Antenna device
The antenna device uses a single patch antenna with a cavity on a dielectric substrate to achieve wide-angle radiation directivity and high gain in the front direction, addressing size and cost challenges by optimizing cavity height and eliminating the need for arraying and beamforming circuits.
Patent Information
- Application Number
- JP2024081783
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-05-20
- Publication Date
- 2025-12-03
AI Technical Summary
Antenna devices using dielectric substrates face challenges in achieving both wide-angle radiation directivity and high gain in the front direction while maintaining a small size and low cost, due to the need for space and complex electronic circuits in array antennas.
An antenna device is constructed using a dielectric substrate with a single patch antenna and a cavity above it, where the cavity height is set within a specific range (0.8λ to 1.0λ) to broaden radiation direction and increase front-direction gain, eliminating the need for arraying and beamforming circuits.
The device achieves both wide-angle radiation directivity and high gain in the front direction without increasing size or cost, while reducing component and mounting costs by eliminating the need for arraying and complex electronic circuits.
Smart Images
Figure 2025175597000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to an antenna device configured using a dielectric substrate. [Background technology]
[0002] In mobile communications such as 5G and 6G, high-frequency radio waves are transmitted and received in various environments, such as inside and outside buildings. Therefore, antenna devices are required to have a wide-angle radiation directivity that enables radio waves to be transmitted and received in various directions. Furthermore, in addition to obtaining a wide-angle radiation directivity, such antenna devices are also required to sufficiently increase the peak of the antenna gain in the front direction of the radiation directivity. To meet these requirements, a known technique is to configure an array antenna in which multiple antenna elements are arranged in an array to achieve a wide-angle radiation directivity overall. For example, Patent Document 1 discloses a technology that can obtain a wide-angle radiation directivity by applying a phase difference to each antenna in an array antenna in which multiple antennas are arranged in an array, thereby performing beamforming. [Prior art documents] [Patent documents]
[0003] Patent No. 6818757 Summary of the Invention [Problem to be solved by the invention]
[0004] In recent years, antenna devices have widely adopted structures that use dielectric substrates in order to reduce size and weight. For example, forming a single patch antenna on a dielectric substrate makes it easy to reduce the size of the antenna device, but it is difficult to achieve a wide-angle radiation directivity. As mentioned above, to achieve both a wide-angle radiation directivity and high gain in the front direction of an antenna device, it is necessary to configure an array antenna by arranging multiple antennas, such as patch antennas, in an array on a dielectric substrate. However, array antennas using dielectric substrates require space for arranging multiple antennas, which increases the size and makes it difficult to miniaturize the antenna device. Furthermore, complex electronic circuits are required to provide phase differences for beamforming to multiple antennas, which increases both component and mounting costs and requires strict dimensional tolerances when manufacturing the dielectric substrate. As described above, when constructing an antenna device using a dielectric substrate using the above-mentioned conventional method, it has been difficult to achieve both a wide-angle radiation directivity and high gain in the front direction while also being small and low cost.
[0005] The present invention has been made to solve the above-mentioned problems, and realizes an antenna device that can be made smaller and less expensive by arranging only one patch antenna when constructing an antenna device using a dielectric substrate, while achieving both wide-angle radiation directivity and high gain in the front direction. [Means for solving the problem]
[0006] In order to solve the above problem, the antenna device (1) of the present invention is an antenna device constructed using a dielectric substrate, and comprises: a patch antenna (20) formed on a predetermined conductor layer of the dielectric substrate; a cavity (12) formed on a dielectric layer (11) arranged above the predetermined conductor layer of the dielectric substrate, and having a shape that surrounds the patch antenna in a planar view seen from a first direction (Z) that is the thickness direction of the dielectric substrate; and ground conductors (21, 22, 23) arranged opposite the dielectric layer in the first direction, sandwiching the predetermined conductor layer therebetween, and characterized in that the height (Z2) of the cavity along the first direction is set within a range of 0.8λ to 1.0λ, where λ is the wavelength of the operating frequency of the dielectric substrate.
