Antenna device

Abstract

To provide an antenna device capable of easily adjusting a resonance frequency with a simple configuration.SOLUTION: An antenna device 10 includes a rectangular substrate 100, and a first element part 101 whose both ends are provided on a third side S3 and a fourth side S4 and which is formed in a rectangular shape. Further, the antenna device 10 includes the second element part 102 that is in contact with the third side S3 and the fifth side S5, which is one side of the first element part 101, in a region different from the first element part 101. Further, the antenna device 10 includes the third element part 103 that is in contact with the fourth side S4 and the fifth side S5 in a region different from the first element part 101 and the second element part 102. The fifth side S5 has a side having a predetermined length in which the first element portion 101 is not in contact with the second element portion 102 and the third element portion 103 between the side in which the first element portion 101 is in contact with the second element portion 102 and the side in which the first element portion 101 is in contact with the third element portion 103.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an antenna device. [Background technology]

[0002] Conventionally, in a planar antenna, a technology has been proposed for obtaining desired characteristics in a communication environment by changing the shape of the conductor that is the antenna element. Patent Document 1 discloses a printed circuit board dipole antenna. The dipole antenna disclosed in Patent Document 1 has a wide resonant frequency band and allows for flexible design by adjusting the shape of the antenna element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-220739 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to obtain resonance at a desired frequency in the dipole antenna disclosed in Patent Document 1, it is necessary to adjust each parameter of the antenna. However, in this dipole antenna, the shape of the antenna element is complex, and it may be difficult to appropriately adjust the parameters to obtain resonance at a desired frequency.

[0005] The present invention has been made in view of the problems inherent in the conventional technology, and an object of the present invention is to provide an antenna device that has a simple configuration and is capable of easily adjusting the resonant frequency. [Means for solving the problem]

[0006] An antenna device according to an aspect of the present invention comprises: a rectangular substrate defined by a first side and a second side that are parallel in a first direction, and a third side and a fourth side that are parallel in a second direction that is perpendicular to the first direction and whose length is longer than the lengths of the first and second sides; an antenna element made of metal foil on the surface of the substrate, the first element portion being formed in a rectangular shape with both ends provided on the third and fourth sides and the first direction being its longitudinal direction; an antenna element made of metal foil on the surface of the substrate, the second element portion being in contact with the third side and a fifth side that is one side of the first element portion in an area different from the first element portion; and an antenna element made of metal foil on the surface of the substrate, the third element portion being in contact with the fourth side and the fifth side in an area different from the first element portion and the second element portion, the fifth side having a predetermined length between the side where the first element portion and the second element portion are in contact and the side where the first element portion and the third element portion are in contact, along which the first element portion does not come into contact with the second element portion and the third element portion. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an antenna device that has a simple configuration and is capable of easily adjusting the resonant frequency. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a plan view showing a configuration of an antenna device according to an embodiment of the present invention. [Figure 2] 1 is a plan view showing a configuration of an antenna device according to an embodiment of the present invention. [Figure 3] 1 is a side view showing the configuration of an antenna device according to an embodiment of the present invention. [Figure 4A] 10A and 10B are diagrams for explaining the influence of the widthwise length of the antenna device on the antenna characteristics. [Figure 4B] 10A and 10B are diagrams for explaining the influence of the widthwise length of the antenna device on the antenna characteristics. [Figure 5] 10A and 10B are diagrams for explaining the relationship between the width direction length of the antenna device and the VSWR characteristics. [Figure 6A] 1 is a diagram illustrating an example of the configuration of an antenna device according to an embodiment of the present invention. [Figure 6B] 1 is a diagram illustrating an example of the configuration of an antenna device according to an embodiment of the present invention. [Figure 6C] 1 is a diagram illustrating an example of the configuration of an antenna device according to an embodiment of the present invention. [Figure 7] 3 is a diagram showing the relationship between each configuration of the antenna device according to the present embodiment and the VSWR characteristic. FIG. [Figure 8A] 1 is a diagram showing a configuration in which the antenna device according to the present embodiment is sandwiched between metal plates. [Figure 8B] 1 is a side view showing a configuration in which the antenna device according to the present embodiment is sandwiched between metal plates. [Figure 9] 10 is a diagram showing VSWR characteristics in a configuration in which the antenna device according to the present embodiment is sandwiched between metal plates. FIG. [Figure 10A] FIG. 10 is a diagram illustrating an example of the configuration of an antenna device according to another embodiment. [Figure 10B] 10A and 10B are diagrams for explaining changes in resonant frequency with respect to the configuration of an antenna device according to another embodiment. [Figure 11A] FIG. 10 is a diagram illustrating an example of the configuration of an antenna device according to another embodiment. [Figure 11B] 10A and 10B are diagrams for explaining changes in resonant frequency with respect to the configuration of an antenna device according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The antenna device 10 according to this embodiment will be described in detail below with reference to the drawings. Note that the dimensional proportions in the drawings are exaggerated for the sake of explanation and may differ from the actual proportions. In addition, in the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0010] (Configuration of antenna device 10) Fig. 1 is a plan view showing the configuration of an antenna device 10 according to this embodiment. Fig. 2 is a plan view corresponding to the rear surface of the antenna device 10 of Fig. 1. Fig. 3 is a side view showing the configuration of the antenna device 10 according to this embodiment.

