Antenna equipment

Abstract

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

Description

Technical Field

[0001] The present disclosure relates to an antenna device.

Background Art

[0002] Conventionally, there has been provided a main reflector for radiating microwaves, and a support substrate disposed at an opening of the main reflector and having a sub-reflection pattern formed of a plurality of small metal bodies. In the sub-reflection pattern, the small metal bodies at the center in the magnetic field direction are arranged with a predetermined first gap therebetween, and the small metal bodies outside the small metal bodies at the center are arranged with a second gap smaller than the first gap. An inclined portion is provided between the bottom surface and the inner surface of the main reflector (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, 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), but there is no particular description about the height of the inclined portion. If the height of the inclined portion is not sufficiently high, a reflected wave reflected toward between the plurality of sub-reflection patterns of the support substrate cannot be sufficiently obtained, and the gain of the microwave antenna cannot be sufficiently obtained.

[0005] Therefore, an object is to provide an antenna device capable of increasing the gain.

Means for Solving the Problems

[0006] An antenna device according to an embodiment of the present disclosure is an EBG (Electromagnetic Band Gap) structure antenna device including a reflector having a reflector plate, a partial reflector provided opposite to the reflector plate of the reflector, and a primary radiator that radiates radio waves into the space between the reflector plate and the partial reflector, wherein the reflector further has an inclined portion arranged on at least a portion of the end of the reflector plate and extending toward the partial reflector plate at an angle to the reflector plate, and the height of the upper end of the inclined portion relative to the reflector plate is at least half the height of the partial reflector plate relative to the reflector plate. [Effects of the Invention]

[0007] We can provide an antenna device capable of increasing gain. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view showing an example of the configuration of the antenna device according to the embodiment. [Figure 2] This is a plan view showing an example of the configuration of an antenna device. [Figure 3] This figure shows an example of the configuration of the cross-section as seen by arrow AA in Figures 1 and 2. [Figure 4] This is a perspective view showing an example of the configuration of a partial reflector. [Figure 5] This figure shows an example of the configuration of the lower surface of a partial reflector. [Figure 6] This figure shows an example of EBG mode and propagation mode. [Figure 7] This figure shows an example of the position of an inclined surface. [Figure 8] This figure shows an example of the simulation results for the frequency characteristics of the maximum gain of an antenna device. [Figure 9A] This figure shows an example of simulation results for the directivity of an antenna device. [Figure 9B] This figure shows an example of simulation results for the directivity of an antenna device. [Figure 10]It is a diagram showing an example of the simulation result of the frequency characteristics of the maximum gain of the antenna device for comparison. [Figure 11A] It is a diagram showing an example of the simulation result of the directivity of the antenna device for comparison. [Figure 11B] It is a diagram showing an example of the simulation result of the directivity of the antenna device for comparison. [Figure 12] It is a diagram showing an example of the cross-sectional structure of the antenna device according to the first modification of the embodiment. [Figure 13] It is a diagram showing an example of the cross-sectional structure of the antenna device according to the second modification of the embodiment. [Figure 14] It is a diagram showing an example of the planar structure of the antenna device according to the third modification of the embodiment. [Figure 15] It is a diagram showing an example of the planar structure of the antenna device according to the fourth modification of the embodiment. [Figure 16] It is a diagram showing an example of the configuration of the cross-section taken along the line B-B in FIG. 15. [Figure 17] It is a diagram showing an example of the electric field distribution of the radio wave in the EBG mode and the radio wave in the propagation mode. [Figure 18] It is a diagram showing an example of the simulation result of the frequency characteristics of the maximum gain of the antenna device according to the fourth modification of the embodiment. [Figure 19A] It is a diagram showing an example of the simulation result of the directivity of the antenna device according to the fourth modification of the embodiment. [Figure 19B] It is a diagram showing an example of the simulation result of the directivity of the antenna device according to the fourth modification of the embodiment. [Figure 20] It is a diagram showing an example of the planar structure of the antenna device according to the fifth modification of the embodiment. [Figure 21] It is a diagram showing an example of the configuration of the cross-section taken along the line C-C in FIG. 20. [Figure 22A] It is a diagram showing an example of a cell. [Figure 22B] It is a diagram showing an example of a cell.

Embodiments of the Invention

[0009] The following describes embodiments to which the antenna device of this disclosure is applied. In the following, the same number may be used for the same element, and redundant explanations may be omitted.

[0010] The following describes the XYZ coordinate system. The directions parallel to the X-axis (X direction), parallel to the Y-axis (Y direction), and parallel to the Z-axis (Z direction) are mutually orthogonal. Also, for the sake of explanation, the -Z direction may be referred to as the lower side or bottom, and the +Z direction as the upper side or top. Furthermore, a plan view refers to a view from the XY plane. Also, in the following, the length, width, thickness, etc. of each part may be exaggerated to make the structure easier to understand. Furthermore, the terms parallel, right angle, orthogonal, horizontal, vertical, up and down, etc., should be used with a degree of deviation that does not impair the effect of the embodiment.

[0011] Furthermore, in the following explanation, "radio waves" refer to a type of electromagnetic wave, and generally, electromagnetic waves below 3 THz are called radio waves. Below, electromagnetic waves radiated from outdoor base stations or relay stations will be referred to as "radio waves," and when referring to electromagnetic waves in general, the term "electromagnetic wave" will be used. Also, below, when referring to "millimeter waves" or "millimeter wave band," it will include the quasi-millimeter wave band of 24 GHz to 30 GHz in addition to the frequency band of 30 GHz to 300 GHz.

[0012] The antenna device of this embodiment is, for example, a base station that is fixedly attached to an outdoor structure, and by adjusting the amount of radio wave transmission, it transmits and outputs radio waves of a predetermined frequency.

[0013] The radio waves radiated by the antenna device of this embodiment are preferably in the millimeter wave band, such as 5G, or in the frequency band of 1GHz to 40GHz, including Sub-6. Alternatively, the radio waves radiated by the antenna device of this embodiment may be LTE (Long Term Evolution), LTE-A (LTE-Advanced), or UMB (Ultra Mobile Broadband). Furthermore, the radio waves radiated by the antenna device of this embodiment may be IEEE802.11 (Wi-Fi®), IEEE802.16 (WiMAX®), IEEE802.20, UWB (Ultra-Wideband), Bluetooth®, or LPWA (Low Power Wide Area), etc. As the frequency of radio waves increases, propagation losses due to reflection and diffraction increase, requiring an antenna device with high gain. Therefore, the antenna device of this embodiment is more suitable for communications handling relatively high frequencies. In the following explanation, unless otherwise specified, millimeter wave and Sub-6 radio waves will be used as examples.

[0014] <Embodiment> Figure 1 is a perspective view showing an example of the configuration of the antenna device 100 according to the embodiment. Figure 2 is a plan view showing an example of the configuration of the antenna device 100. Figure 3 is a diagram showing an example of the configuration in the cross-section as seen by arrow AA in Figures 1 and 2.

[0015] <Configuration of antenna device 100> The antenna device 100 includes a reflector 110, a partial reflector 120, and a slot antenna 130. The slot antenna 130 is an example of a primary radiator. In the following description, in addition to Figures 1 to 3, Figures 4 and 5 will be used. Figure 4 is a perspective view showing an example of the configuration of the partial reflector 120. Figure 5 is a diagram showing an example of the configuration of the lower surface of the partial reflector 120.

