Antenna device

Abstract

To provide an antenna device which has a housing with an opening corresponding to electric waves of an antenna element, and which can reduce a height of the opening.SOLUTION: An antenna device 10 comprises a housing 20 and an antenna element 42. The antenna element 42 is disposed inside the housing 20, and it emits electric waves with a predetermined frequency having a polarization plane parallel to a predetermined plane (an XY-plane). The housing 20 is provided with a predetermined opening 30 having two main openings 32 and a connection opening 38. The two main openings 32 are spaced away from each other in a first direction (a Z-direction). The connection opening 38 connects the two main openings 32 to each other in the first direction. In a second direction (a Y-direction), the connection opening 38 is smaller than each of the main openings 32. The predetermined opening 30 forms a split-ring resonator which resonates at the predetermined frequency, and it emits, to the outside of the housing 20, electric waves corresponding to the electric waves emitted from the antenna element 42.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an antenna device including a housing made of a conductive material and an antenna element disposed inside the housing. [Background technology]

[0002] For example, Patent Document 1 discloses an antenna device of this type.

[0003] 7, the antenna device 90 of Patent Document 1 includes a housing 92 made of a metal plate and an antenna element 98 arranged inside the housing 92. A slot 94 extending vertically is formed in a side plate of the housing 92. The slot 94 has a length according to the frequency (predetermined frequency) of radio waves radiated from the antenna element 98. Specifically, the length of the slot 94 is set to approximately 1 / 2 the wavelength of radio waves of the predetermined frequency. The slot 94 thus formed resonates with the radio waves radiated from the antenna element 98, and as a result, radio waves of the predetermined frequency are radiated outside the housing 92. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-098872 A Summary of the Invention [Problem to be solved by the invention]

[0005] For example, when the predetermined frequency of the antenna element 98 is 2.4 GHz, a slot 94 (opening) with a length of about 60 mm is required. On the other hand, the housing 92 is a housing member for housing members such as the antenna element 98 and a circuit board. When only the necessity of the housing 92 as a housing member is considered, the height of the housing 92 may be lower than 60 mm. In this case, it is necessary to make the housing 92 higher than the height required to house the members and form a high opening in the side plate, or to form an opening across the upper plate and lower plate of the low housing 92 as shown in FIG. 7. In the former case, the strength of the housing 92 is not significantly reduced, but the housing 92 must be made higher at the expense of the degree of freedom in design. In the latter case, the height of the housing 92 can be reduced, but the opening formed in the housing 92 reduces the strength of the housing 92. In order to satisfy both the strength of the housing 92 and the degree of freedom in design, it is necessary to lower the height of the opening formed in the housing 92.

[0006] SUMMARY OF THE PRESENT DISCLOSURE In view of the above, an object of the present invention is to provide an antenna device having a housing in which an opening corresponding to radio waves from an antenna element is formed, the height of the opening being able to be reduced. [Means for solving the problem]

[0007] The present invention provides a first antenna device, An antenna device comprising a housing made of a conductor and an antenna element, the antenna element is disposed inside the housing and emits radio waves of a predetermined frequency having a plane of polarization parallel to a predetermined plane; The housing has a predetermined opening formed therein, The predetermined opening has two main openings and a connecting opening, The two main openings are spaced apart from each other in a first direction perpendicular to the predetermined plane, the connecting opening connects the two main openings to each other in the first direction, The connecting opening has a size smaller than each of the main openings in a second direction perpendicular to the first direction, The predetermined opening forms a split ring resonator that resonates at the predetermined frequency, and radiates radio waves corresponding to the radio waves radiated from the antenna element to the outside of the housing. An antenna device is provided.

[0008] The present invention provides a second antenna device, which is a first antenna device, Each of the main openings has a rectangular shape, The connecting opening extends linearly along the first direction, The size of the connecting opening in the first direction is larger than the size of the connecting opening in the second direction. An antenna device is provided.

[0009] The present invention provides a third antenna device, which is the first or second antenna device, The two main openings have the same shape. An antenna device is provided.

[0010] The present invention provides a fourth antenna device, which is the first or second antenna device, The housing is formed from a metal plate, The size of the connecting opening in the second direction is four times or less the thickness of the metal plate. An antenna device is provided.