[0007] According to the antenna device of the present invention, the antenna device uses a dielectric substrate, and includes a patch antenna and a ground conductor directly below the patch antenna. A cavity is formed in a dielectric layer stacked above the patch antenna, surrounding the patch antenna in a plan view from a first direction. The height of the cavity is set within a range of 0.8λ to 1.0λ, where λ is the wavelength of the operating frequency. With this structure, the electromagnetic field distribution on the dielectric surface on the side surface of the cavity above the patch antenna broadens the radiation direction of radio waves radiated from the patch antenna, widening the radiation angle. Furthermore, setting the cavity height within the above range increases the gain in the front direction. Therefore, the antenna device can be made smaller and less expensive without requiring the increased space required for arraying or the complex electronic circuitry required for beamforming, while simultaneously achieving a wide radiation angle and high gain in the front direction.
[0008] In the present invention, the patch antenna and the cavity can each have a variety of shapes when viewed from a first direction. For example, when viewed from the first direction, the patch antenna and the cavity can have a rectangular shape or a circular shape. Furthermore, when viewed from the first direction, it is desirable that the four sides of the cavity rectangle be larger than the four sides of the patch antenna rectangle by a distance in the range of 0.03λ to 0.07λ.
[0009] In the present invention, the patch antenna and the cavity can be arranged symmetrically with respect to the center of the dielectric substrate in a plan view seen from a first direction, thereby providing the antenna device with symmetric radiation directivity in each direction from approximately the center of the substrate plane.
[0010] In the present invention, the ground conductor can be formed on multiple conductor layers that are connected to each other through multiple via conductors extending in the first direction, thereby increasing the area of the ground conductor and strengthening the ground, thereby improving the antenna characteristics.
[0011] In the present invention, the patch antenna can be provided with a feeding structure for feeding either or both of horizontally polarized waves and vertically polarized waves, thereby enabling a single patch antenna to transmit and receive at least either or both of horizontally polarized radio waves and vertically polarized radio waves, and allowing each to be used appropriately depending on the usage situation. [Effects of the Invention]
[0012] According to the present invention, a single patch antenna is placed on a dielectric substrate, a cavity is placed above it, and the height of the cavity is set within a predetermined range. This makes it possible to realize an excellent antenna device that can achieve both a wide angle of radiation directivity and high gain in the front direction while avoiding the increase in size and cost that would accompany arraying the antenna device. [Brief explanation of the drawings]
[0013] [Figure 1] FIG. 1 is a perspective view of an antenna device 1 of the present embodiment, seen obliquely from above. [Figure 2] 2 is a cross-sectional structural diagram of the antenna device 1 of FIG. 1 taken along the line AA. [Figure 3] FIG. 1 is a plan view of the antenna device 1 of the present embodiment as viewed from above. [Figure 4] 10A and 10B are diagrams illustrating the conductor structure at the bottom of another antenna device 1 according to this embodiment. [Figure 5] 3 is a diagram showing radiation directivity in the XZ plane for the antenna device 1 of the present embodiment. FIG. [Figure 6] 3 is a diagram showing radiation directivity in the YZ plane for the antenna device 1 of the present embodiment. FIG. [Figure 7] FIG. 3 is a cross-sectional view of an antenna device 1a of a comparative example, and corresponds to FIG. 2. [Figure 8] FIG. 10 is a diagram showing radiation directivity in the XZ plane of an antenna device 1a as a comparative example of this embodiment. [Figure 9] FIG. 10 is a diagram showing radiation directivity in the YZ plane for an antenna device 1a as a comparative example of this embodiment. DETAILED DESCRIPTION OF THE INVENTION
[0014] Preferred embodiments of the present invention will be described below with reference to Figures 1 to 9. In these embodiments, an antenna device embodying the present invention will be described. However, the embodiments described below are merely examples of applications of the present invention, and the present invention is not limited to the content of these embodiments.
[0015] The structure of an antenna device 1 according to one embodiment of this invention will be described with reference to Figs. 1 to 4. Fig. 1 is a perspective view of the antenna device 1 as seen obliquely from above. Fig. 2 is a cross-sectional view of the antenna device 1 taken along the line AA in Fig. 1. Fig. 3 is a plan view of the antenna device 1 as seen from above. Fig. 4 is a diagram illustrating the conductor structure of the lower part of the antenna device 1. For ease of explanation, the mutually orthogonal X, Y, and Z directions (first directions according to the invention) are indicated by arrows in Figs. 1 to 4.