[0016] In the antenna device 100, the height h between the reflective surface 111A of the reflector plate 111 of the reflector 110 shown in Figure 3 and the lower surface 120A of the partial reflector 120 is set to a distance equivalent to approximately half the wavelength λ of the radio waves used by the antenna device 100 for communication. Therefore, the reflector 110 and the partial reflector 120 behave as resonators for radio waves radiated from the slot antenna 130 and propagating in the Z direction between the reflector plate 111 and the partial reflector 120. Since resonators have a cutoff frequency, the antenna device 100 is an EBG (Electromagnetic Band Gap) antenna device. Regarding the height h, an error of approximately ±5% to ±10% is acceptable relative to half the wavelength λ of the radio waves used by the antenna device 100 for communication.

[0017] Furthermore, simulation results have shown that some of the radio waves radiated from the slot antenna 130 do not resonate in the resonators of the reflector 110 and the partial reflector 120, but propagate between the reflector 110 and the partial reflector 120 in the ±X direction. The antenna device 100 reflects the radio waves propagating between the reflector 110 and the partial reflector 120 in the +Z direction at the inclined portion 112 of the reflector 110, and radiates them in the +Z direction through the partial reflector 120. This improves the gain of the antenna device 100. Here, as an example, the slot antenna 130 is configured to radiate radio waves that propagate in the XZ plane.

[0018] <Configuration of reflector 110> The reflector 110 has a reflector plate 111 and two inclined portions 112. The reflector plate 111 is a plate-shaped portion located in the center of the reflector 110 in a plan view, and its upper surface is the reflective surface 111A. The reflective surface 111A is a flat surface parallel to the XY plane. The reflector plate 111 is provided to reflect radio waves radiated from the slot antenna 130 and reflected by the lower surface 120A of the partial reflector plate 120 in the +Z direction.

[0019] The two inclined portions 112 are provided at the ±X-direction ends of the rectangular reflector 111 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 reflector 111 in plan view. The two inclined portions 112 are arranged so that their inclined surfaces 112A face each other in the X direction, but as an example, the shapes of the two inclined portions 112 are identical.

[0020] The inclined surface 112A extends from the same height as the reflective surface 111A at the lower end of the inclined section 112 to its upper end and functions as a reflective surface that reflects radio waves. The inclined surfaces 112A of the two inclined sections 112 are provided to reflect radio waves radiated from the slot antenna 130 and propagating between the reflector 111 and the partial reflector 120 in the +X and -X directions in the +Z direction. The inclined section 112 is a columnar portion with a triangular XZ cross-section extending in the Y direction. The upper end of the inclined section 112 is in contact with the lower surface 120A of the partial reflector 120 and supports the partial reflector 120.

[0021] Such inclined portions 112 only need to be positioned on at least a portion of the end of the reflector 111 and extend toward the partial reflector 120 at an angle to the reflector 111. This is because the positioning of the inclined portions 112 on at least a portion of the end of the reflector 111 allows radio waves propagating in the ±X direction between the reflector 111 and the partial reflector 120 to be reflected in the +Z direction. In addition, openings may be provided at the ±Y direction ends of the reflector 111, or walls may be provided to cover at least a portion of the ±Y direction ends of the reflector 111.

[0022] Here, as an example, a configuration in which the reflector 111 and the two inclined portions 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 a configuration 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 metal foil or the like may be formed on the reflective surface 111A and the inclined surface 112A. Alternatively, the reflector 110 may be made of a metal plate formed by bending 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, or brass can be used.

[0023] Furthermore, in order to efficiently reflect radio waves radiated from the slot antenna 130 and propagating between the reflector 111 and the partial reflector 120 in the +X and -X directions in the +Z direction, the height of the upper end of the inclined portion 112 relative to the reflector 111 should be at least half the height h of the partial reflector 120 relative to the reflector 111. More specifically, the height of the upper end of the inclined portion 112 relative to the reflective surface 111A of the reflector 111 should be at least half the height h of the lower surface 120A of the partial reflector 120 relative to the reflective surface 111A of the reflector 111.

[0024] By making the height of the upper end of the inclined portion 112 relative to the reflector 111 h / 2 or more, radio waves radiated from the slot antenna 130 and propagating between the reflector 111 and the partial reflector 120 in the +X and -X directions can be efficiently reflected in the +Z direction by the inclined surface 112A, thereby improving the gain of the antenna device 100. Here, we describe a configuration in which the inclined surface 112A extends from a position at the same height as the reflector surface 111A on the lower end of the inclined portion 112 down to the lower surface 120A of the partial reflector 120. However, the upper end of the inclined surface 112A may be lower than the lower surface 120A of the partial reflector 120, as long as it extends to a height of at least half the height h of the partial reflector 120 relative to the reflector 111. 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.

[0025] The inclination angle α of the inclined surface 112A is 45 degrees as an example, but any angle within the range of 30 to 60 degrees is acceptable. The inclination angle α is the angle of the inclined surface 112A relative to the reflective surface 111A, which is parallel to the XY plane, within the XZ plane. By setting the angle α within this range, radio waves propagating between the reflector 111 and the partial reflector 120 in the +X and -X directions can be efficiently reflected in the +Z direction.

[0026] Furthermore, although this description focuses on a configuration in which the partial reflector 120 is supported at the upper end of the inclined portion 112, the partial reflector 120 may also be supported by a support column or the like, which is provided separately from the inclined portion 112. Additionally, the reflector 111 and the two inclined portions 112 may be provided as separate components with fixed relative positions.

[0027] <Partial reflector 120> The partial reflector 120 has a substrate 121 and an FSS (Frequency Selective Surface) structure 122. The FSS structure 122 is an example of a first FSS structure.

[0028] The substrate 121 is an insulating substrate, and an FSS structure 122 is provided on its 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 to a degree that is visible to the naked eye. If the substrate 121 is a rigid substrate, for example, a substrate made by bonding a prepreg (glass cloth impregnated with epoxy resin, etc.) and a core material, a substrate made of fluororesin such as PTFE (polytetrafluoroethylene), or a glass plate can be used. The lower surface of the substrate 121 is the lower surface 120A of the partial reflector 120, and is the 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.

[0029] The FSS structure 122 has a plurality of conductor portions 122A arranged on the upper surface of the substrate 121 and a single conductor portion 122B arranged on the lower surface of the substrate 121. The FSS structure 122 is positioned to overlap with the reflector 111 in a plan view. Here, as an example, a configuration in which the FSS structure 122 is positioned to overlap with the reflector 111 in a plan view but not with the inclined portion 112 is described, but for example, the outer edge of the FSS structure 122 on the ±X direction side may have a portion that overlaps with the inclined portion 112.

[0030] Each conductor portion 122A is, for example, a rectangular conductor pattern in plan view. Each conductor portion 122B is positioned to overlap with multiple conductor portions 122A in plan view, and has a rectangular opening formed in the portion that overlaps with each conductor portion 122A. The conductor portions 122A and 122B can be formed from, for example, a thin metal film such as copper, nickel, or gold.

