 122 is provided on the upper surface. The substrate 121 is, for example, a rigid substrate that does not have flexibility. Flexibility is the property of an object to bend without breaking, as can be seen from its appearance. When the substrate 121 is a rigid substrate, for example, a substrate made of a prepreg made of glass cloth impregnated with epoxy resin and a core material bonded together, a substrate made of fluororesin such as PTFE (polytetrafluoroethylene), or a glass plate. etc. can be used. The lower surface of the substrate 121 is a lower surface 120A of the partial reflector 120, and is an opposing surface facing the reflective surface 111A of the reflector 111 of the reflector 110. The lower surface 120A is a flat surface parallel to the XY plane.

The FSS structure section 122 includes a plurality of conductor sections 122A arranged on the upper surface of the substrate 121 and one conductor section 122B arranged on the lower surface of the substrate 121. The FSS structure portion 122 is arranged at a position overlapping the reflection plate 111 in a plan view. Here, as an example, a configuration will be described in which the FSS structure part 122 is arranged at a position that overlaps with the reflection plate 111 in plan view but does not overlap with the inclined part 112. For example, on the ±X direction side of the FSS structure part 122 The outer edge of may have a portion that overlaps with the inclined portion 112.

Each conductor portion 122A is, for example, a rectangular conductor pattern when viewed from above. The conductor portion 122B is a conductor pattern that is arranged at a position overlapping with the plurality of conductor portions 122A in a plan view, and has a rectangular opening formed in the portion overlapping with each conductor portion 122A. The conductor parts 122A and 122B can be formed of a metal thin film such as copper, nickel, or gold, for example.

The length of the opening of the conductor portion 122B in the X direction and the Y direction is longer than the length of the conductor portion 122A in the X direction and the Y direction. Therefore, each conductor portion 122A is located inside the plurality of openings of the conductor portion 122A in plan view. A portion corresponding to one conductor portion 122A extracted and enlarged in FIG. 4 (one conductor portion 122A and a portion surrounding one opening of the conductor portion 122B) constitutes an FSS cell. The FSS structure section 122 has a periodic structure in which a plurality of FSS cells are arranged periodically.

The number Nx of the conductor sections 122A in the X direction and the number Ny of the conductor sections 122A in the Y direction are equal to the number of openings in the conductor section 122B in the X direction and the number of openings in the Y direction. Here, as an example, Nx=5 and Ny=5. Nx and Ny are determined appropriately according to the lengths and pitches of the conductor parts 122A and 122B in the X and Y directions when setting the lengths of the FSS structure part 122 in the X and Y directions to 0.7λ or more. You can set it to a suitable number. The pitch of the conductor portions 122A is the distance between the centers of the conductor portions 122A adjacent to each other in the X direction and the Y direction, and the pitch of the conductor portions 122A is the distance between the centers of the conductor portions 122A adjacent to each other in the X direction and the Y direction. It is the interval. λ is the wavelength of radio waves used by the antenna device 100 for communication. Note that the lengths of the conductor portions 122A and 122B in the X direction and the Y direction may be λ/2 or less, preferably λ/4 or less, and may be about λ/8.

The FSS structure portion 122 has a property of transmitting radio waves in a predetermined frequency band and blocking radio waves having frequencies other than the predetermined frequency band. The predetermined frequency band is set to a frequency band that includes the frequency of radio waves radiated by the antenna device 100, and is a frequency band that includes the resonant frequency of radio waves that resonate in the resonator between the reflector 111 and the partial reflector 120. It is. The FSS structure section 122 is configured so that the power of the radio waves transmitted in the +Z direction is an appropriate value, and the phase of the radio waves reflected in the -Z direction is approximately 180 degrees. The radio waves resonating in the resonator between the reflector 110 and the partial reflector 120 are transmitted little by little (partially) in the +Z direction. The expression that the phase upon reflection is approximately 180 degrees means, for example, that the phase upon reflection is 180 degrees ±30 degrees. Further, since the height h of the EBG structure is half a wavelength, the band is narrow, but by using the FSS structure section 122, the band can be widened while causing resonance. While the frequency of the radio waves radiated by the slot antenna 130 is 5 GHz, the frequency band in which the FSS structure section 122 resonates with the partial reflector is, for example, a 500 MHz band around 5 GHz. Furthermore, the smaller the amount of transmission through the partial reflector in the +Z direction, the higher the gain of the antenna, and in one example, the amount of transmission is from -1.3 dB to -2 dB near 5 GHz. Note that the power feeding section may be provided near the edge of the slot antenna 130 along the longitudinal direction, for example.

In addition, as an example, the pitch Px between the conductor parts 122A adjacent to each other in the X direction is 8 mm. The pitch Px is the distance between the centers of adjacent conductor portions 122A in the X direction. Further, the pitch Py between the conductor portions 122A adjacent to each other in the Y direction is, for example, 8 mm. The pitch Py is the distance between the centers of adjacent conductor portions 122A in the Y direction. The lengths of the conductor portion 122A in the X direction and the Y direction are both 7.3 mm, for example. Note that the pitch Px and the pitch Py may be different. Further, the lengths of the conductor portion 122A in the X direction and the Y direction may be different.

Further, the lengths of the opening of the conductor portion 122B in the X direction and the Y direction are both 6.5 mm, for example. Further, as an example, the thickness of the substrate 121 is 1.6 mm, the dielectric constant is 3, and the dielectric loss tan δ is 0.01. The metal used for the conductor parts 122A and 122B is copper, for example, and the thickness is 35 μm.

The FSS structure section 122 having such a configuration may have a rectangular shape with one side of 0.7λ or more in plan view, where λ is the wavelength in free space of the radio wave output by the antenna device 100. Here, as an example, the length of the conductor portion 122B on the lower surface of the substrate 121 (lower surface 120A of the partial reflector 120) is longer than the length in the X and Y directions of the region where the plurality of conductor portions 122A are provided on the upper surface of the substrate 121. Since the lengths in the X and Y directions are longer, the lengths of the conductor portion 122B in the X and Y directions need only be 0.7λ or more. By setting the lengths of the FSS structure section 122 in the X and Y directions to 0.7λ or more, the maximum gain can be increased by 3 dB or more compared to an antenna device that does not include the FSS structure section 122.

