Antenna device

Abstract

The invention discloses an antenna device which comprises a shell and an antenna element. The antenna element is disposed in the housing and radiates a radio wave having a predetermined frequency, the radio wave having a polarization plane parallel to a predetermined plane. The housing is formed with a predetermined opening. The predetermined opening has two main openings and a coupling opening. The two main openings are separated from each other in a first direction perpendicular to the predetermined plane. A coupling opening couples the two main openings together in a first direction. A size of the coupling opening in a second direction perpendicular to the first direction is smaller than a size of each of the two main openings. The predetermined opening forms a split ring resonator that resonates at a predetermined frequency, the split ring resonator radiating a radio wave corresponding to a radio wave radiated from the antenna element. The present invention includes a housing in which an opening is formed, the opening corresponding to radio waves of an antenna element and the height of which can be reduced.

Description

Technical Field

[0001] The present invention relates to an antenna device including a housing made of a conductor and an antenna element arranged in the housing. Background Art

[0002] This type of antenna device is disclosed, for example, in JP2017-098872A (Patent Document 1), the contents of which are incorporated herein by reference.

[0003] Reference Figure 7 Patent Document 1 discloses an antenna device 90 comprising a housing 92 formed from a metal plate and an antenna element 98 disposed within housing 92. Housing 92 has a side panel formed with a vertically extending slot 94. Slot 94 has a length corresponding to a predetermined frequency, which is the frequency of radio waves radiated from antenna element 98. Specifically, slot 94 is designed to have a length approximately half the wavelength of the radio waves having the predetermined frequency. This formed slot 94 resonates with the radio waves radiated from antenna element 98, causing radio waves having the predetermined frequency to radiate outward from housing 92.

[0004] For example, when the predetermined frequency of the antenna element 98 is 2.4 GHz, the slot 94 (opening) needs to have a length of about 60 mm. From another perspective, the housing 92 is a containing member for containing components such as the antenna element 98 and the circuit board. Considering only the necessity of the housing 92 as a containing member, the housing 92 may have a height of less than 60 mm. When the necessary height of the housing for containing components is less than 60 mm, the housing 92 should be made higher than the necessary height so that the side panels of the housing 92 can be formed with high openings, or the housing 92 should be formed with openings extending above the upper and lower panels of the low housing 92, such as Figure 7 As shown. According to the former solution, the strength of the housing 92 will not be greatly reduced, but the housing 92 must be made taller at the expense of design flexibility. According to the latter solution, the height of the housing 92 can be reduced, but the strength of the housing 92 is reduced due to the opening formed in the housing 92. The height of the opening formed in the housing 92 should be reduced to meet the requirements of both the strength of the housing 92 and the design flexibility. Summary of the Invention

[0005] An object of the present invention is to provide an antenna device including a housing formed with an opening corresponding to radio waves of an antenna element and capable of reducing the height.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In one aspect, the present invention provides an antenna device comprising a housing made of a conductor and an antenna element. The antenna element is arranged in the housing and configured to radiate radio waves having a predetermined frequency, the radio waves having a polarization plane parallel to a predetermined plane. The housing is formed with a predetermined opening. The predetermined opening has two main openings and a coupling opening. The two main openings are separated from each other in a first direction perpendicular to the predetermined plane. The coupling opening couples the two main openings together along the first direction. The dimension of the coupling opening in a second direction perpendicular to the first direction is smaller than the dimension of each main opening. The predetermined opening forms a split ring resonator that resonates at a predetermined frequency. The predetermined opening is configured to radiate radio waves corresponding to the radio waves radiated from the antenna element outward from the housing.

[0008] In one aspect of the present invention, the predetermined opening functions as an LC resonator, which has an inductive component primarily formed by the main opening and a capacitive component primarily formed by the connection opening. This LC resonator can resonate with various radio waves of varying frequencies, for example, by adjusting the shapes and sizes of the main opening and the connection opening, while maintaining the height of the housing. Thus, in one aspect, the present invention provides an antenna device including a housing having an opening formed therein, the opening corresponding to the radio waves of the antenna element and capable of reducing its height. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 FIG. 1 is a perspective view of an antenna device according to an embodiment of the present invention, wherein the position of the antenna element arranged in the housing is shown by a dotted line.