[0031] The lengths of the openings in the conductor portion 122B in the X and Y directions are longer than the lengths of the conductor portion 122A in the X and Y directions. Therefore, in a plan view, each conductor portion 122A is located inside one of the multiple openings of the conductor portion 122A. The portion corresponding to one conductor portion 122A (one conductor portion 122A and the portion surrounding one of the openings in the conductor portion 122B), which is extracted and enlarged in Figure 4, constitutes an FSS cell. The FSS structure portion 122 has a periodic structure in which multiple FSS cells are arranged periodically.

[0032] The number of conductors 122A in the X direction, Nx, and the number of conductors 122A in the Y direction, Ny, are equal to the number of openings in the X direction and Y direction of conductors 122B. Here, as an example, Nx=5 and Ny=5. Nx and Ny should be set to appropriate numbers according to the length and pitch of conductors 122A and 122B in the X and Y directions when setting the length of the FSS structure 122 in the X and Y directions to 0.7λ or more. The pitch of conductors 122A is the distance between the centers of adjacent conductors 122A in the X and Y directions. λ is the wavelength of the radio waves used by the antenna device 100 for communication. The length of conductors 122A and 122B in the X and Y directions should be λ / 2 or less, preferably λ / 4 or less, and may be around λ / 8.

[0033] The FSS structure 122 has the property of transmitting radio waves in a predetermined frequency band and blocking radio waves of frequencies other than the predetermined frequency band. The predetermined frequency band is set to include the frequency of the radio waves radiated by the antenna device 100, and is the frequency band that includes the resonant frequency of the radio waves that resonate in the resonator between the reflector 111 and the partial reflector 120. The FSS structure 122 is configured such that the power of the radio waves transmitted in the +Z direction becomes an appropriate value, and the phase of the radio waves reflected in the -Z direction at the time of reflection is approximately 180 degrees, thereby transmitting the radio waves that resonate in the resonator between the reflector 110 and the partial reflector 120 little by little (partially) in the +Z direction. An approximately 180-degree phase at the time of reflection means, for example, that the phase at the time of reflection is 180 degrees ± 30 degrees. Furthermore, although the EBG structure has a narrow bandwidth because its height h is half a wavelength, the bandwidth can be widened while maintaining resonance by using the FSS structure 122. While the frequency of the radio waves radiated by the slot antenna 130 is 5 GHz, the frequency band in which the FSS structure 122 resonates due to the partial reflector is, for example, a 500 MHz bandwidth around 5 GHz. Furthermore, the smaller the amount of transmission through the partial reflector in the +Z direction, the greater the gain of the antenna; for example, the transmission amount is -1.3 dB to -2 dB around 5 GHz. The feed point can be provided, for example, near the edge along the longitudinal direction of the slot antenna 130.

[0034] For example, the pitch Px between adjacent conductor sections 122A in the X direction is 8 mm. Px is the distance between the centers of adjacent conductor sections 122A in the X direction. Similarly, the pitch Py between adjacent conductor sections 122A in the Y direction is 8 mm. Py is the distance between the centers of adjacent conductor sections 122A in the Y direction. For example, the length of the conductor section 122A in the X and Y directions is 7.3 mm in both directions. Note that pitch Px and pitch Py may be different. Also, the length of the conductor section 122A in the X and Y directions may be different.

[0035] Furthermore, the length of the opening of the conductor portion 122B in both the X and Y directions is, for example, 6.5 mm. Also, for example, the thickness of the substrate 121 is 1.6 mm, the relative permittivity is 3, and the dielectric loss tanδ is 0.01. The metal used for the conductor portions 122A and 122B is, for example, copper, with a thickness of 35 μm.

[0036] The FSS structure 122 with this configuration only needs to have a rectangular shape with sides of 0.7λ or more in a plan view, where λ is the wavelength of the radio waves output by the antenna device 100 in free space. Here, as an example, the lengths of the conductor portion 122B on the lower surface of the substrate 121 (lower surface 120A of the partial reflector 120) are longer in the X and Y directions than the lengths in the X and Y directions of the area on the upper surface of the substrate 121 in which the multiple conductor portions 122A are provided. Therefore, the lengths of the conductor portion 122B in the X and Y directions only need to be 0.7λ or more. By setting the lengths of the FSS structure 122 in the X and Y directions to 0.7λ or more, the maximum gain can be increased by 3dB or more compared to an antenna device that does not include the FSS structure 122.

[0037] <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. For example, the longitudinal direction of the slot antenna 130 is the Y direction, and the short direction (the direction perpendicular to the longitudinal direction in a plan view) is the X direction.

[0038] The slot antenna 130 excites an electromagnetic field when power is supplied to a feeding point (not shown), and radiates radio waves with a polarization direction in the X direction in the +Z direction. At this time, since the radio waves propagate so as to spread in the XZ plane including the slot antenna 130, components of a mode that resonates between the reflector 110 and the partial reflector 120 (hereinafter referred to as the EBG mode), and components of a mode that propagates in the ±X direction between the reflector 110 and the partial reflector 120 (hereinafter referred to as the propagation mode) occur. The slot antenna 130 is likely to generate components of the propagation mode that propagates in the ±X direction. The frequency of the radio waves radiated from the slot antenna 130 and resonating is, for example, 5 GHz.

[0039] Here, a form using the slot antenna 130 provided on the reflector 111 of the reflector 110 as a primary radiator will be described. However, the reflector 111 is provided with an opening, and the slot antenna 130 may be disposed below the opening. Such a configuration will be described later with reference to FIG. 13. Here, a form using the slot antenna 130 as a primary radiator will be described, but the primary radiator may be an antenna other than the slot antenna, for example, a patch antenna.

[0040] <EBG Mode and Propagation Mode> FIG. 6 is a diagram showing an example of the EBG mode and the propagation mode. In FIG. 6, the white dashed arrow pointing in the +Z direction indicates the propagation direction of the radio waves of the EBG mode, and the dashed arrow in the +X direction indicates the polarization direction of the radio waves of the EBG mode at a certain moment. The radio waves of the EBG mode resonate in the resonator between the reflector 110 and the partial reflector 120, and the transmission amount of the radio waves is adjusted by the FSS structure portion 122, and components of a predetermined frequency pass through the partial reflector 120 and are output in the +Z direction. In FIG. 6, the elliptical region indicated by fine dots between the reflector 110 and the partial reflector 120 indicates the region where the resonance of the radio waves of the EBG mode mainly occurs. The radio waves of the EBG mode resonate in the resonator between the reflector 110 and the partial reflector 120, so that the in-phase radio waves spread spherically in a plan view, and resonance occurs in the elliptical region indicated in gray.

[0041] Furthermore, in Figure 6, the white dotted arrows pointing in the ±X directions toward the inclined surface 112A and the white dotted arrows pointing from the inclined surface 112A in the +Z direction indicate the propagation direction of the radio waves in propagation mode, and the solid arrows perpendicular to the white dotted arrows indicate the polarization direction of the radio waves in propagation mode at a given moment. The radio waves in propagation mode propagate in the ±X directions between the reflector 110 and the partial reflector 120, are reflected in the +Z direction by the inclined surface 112A, pass through the portion of the substrate 121 at the ±X direction end of the partial reflector 120 (the portion where the FSS structure 122 is not provided), and are output in the +Z direction.