<Slot antenna 130>
The slot antenna 130 is realized, for example, by a slot (elongated opening) provided in the center of the reflector 111 in a plan view. As an example, the longitudinal direction of the slot antenna 130 is the Y direction, and the lateral direction (direction perpendicular to the longitudinal direction in plan view) is the X direction.

The slot antenna 130 excites an electromagnetic field when power is supplied to a feed point (not shown), and radiates radio waves whose polarization direction is in the X direction in the +Z direction. At this time, since the radio waves propagate to spread within the XZ plane including the slot antenna 130, the components of the mode (hereinafter referred to as EBG mode) that resonates between the reflector 110 and the partial reflector 120 and the reflected A mode component (hereinafter referred to as a propagation mode) that propagates in the ±X direction is generated between the reflector 110 and the partial reflector 120. In the slot antenna 130, propagation mode components that propagate in the ±X directions are likely to occur. The frequency of the radio waves radiated from the slot antenna 130 and resonated is, for example, 5 GHz.

Note that here, an embodiment will be described in which the slot antenna 130 provided on the reflecting plate 111 of the reflector 110 is used as the primary radiator. An antenna 130 may be arranged. Such a configuration will be described later using FIG. 13. Furthermore, although a mode in which the slot antenna 130 is used as the primary radiator will be described here, the primary radiator may be an antenna other than the slot antenna, such as a patch antenna.

<EBG mode and propagation mode>
FIG. 6 is a diagram showing an example of EBG mode and propagation mode. In FIG. 6, the white dashed arrow pointing in the +Z direction indicates the propagation direction of the EBG mode radio wave, and the dashed arrow pointing in the +X direction indicates the polarization direction of the EBG mode radio wave at a certain moment. EBG mode radio waves resonate in the resonator between the reflector 110 and the partial reflector 120, and the amount of radio wave transmission is adjusted by the FSS structure 122, so that components of a predetermined frequency are transmitted to the partial reflector 120. is transmitted and output in the +Z direction. In FIG. 6, an elliptical region indicated by fine dots between the reflector 110 and the partial reflector 120 indicates a region where resonance of EBG mode radio waves mainly occurs. EBG mode radio waves resonate in the resonator between the reflector 110 and the partial reflector 120, and the in-phase radio waves spread spherically in plan view, so resonance occurs in the elliptical region shown in gray.

In addition, in FIG. 6, the white dot-dash line arrows pointing in the ±X direction toward the inclined surface 112A and the white dot-dash line arrows pointing in the +Z direction from the inclined surface 112A refer to the propagation of radio waves in the propagation mode. A solid arrow that indicates the direction and is perpendicular to the white dot-dash line arrow indicates the polarization direction of the radio wave in the propagation mode at a certain moment. The radio wave in the propagation mode propagates in the ±X direction between the reflector 110 and the partial reflector 120, is reflected in the +Z direction by the inclined surface 112A, and is reflected by the substrate 121 at the end of the partial reflector 120 in the ±X direction. The signal passes through the section (the section where the FSS structure section 122 is not provided) and is output in the +Z direction.

The radio waves radiated from the slot antenna 130 into the space between the reflector 110 and the partial reflector 120 mainly have EBG mode components, and the proportion of propagation mode components is small. However, by reflecting the propagation mode component in the +Z direction on the inclined surface 112A, it is possible to increase the radio waves output from the partial reflector 120 in the +Z direction, so the gain of the antenna device 100 can be improved. Furthermore, if the outer edge of the FSS structure section 122 on the ±X direction side has a portion that overlaps with the inclined section 112, a structure that easily absorbs the shift in the X direction when attaching the partial reflector 120 to the reflector 110 can be obtained. It will be done.

Note that instead of using the partial reflector 120 having the FSS structure 122 as described above, the thickness of the substrate 121 can be changed to the electrical length λe of the wavelength λ of the radio wave output by the antenna device 100 without having the FSS structure 122. A partial reflection plate set to approximately 1/4 of that may be used. The electrical length λe is determined by the dielectric constant of the substrate 121. In this case, as the material of the substrate 121, it is preferable to use a dielectric material having a relatively large dielectric constant. This is because the wavelength shortening effect is large, contributing to miniaturization, etc., and since the amount of transmission through the partial reflection plate is small, the radio waves resonating in the resonator become stronger and the gain can be increased.

By using a partial reflector made of a substrate 121 with a thickness of λe/4, EBG mode radio waves are reflected at the lower surface of the partial reflector and reflected at the upper surface of the partial reflector 120 inside the partial reflector. The EBG mode radio waves transmitted are in the same phase, and the amount of transmission through the partial reflector can be reduced. When reflected by the lower surface of the partial reflector, the phase of the EBG mode radio wave advances by 180 degrees. Furthermore, the EBG mode radio waves that propagate inward from the lower surface of the partial reflector and are reflected at the upper surface have a longer path by λe/2 than the radio waves that are reflected from the lower surface of the partial reflector. Therefore, even if a partial reflector is used without the FSS structure 122 and the thickness of the substrate 121 is set to λe/4, the EBG mode radio waves are transmitted to the resonator between the reflector 110 and the partial reflector. It is possible to achieve a state of resonance. Even when including such a partial reflector, the antenna device 100 is an antenna device with an EBG structure.

<Position of inclined surface 112A>
FIG. 7 is a diagram showing an example of the position of the inclined surface 112A. In FIG. 7, similarly to FIG. 6, the broken line arrow indicates the polarization direction of the EBG mode radio wave at a certain moment, and the solid line arrow indicates the polarization direction of the propagation mode radio wave at a certain moment. The polarization direction of the EBG mode radio wave and the polarization direction of the propagation mode radio wave are at the same instant. Further, in FIG. 7, the position of the inclined surface 112A in the X direction will be described with the center 130C of the slot antenna 130 in the X direction as a point where the X coordinate is zero.