[0011] The present invention provides a fifth antenna device, which is the first or second antenna device, The size of the connecting opening in the second direction is 1 / 50 or less of the length of the inner edge of each of the main openings. An antenna device is provided. Effect of the Invention

[0012] The predetermined opening of the present invention functions as an LC resonator having an inductor component formed mainly from the main opening and a capacitor component formed mainly from the connecting opening. The LC resonator formed in this way resonates with radio waves of various frequencies without changing the height of the housing, for example, by adjusting the shape and size of the main opening and the connecting opening. According to the present invention, it is possible to provide an antenna device including a housing in which an opening corresponding to the radio wave of the antenna element is formed, and in which the height of the opening can be reduced. [Brief description of the drawings]

[0013] [Figure 1] 1 is a perspective view showing an antenna device according to an embodiment of the present invention, in which the position of an antenna element disposed inside a housing is drawn by a dashed line. [Diagram 2] 2 is a front view showing the antenna device of FIG 1. The position of the hidden upper surface of the printed circuit board is drawn by a dashed line. [Diagram 3] 3 is a front view showing an example of a predetermined opening of the antenna device of FIG. 2. [Figure 4] FIG. 4 is a diagram showing an LC resonator formed by the predetermined opening in FIG. 3. [Diagram 5] 3 is a cross-sectional view showing the antenna device of FIG. 2 taken along line VV. [Figure 6] 6 is an enlarged cross-sectional view showing a part (a part surrounded by a dashed dotted line A) of the antenna device of FIG. 5. [Figure 7] 1 is a perspective view showing the antenna device of Patent Document 1. The outline of the antenna element disposed inside the housing is drawn with a dashed line. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Referring to Fig. 1, an antenna device 10 according to an embodiment of the present invention includes a housing 20 made of a conductor and an antenna element 42 made of a conductor. The housing 20 of this embodiment is formed into a rectangular parallelepiped shape by six metal plates 22 connected to each other. The antenna element 42 of this embodiment is disposed inside the housing 20 and surrounded by the six metal plates 22. The antenna device 10 of this embodiment has the above-mentioned structure. However, the present invention is not limited to this. For example, the material and shape of the housing 20 can be variously modified as necessary.

[0015] Referring to FIG. 5, the antenna device 10 of this embodiment includes a printed circuit board 40. The printed circuit board 40 is disposed inside the housing 20. The antenna element 42 is provided on the upper surface of the printed circuit board 40. In addition to the antenna element 42, a power supply unit 48 is provided on the printed circuit board 40. The antenna element 42 emits radio waves of a predetermined frequency in response to a signal fed from the power supply unit 48. The printed circuit board 40 of this embodiment includes the above-mentioned components. However, the present invention is not limited to this. For example, the printed circuit board 40 may include various components, such as a processing device that transmits and receives signals, in addition to the above-mentioned components.

[0016] 5 and 6, the antenna element 42 of this embodiment is a split ring resonator formed on the upper surface of the printed circuit board 40. The antenna element 42 of this embodiment is a 2.4 GHz band single band antenna. However, the antenna element 42 of the present invention is not particularly limited. For example, the antenna element 42 may be a dipole antenna. The frequency band of the antenna element 42 is not limited to the 2.4 GHz band.

[0017] 5, the printed circuit board 40 of this embodiment extends along a horizontal plane perpendicular to the up-down direction. The up-down direction in this embodiment is the direction of gravity, which is the Z direction. In this embodiment, the up direction is the +Z direction, and the down direction is the -Z direction. The horizontal plane in this embodiment is the XY plane.

[0018] The antenna element 42 of this embodiment is located on the upper surface of the printed circuit board 40 and extends along a horizontal plane. The antenna element 42 thus formed radiates horizontally polarized waves having a polarization plane parallel to the ground. Specifically, the electric field EF of the radio waves radiated from the antenna element 42 vibrates parallel to the ground. However, the present invention is not limited to this. For example, the printed circuit board 40 may extend along a vertical plane (XZ plane) parallel to the up-down direction, and the antenna element 42 may extend along the vertical plane. More specifically, the housing 20 may be arranged so that the illustrated printed circuit board 40 extends along the vertical plane.

[0019] To summarize the above description, the antenna element 42 emits radio waves of a predetermined frequency having a polarization plane parallel to a predetermined plane. The predetermined plane in this embodiment is a horizontal plane (XY plane) parallel to the ground. However, the present invention is not limited to this. For example, the predetermined plane may be a vertical plane (XZ plane) perpendicular to the ground.

[0020] 1 and 2, the housing 20 has a designated plate 24. In this embodiment, the designated plate 24 is one of the metal plates 22, and is a plate on the front side of the housing 20 in the front-rear direction perpendicular to the up-down direction. That is, the designated plate 24 is neither an upper plate nor a lower plate of the housing 20. The front-rear direction in this embodiment is the X direction. In this embodiment, the front is the +X direction, and the rear is the -X direction.