[0016] The antenna device 1 of this embodiment is configured using a dielectric substrate made of a dielectric material, and the dielectric substrate has a laminated structure of a lower dielectric layer 10 and an upper dielectric layer 11. A patch antenna 20 is formed at the center of the surface of the lower dielectric layer 10, and a cavity 12 is formed at the center of the upper dielectric layer 11. In other words, the cavity 12 is a hollow portion formed by removing a rectangular portion of the dielectric material in the center of the dielectric layer 11. In addition, a three-layer structure of ground conductors 21, 22, and 23 is arranged on the lower part of the lower dielectric layer 10 facing the patch antenna 20.
[0017] 2 and 3, in a plan view seen from the Z direction, the upper and lower dielectric layers 10 and 11 both have rectangular planar shapes of the same size, the patch antenna 20 has a rectangular planar shape that is sufficiently smaller than the dielectric layer 11, and the cavity 12 has a rectangular planar shape that is slightly larger than the patch antenna 20. In other words, since the cavity 12 is arranged to surround the patch antenna 20 in a planar view, the patch antenna 20 faces the air inside the cavity 12 directly above, resulting in a structure in which the patch antenna 20 is exposed to the outside.
[0018] FIG. 2 shows the height Z1 of the lower dielectric layer 10 in the Z direction and the height Z2 of the upper dielectric layer 11 in the Z direction (height Z2 of the cavity 12). It can be seen that Z2 is set to be larger than Z1. FIG. 3 shows the length X1 in the X direction and the length Y1 in the Y direction of the upper and lower dielectric layers 10 and 11, and the length X2 in the X direction and the length Y2 in the Y direction of the cavity 12, respectively. As already mentioned, X1 and Y1 are set to be larger than X2 and Y2. Furthermore, the size of the patch antenna 20 is set to be slightly smaller than X2 and Y2. FIGS. 1 to 4 illustrate a case where the dielectric layers 10 and 11 and the cavity 12 all have a square planar shape, and X1 = Y1 and X2 = Y2.
[0019] In this embodiment, the specific dimensional conditions, such as X1, X2, Y1, Y2, Z1, and Z2, must be appropriately determined depending on the frequency band used, antenna characteristics, and the like. For example, assuming a frequency of 28 GHz, one example of setting the dimensional conditions is as follows: X1 = Y1 = 7.6 mm, Z1 = 0.6 mm, and Z2 = 4.0 mm for the dielectric layers 10 and 11, and X2 = Y2 = 2.35 mm for the cavity 12. In this embodiment, appropriately setting the cavity height Z2 is important for ensuring sufficient gain in the front direction of the antenna device 1, as will be described later. The size of the patch antenna 20 is approximately 2 mm, slightly smaller than X2 and Y2. Generally, the lower the frequency band used, the larger the dimensional parameters should be set, and the higher the frequency band used, the smaller the dimensional parameters should be set.
[0020] Next, the conductor structure of the antenna device 1 will be described with reference to FIG. 4. In FIG. 4, the upper dielectric layer 11 is removed and only the lower dielectric layer 10 is shown. In addition to the patch antenna 20 and ground conductors 21, 22, and 23, multiple via conductors 30, 31, and 32 extending through the dielectric layer 10 in the stacking direction are also shown. The three-layer ground conductors 21, 22, and 23 are arranged in this order from the bottom up: ground conductor 21, ground conductor 22, and ground conductor 23. Each of the ground conductors 21, 22, and 23 is formed to extend over substantially the entire rectangular region of the dielectric layer 10. The three-layer ground conductors 21, 22, and 23 are electrically connected to each other via multiple via conductors 30. Since the large-area ground conductors 21, 22, and 23 are arranged facing the upper patch antenna 20, the ground of the antenna device 1 is strengthened, which is effective in improving the antenna characteristics.