In order to ultimately improve the gain of the radio waves radiated in the +Z direction from the partial reflector 120 of the antenna device 100, the polarization direction of the EBG mode radio waves must be adjusted at the same height from the top surface of the partial reflector 120. (1), the polarization direction of the radio waves in the propagation mode radiated from the +X direction side of the FSS structure section 122, and (2) the polarization direction of the radio waves in the propagation mode radiated from the -X direction side of the FSS structure section 122. The direction (3) needs to be the same. This is because if the EBG mode radio wave and the propagation mode radio wave have the same phase, the radio waves will strengthen each other and the gain can be improved, but if they have opposite phases, they will weaken each other and the gain will decrease.

Here, ignoring the thickness of the partial reflector 120, the polarization direction (1) of the EBG mode radio wave on the upper surface of the partial reflector 120 and the polarization directions (2) and (3) of the propagation mode radio wave are Consider.

The EBG mode radio waves are radiated from the slot antenna 130 in the +Z direction and propagate by a height h (distance h) before reaching the upper surface of the partial reflector 120. Here, the height h is h=λ/2. That is, the EBG mode radio wave is radiated from the slot antenna 130 in the +Z direction and propagates by λ/2 before reaching the upper surface of the partial reflector 120.

Here, positions at a distance of 1/4 of the wavelength λ of the radio wave in the ±X direction from the center 130C of the slot antenna 130 in the X direction are defined as +X1 and -X1. A radio wave in a propagation mode that propagates in the +X direction from the slot antenna 130 between the reflector 110 and the partial reflector 120 has a polarization direction (2A1) at the +X1 position, and when the radio wave further propagates in the +X direction, Since it has a polarization direction (2A2) and is reflected by the inclined surface 112A at the +X2 position, it has a polarization direction (2A3) in the -Z direction and a polarization direction (2A4) of the reflected radio wave. become.

Similarly, the radio wave in the propagation mode that propagates in the -X direction from the slot antenna 130 between the reflector 110 and the partial reflector 120 has a polarization direction (3A1) at the -X1 position, and the radio wave further When propagating in the -X direction, it has a polarization direction (3A2), and at the -X2 position, it is reflected by the inclined surface 112A, so the polarization direction (3A3) in the +Z direction and the polarization direction of the reflected radio wave ( 3A4).

Polarization direction (2) of the radio wave in the propagation mode that is reflected in the +Z direction at a point S where the height of the inclined surface 112A with respect to the reflective surface 111A of the reflector plate 111 is h/2 and is radiated from the antenna device 100 in the +Z direction. In order for (3) and (3) to be in the same direction as the polarization direction (1) of the EBG mode radio wave, the difference in propagation distance between the propagation mode radio wave and the EBG mode radio wave on the upper surface of the partial reflector 120 must be should be nλ. Note that n is an integer of 1 or more.

The radio wave in the propagation mode is reflected at a point S where the height of the inclined surface 112A becomes h/2, and then propagates in the +Z direction by λ/4. Therefore, in order to make the difference in propagation distance nλ, the distance dx that the radio wave in the propagation mode propagates from the center 130C of the slot antenna 130 to the point S in the X direction should be (n+1/4)λ. . By setting the propagation distance dx from the center 130C of the slot antenna 130 to the point S to (n+1/4)λ, the radio wave in the propagation mode passes from the center 130C of the slot antenna 130 to the point S and reaches the upper surface of the partial reflector 120. It will propagate by a distance (n+1/2)λ before reaching , and the difference in propagation distance will be nλ. Note that the antenna device 100 is configured such that the value of n in the propagation distance difference nλ is different between the path reflected by the slope 112A on the +X direction side and the path reflected on the slope 112A on the -X direction side. There may be.

If the difference in propagation distance between the propagation mode radio wave and the EBG mode radio wave is nλ, the propagation mode radio wave and the EBG mode radio wave will be in the same phase on the surface of the partial reflector 120, and the EBG mode radio wave will be The polarization direction (1) is equal to the polarization directions (2) and (3) of the radio waves in the propagation mode. As a result, the EBG mode radio waves and the propagation mode radio waves have a reinforcing relationship. Such a phase relationship between the EBG mode radio waves and the propagation mode radio waves is maintained even when they are separated from the surface of the partial reflector 120 in the +Z direction.

In addition, although the polarization directions (2) and (3) of the radio waves in the propagation mode reflected at the point S where the height of the inclined surface 112A with respect to the reflecting surface 111A is h/2 have been explained, the inclined surface with respect to the reflecting surface 111A At the point where the height of 112A is lower than h/2, the propagation distance in the X direction becomes shorter and the propagation distance in the +Z direction becomes longer, so the total propagation distance is the same. The same holds true for the point where the height of the inclined surface 112A with respect to the reflecting surface 111A is higher than h/2, and the total propagation distance is the same. In order to explain the position of the inclined portion 112 with respect to the center 130C of the slot antenna 130, it is easiest to use a point S where the height becomes h/2, so here, as an example, the height becomes h/2. This is explained using point S.

In addition, although the case where the inclination angle α of the inclined surface 112A is 45 degrees has been described here, the same applies even if the inclination angle α is an angle other than 45 degrees. The inclined portion 112 may be arranged so that the distance dx to S is (n+1/4)λ. The tilt angle α may be set within a range of 30 degrees to 60 degrees.

<Simulation results>
FIG. 8 is a diagram showing an example of a simulation result of the maximum gain frequency characteristic of the antenna device 100. The horizontal axis shows the frequency (GHz), and the vertical axis shows the maximum gain (dBi) of the antenna device 100. Height h = 30 mm, distance dx from center 130C of slot antenna 130 in X direction to point S of inclined surface 112A on the ±X direction side is 79 mm, inclination angle α is 45 degrees, X direction and Y direction of conductor portion 122A The numbers Nx and Ny were both set to 21. These values are values when the resonant frequency of the resonator of the reflector 110 and the partial reflection plate 120 is set to 5 GHz. Further, the reflector 110 was a perfect conductor with a length in the X direction of 200 mm and a length in the Y direction of 400 mm.