[0010] Figure 2 yes Figure 1 A front view of the antenna device is shown, wherein the position of the upper surface of the circuit board is hidden by the dotted line.

[0011] Figure 3 yes Figure 2 A front view showing an example of a predetermined opening for an antenna device is shown.

[0012] Figure 4 is Figure 3 A view showing an LC resonator formed by predetermined openings.

[0013] Figure 5 yes Figure 2 A cross-sectional view of the antenna device taken along the line VV is shown.

[0014] Figure 6 is Figure 5 An enlarged cross-sectional view of a portion of the antenna device enclosed by a dashed line is shown.

[0015] Figure 7 is a perspective view of the antenna device of Patent Document 1, in which the outline of the antenna element arranged in the housing is shown by a dotted line. DETAILED DESCRIPTION

[0016] Reference Figure 1 The antenna device 10 of the present embodiment 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 of six interconnected metal plates 22 and has a rectangular parallelepiped shape. The antenna element 42 of this embodiment is arranged in the housing 20 and surrounded by the six metal plates 22. The antenna device 10 of this embodiment has the above-described structure. However, the present invention is not limited thereto. For example, the material and shape of the housing 20 can be variously modified as needed.

[0017] Reference Figure 5 The antenna device 10 of this embodiment includes a printed circuit board 40. The printed circuit board 40 is arranged in the housing 20. An antenna element 42 is provided on the upper surface of the printed circuit board 40. In addition to the antenna element 42, the printed circuit board 40 is also provided with a feeder 48. The antenna element 42 radiates radio waves having a predetermined frequency in response to a signal fed by the feeder 48. The printed circuit board 40 of this embodiment includes the above-mentioned components. However, the present invention is not limited thereto. For example, in addition to the above-mentioned components, the printed circuit board 40 may also include various components such as a processing device for sending and receiving signals.

[0018] Reference Figure 5 and Figure 6 In this embodiment, antenna element 42 is a split-ring resonator formed on the upper surface of printed circuit board 40. Furthermore, antenna element 42 in this embodiment is a 2.4 GHz single-band antenna. However, there are no particular limitations on antenna element 42 of the present invention. For example, antenna element 42 may be a dipole antenna. The frequency band of antenna element 42 is not limited to the 2.4 GHz band.

[0019] Reference Figure 5 In this embodiment, the printed circuit board 40 extends along a horizontal plane perpendicular to the vertical direction. The vertical direction in this embodiment is the direction of gravity and the Z direction. In this embodiment, "upward" refers to the positive Z direction, and "downward" refers to the negative Z direction. The horizontal plane in this embodiment is the XY plane.

[0020] 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 formed in this way radiates horizontally polarized waves having a polarization plane parallel to the ground. In detail, the radio waves radiated from the antenna element 42 have an electric field EF oscillating parallel to the ground. However, the present invention is not limited to this. For example, the printed circuit board 40 can extend along a vertical plane (XZ plane) parallel to the up and down direction, and the antenna element 42 can extend along the vertical plane. More specifically, the housing 20 can be arranged so that the printed circuit board 40 shown extends along a vertical plane.

[0021] To summarize the above description, antenna element 42 is configured to radiate radio waves having a predetermined frequency, the radio waves having a polarization plane parallel to a predetermined plane. In the present embodiment, the predetermined plane is a horizontal plane parallel to the ground (XY plane). However, the present invention is not limited thereto. For example, the predetermined plane may be a vertical plane perpendicular to the ground (XZ plane).

[0022] like Figure 1 and Figure 2 As shown, the housing 20 has a predetermined plate 24. In this embodiment, the predetermined plate 24 is one of the metal plates 22. More specifically, the predetermined plate 24 is the front plate of the housing 20 in the front-to-back direction, which is perpendicular to the up-down direction. Therefore, the predetermined plate 24 is neither the upper plate nor the lower plate of the housing 20. The front-to-back direction in this embodiment is the X direction. In this embodiment, "forward" refers to the positive X direction, and "rearward" refers to the negative X direction.

[0023] The predetermined plate 24 is formed with a predetermined opening 30. The predetermined opening 30 is a hole that passes through the predetermined plate 24 in the front-to-back direction. Therefore, the housing 20 is formed with the predetermined opening 30 as a hole. The housing 20 of this embodiment has no other holes other than the predetermined opening 30. Aside from the predetermined opening 30, the antenna element 42 of this embodiment is completely surrounded by the conductive body or metal plate 22. However, the present invention is not limited to this. For example, one or more metal plates 22 may be formed with multiple small holes for dissipating heat.