[0042] The radio waves radiated from the slot antenna 130 into the space between the reflector 110 and the partial reflector 120 are predominantly composed of EBG mode components, with a small proportion being propagation mode components. However, by reflecting the propagation mode components in the +Z direction at the inclined surface 112A, the amount of radio waves output from the partial reflector 120 in the +Z direction can be increased, thereby improving the gain of the antenna device 100. Furthermore, if the outer edge of the FSS structure 122 on the ±X direction side overlaps with the inclined portion 112, a structure can be obtained that easily absorbs the X-direction displacement when attaching the partial reflector 120 to the reflector 110.

[0043] Alternatively, instead of the partial reflector 120 having the FSS structure 122 described above, a partial reflector without the FSS structure 122 may be used, with the thickness of the substrate 121 set to approximately 1 / 4 of the electrical length λe of the wavelength λ of the radio waves output by the antenna device 100. The electrical length λe is determined by the relative permittivity of the substrate 121. In this case, it is preferable to use a dielectric material with a relatively high relative permittivity for the substrate 121. This is because it has a large wavelength shortening effect, contributes to miniaturization, and the amount of transmission through the partial reflector is small, which strengthens the radio waves resonating in the resonator and increases the gain.

[0044] By using a partial reflector composed of a substrate 121 with a thickness of λe / 4, the EBG mode radio waves reflected from the lower surface of the partial reflector and the EBG mode radio waves reflected from the upper surface of the partial reflector 120 within the partial reflector become in phase, thereby reducing the amount transmitted through the partial reflector. When reflected from the lower surface of the partial reflector, the phase of the EBG mode radio waves advances by 180 degrees. In addition, the path of the EBG mode radio waves that propagate from the lower surface into the interior of the partial reflector and are reflected from the upper surface is λe / 2 longer than that of the radio waves reflected from the lower surface of the partial reflector. For this reason, even if a partial reflector with a substrate thickness of λe / 4 is used without the FSS structure 122, it is possible to achieve a state in which the EBG mode radio waves resonate in the resonator between the reflector 110 and the partial reflector. Even when such a partial reflector is included, the antenna device 100 is an antenna device with an EBG structure.

[0045] <Position of inclined surface 112A> Figure 7 shows an example of the position of the inclined surface 112A. In Figure 7, as in Figure 6, the dashed arrows indicate the polarization direction of the EBG mode radio waves at a given moment, and the solid arrows indicate the polarization direction of the propagation mode radio waves at a given moment. The polarization direction of the EBG mode radio waves and the polarization direction of the propagation mode radio waves are for the same moment. Also, in Figure 7, the position of the inclined surface 112A in the X direction is explained by defining the center 130C of the slot antenna 130 in the X direction as the point with an X coordinate of zero.

[0046] 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 (1) of the EBG mode radio waves, the polarization direction (2) of the propagation mode radio waves radiated from the +X side of the FSS structure 122, and the polarization direction (3) of the propagation mode radio waves radiated from the -X side of the FSS structure 122 must be the same at positions at equal height from the top surface of the partial reflector 120. This is because if the EBG mode radio waves and the propagation mode radio waves are in the same phase, they reinforce each other and can improve the gain, but if they are out of phase, they destructively cancel each other out and the gain decreases.

[0047] Here, we will ignore the thickness of the partial reflector 120 and consider the polarization direction (1) of the EBG mode radio waves and the polarization directions (2) and (3) of the propagation mode radio waves on the upper surface of the partial reflector 120.

[0048] The EBG mode radio waves are radiated from the slot antenna 130 in the +Z direction and propagate a distance h (height h) before reaching the upper surface of the partial reflector 120. Here, the height h is h = λ / 2. In other words, the EBG mode radio waves are radiated from the slot antenna 130 in the +Z direction and propagate a distance of λ / 2 before reaching the upper surface of the partial reflector 120.

[0049] Here, +X1 and -X1 are defined as 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. Between the reflector 110 and the partial reflector 120, the radio wave of the propagation mode that propagates in the +X direction from the slot antenna 130 has a polarization direction (2A1) at position +X1, a polarization direction (2A2) as the radio wave propagates further in the +X direction, and at position +X2, it is reflected by the inclined surface 112A, so it has a polarization direction in the -Z direction (2A3) and a polarization direction of the reflected radio wave (2A4).

[0050] Similarly, radio waves in propagation modes that propagate in the -X direction from the slot antenna 130 between the reflector 110 and the partial reflector 120 have a polarization direction (3A1) at position -X1, a polarization direction (3A2) as the radio waves propagate further in the -X direction, and at position -X2, they are reflected by the inclined surface 112A, so they have a polarization direction in the +Z direction (3A3) and a polarization direction of the reflected radio waves (3A4).

[0051] For the polarization directions (2) and (3) of the propagation mode radio waves reflected in the +Z direction at point S where the height of the inclined surface 112A with respect to the reflective surface 111A of the reflector 111 is h / 2, and radiated from the antenna device 100 in the +Z direction, to be the same as the polarization direction (1) of the EBG mode radio waves, then at the upper surface of the partial reflector 120, the difference in propagation distance between the propagation mode radio waves and the EBG mode radio waves must be nλ. Herein, n is an integer of 1 or more.

[0052] The propagation mode radio waves are reflected at point S where the height of the inclined surface 112A is h / 2, and then propagate for λ / 4 in the +Z direction. Therefore, in order for the difference in propagation distance to be nλ, the distance dx that the propagation mode radio waves travel from the center 130C of the slot antenna 130 to point S in the X direction should be (n+1 / 4)λ. By setting the distance dx that the propagation mode radio waves travel from the center 130C of the slot antenna 130 to point S to (n+1 / 4)λ, the propagation mode radio waves will travel a distance of (n+1 / 2)λ from the center 130C of the slot antenna 130 through point S to the upper surface of the partial reflector 120, and the difference in propagation distance will be nλ. Note that the antenna device 100 may have a configuration where the value of n in the difference in propagation distance nλ is different for the path reflected by the inclined surface 112A on the +X direction side and the path reflected by the inclined surface 112A on the -X direction side.

[0053] When 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 become in phase at the surface of the partial reflector 120, and the polarization direction (1) of the EBG mode radio wave becomes equal to the polarization directions (2) and (3) of the propagation mode radio wave. As a result, the EBG mode radio wave and the propagation mode radio wave reinforce each other. This phase relationship between the EBG mode radio wave and the propagation mode radio wave is maintained even when the radio wave moves away from the surface of the partial reflector 120 in the +Z direction.

[0054] The polarization directions (2) and (3) of the radio waves of the propagation mode reflected at point S where the height of the inclined surface 112A relative to the reflective surface 111A is h / 2 have been explained. However, at points where the height of the inclined surface 112A relative to the reflective surface 111A is less 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 is true at points where the height of the inclined surface 112A relative to the reflective surface 111A is greater than h / 2, and the total propagation distance is the same. 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 point S where the height is h / 2, so here, as an example, point S where the height is h / 2 is used for explanation.

[0055] Furthermore, 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 section 112 should be positioned such that, in the X direction, the distance dx from the center 130C of the slot antenna 130 to point S is (n+1 / 4)λ. The inclination angle α can be set within the range of 30 to 60 degrees.