When an electromagnetic field simulation was performed under these conditions, as shown in FIG. 8, the maximum gain of the antenna device 100 reached its maximum value (approximately 16.5 dBi) at 5 GHz.

9A and 9B are diagrams illustrating an example of a simulation result of the directivity of the antenna device 100. FIG. 9A shows the directivity in the XZ plane, and FIG. 9B shows the directivity in the YZ plane. The solid line shown in the direction of approximately ±10 degrees in FIGS. 9A and 9B indicates the half width of the main lobe, which is 18.2 degrees in FIG. 9A and 28.6 degrees in FIG. 9B. The directivity will be described later in comparison with the results of a comparative antenna device.

FIG. 10 is a diagram illustrating an example of simulation results of maximum gain frequency characteristics of a comparison antenna device. The horizontal axis shows the frequency (GHz), and the vertical axis shows the maximum gain (dBi) of the antenna device for comparison. The comparative antenna device has a configuration in which the inclined portion 112 of the reflector 110 is removed and the reflector 111 is enlarged in plan view along the XZ plane.

When an electromagnetic field simulation was performed under the same conditions as the antenna device 100, as shown in FIG. 10, the maximum gain of the comparative antenna device was the maximum value (approximately 15.5 dBi) at 5.2 GHz. . This value was about 1 dB lower than the maximum gain of the antenna device 100. That is, it was found that the antenna device 100 was able to improve the maximum gain by about 1 dB by having the inclined portion 112.

FIG. 11A and FIG. 11B are diagrams illustrating an example of a simulation result of directivity of an antenna device for comparison. FIG. 11A shows the directivity in the XZ plane, and FIG. 11B shows the directivity in the YZ plane. The solid line shown in the direction of approximately ±15 degrees in FIGS. 11A and 11B indicates the half width of the main lobe, which is 32.2 degrees in FIG. 11A and 26.8 degrees in FIG. 11B.

The directivity in the XZ plane of the antenna device 100 shown in FIG. 9A has reduced side lobes and a larger main lobe compared to the directivity in the XZ plane of the comparative antenna device shown in FIG. 11A. I understand. More specifically, the main lobe increased from 13.9 dBi in the comparative antenna device to 16.7 dBi in antenna device 100, and the side lobe ratio decreased from −11.5 dB to −16.9 dB. In FIGS. 9A and 11A, the level of the sidelobe ratio is indicated by a circle. This is considered to be because the radio waves in the propagation mode are efficiently reflected in the +Z direction, increasing the gain of the antenna device 100.

Further, the directivity in the YZ plane of the antenna device 100 shown in FIG. 9B is approximately the same in shape and size of the main lobe and side lobes as compared to the directivity in the YZ plane of the comparative antenna device shown in FIG. 11B. It was confirmed that the addition of the inclined portion 112 had no effect on the directivity in the YZ plane. Note that also in FIGS. 9B and 11B, the level of the sidelobe ratio is indicated by a circle.

Here, as an example, a configuration in which the inclined portion 112 is arranged such that the distance dx from the center 130C of the slot antenna 130 to the point S in the X direction is (n+1/4)λ has been described. . However, the position of the inclined portion 112 is not limited to such a position. As an example, if the distance dx from the center 130C of the slot antenna 130 to the point S in the X direction has a relationship of (n+1/4)λ±λ/8, then on the +Z direction side of the partial reflector 120, It was confirmed that the phase of the EBG mode radio wave and the phase of the propagation mode radio wave could be made substantially the same, and that the gain of the antenna device 100 could be improved. This is because if the difference between the phase of the EBG mode radio wave and the phase of the propagation mode radio wave is within ±45 degrees, they are considered to be substantially in phase.

<Effect>
As described above, the antenna device 100 includes a reflector 110 having a reflector 111, a partial reflector 120 provided opposite to the reflector 111 of the reflector 110, and a space between the reflector 111 and the partial reflector 120. This is an antenna device 100 with an EBG structure including a slot antenna 130 that radiates radio waves into a space. The reflector 110 further includes an inclined portion 112 disposed on at least a portion of the end portion of the reflecting plate 111 and extending toward the partial reflecting plate 120 at an angle with respect to the reflecting plate 111. The height of the upper end of the partial reflector 112 with respect to the reflector 111 is more than half the height of the partial reflector 120 with respect to the reflector 111. Therefore, among the radio waves radiated from the slot antenna 130 , components in the propagation mode rather than in the EBG mode can be efficiently reflected toward the partial reflector 120 at the inclined portion 112 .

Therefore, it is possible to provide the antenna device 100 that can increase the gain. Further, by adding the inclined portion 112 to the reflector 110, it is possible to realize the antenna device 100 that can increase the gain, so that the antenna device 100 can be made smaller and lower in price. Furthermore, the distribution of the EBG mode radio waves that pass through the partial reflector 120 and the radio waves that are reflected by the incline 112 and pass through the partial reflector 120 can be set depending on the position of the inclined portion 112, so the gain can be set. A possible antenna device 100 can be provided.

In addition, since the inclined portions 112 are provided at least on two opposing sides of the outer edge of the reflector 111 in a plan view, the radio waves in the propagation mode that are radiated from the slot antenna 130 and propagate in the direction toward the two sides are efficiently controlled. can be reflected toward the partial reflector 120. Therefore, it is possible to provide the antenna device 100 that can increase the gain by efficiently reflecting the radio waves in the propagation mode propagating in the direction toward the two sides.

In addition, since the inclination angle α of the inclined portion 112 with respect to the reflection plate 111 is within the range of 30 degrees to 60 degrees, efficient reflection of radio waves in the propagation mode at the inclined portion 112 and miniaturization can be achieved. A possible antenna device 100 can be provided.