[0021] As shown in FIG. 4, two via conductors 31 and 32 functioning as feed lines are connected to the patch antenna 20. A horizontally polarized high-frequency signal is fed to one via conductor 31, and a vertically polarized high-frequency signal is fed to the other via conductor 32. The patch antenna 20 in FIG. 3 shows an upper end 31a of the via conductor 31 for horizontal polarization and an upper end 32a of the via conductor 32 for vertical polarization, which are connected at positions offset horizontally and vertically from the center of the patch antenna 20, respectively. The lower ends of the via conductors 31 and 32 are connected to a pair of pads (not shown) on the bottom surface of the dielectric layer 10, enabling the pair of feed lines to be fed externally. This structure enables the antenna device 1 to radiate either or both of horizontally polarized and vertically polarized waves via the feed structure.
[0022] When a high-frequency signal is externally supplied to the antenna device 1 of this embodiment, radio waves are generally emitted upward in the Z direction (toward the front). In this case, in a conventional structure, the entire area above the patch antenna 20 on the surface of the dielectric layer 10 in the structure shown in FIG. 4 is air. In contrast, in this embodiment, a cavity 12 is present above the patch antenna 20. The role of the cavity 12 in this embodiment is to widen the radiation directivity of the antenna device 1 and to ensure sufficient gain in the front direction of the patch antenna 20 by setting the height Z2 of the cavity 12 within an appropriate range. It has been difficult to achieve both wide-angle radiation directivity and high gain in the front direction simply by providing a single patch antenna 20, as in the past. The antenna device 1 of this embodiment can achieve both wide-angle radiation directivity and high gain in the front direction, mainly due to the effect of providing the cavity 12. Verification results for this point will be described later.
[0023] Below, the results of verifying the antenna characteristics of the antenna device 1 of this embodiment will be described with reference to Figs. 5 to 9. Figs. 5 and 6 are diagrams showing the radiation directivity of the antenna device 1 of this embodiment when the height Z2 of the cavity 12 is changed, with the radiation directivity superimposed. Fig. 5 shows the directivity in the XZ plane, and Fig. 6 shows the directivity in the YZ plane. Both are the results of verifying, by simulation, the radiation directivity of radio waves radiated from the patch antenna 20 when a signal with a frequency of 28 GHz is input. In Figs. 5 and 6, the front direction (upward in the Z direction) is 0° on the horizontal axis, and the change in gain when tilted from there is shown using the height Z2 of the cavity 12 as a parameter.
[0024] 5 and 6, four gain graphs are shown overlapping one another for the height Z2 of the cavity 12: Z2=3.3 mm, Z2=3.6 mm, Z2=3.9 mm, and Z2=4.5 mm. In both the XZ plane and the YZ plane, the radiation directivity has a peak gain when the radiation direction is 0° (front direction), and the gain tends to gradually decrease as the radiation direction tilts away from 0°. Here, in FIGS. 5 and 6, the gain in the front direction according to the height Z2 of the cavity 12 is When Z2=3.3mm, 2.3dBi 6.4dBi when Z2=3.6mm When Z2=3.9mm, 8.2dBi When Z2=4.5mm, 9.6dBi It is expressed as:
[0025] 5 and 6, the angular range where the gain is half its peak value is defined as the half-width. As for the height Z2 of the cavity 12, the half-width tends to decrease as Z2 increases in both Figures 5 and 6. That is, the half-width according to the height Z2 of the cavity 12 is When Z2=3.3mm, 180° or more (Fig. 5 and Fig. 6) When Z2=3.6mm, it is approximately 70° (Fig. 5) and approximately 60° (Fig. 6). When Z2=3.9mm, the angle is approximately 60° (Fig. 5) and approximately 50° (Fig. 6). When Z2=4.5mm, it is approximately 50° (Fig. 5 and Fig. 6). It is expressed as:
[0026] The desired antenna performance of the antenna device 1 of this embodiment is to achieve both sufficient gain in the front direction and wide-angle radiation directivity. It is desirable to ensure a gain of approximately 3 dBi in the front direction. Furthermore, it is desirable for the radiation directivity to have a half-width of approximately 50° or more, and it is even more desirable for the gain to decrease less over a wider angular range. According to the results shown in Figures 5 and 6, when Z2 = 3.3 mm, the gain in the front direction is slightly insufficient. When Z2 is greater than this, sufficient gain in the front direction is obtained, and a half-width of 50° or more is obtained for all four Z2 values. However, since the half-width is estimated to fall below 50° when Z2 exceeds 4.5 mm, Z2 = 4.5 mm is considered to be the upper limit. From the above, it is possible to achieve both sufficient gain in the front direction and wide-angle radiation directivity when the height Z2 of the cavity 12 is within the range of approximately 3.5 mm to 4.5 mm.