[0021] The predetermined plate 24 has a predetermined opening 30 formed therein. The predetermined opening 30 is a hole penetrating the predetermined plate 24 in the front-rear direction. That is, the housing 20 has the predetermined opening 30, which is a hole. The housing 20 of this embodiment has no holes formed therein except for the predetermined opening 30. The antenna element 42 of this embodiment is completely surrounded by the metal plate 22, which is a conductor, except for the predetermined opening 30. However, the present invention is not limited to this. For example, one or more metal plates 22 may have a plurality of small holes formed therein for heat dissipation.

[0022] 1 to 3, the predetermined opening 30 has two main openings 32 and a connecting opening 38. The two main openings 32 are separated from each other in a first direction perpendicular to the predetermined plane (XY plane). The first direction in this embodiment is the up-down direction, which is the Z direction. However, as long as the first direction is perpendicular to the predetermined plane, the first direction is not limited to this embodiment. For example, when the antenna element 42 radiates vertically polarized waves, the predetermined plane may be the XZ plane, and the first direction may be a horizontal direction perpendicular to the predetermined plane (XZ plane). The horizontal direction in this embodiment is the Y direction.

[0023] 3, the connecting opening 38 connects the two main openings 32 to each other in a first direction (Z direction). The connecting opening 38 has a size (width WS) smaller than each of the main openings 32 in a second direction (Y direction) perpendicular to the first direction.

[0024] 4 together with FIG. 3, the predetermined opening 30 having the above-described structure functions as an LC resonator having an inductor component L0 formed mainly from the main opening 32 and a capacitor component C0 formed mainly from the connecting opening 38. More specifically, the predetermined opening 30 functions as a split ring resonator.

[0025] 5 and 6 together with Figures 3 and 4, when the radio waves radiated from the antenna element 42 propagate to the predetermined opening 30, an induced current corresponding to the radio waves radiated from the antenna element 42 flows around the periphery of the predetermined opening 30. When the predetermined frequency of the radio waves radiated from the antenna element 42 substantially matches the resonant frequency of the LC resonator formed by the predetermined opening 30, the LC resonator is excited and radiates radio waves of the predetermined frequency to the outside of the housing 20.

[0026] 1, 3 and 4, the LC resonator formed as described above resonates with radio waves of various frequencies without changing the height of the housing 20, for example, by adjusting the shape and size of the main opening 32 and the connecting opening 38. In detail, the resonant frequency of the illustrated LC resonator is inversely proportional to the square root of L0×C0. The value of L0 increases when the length of the inner edge 34 of the main opening 32 is increased, and decreases when the length of the inner edge 34 is decreased. The value of C0 decreases when the length LS of the connecting opening 38 is decreased or the width WS is increased, and increases when the length LS is increased or the width WS is narrowed. For example, by narrowing the width WS, the resonant frequency of the LC resonator can be made to match the predetermined frequency of the antenna element 42 while keeping the height of the predetermined opening 30 low.

[0027] As described above, the predetermined opening 30 of the present embodiment forms a split ring resonator that resonates at a predetermined frequency, and radiates radio waves corresponding to the radio waves radiated from the antenna element 42 to the outside of the housing 20. According to the present embodiment, it is possible to provide an antenna device 10 that includes a housing 20 in which an opening corresponding to the radio waves of the antenna element 42 is formed, and that allows the height of the opening to be reduced.

[0028] 3, the length of the inner edge 34 of each of the illustrated main openings 32 is 59.5 mm. In the illustrated connecting opening 38, the width WS is 0.5 mm and the length is 5 mm. The height of the illustrated predetermined opening 30 is 25 mm, which is less than half the height required for the slot antenna shown in FIG. 7. Although the predetermined opening 30 has a low height as described above, it can radiate radio waves of a frequency of 2.4 GHz corresponding to the antenna element 42 of this embodiment to the outside of the housing 20.

[0029] According to this embodiment, each of the main openings 32 has a rectangular shape. The connecting opening 38 extends linearly along the first direction (Z direction). The size (length LS) of the connecting opening 38 in the first direction is larger than the size (width WS) of the connecting opening 38 in the second direction (Y direction). The predetermined opening 30 having the above-mentioned simple shape is easy to form. However, the present invention is not limited to this, and the shape of the predetermined opening 30 can be modified in various ways as long as it is possible to form a split ring resonator having a resonant frequency equal to the predetermined frequency of the antenna element 42.