Further, the primary radiator is the slot antenna 130, and the inclined portion 112 is arranged at a portion of the end portion of the reflecting plate 111 that is located on the extension of the slot antenna 130 in the lateral direction. Since the radio waves radiated from the slot antenna 130 propagate in the lateral direction of the slot antenna 130, a sloped portion 112 is formed at the end of the reflector 111 at a portion located on the extension of the slot antenna 130 in the lateral direction. By arranging the antenna device 100, it is possible to reliably reflect propagation mode radio waves toward the partial reflector 120 and increase the gain more efficiently.

Furthermore, since the upper end of the inclined portion 112 extends to the partial reflector 120, it is possible to reflect radio waves of all propagation modes in the space between the reflector 110 and the partial reflector 120, further increasing the gain. A possible antenna device 100 can be provided.

Further, the distance dx in plan view between the position in the X direction of the point S at which the height of the inclined surface 112A of the inclined part 112 reaches a predetermined height and the center of the radiating part of the slot antenna 130 is the free space of radio waves. When the wavelength in is λ, it is (n+1/4)λ±λ/8 (n is an integer of 1 or more), and the predetermined height is half the height h of the partial reflector 120 with respect to the reflector 111. (h/2). Therefore, the EBG mode radio waves and the propagation mode radio waves radiated from the partial reflector 120 in the +Z direction can be made to have the same phase, and it is possible to provide the antenna device 100 that can increase the gain more effectively. Note that the X direction is a direction connecting the inclined portion 112 and the slot antenna 130.

Further, the partial reflector 120 has an FSS structure 122 arranged at a position overlapping with the reflector 111 in plan view, and the FSS structure 122 defines the wavelength in free space of the radio waves radiated by the slot antenna 130 as λ. Then, it has a rectangular shape with one side of 0.7λ or more in plan view. Therefore, a resonator in which the EBG mode radio waves resonate in the space between the reflector 110 and the partial reflector 120 can be realized, and the area of the radiation surface of the EBG mode radio waves transmitted through the partial reflector 120 in the +Z direction can be reduced. It is possible to provide the antenna device 100 that can increase the gain more effectively. Further, since the height h of the EBG structure is half a wavelength, the band is narrow, but by using the FSS structure section 122, the band can be widened, and the antenna device 100 can have a wide band.

In addition, when the antenna device 100 has a portion where the outer edge of the FSS structure portion 122 and the inclined portion 112 overlap in a plan view, the antenna device 100 absorbs a shift in the X direction when the partial reflector 120 is attached to the reflector 110. It is possible to provide the antenna device 100 with an easy configuration.

<First modification example>
FIG. 12 is a diagram showing an example of a cross-sectional structure of an antenna device 100M1 according to a first modification of the embodiment. The cross section shown in FIG. 12 corresponds to the cross section shown in FIG. 3.

The antenna device 100M1 differs from the antenna device 100 shown in FIG. 3 in that the slope angle α of the slope portion 112 on the +X direction side is set to 30 degrees. The other configurations are similar to the antenna device 100 shown in FIG. 3.

In the antenna device 100M1, the inclined portion 112 on the +X direction side and the inclined portion 112 on the −X direction side have different inclination angles. Therefore, the distance dx1 between the position in the X direction of the point S of the inclined part 112 on the +X direction side and the center 130C of the radiating part of the slot antenna 130, and the distance The position in the direction and the distance dx2 between the center 130C of the radiation part of the slot antenna 130 are different.

In this way, even if the inclination angles of the two inclined parts 112 are different, the propagation mode component of the radio waves radiated from the slot antenna 130 can be efficiently directed toward the partial reflector 120 at the inclined part 112. It can be reflected. Therefore, it is possible to provide an antenna device 100M1 that can increase the gain. Furthermore, it is possible to provide an antenna device 100M1 that can be made smaller and lower in price, and whose gain can be set.

<Second modification example>
FIG. 13 is a diagram showing an example of a cross-sectional structure of an antenna device 100M2 according to a second modification of the embodiment. The cross section shown in FIG. 13 corresponds to the cross section shown in FIG.

In the antenna device 100M2, the reflecting plate 111 of the reflector 110 has an opening 111B instead of the slot antenna 130, and the waveguide 140 having the slot antenna 130 is arranged below the reflecting plate 111. The antenna device 100M2 has a configuration including a reflector 110, a partial reflector 120, and a waveguide 140 having a slot antenna 130.

The opening 111B of the reflector 111 is larger than the opening of the slot antenna 130 in plan view, and the waveguide 140 is arranged so that the slot antenna 130 is included in the opening 111B in plan view. The waveguide 140 may be fixed to the reflector 110 or the like using a member (not shown) or the like. The slot antenna 130 radiates radio waves into the space between the reflector 111 and the partial reflector 120 through the opening 111B.

Furthermore, since the distance dx from the center 130C of the slot antenna 130 to the point S has a relationship of (n+1/4)λ±λ/8, the phase of the EBG mode radio wave is and the phase of the radio wave in the propagation mode can be made substantially the same phase.

Also in such an antenna device 100M2, similarly to the antenna device 100, among the radio waves radiated from the slot antenna 130 and radiated into the space between the reflector 110 and the partial reflector 120 through the opening 111B, the propagation mode The resulting component can be efficiently reflected by the inclined portion 112 toward the partial reflection plate 120. Therefore, it is possible to provide the antenna device 100M2 that can increase the gain. Furthermore, by making the waveguide 140 thinner, the antenna device 100M2 can be made smaller.

<Third modification example>
FIG. 14 is a diagram illustrating an example of a planar structure of an antenna device 100M3 according to a third modification of the embodiment. The planar structure shown in FIG. 14 corresponds to the planar structure shown in FIG. 2.

Antenna device 100M3 adds two inclined portions 113 provided at the ends of the reflection plate 111 in the ±Y direction to antenna device 100 shown in FIG. 2, and instead of slot antenna 130 shown in FIG. It has a configuration in which two slot antennas 130A and 130B are provided on a reflecting plate 111 of a reflector 110.

The slot antenna 130A is obtained by moving the slot antenna 130 shown in FIG. 2 slightly in the -X direction, with the longitudinal direction being the Y direction and the transverse direction being the X direction, and is different from the slot antenna 130 shown in FIG. Similarly, it emits radio waves.