[0027] When setting the dimensional parameters of the antenna device 1, it is desirable to express the appropriate range of the height Z2 of the cavity 12 in terms of the wavelength λ corresponding to the frequency used in the dielectric substrate. This wavelength λ takes into consideration the wavelength shortening effect of the dielectric substrate. In this case, it is desirable to set the appropriate range of the height Z2 of the cavity 12 within the range of 0.8λ to 1.0λ relative to the wavelength λ. Note that if the height Z2 is set so that Z2 > 1.0λ, the electromagnetic field distribution flowing on the dielectric surface becomes unbalanced, making it difficult to ensure sufficient gain. Therefore, by setting the height Z2 within the range of 0.8λ to 1.0λ, the antenna device 1 can achieve both sufficient gain in the forward direction and wide radiation directivity.
[0028] Here, for comparison with the antenna device 1 of this embodiment, an antenna device having a structure without an upper cavity 12 was used as a comparative example to compare the antenna characteristics. FIG. 7 is a cross-sectional structural diagram of the antenna device 1a of the comparative example, and corresponds to FIG. 2. That is, in the antenna device 1a of the comparative example, a patch antenna 20 is disposed at the center of the surface of the dielectric layer 10, but a cavity 12 surrounding the patch antenna 20 is not formed in the dielectric layer 11 above the dielectric layer 10. In other words, the patch antenna 20 does not face the air, but faces the dielectric material of the dielectric layer 11 as a whole. The dimensional parameters of the comparative example are the same as those of FIG. 2 of this embodiment, except for the portion of the cavity 12. The lower dielectric layer 10 has a height Z1 in the Z direction, and the upper dielectric layer 11 has a height Z2 in the Z direction.
[0029] Figures 8 and 9 are diagrams showing the radiation directivity of the antenna device 1a of the comparative example when the height Z2 of the dielectric layer 11 is changed, with the diagrams overlapping. Figure 8 corresponds to Figure 5 and shows the directivity in the XZ plane, while Figure 9 corresponds to Figure 6 and shows the directivity in the YZ plane. The radiation directivity in Figures 5 and 6 is the result of verification by the same simulation as Figures 5 and 6, but with regard to the parameter Z2, only two cases, Z2 = 3.3 mm and Z2 = 4.5 mm, are shown overlapping.
[0030] As shown in Figures 8 and 9, the gain of the antenna device 1 of the comparative example in the front direction is 5.1 dBi when Z2 = 3.3 mm and 3.8 dBi when Z2 = 4.5 mm, which is sufficient as a gain peak. However, with regard to the radiation directivity, the gain drops sharply around the radiation direction of 0°. In addition to the small half-width mentioned above, the degree of gain decrease is significant over a wider radiation angle range. Therefore, even if the antenna device 1 of the comparative example can ensure gain in the front direction, it is difficult to achieve wide-angle radiation directivity. In this regard, by adopting the structure of this embodiment, it is expected that the radio waves radiated from the patch antenna 20 will generate an electromagnetic field distribution on the dielectric surfaces constituting the four side surfaces of the cavity 12. When this electromagnetic field distribution propagates to the opening at the top of the cavity 12, it will spread in various directions, resulting in a wide-angle radiation directivity.
[0031] As described above, by adopting the structure of the antenna device 1 to which the present invention is applied, it is possible to realize antenna characteristics that can ensure both sufficient gain in the front direction and wide-angle radiation directivity. In other words, when no cavity 12 is provided as shown in FIG. 7, the radiation directivity is relatively narrow-angle, whereas in this embodiment, the effect of providing the cavity 12 in the dielectric layer 11 laminated on top of the dielectric layer 10 makes it possible to widen the radiation directivity angle. Furthermore, while the gain in the front direction decreases when the height Z2 of the cavity 12 is particularly small, by setting this height Z2 within the range of 0.8λ to 1.0λ relative to the wavelength λ, it is possible to ensure sufficient gain in the front direction.