[0024] Reference Figures 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 of the present embodiment is the up and down direction and the Z direction. However, the first direction is not limited to the direction of the present embodiment, as long as the first direction is perpendicular to the predetermined plane. For example, in the case where the antenna element 42 radiates vertically polarized waves, the predetermined plane can be an XZ plane, and the first direction can be a lateral direction perpendicular to the predetermined plane (XZ plane). The lateral direction of the present embodiment is the Y direction.

[0025] Reference Figure 3 The coupling opening 38 couples the two main openings 32 together along a first direction (Z direction). The dimension (width WS) of the coupling opening 38 in a second direction (Y direction) perpendicular to the first direction is smaller than that of each main opening 32 .

[0026] and Figure 3 Reference together Figure 4 The predetermined opening 30 having the above-described structure functions as an LC resonator having an inductance component L0 mainly formed by the main opening 32 and a capacitance component C0 mainly formed by the coupling opening 38. More specifically, the predetermined opening 30 functions as a split ring resonator.

[0027] Combine Figure 3 and Figure 4 Come and see Figure 5 and Figure 6 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 through the inner edge located around the predetermined opening 30. When the predetermined frequency of the radio waves radiated from the antenna element 42 is substantially equal to the resonant frequency of the LC resonator formed by the predetermined opening 30, the LC resonator is excited, thereby radiating radio waves having the predetermined frequency outward from the housing 20.

[0028] Reference Figure 1 、 Figure 3 and Figure 4 The LC resonator formed as described above can resonate with various radio waves having various frequencies by adjusting the shapes and sizes of the main opening 32 and the connecting opening 38, for example, while maintaining the height of the housing 20. Specifically, the resonant frequency of the LC resonator shown is inversely proportional to the square root of L0×C0. The value of L0 increases as the length of the inner edge 34 of each main opening 32 becomes longer, and decreases as the length of the inner edge 34 becomes shorter. The value of C0 decreases as the length LS of the connecting opening 38 becomes shorter or as the width WS of the connecting opening 38 becomes wider. The value of C0 increases as the length LS becomes longer or as the width WS becomes narrower. For example, by narrowing the width WS while maintaining the height of the predetermined opening 30 low, the resonant frequency of the LC resonator can be made equal to the predetermined frequency of the antenna element 42.

[0029] As described above, the predetermined opening 30 of this embodiment forms a split ring resonator that resonates at a predetermined frequency. Furthermore, the predetermined opening 30 of this embodiment is configured to radiate radio waves corresponding to the radio waves radiated from the antenna element 42 outward from the housing 20. This embodiment provides an antenna device 10 that includes the housing 20 having an opening formed therein that corresponds to the radio waves radiated from the antenna element 42 and that can be reduced in height.

[0030] Reference Figure 3 , the length of the inner edge 34 of each main opening 32 shown is 59.5 mm. In the illustrated connecting opening 38, the width WS is 0.5 mm and the length LS is 5 mm. The predetermined opening 30 shown has a height of 25 mm, which is equal to or less than Figure 7 Although the predetermined opening 30 has a reduced height as described above, the predetermined opening 30 can radiate radio waves having a frequency of 2.4 GHz outward from the housing 20 , which corresponds to the antenna element 42 of the present embodiment.

[0031] According to the present embodiment, each main opening 32 has a rectangular shape. The connecting opening 38 extends linearly along the first direction (Z direction). The connecting opening 38 has a first dimension (length LS) in the first direction and a second dimension (width WS) in the second direction (Y direction). The first dimension is larger than the second dimension. The predetermined opening 30 having the above-mentioned simple shape can be easily formed. However, the present invention is not limited thereto, and as long as the predetermined opening 30 can form an open ring resonator having a resonant frequency equal to the predetermined frequency of the antenna element 42, the shape of the predetermined opening 30 can be variously modified.

[0032] The two main openings 32 of this embodiment have the same shape. Specifically, the two main openings 32 have the same consistent shape in a plane defined by a first direction (Z direction) and a second direction (Y direction). According to 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. Therefore, the size of the predetermined opening 30 in the first direction can be easily reduced. However, the present invention is not limited to this. For example, the two main openings 32 can have different shapes.