The slot antenna 130B is provided on the +X direction side of the slot antenna 130A, and its longitudinal direction is the X direction and its transversal direction is the Y direction. The slot antenna 130B excites an electromagnetic field when power is supplied to a feeding point (not shown), and radiates radio waves whose polarization direction is in the Y direction in the +Z direction. At this time, since the radio waves propagate to spread within the YZ plane including the slot antenna 130B, the EBG mode component that resonates between the reflector 110 and the partial reflector 120 and the component of the EBG mode that resonates between the reflector 110 and the partial reflector 120 A propagation mode component propagating in the ±Y direction is generated between the two. In the slot antenna 130B, propagation mode components that propagate in the ±Y direction are likely to occur.

The radio waves in the propagation mode propagating in the ±Y direction are reflected in the +Z direction by the inclined portion 113 and radiated in the +Z direction from the portion of the partial reflector 120 that does not overlap with the FSS structure portion 122.

In the antenna device 100M3, the EBG mode radio waves among the radio waves radiated from the slot antenna 130A and the EBG mode radio waves among the radio waves radiated from the slot antenna 130B are transmitted to the reflecting plate 111 of the reflector 110. The light resonates with the partial reflector 120 and is radiated in the +Z direction of the partial reflector 120.

Furthermore, in the antenna device 100M3, among the radio waves radiated from the slot antenna 130A, radio waves in a propagation mode are reflected in the +Z direction by the inclined portion 112 and radiated in the +Z direction of the partial reflector 120. Further, among the radio waves radiated from the slot antenna 130B, radio waves in a propagation mode are reflected in the +Z direction by the inclined portion 113 and radiated in the +Z direction of the partial reflector 120.

The antenna device 100M3 includes two slot antennas 130A and 130B and two sets of inclined parts 112 and 113, so that one antenna device 100M3 can radiate two orthogonal polarized waves. Note that the frequencies of the radio waves radiated from the two slot antennas 130A and 130B may be different. When the frequencies of radio waves are different, the band in which antenna device 100M3 can communicate can be further expanded.

<Fourth variation>
FIG. 15 is a diagram illustrating an example of a planar structure of an antenna device 100M4 according to a fourth modification of the embodiment. The planar structure shown in FIG. 15 corresponds to the planar structure shown in FIG. 2. FIG. 16 is a diagram showing an example of the configuration of a cross section taken along the line BB in FIG. 15. The cross section shown in FIG. 16 corresponds to the cross section shown in FIG. 3.

The antenna device 100M4 differs from the antenna device 100 shown in FIGS. 2 and 3 in that it includes a dielectric 150 disposed on a portion of the upper surface of the partial reflector 120 that overlaps with the inclined portion 112. The other configurations are similar to the antenna device 100 shown in FIGS. 2 and 3.

Here, before explaining the configuration, operation, and effect of the antenna device 100M4 using FIGS. 15 and 16, the relationship between the distribution and gain of EBG mode radio waves and propagation mode radio waves will be explained using FIG. 17. do. FIG. 17 is a diagram showing an example of electric field distribution of EBG mode radio waves and propagation mode radio waves on the upper surface of the partial reflection plate 120.

In FIGS. 17A to 17C, the darker the color, the stronger the electric field, and the lighter the color, the weaker the electric field. In addition, in FIGS. 17(A) to (C), the concentric electric field distribution at the center in the X direction indicates the electric field distribution of EBG mode radio waves, and the electric field distribution in the Y direction on the ±X direction side of the EBG mode electric field distribution The long elliptical electric field distribution indicates the electric field distribution of a radio wave whose propagation mode is reflected by the inclined portion 112 and radiated in the +Z direction. The way the electric field distribution in the EBG mode spreads varies depending on the design of the partial reflector 120.

The distribution of EBG mode radio waves and propagation mode radio waves is as shown in FIG. 17(A) as an example. Ideally, there should be an electric field distribution. In this case, as shown in FIG. 17B, if the electric field distribution of the EBG mode radio wave and the electric field distribution of the propagation mode radio wave overlap, the effective area does not increase and it is difficult to improve the gain. Furthermore, as shown in Fig. 17(C), if the electric field distribution of the propagation mode radio wave is separated from the electric field distribution of the EBG mode radio wave like an isolated island, the effective area will increase, so an improvement in gain can be expected. , which causes characteristic deterioration such as the generation of side lobes. Therefore, as shown in FIG. 17A, the ideal positional relationship is such that the electric field distribution of the propagation mode radio waves is adjacent to the electric field distribution of the EBG mode radio waves in the ±X direction.

In order to realize such a relationship between the electric field distribution of EBG mode radio waves and the electric field distribution of propagation mode radio waves, the position of the inclined portion 112 in the X direction can be controlled at the design stage. If it can be brought closer to the portion 122, it becomes easier to realize an ideal positional relationship.

From this point of view, in the antenna device 100M4, the dielectric 150 is arranged in a portion of the upper surface of the partial reflector 120 that overlaps with the inclined portion 112. When a propagation mode radio wave reflected in the +Z direction by the inclined portion 112 passes through the dielectric 150, the electrical length is extended due to the wavelength shortening effect according to the dielectric constant of the dielectric 150. Therefore, compared to the antenna device 100 (see FIGS. 1 to 6) that does not include the dielectric 150, the distance between the two inclined portions 112 in the X direction can be shortened.

In such a case, the thickness t of the dielectric 150 is such that the EBG mode radio waves transmitted through the partial reflector 120 in the +Z direction and the propagation mode radio waves transmitted through the partial reflector 120 and the dielectric 150 are in phase. is expressed by the following equation (1). Note that the distance in the X direction between the point S where the height of the inclined surface 112A of the inclined part 112 becomes h/2 and the center 130C of the slot antenna 130 is dx, n is an integer of 1 or more, and λ is the radio wave. The wavelength εr is the relative dielectric constant of the dielectric 150 at the wavelength λ. Note that ±λ/8√εr in equation (1) means that the range of phase difference of ±45 degrees is treated as the same phase.