[0056] <Simulation Results> Figure 8 shows an example of the simulation results of the frequency characteristics of the maximum gain of the antenna device 100. The horizontal axis represents frequency (GHz), and the vertical axis represents the maximum gain (dBi) of the antenna device 100. The height h = 30 mm, the distance dx from the center 130C of the slot antenna 130 in the X direction to point S on the inclined surface 112A on the ±X direction side was set to 79 mm, the inclination angle α was set to 45 degrees, and the number of conductors Nx and Ny in the X and Y directions of the conductor section 122A were both set to 21. These values ​​are for when the resonant frequency of the resonator of the reflector 110 and the partial reflector 120 is set to 5 GHz. The reflector 110 is a perfect conductor with a length of 200 mm in the X direction and a length of 400 mm in the Y direction.

[0057] Under these conditions, when an electromagnetic field simulation was performed, as shown in Figure 8, the maximum gain of the antenna device 100 reached its maximum value (approximately 16.5 dBi) at 5 GHz.

[0058] Figures 9A and 9B show examples of simulation results for the directivity of antenna device 100. Figure 9A shows the directivity in the XZ plane, and Figure 9B shows the directivity in the YZ plane. The solid lines in the directions of approximately ±10 degrees in Figures 9A and 9B represent the full width at half maximum of the main lobe, which is 18.2 degrees in Figure 9A and 28.6 degrees in Figure 9B. The directivity will be discussed later in comparison with the results of a comparative antenna device.

[0059] Figure 10 shows an example of the simulation results of the frequency characteristics of the maximum gain of a comparative antenna device. The horizontal axis represents frequency (GHz), and the vertical axis represents the maximum gain (dBi) of the comparative antenna device. The comparative antenna device has a configuration in which the inclined portion 112 of the reflector 110 is removed and the reflector plate 111 is enlarged in plan view along the XZ plane.

[0060] When electromagnetic field simulations were performed under the same conditions as antenna device 100, as shown in Figure 10, the maximum gain of the comparison antenna device reached its maximum value (approximately 15.5 dBi) at 5.2 GHz. This was approximately 1 dB lower than the maximum gain of antenna device 100. In other words, it was found that the antenna device 100 was able to improve its maximum gain by approximately 1 dB by having the inclined section 112.

[0061] Figures 11A and 11B show examples of simulation results for the directivity of a comparative antenna device. Figure 11A shows the directivity in the XZ plane, and Figure 11B shows the directivity in the YZ plane. The solid lines in the directions of approximately ±15 degrees in Figures 11A and 11B represent the full width at half maximum of the main lobe, which is 32.2 degrees in Figure 11A and 26.8 degrees in Figure 11B.

[0062] The directivity of antenna device 100 in the XZ plane, as shown in Figure 9A, showed a reduction in side lobes and an increase in main lobes compared to the directivity of the comparative antenna device shown in Figure 11A. More specifically, the main lobe increased from 13.9 dBi for the comparative antenna device to 16.7 dBi for antenna device 100, and the side lobe ratio decreased from -11.5 dB to -16.9 dB. In Figures 9A and 11A, the side lobe ratio levels are shown as circles. This is thought to be because the radio waves of the propagation mode were efficiently reflected in the +Z direction, increasing the gain of antenna device 100.

[0063] Furthermore, the directivity of the antenna device 100 shown in Figure 9B in the YZ plane is approximately identical in shape and size of the main lobe and side lobes to that of the comparative antenna device shown in Figure 11B, confirming that the addition of the inclined section 112 did not affect the directivity in the YZ plane. Note that the side lobe ratio levels are also shown as circles in Figures 9B and 11B.

[0064] Here, as an example, we have described a configuration in which the inclined portion 112 is positioned such that the distance dx from the center 130C of the slot antenna 130 to point S in the X direction is (n+1 / 4)λ. However, the position of the inclined portion 112 is not limited to this position. For example, if the distance dx from the center 130C of the slot antenna 130 to point S in the X direction is (n+1 / 4)λ±λ / 8, it has been confirmed that the phase of the EBG mode radio wave and the phase of the propagation mode radio wave can be made approximately in phase on the +Z direction side of the partial reflector 120, thereby improving the gain of the antenna device 100. 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 can be considered approximately in phase.

[0065] <Effects> As described above, the antenna device 100 is an EBG structure antenna device 100 that includes a reflector 110 having a reflector plate 111, a partial reflector plate 120 provided opposite the reflector plate 111 of the reflector 110, and a slot antenna 130 that radiates radio waves into the space between the reflector plate 111 and the partial reflector plate 120. The reflector 110 further has an inclined portion 112 that is positioned at least on a part of the end of the reflector plate 111 and extends toward the partial reflector plate 120 at an angle to the reflector plate 111, and the height of the upper end of the inclined portion 112 relative to the reflector plate 111 is at least half the height of the partial reflector plate 120 relative to the reflector plate 111. Therefore, the inclined portion 112 can efficiently reflect the components of the radio waves radiated from the slot antenna 130 that have become propagation mode rather than EBG mode toward the partial reflector plate 120.

[0066] Therefore, an antenna device 100 capable of increasing gain can be provided. Furthermore, by adding a slanted section 112 to the reflector 110, an antenna device 100 capable of increasing gain can be realized, thus enabling miniaturization and cost reduction of the antenna device 100. In addition, by setting the distribution of EBG mode radio waves that pass through the partial reflector 120 and radio waves that are reflected by the slanted section 112 and pass through the partial reflector 120 according to the position of the slanted section 112, an antenna device 100 with adjustable gain can be provided.

[0067] Furthermore, since the inclined portion 112 is provided on at least two opposing sides of the outer edge of the reflector 111 in a plan view, it can efficiently reflect radio waves of propagation mode radiated from the slot antenna 130 and propagating in the direction toward the two sides toward the partial reflector 120. Therefore, an antenna device 100 can be provided that can increase gain by efficiently reflecting radio waves of propagation mode propagating in the direction toward the two sides.

[0068] Furthermore, since the inclination angle α of the inclined section 112 with respect to the reflector 111 is within the range of 30 to 60 degrees, it is possible to provide an antenna device 100 that can achieve both efficient reflection of radio waves in propagation mode at the inclined section 112 and miniaturization.

[0069] Furthermore, the primary radiator is a slot antenna 130, and the inclined portion 112 is positioned on the end of the reflector 111 that lies on the extension of the slot antenna 130 in the short direction. Since the radio waves radiated from the slot antenna 130 propagate in the short direction of the slot antenna 130, by positioning the inclined portion 112 on the end of the reflector 111 that lies on the extension of the slot antenna 130 in the short direction, the radio waves in propagation mode can be reliably reflected towards the partial reflector 120, providing an antenna device 100 that can increase gain more efficiently.

[0070] 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, thereby providing an antenna device 100 that can further increase the gain.

[0071] Furthermore, the distance dx in a plan view between the position in the X direction of point S where the height of the inclined surface 112A of the inclined section 112 reaches a predetermined height, and the center of the radiating section of the slot antenna 130, is (n+1 / 4)λ±λ / 8 (where n is an integer greater than or equal to 1), where λ is the wavelength of the radio wave in free space. The predetermined height is half the height h of the partial reflector 120 relative to the reflector 111 (h / 2). Therefore, the EBG mode radio waves radiated from the partial reflector 120 in the +Z direction and the propagation mode radio waves can be made in phase, providing an antenna device 100 that can more effectively increase the gain. Note that the X direction is the direction connecting the inclined section 112 and the slot antenna 130.