[0033] Reference Figure 6 , the housing 20 of this embodiment is formed by the aforementioned metal plate 22. The metal plates 22 of this embodiment have the same thickness TP as each other. In particular, the predetermined plate 24 as one of the metal plates 22 has a substantially constant thickness TP regardless of its position. The dimension (width WS) of the coupling opening 38 in the second direction (Y direction) is equal to or less than four times the thickness TP of the metal plate 22. According to this structure, the capacitance component C0 (see Figure 4 However, the present invention is not limited thereto, and the relationship between the width WS and the thickness TP may be modified as needed.

[0034] Reference Figure 3 According to this embodiment, the dimension (width WS) of the coupling opening 38 in the second direction (Y direction) is equal to or less than one-fiftieth of the length of the inner edge 34 of each main opening 32. According to this structure, the capacitance component C0 (see FIG. 1 ) formed by the coupling opening 38 Figure 4 However, the present invention is not limited thereto, and the relationship between the width WS of each main opening 32 and the length of the inner edge 34 may be modified as needed.

[0035] Reference Figure 1 In addition to the various modifications already described, various modifications can be made to the antenna device 10. For example, in this embodiment, the predetermined opening 30 is visible from the outside. However, the predetermined opening 30 can be covered with a cover made of an insulator such as resin. In other words, the predetermined opening 30 can be invisible from the outside.

[0036] In this embodiment, the antenna element 42 provided in the housing 20 is composed of only one single-band antenna, and the number of 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 at predetermined frequencies different from each other. The antenna element 42 may be a multi-band antenna that radiates two or more radio waves at predetermined frequencies different from each other. In these cases, the housing 20 may be formed with two or more predetermined openings 30 having resonant frequencies corresponding to the two or more predetermined frequencies, respectively.

[0037] Reference Figure 2 , the printed circuit board 40 of this embodiment is located in the middle of the housing 20 in the vertical direction. In detail, the position of the upper surface of the printed circuit board 40 in the vertical direction is equal to the position of the midpoint of the connection opening 38 in the vertical direction. In other words, the antenna element 42 (such as Figure 5 ) is located vertically in the middle of the coupling opening 38. This arrangement is preferred from the perspective of radiating radio waves having a predetermined frequency outward from the housing 20. However, the present invention is not limited thereto. For example, the upper surface of the printed circuit board 40 may be vertically offset to a certain extent relative to the vertical midpoint of the coupling opening 38.

[0038] The above are preferred embodiments of the present invention and the technical principles used therein. For those skilled in the art, any obvious changes such as equivalent transformations, simple replacements, etc. based on the technical solution of the present invention, without departing from the spirit and scope of the present invention, are within the scope of protection of the present invention.

Claims

1. An antenna device comprising a housing made of a conductor and an antenna element, Features: The antenna element is arranged in the housing and configured to radiate radio waves having a predetermined frequency, the radio waves having a polarization plane parallel to a predetermined plane; The housing is formed with a predetermined opening; The predetermined opening has two main openings and a connecting opening; The two main openings are separated from each other in a first direction perpendicular to the predetermined plane; The connecting opening connects the two main openings together along the first direction; The coupling opening has a dimension in a second direction perpendicular to the first direction that is smaller than a dimension of each of the main openings; The predetermined opening forms a split ring resonator that resonates at the predetermined frequency; as well as The predetermined opening is configured to radiate radio waves corresponding to the radio waves radiated from the antenna element outwardly from the housing.

2. The antenna device according to claim 1, Features: Each of said main openings has a rectangular shape; The coupling opening extends linearly along the first direction; The coupling opening has a first dimension in the first direction and a second dimension in the second direction; as well as The first size is greater than the second size.

3. The antenna device according to claim 1 or 2, Features: The two main openings have the same shape as each other.

4. The antenna device according to claim 1 or 2, Features: The housing is formed of sheet metal; and A dimension of the coupling opening in the second direction is equal to or less than four times a thickness of the metal plate.

5. The antenna device according to claim 1 or 2, Features: A dimension of the coupling opening in the second direction is equal to or smaller than one fiftieth of a length of an inner edge of each of the main openings.

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