[0032] Furthermore, in conventional configurations, achieving a wide-angle radiation directivity required an array antenna in which multiple antennas were arranged in an array and a method of controlling the phase of each antenna using beamforming. In contrast, the antenna device 1 of this embodiment achieves a wide-angle radiation directivity using only a single patch antenna 20 without configuring an array antenna. This eliminates the need for space for multiple antennas and the need for complex electronic circuits to impart phase differences to each antenna. Therefore, in addition to the superior antenna performance described above, the antenna device 1 of this embodiment is suitable for miniaturizing the antenna device 1 by reducing the size of the dielectric substrate compared to arrays using conventional configurations. This also allows for relaxed dimensional tolerances during the manufacture of the dielectric substrate, reducing component and mounting costs and enabling cost reductions.
[0033] In this embodiment, as described above, appropriate setting of dimensional parameters is important for achieving good antenna characteristics, including wide-angle radiation directivity. That is, the dimensional parameters of the antenna device 1 are not limited to the structures shown in FIGS. 1 to 4, but are preferably set to match the wavelength λ described above. The height Z2 of the cavity 12 in the Z direction is as described above, but the lengths X2 and Y2 of the cavity 12 in the X and Y directions are preferably set to be larger by a distance within a range of 0.03λ to 0.07λ than the lengths X and Y of the rectangular patch antenna 20 in the X and Y directions. These dimensional parameter conditions are desirable settings for ensuring the desired antenna characteristics of the antenna device 1.
[0034] In addition, in this embodiment, as shown in Fig. 3, the patch antenna 20 and the cavity 12 have a rectangular planar shape when viewed from the Z direction, but they may have a different planar shape without being limited to a rectangle. For example, the present invention can be applied even when the patch antenna 20 and the cavity 12 have a circular or polygonal planar shape other than a rectangle. Even in this case, the effects of the antenna device 1 to which the present invention is applied can be obtained. Furthermore, in this embodiment, the patch antenna 20 and the cavity 12 are arranged symmetrically with respect to the center of the dielectric substrates 10 and 11 when viewed from the Z direction, but the present invention can be applied even when they are arranged asymmetrically with respect to the center.
[0035] Although the present invention has been specifically described above based on the present embodiment, the present invention is not limited to the above embodiment and can be modified without departing from the spirit of the present invention. In other words, the basic structure of the antenna device 1 described using Figures 1 to 4 can be widely applied to various antenna devices 1 with other structures and shapes, as long as the effects of the present invention can be obtained. For example, various changes can be made to the shape, power feeding method, size, etc. of the patch antenna 20, as long as the effects of the present invention can be obtained. [Explanation of symbols]
[0036] 1...Antenna device 10, 11...Dielectric layers 12...cavity 20...Patch antenna 21, 22, 23...Ground conductors 33, 31, 32...Via conductors
Claims
1. An antenna device configured using a dielectric substrate, a patch antenna formed on a predetermined conductor layer of the dielectric substrate; a cavity formed in a dielectric layer disposed above the predetermined conductor layer of the dielectric substrate, the cavity having a shape surrounding the patch antenna in a plan view seen from a first direction which is a thickness direction of the dielectric substrate; a ground conductor disposed opposite the dielectric layer across the predetermined conductor layer in the first direction; Equipped with 2. The antenna device according to claim 1, wherein the height of the cavity in the first direction is set within a range of 0.8λ to 1.0λ, where λ is the wavelength of the frequency used in the dielectric substrate.
2. 2. The antenna device according to claim 1, wherein the patch antenna and the cavity each have a rectangular shape in a plan view seen from the first direction.
3. The antenna device according to claim 2, characterized in that, in a planar view from the first direction, the four sides of the cavity rectangle are set to be larger than the four sides of the patch antenna rectangle by a distance in the range of 0.03λ to 0.07λ.
4. 2. The antenna device according to claim 1, wherein the patch antenna and the cavity are arranged symmetrically with respect to the center of the dielectric substrate in a plan view seen from the first direction.
5. The antenna device according to claim 1 , wherein the ground conductor is formed on a plurality of conductor layers that are connected to each other through a plurality of via conductors that extend in the first direction.
6. 2. The antenna device according to claim 1, wherein the patch antenna is provided with a feeding structure for feeding either or both of horizontally polarized waves and vertically polarized waves.