[0072] Furthermore, the partial reflector 120 has an FSS structure 122 positioned to overlap with the reflector 111 in a plan view. The FSS structure 122 has a rectangular shape with sides of 0.7λ or more in a plan view, where λ is the wavelength of the radio waves radiated by the slot antenna 130 in free space. As a result, a resonator can be realized in the space between the reflector 110 and the partial reflector 120 where EBG mode radio waves resonate, increasing the area of ​​the radiating surface for EBG mode radio waves that pass through the partial reflector 120 in the +Z direction, thereby providing an antenna device 100 that can more effectively increase gain. In addition, although the EBG structure has a narrow bandwidth because its height h is half a wavelength, the bandwidth can be widened by using the FSS structure 122, thereby enabling a broadband antenna device 100.

[0073] Furthermore, if the antenna device 100 has a portion where the outer edge of the FSS structure 122 and the inclined portion 112 overlap in a plan view, it is possible to provide an antenna device 100 with a configuration that easily absorbs the X-direction displacement when attaching the partial reflector 120 to the reflector 110.

[0074] <First variation> Figure 12 shows an example of the cross-sectional structure of the antenna device 100M1 of the first modified embodiment. The cross-section shown in Figure 12 corresponds to the cross-section shown in Figure 3.

[0075] Antenna device 100M1 differs from antenna device 100 shown in Figure 3 in that the inclination angle α of the inclined section 112 on the +X direction side is set to 30 degrees. The other configurations are the same as those of antenna device 100 shown in Figure 3.

[0076] The antenna device 100M1 has different inclination angles between the inclined portion 112 on the +X side and the inclined portion 112 on the -X side. As a result, the distance dx1 between the position of point S on the inclined portion 112 on the +X side in the X direction and the center 130C of the radiating portion of the slot antenna 130, and the distance dx2 between the position of point S on the inclined portion 112 on the -X side in the X direction and the center 130C of the radiating portion of the slot antenna 130 are different.

[0077] Thus, even if the inclination angles of the two inclined sections 112 are different, the inclined sections 112 can efficiently reflect the component of the radio waves radiated from the slot antenna 130 that has entered propagation mode towards the partial reflector 120. Therefore, an antenna device 100M1 capable of increasing gain can be provided. Furthermore, it is possible to provide an antenna device 100M1 that can be made smaller and less expensive, and whose gain can be set.

[0078] <Second variation> Figure 13 shows an example of the cross-sectional structure of the antenna device 100M2, a second modified example of the embodiment. The cross-section shown in Figure 13 corresponds to the cross-section shown in Figure 3.

[0079] Antenna device 100M2 has a reflector 110 whose reflector plate 111 has an opening 111B instead of a slot antenna 130, and a waveguide 140 having a slot antenna 130 is positioned below the reflector plate 111. Antenna device 100M2 is configured to include a reflector 110, a partial reflector 120, and a waveguide 140 having a slot antenna 130.

[0080] The opening 111B of the reflector 111 is larger than the opening of the slot antenna 130 in a plan view, and the waveguide 140 is positioned so that the slot antenna 130 is contained within the opening 111B in a plan view. The waveguide 140 can be fixed to the reflector 110, etc., by a member not shown. The slot antenna 130 radiates radio waves through the opening 111B into the space between the reflector 111 and the partial reflector 120.

[0081] Furthermore, the distance dx from the center 130C of the slot antenna 130 to point S is (n+1 / 4)λ±λ / 8, which allows the phase of the EBG mode radio wave and the phase of the propagation mode radio wave to be approximately in phase on the +Z direction side of the partial reflector 120.

[0082] In this antenna device 100M2, as with antenna device 100, the component of the radio waves radiated from the slot antenna 130 and radiated through the opening 111B into the space between the reflector 110 and the partial reflector 120 that has entered propagation mode can be efficiently reflected by the inclined section 112 toward the partial reflector 120. Therefore, an antenna device 100M2 capable of increasing gain can be provided. Furthermore, by making the waveguide 140 thinner, the antenna device 100M2 can be miniaturized.

[0083] <Third variation> Figure 14 shows an example of the planar structure of the antenna device 100M3, a third modified example of the embodiment. The planar structure shown in Figure 14 corresponds to the planar structure shown in Figure 2.

[0084] Antenna device 100M3 has the following configuration compared to antenna device 100 shown in Figure 2: two inclined portions 113 are added to the ±Y ends of the reflector plate 111, and instead of the slot antenna 130 shown in Figure 2, two slot antennas 130A and 130B are provided on the reflector plate 111 of the reflector 110.

[0085] Slot antenna 130A is a modified version of slot antenna 130 shown in Figure 2, with the slot antenna 130 slightly shifted towards the -X direction. Its longitudinal direction is the Y direction, and its transverse direction is the X direction. It radiates radio waves in the same way as slot antenna 130 shown in Figure 2.

[0086] The slot antenna 130B is located on the +X side of the slot antenna 130A, with its longitudinal direction being the X direction and its short direction being the Y direction. The slot antenna 130B is excited by power supplied to a feed point (not shown in the figure), causing it to radiate radio waves with polarization in the Y direction in the +Z direction. At this time, the radio waves propagate in a way that spreads within the YZ plane including the slot antenna 130B, resulting in components of EBG mode that resonate between the reflector 110 and the partial reflector 120, and components of propagation mode that propagate in the ±Y direction between the reflector 110 and the partial reflector 120. The slot antenna 130B is prone to generating components of propagation mode that propagate in the ±Y direction.

[0087] Radio waves in propagation modes that propagate in the ±Y directions are reflected in the +Z direction by the inclined section 113 and radiated in the +Z direction from the portion of the partial reflector 120 that does not overlap with the FSS structure section 122.

[0088] In the antenna device 100M3, the EBG mode radio waves radiated from slot antenna 130A and the EBG mode radio waves radiated from slot antenna 130B resonate between the reflector 111 and the partial reflector 120 of the reflector 110 and are radiated in the +Z direction of the partial reflector 120.

[0089] Furthermore, in the antenna device 100M3, the radio waves that propagate from the slot antenna 130A are reflected in the +Z direction by the inclined section 112 and radiated in the +Z direction by the partial reflector 120. Also, the radio waves that propagate from the slot antenna 130B are reflected in the +Z direction by the inclined section 113 and radiated in the +Z direction by the partial reflector 120.

[0090] The antenna device 100M3 includes two slot antennas 130A and 130B and two sets of inclined sections 112 and 113, enabling it to radiate two orthogonal polarizations with a single antenna device 100M3. The frequencies of the radio waves radiated from the two slot antennas 130A and 130B may be different. If the radio wave frequencies are different, the communication bandwidth of the antenna device 100M3 can be further expanded.

[0091] <Fourth variation> Figure 15 shows an example of the planar structure of the antenna device 100M4 of the fourth modified embodiment. The planar structure shown in Figure 15 corresponds to the planar structure shown in Figure 2. Figure 16 shows an example of the configuration of the cross-section in the direction of arrow BB in Figure 15. The cross-section shown in Figure 16 corresponds to the cross-section shown in Figure 3.