Furthermore, when formula (1) is modified, the distance dx is expressed by the following formula (2).

That is, by providing the dielectric 150, the distance dx in the X direction from the center 130C of the slot antenna 130 can be shortened by t(√εr−1). Note that the two dielectrics 150 are the same, and the two inclined portions 112 have a shape that is line symmetrical with respect to an axis parallel to the Z axis passing through the center 130C of the slot antenna 130 in the XZ cross section shown in FIG. Therefore, the arrangement of the two dielectrics 150 is symmetrical with respect to an axis parallel to the Z-axis passing through the center 130C of the slot antenna 130. Note that the antenna device 100M4 has a configuration in which the value of n of the propagation distance difference nλ differs between the path reflected by the slope 112A on the +X direction side and the path reflected by the slope 112A on the -X direction side. There may be. In this case, the arrangement of the two dielectrics 150 is asymmetrical with respect to an axis passing through the center 130C of the slot antenna 130 and parallel to the Z-axis.

<Simulation results>
FIG. 18 is a diagram showing an example of a simulation result of the maximum gain frequency characteristic of the antenna device 100M4. The horizontal axis shows the frequency (GHz), and the vertical axis shows the maximum gain (dBi) of the antenna device 100M4. Height h = 30 mm, distance dx from center 130C of slot antenna 130 in X direction to point S of inclined surface 112A on the ±X direction side is 65 mm, inclination angle α is 45 degrees, X direction and Y direction of conductor portion 122A The numbers Nx and Ny of the two dielectrics 150 were both set to 13, and the thickness t of the two dielectrics 150 was set to 17 mm. These values are values when the resonant frequency of the resonator of the reflector 110 and the partial reflection plate 120 is set to 5 GHz.

When an electromagnetic field simulation was performed under these conditions, as shown in FIG. 18, the maximum gain of the antenna device 100M4 reached its maximum value (approximately 15.3 dBi) at 5 GHz.

FIG. 19A and FIG. 19B are diagrams showing an example of a simulation result of the directivity of the antenna device 100M4. FIG. 19A shows the directivity in the XZ plane, and FIG. 19B shows the directivity in the YZ plane. The solid line shown in the direction of approximately ±15 degrees in FIGS. 19A and 19B indicates the half width of the main lobe, which is 26.8 degrees in FIG. 19A and 28.5 degrees in FIG. 9B.

The directivity in the XZ plane of the antenna device 100M4 shown in FIG. 19A has a slightly larger side lobe compared to the directivity in the XZ plane of the antenna device 100 shown in FIG. 9A, but it is better than the comparative antenna device shown in FIG. It was also found that the main lobe had become larger. The main lobe was 15.3 dBi, and the side lobe ratio was -12.2 dB. In FIG. 19A, the level of the sidelobe ratio is indicated by a circle.

Further, it was confirmed that the directivity in the YZ plane of the antenna device 100M4 shown in FIG. 19B is similar to the directivity in the YZ plane of the antenna device 100 shown in FIG. 9B, but the main lobe is slightly smaller. The main lobe was 15.7 dBi, and the side lobe ratio was -20.4 dB. In FIG. 19B, the level of the sidelobe ratio is indicated by a circle.

As described above, if the positional relationship between the electric field distribution of the EBG mode radio wave and the electric field distribution of the propagation mode radio wave is determined based on equation (2), the electric field distribution of the propagation mode radio wave and the EBG mode radio wave can be determined. The effective area with the electric field distribution can be effectively increased, and the gain can be effectively improved. Note that the dielectric 150 may be disposed only on either the +X direction side or the -X direction side.

<Fifth modification example>
FIG. 20 is a diagram illustrating an example of a planar structure of an antenna device 100M5 according to a fifth modification of the embodiment. The planar structure shown in FIG. 20 corresponds to the planar structure shown in FIG. 2. FIG. 21 is a diagram showing an example of the configuration of a cross section taken along the line CC in FIG. 20. The cross section shown in FIG. 21 corresponds to the cross section shown in FIG. 3.

The antenna device 100M5 differs from the antenna device 100 shown in FIGS. 2 and 3 in that it includes an FSS structure portion 160 disposed on a portion of the upper surface of the partial reflector 120 that overlaps with the slope portion 112. The FSS structure section 160 is an example of a second FSS structure section. The other configurations are similar to the antenna device 100 shown in FIGS. 2 and 3.

The FSS structure section 160 includes a plurality of cells 160C that can advance or delay the phase of transmitted radio waves. 22A and 22B are diagrams showing an example of a cell 160C. 22A and 22B, like the enlarged portion in FIG. 4, a portion corresponding to one cell 160C of the substrate 121 of the partial reflection plate 120 is extracted and shown. Note that, as an example, the FSS structure section 160 does not have a conductor on the lower surface (the surface on the -Z direction side) of the substrate 121. However, even if the FSS structure section 160 has a conductor on the lower surface of the substrate 121 (the surface on the -Z direction side) and does not have a conductor on the upper surface of the substrate 121 (the surface on the +Z direction side), good. Further, the FSS structure section 160 may have a conductor on both the lower surface and the upper surface of the substrate 121.

A cell 160C shown in FIG. 22A is a rectangular metal foil formed on the upper surface (+Z direction side surface) of the substrate 121. Such a cell 160C delays the phase of the radio wave that enters and passes from the −Z direction side.

A cell 160C shown in FIG. 22B is a rectangular ring-shaped (rectangular forehead-shaped) metal foil formed on the upper surface (+Z direction side surface) of the substrate 121. Such a cell 160C advances the phase of a radio wave that is incident and transmitted from the -Z direction side. Note that the cell 160C shown in FIGS. 22A and 22B can be formed of a metal thin film such as copper, nickel, or gold, for example.