[0030] The two main openings 32 in this embodiment have the same shape. More specifically, in a plane defined by the first direction (Z direction) and the second direction (Y direction), the two main openings 32 have shapes that are congruent with each other. With this structure, when the resonant frequency of the LC resonator is set to a desired value, the total area of ​​the main openings 32 can be minimized. That is, it is easy to reduce the size of the predetermined opening 30 in the first direction. However, the present invention is not limited to this. For example, the two main openings 32 may have shapes different from each other.

[0031] Referring to FIG. 6, the housing 20 of this embodiment is formed from the metal plate 22 as described above. The metal plates 22 of this embodiment have the same plate thickness TP. In particular, the specified plate 24, which is one of the metal plates 22, has a substantially constant plate thickness TP regardless of the location. The size (width WS) of the connecting opening 38 in the second direction (Y direction) is four times or less the plate thickness TP of the metal plate 24. This structure makes it easy to increase the value of the capacitor component C0 (see FIG. 4) formed by the connecting opening 38. However, the present invention is not limited to this, and the relationship between the width WS and the plate thickness TP can be modified as necessary.

[0032] 3, in this embodiment, the size (width WS) of the connecting opening 38 in the second direction (Y direction) is 1 / 50 or less of the length of each inner edge 34 of the main openings 32. This structure also makes it easy to increase the value of the capacitor component C0 (see FIG. 4) formed by the connecting opening 38. However, the present invention is not limited to this, and the relationship between the width WS and the length of the inner edge 34 of the main opening 32 can be modified as necessary.

[0033] 1, in addition to the various modifications already described, the antenna device 10 can be modified in various ways. For example, the predetermined opening 30 in this embodiment is visible from the outside. On the other hand, the predetermined opening 30 may be covered with a cover made of an insulating material such as resin. In other words, the predetermined opening 30 does not have to be visible from the outside.

[0034] In this embodiment, the antenna element 42 arranged inside the housing 20 is composed of only one single-band antenna, and the number of the predetermined openings 30 formed in the housing 20 is one. However, the present invention is not limited to this. For example, the antenna element 42 may include two or more single-band antennas that radiate radio waves of different predetermined frequencies, or may be a multi-band antenna that radiates radio waves of two or more predetermined frequencies that are different from each other. In this case, two or more predetermined openings 30 having resonant frequencies corresponding to the two or more predetermined frequencies may be formed in the housing 20.

[0035] 2, the printed circuit board 40 of this embodiment is located at the vertical middle of the housing 20. More specifically, the vertical position of the top surface of the printed circuit board 40 coincides with the vertical middle of the connecting opening 38. That is, the antenna element 42 (see FIG. 5) is located at the vertical middle of the connecting opening 38. This arrangement is preferable from the viewpoint of radiating radio waves of a predetermined frequency to the outside of the housing 20. However, the present invention is not limited to this. For example, the vertical position of the top surface of the printed circuit board 40 may be shifted up or down to some extent compared to the vertical middle of the connecting opening 38. [Explanation of symbols]

[0036] 10 Antenna device 20. Cabinet 22 Metal plate 24 Specified plate (metal plate) 30 Predetermined opening 32 Main opening 34 Common-law marriage 38 Connecting opening 40 Printed Circuit Board 42 Antenna elements 48 Power supply unit EF Electric field

Claims

1. An antenna device comprising a housing made of a conductor and an antenna element, the antenna element is disposed inside the housing and emits radio waves of a predetermined frequency having a plane of polarization parallel to a predetermined plane; The housing has a predetermined opening formed therein, The predetermined opening has two main openings and a connecting opening, The two main openings are spaced apart from each other in a first direction perpendicular to the predetermined plane, the connecting opening connects the two main openings to each other in the first direction, The connecting opening has a size smaller than each of the main openings in a second direction perpendicular to the first direction, The predetermined opening forms a split ring resonator that resonates at the predetermined frequency, and radiates radio waves corresponding to the radio waves radiated from the antenna element to the outside of the housing. Antenna device.

2. 2. The antenna device according to claim 1, Each of the main openings has a rectangular shape, The connecting opening extends linearly along the first direction, The size of the connecting opening in the first direction is larger than the size of the connecting opening in the second direction. Antenna device.

3. 3. The antenna device according to claim 1, The two main openings have the same shape. Antenna device.

4. 3. The antenna device according to claim 1, The housing is formed from a metal plate, The size of the connecting opening in the second direction is four times or less the plate thickness of the metal plate. Antenna device.

5. 3. The antenna device according to claim 1, The size of the connecting opening in the second direction is 1 / 50 or less of the length of the inner edge of each of the main openings. Antenna device.

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