[0092] Antenna device 100M4 differs from antenna device 100 shown in Figures 2 and 3 in that it includes a dielectric 150 positioned on the upper surface of the partial reflector 120 in the portion that overlaps with the inclined portion 112. The other configurations are the same as those of antenna device 100 shown in Figures 2 and 3.

[0093] Before describing the configuration, operation, and effects of the antenna device 100M4 using Figures 15 and 16, we will first explain the relationship between the distribution and gain of EBG mode and propagation mode radio waves using Figure 17. Figure 17 shows an example of the electric field distribution of EBG mode and propagation mode radio waves on the upper surface of the partial reflector 120.

[0094] In Figures 17(A) to (C), darker colors indicate stronger electric fields, while lighter colors indicate weaker electric fields. Furthermore, in Figures 17(A) to (C), the concentric electric field distribution at the center in the X direction represents the electric field distribution of the EBG mode radio wave, while the elongated elliptical electric field distribution in the Y direction, located on the ±X side of the EBG mode electric field distribution, represents the electric field distribution of the radio wave reflected by the inclined section 112 and radiated in the +Z direction. The extent of the EBG mode electric field distribution changes depending on the design of the partial reflector 120.

[0095] Ideally, the distribution of EBG mode radio waves and propagation mode radio waves should be such that the propagation mode radio wave's electric field distribution is adjacent to the EBG mode radio wave's electric field distribution in the ±X directions, as shown in Figure 17(A) as an example. In this case, as shown in Figure 17(B), if the electric field distributions of the EBG mode radio wave and the propagation mode radio wave overlap, the effective area does not increase, making it difficult to improve the gain. Also, as shown in Figure 17(C), if the propagation mode radio wave's electric field distribution is isolated from the EBG mode radio wave's electric field distribution like an island, the effective area increases, and an improvement in gain can be expected, but it can cause characteristic degradation such as the generation of side lobes. For this reason, as shown in Figure 17(A), the ideal positional relationship is that the propagation mode radio wave's electric field distribution is adjacent to the EBG mode radio wave's electric field distribution in the ±X directions.

[0096] To achieve this relationship between the electric field distribution of the EBG mode radio waves and the electric field distribution of the propagation mode radio waves, it is sufficient to control the position of the inclined portion 112 in the X direction during the design phase. In particular, bringing it closer to the FSS structure 122 makes it easier to achieve an ideal positional relationship.

[0097] From this perspective, the antenna device 100M4 places the dielectric 150 on the portion of the upper surface of the partial reflector 120 that overlaps with the inclined portion 112. When radio waves of the propagation mode reflected in the +Z direction by the inclined portion 112 pass through the dielectric 150, the electrical length is extended due to the wavelength shortening effect corresponding to the relative permittivity of the dielectric 150. For this reason, the distance in the X direction between the two inclined portions 112 can be shortened compared to the antenna device 100 (see Figures 1 to 6) which does not include the dielectric 150.

[0098] In such a case, the thickness t of the dielectric 150 that causes 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 to be in phase is expressed by the following equation (1). Note that dx is the distance in the X direction between point S, where the height of the inclined surface 112A of the inclined portion 112 is h / 2, and the center 130C of the slot antenna 130, n is an integer of 1 or more, λ is the wavelength of the radio wave, and εr is the relative permittivity of the dielectric 150 at wavelength λ. Note that ±λ / 8√εr in equation (1) means that a phase difference within ±45 degrees is treated as being in phase.

[0099]

number

[0100] Furthermore, by rearranging equation (1), the distance dx can be expressed by the following equation (2).

[0101]

number

[0102] In other words, by providing the dielectric 150, the distance dx in the X direction between the center 130C of the slot antenna 130 and the dielectric 150 can be shortened by t(√εr-1). Note that the two dielectrics 150 are identical, and the two inclined portions 112 have a shape that is symmetric 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 Figure 16. Therefore, the arrangement of the two dielectrics 150 is symmetric 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 may have a configuration in which the value of n in the difference in propagation distance nλ differs between the path reflected by the inclined surface 112A on the +X direction side and the path reflected by the inclined surface 112A on the -X direction side. In this case, the arrangement of the two dielectrics 150 will be asymmetric with respect to an axis parallel to the Z axis passing through the center 130C of the slot antenna 130.

[0103] <Simulation Results> Figure 18 shows an example of the simulation results of the frequency characteristics of the maximum gain of the antenna device 100M4. The horizontal axis represents frequency (GHz), and the vertical axis represents the maximum gain (dBi) of the antenna device 100M4. The height h = 30 mm, the distance dx from the center 130C of the slot antenna 130 in the X direction to point S on the inclined surface 112A on the ±X direction side is set to 65 mm, the inclination angle α is set to 45 degrees, the number of conductors Nx and Ny in the X and Y directions of the conductor section 122A are both set to 13, and the thickness t of the two dielectrics 150 is set to 17 mm. These values ​​are for when the resonant frequency of the resonator of the reflector 110 and the partial reflector 120 is set to 5 GHz.

[0104] Under these conditions, when an electromagnetic field simulation was performed, as shown in Figure 18, the maximum gain of the antenna device 100M4 was found to be at 5 GHz (approximately 15.3 dBi).

[0105] Figures 19A and 19B show examples of simulation results for the directivity of antenna device 100M4. Figure 19A shows the directivity in the XZ plane, and Figure 19B shows the directivity in the YZ plane. The solid lines in the directions of approximately ±15 degrees in Figures 19A and 19B represent the full width at half maximum of the main lobe, which is 26.8 degrees in Figure 19A and 28.5 degrees in Figure 19B.

[0106] The directivity of antenna device 100M4 in the XZ plane, shown in Figure 19A, shows slightly larger side lobes compared to the directivity of antenna device 100 in the XZ plane, shown in Figure 9A. However, the main lobe is larger than that of the comparison antenna device shown in Figure 11A. The main lobe was 15.3 dBi, and the side lobe ratio was -12.2 dB. In Figure 19A, the side lobe ratio level is shown by a circle.

[0107] Furthermore, the directivity of antenna device 100M4 in the YZ plane, as shown in Figure 19B, was similar to that of antenna device 100 in the YZ plane, as shown in Figure 9B, but the main lobe was slightly smaller. The main lobe was 15.7 dBi, and the side lobe ratio was -20.4 dB. In Figure 19B, the side lobe ratio levels are shown by circles.

[0108] As described above, by determining 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 based on equation (2), the effective area between the electric field distribution of the propagation mode radio wave and the electric field distribution of the EBG mode radio wave can be effectively increased, and the gain can be effectively improved. Note that the dielectric 150 may be placed only on either the +X direction side or the -X direction side.

[0109] <Fifth variation> Figure 20 shows an example of the planar structure of the antenna device 100M5, a fifth modified example of the embodiment. The planar structure shown in Figure 20 corresponds to the planar structure shown in Figure 2. Figure 21 shows an example of the configuration of the cross-section in the direction of arrow CC in Figure 20. The cross-section shown in Figure 21 corresponds to the cross-section shown in Figure 3.

[0110] Antenna device 100M5 differs from antenna device 100 shown in Figures 2 and 3 in that it includes an FSS structure 160 positioned on the upper surface of the partial reflector 120 in the portion that overlaps with the inclined portion 112. The FSS structure 160 is an example of a second FSS structure. The other configurations are the same as those of antenna device 100 shown in Figures 2 and 3.