The FSS structure section 160 has a configuration in which cells 160C shown in FIG. 22A or 22B are periodically arranged in the X direction and the Y direction. The amount of phase change given to the radio wave by the cell 160C shown in FIGS. 22A and 22B is, for example, ±45 degrees. When the amount of phase change given to the radio wave by the cell 160C is ±45 degrees, the transmittance of the radio wave is approximately 50%. Although it is possible to make the amount of phase change larger in absolute value than ±45 degrees, the transmittance of radio waves will further decrease, so if the amount of phase change is within the range of ±45 degrees, it is relatively unusable. Cheap.

The radio wave in the propagation mode is transmitted through the partial reflector 120 and the FSS structure 160, and is radiated in the +Z direction. Since the phase of the radio wave is advanced or delayed when passing through the FSS structure portion 160, the effect of shortening or lengthening the path length can be obtained, substantially similar to the antenna device 100M4 of Modification 4. Therefore, in order to make the EBG mode radio waves that pass through the FSS structure section 122 and the propagation mode radio waves that pass through the FSS structure section 160 have the same phase, the antenna device 100 (see FIGS. 1 to 6) The distance between the two inclined portions 112 can be made longer or shorter than that shown in FIG. The positional relationship between the electric field distribution of EBG mode radio waves and the electric field distribution of propagation mode radio waves can be controlled.

Specifically, the position of the inclined portion 112 may be determined as follows. When the amount of phase change given by the FSS structure 122 to the radio wave passing through the FSS structure 122 is φ(rad), and the amount of phase change given to the radio wave by the FSS structure 160 is δ(rad), in the X direction, The inclined portion 112 may be arranged so that the point S is located at a distance dx expressed by the following equation (3) from the center 130C of the slot antenna 130. Point S is a point where the height of the inclined surface 112A with respect to the reflective surface 111A is h/2.
dx=(n+1/4+φ/2π+δ/2π)λ (3)

When δ is positive (δ>0), the FSS structure 160 includes a cell 160C shown in FIG. 22B and advances the phase of the transmitted radio wave. When δ is negative (δ<0), the FSS structure 160 includes a cell 160C shown in FIG. 22A and delays the phase of the transmitted radio wave.

According to modification 5, by controlling the positional relationship between the electric field distribution of EBG mode radio waves and the electric field distribution of propagation mode radio waves at the design stage, the electric field distribution of propagation mode radio waves and the electric field distribution of EBG mode radio waves can be changed. It is possible to provide an antenna device 100M5 that can effectively increase the execution area and effectively improve the gain. Note that the FSS structure section 160 may be arranged only on either the +X direction side or the -X direction side. Further, the FSS structure portions 160 on the +X direction side and the −X direction side may have different shapes and may give different amounts of phase change to the radio waves.

Although the exemplary antenna device of the present disclosure has been described above, the present disclosure is not limited to the specifically disclosed embodiments, and various modifications and changes may be made without departing from the scope of the claims. is possible.

100, 100M1, 100M2, 100M3, 100M4, 100M5 Antenna device 110 Reflector 111 Reflector 111A Reflector 111B Opening 112 Inclined portion 112A Inclined surface 113 Inclined portion 120 Partial reflector 120A Lower surface 121 Substrate 122 FSS structure (first FSS structure example)
130, 130A, 130B Slot antenna 130C Center 140 Waveguide 150 Dielectric 160 FSS structure (an example of the second FSS structure)
160C cell

Claims (11)

a reflector having a reflector;
An EBG (Electromagnetic Band Gap) includes: a partial reflector provided to face the reflector of the reflector; and a primary radiator that radiates radio waves into a space between the reflector and the partial reflector. ) an antenna device having a structure,
The reflector further includes an inclined portion disposed at at least a portion of an end of the reflector, the inclined portion being inclined with respect to the reflector and extending toward the partial reflector,
In the antenna device, the height of the upper end of the inclined portion with respect to the reflector is equal to or more than half the height of the partial reflector with respect to the reflector. The antenna device according to claim 1, wherein the inclined portion is provided on at least two opposing sides of the outer edge of the reflector when viewed from above. The antenna device according to claim 1, wherein an angle of inclination of the inclined portion with respect to the reflector is within a range of 30 degrees to 60 degrees. the primary radiator is a slot antenna;
The antenna device according to claim 1, wherein the inclined portion is disposed at a portion of an end portion of the reflector that is located on an extension of the slot antenna in the lateral direction. The reflector has an opening,
The antenna device according to claim 1, wherein the primary radiator radiates radio waves into a space between the reflector and the partial reflector through the opening. The antenna device according to claim 1, wherein an upper end of the inclined portion extends to the partial reflector. a distance in plan view between a position in a direction connecting the inclined part and the primary radiator of a point at which the height of the inclined surface of the inclined part reaches a predetermined height and the center of the radiation part of the primary radiator; is (n+1/4)λ±λ/8 (n is an integer of 1 or more), where λ is the wavelength of the radio wave,
The antenna device according to any one of claims 1 to 6, wherein the predetermined height is half the height of the partial reflector with respect to the reflector. The partial reflector has a first Frequency Selective Surface (FSS) structure portion arranged at a position overlapping the reflector in plan view,
The antenna device according to claim 1, wherein the first FSS structure has a rectangular shape with one side of 0.7λ or more in plan view, where λ is the wavelength of the radio wave. The antenna device according to claim 8, wherein the outer edge of the first FSS structure portion and the inclined portion have a portion that overlaps in plan view. The partial reflector includes a dielectric provided in a region that overlaps with the inclined portion in a plan view,
The antenna device according to claim 1, wherein the thickness t of the dielectric is expressed by the following equation (1).

Here, n is an integer greater than or equal to 1, λ is the wavelength of the radio wave, εr is the dielectric constant of the dielectric material at the wavelength λ, and dx is the point at which the height of the sloped surface of the sloped portion reaches a predetermined height. The predetermined height is the distance in a plan view between the position in the direction connecting the inclined part and the primary radiator and the center of the radiating part of the primary radiator, and the predetermined height is the distance in a plan view between the position in the direction connecting the inclined part and the primary radiator, and the predetermined height is It is half the height of the board. The antenna device according to claim 1, wherein the partial reflector has a second Frequency Selective Surface (FSS) structure section arranged at a position overlapping the inclined section in a plan view.

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