[0111] The FSS structure 160 has a plurality of cells 160C that can advance or delay the phase of transmitted radio waves. Figures 22A and 22B show an example of a cell 160C. Figures 22A and 22B show an extracted portion of the substrate 121 of the partial reflector 120 corresponding to one cell 160C, similar to the enlarged portion in Figure 4. As an example, the FSS structure 160 does not have a conductor on the lower surface (-Z direction surface) of the substrate 121. However, the FSS structure 160 may have a conductor on the lower surface (-Z direction surface) of the substrate 121 and no conductor on the upper surface (+Z direction surface) of the substrate 121. Alternatively, the FSS structure 160 may have conductors on both the lower and upper surfaces of the substrate 121.

[0112] The cell 160C shown in Figure 22A is a rectangular metal foil formed on the upper surface (the surface on the +Z direction side) of the substrate 121. Such a cell 160C delays the phase of radio waves that are incident from the -Z direction and transmitted through it.

[0113] The cell 160C shown in Figure 22B is a rectangular annular (rectangular frame-shaped) metal foil formed on the upper surface (+Z direction side) of the substrate 121. Such a cell 160C advances the phase of radio waves incident from the -Z direction and transmitted through it. The cell 160C shown in Figures 22A and 22B can be formed from a thin metal film such as copper, nickel, or gold, as an example.

[0114] The FSS structure 160 has a configuration in which cells 160C, as shown in Figure 22A or Figure 22B, are arranged periodically in the X and Y directions. The amount of phase shift that cells 160C impart to radio waves, as shown in Figures 22A and 22B, is, for example, ±45 degrees. When the amount of phase shift that cells 160C impart to radio waves is ±45 degrees, the transmittance of radio waves is approximately 50%. It is possible to increase the absolute value of the phase shift amount beyond ±45, but the transmittance of radio waves will decrease further, so as an example, it is relatively easy to use if the amount of phase shift amount is within the range of ±45 degrees.

[0115] The radio waves in propagation mode pass through the partial reflector 120 and the FSS structure 160 and are radiated in the +Z direction. As the phase of the radio waves advances or is delayed when passing through the FSS structure 160, the effect of shortening or lengthening the path length is obtained, substantially the same as in the antenna device 100M4 of Modified Example 4. For this reason, the distance between the two inclined sections 112 can be made longer or shorter compared to the antenna device 100 (see Figures 1 to 6) in order to make the radio waves in EBG mode that pass through the FSS structure 122 and the radio waves in propagation mode that pass through the FSS structure 160 be in phase. The positional relationship between the electric field distribution of the radio waves in EBG mode and the electric field distribution of the radio waves in propagation mode can be controlled.

[0116] Specifically, the position of the inclined portion 112 can be determined as follows: When the phase change amount that the FSS structure 122 imparts to the radio waves passing through the FSS structure 122 is φ (rad), and the phase change amount that the FSS structure 160 imparts to the radio waves is δ (rad), the inclined portion 112 should be positioned such that point S is located at a distance dx from the center 130C of the slot antenna 130 in the X direction, as expressed by the following equation (3). Point S is the point where the height of the inclined surface 112A relative to the reflective surface 111A is h / 2. dx=(n+1 / 4+φ / 2π+δ / 2π)λ (3)

[0117] When δ is positive (δ>0), the FSS structure 160 includes the cell 160C shown in Figure 22B and advances the phase of the transmitted radio waves. When δ is negative (δ<0), the FSS structure 160 includes the cell 160C shown in Figure 22A and delays the phase of the transmitted radio waves.

[0118] According to Modification 5, by controlling 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 during the design phase, the effective area of ​​the electric field distribution of the propagation mode radio wave and the electric field distribution of the EBG mode radio wave can be effectively increased, thereby providing an antenna device 100M5 that can effectively improve the gain. The FSS structure 160 may be placed only on either the +X direction side or the -X direction side. Furthermore, the FSS structure 160 on the +X direction side and the -X direction side may have different shapes and therefore have different phase shift amounts on the radio wave.

[0119] While exemplary antenna devices of this disclosure have been described above, this disclosure is not limited to the specifically disclosed embodiments, and various modifications and changes are possible without departing from the scope of the claims. [Explanation of symbols]

[0120] 100, 100M1, 100M2, 100M3, 100M4, 100M5 Antenna Equipment 110 Reflector 111 Reflector 111A Reflective surface 111B opening 112 Slope 112A Slope 113 Slope 120 Partial reflector 120A bottom 121 circuit boards 122 FSS Structural Components (An example of a first FSS structural component) 130, 130A, 130B slot antenna 130C center 140 Waveguide 150 Dielectric 160 FSS structural section (an example of a second FSS structural section) 160C Cell

Claims

1. A reflector having a reflector, A partial reflector is provided opposite the reflector plate of the reflector, and transmits radio waves little by little. A primary radiator that emits radio waves into the space between the reflector and the partial reflector, An antenna device having an EBG (Electromagnetic Band Gap) structure, The reflector is positioned on at least a portion of the end of the reflector and further has an inclined portion that is inclined with respect to the reflector and extends toward the partial reflector, An antenna device in which the height of the upper end of the inclined portion relative to the reflector is at least half the height of the partial reflector relative to the reflector.

2. 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 in a plan view.

3. The antenna device according to claim 1, wherein the inclination angle of the inclined portion with respect to the reflector is within the range of 30 to 60 degrees.

4. The primary radiator is a slot antenna, The antenna device according to claim 1, wherein the inclined portion is located on the extension of the short side of the slot antenna, which is part of the end of the reflector.

5. The reflector has an opening, The antenna device according to claim 1, wherein the primary radiator radiates radio waves through the opening into the space between the reflector and the partial reflector.

6. The antenna device according to claim 1, wherein the upper end of the inclined portion extends to the partial reflector.

7. The distance in a plan view between the position in the direction connecting the inclined portion and the primary radiator at the point where the height of the inclined surface of the inclined portion reaches a predetermined height, and the center of the radiating portion of the primary radiator, is (n+1 / 4)λ±λ / 8 (where 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 relative to the reflector.

8. The aforementioned partial reflector has a first FSS (Frequency Selective Surface) structure which is positioned to overlap with the reflector in a plan view, The antenna device according to claim 1, wherein the first FSS structure has a rectangular shape with sides of 0.7λ or more in a plan view, where λ is the wavelength of the radio wave.

9. The antenna device according to claim 8, wherein the outer edge of the first FSS structure and the inclined portion have an overlapping portion in a plan view.

10. The aforementioned partial reflector has a dielectric material provided within the 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 represented by the following formula (1). [Math 1] Here, n is an integer greater than or equal to 1, λ is the wavelength of the radio wave, εr is the relative permittivity of the dielectric at wavelength λ, dx is the distance in a plan view between the position in the direction connecting the inclined portion and the primary radiator at the point where the height of the inclined surface of the inclined portion becomes a predetermined height, and the center of the radiating portion of the primary radiator, wherein the predetermined height is half the height of the partial reflector relative to the reflector.

11. The antenna device according to claim 1, wherein the partial reflector has a second FSS (Frequency Selective Surface) structure that is positioned to overlap with the inclined portion in a plan view.

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