[0011] The antenna device 10 includes a substrate 100, an element portion which is an antenna element provided on the surface of the substrate 100, and a ground portion 201. The antenna device 10 according to this embodiment functions as an antenna compatible with the 2.4 GHz frequency band.

[0012] The substrate 100 is a rectangular substrate defined by a first side S1 and a second side S2 that are parallel in a first direction, and a third side S3 and a fourth side S4 that are parallel in a second direction that is perpendicular to the first direction and have lengths longer than the lengths of the first side S1 and the second side S2.

[0013] 1 to 3, the first direction corresponds to the X-axis direction, the second direction perpendicular to the first direction corresponds to the Y-axis direction, and the thickness direction of the substrate 100 (the depth direction in FIG. 1) corresponds to the Z-axis direction.

[0014] 1, the lengths of the first side S1 and the second side S2 of the substrate 100 are indicated by L1, and the lengths of the third side S3 and the fourth side S4 are indicated by L2. In the antenna device 10 according to this embodiment, L1 is 24 mm and L2 is 42 mm. Note that the lengths of L1 and L2 are not limited to 24 mm and 42 mm, respectively, and may be longer or shorter than 24 mm and 42 mm, respectively. Furthermore, it is preferable that L1 be λ / 2 for the applicable frequency band.

[0015] An element portion, which is a conductor corresponding to an antenna element, is provided on a substrate 100 using metal foil. In the example shown in Fig. 1, the element portion is made up of a first element portion 101, a second element portion 102, and a third element portion 103. In this embodiment, the metal foil is, for example, copper foil.

[0016] The first element portion 101 is an antenna element made of metal foil on the surface of the substrate 100, and is formed in a rectangular shape with both ends provided on the third side S3 and the fourth side S4, and with the first direction as the longitudinal direction. The first element portion 101 includes a power feeding portion 111 for feeding power to the element portion from a power feeding portion 112 on the back surface shown in Fig. 2. The first element portion 101 also includes a short portion 121 connected to a short portion 122 on the back surface shown in Fig. 2.

[0017] The second element portion 102 is an antenna element made of metal foil on the surface of the substrate 100, and is in contact with the third side S3 and the fifth side S5, which is one side of the first element portion 101, in an area different from that of the first element portion 101.

[0018] The third element portion 103 is an antenna element made of metal foil on the surface of the substrate 100, and contacts the fourth side S4 and the fifth side S5 in a region different from the first element portion 101 and the second element portion 102.

[0019] That is, one side of each of the second element portion 102 and the third element portion 103 contacts the third side S3 or the fourth side S4, and the other side contacts the fifth side S5, which is one side of the first element portion 101. In the antenna device 10 according to this embodiment, the first element portion 101, the second element portion 102, and the third element portion 103 form an element portion corresponding to an antenna element.

[0020] Furthermore, the fifth side S5 has a side of a predetermined length where the first element portion 101 does not come into contact with the second element portion 102 or the third element portion 103. This side of the predetermined length is located between the side where the first element portion 101 and the second element portion 102 come into contact and the side where the first element portion 101 and the third element portion 103 come into contact.

[0021] The antenna device 10 also includes a ground section 201 shown in Fig. 1 and a ground section 202 shown on the back side in Fig. 2. The ground sections 201 and 202 are electrically connected via through holes 211 and 212.

[0022] (Antenna characteristics) 4A and 4B are diagrams for explaining the influence of the length of the antenna device 11 in the width direction (short side direction, X-axis direction) on the antenna characteristics. Note that the antenna device 11 is an antenna shown as a comparative example, and is different from the antenna device 10 according to this embodiment. Fig. 4A is a diagram showing the configuration when the length of the antenna device 11 in the width direction is 30 mm, and Fig. 4B is a diagram showing the configuration when the length of the antenna device 11 in the width direction is 24 mm.

[0023] Fig. 5 is a diagram for explaining the relationship between the width direction length of antenna device 11 and the VSWR (Voltage Standing Wave Ratio) characteristics. Two waveforms shown in Fig. 5 show the VSWR characteristics of antenna device 11 shown in Figs. 4A and 4B.

[0024] The VSWR characteristic is used as an index to evaluate the performance of an antenna. Specifically, the VSWR characteristic is expressed as the ratio of the peaks to the valleys of the voltage amplitude distribution of the standing wave generated on the feed line when a reflected wave is generated due to impedance mismatch between the antenna element and the feed line. For example, in an ideal state where the impedance is matched and there is no reflection, the VSWR is 1.0.

[0025] As shown in Fig. 5, the resonant frequency of antenna device 11 becomes higher as the width of antenna device 11 decreases. Therefore, in the configuration of antenna device 11 shown in Fig. 4A and Fig. 4B, it is necessary to adjust the resonant frequency by adjusting each parameter of the antenna device in order to obtain a desired resonance frequency. For example, in the configuration shown in Fig. 4A and Fig. 4B, the resonant frequency is adjusted by changing the width, but detailed adjustment is difficult by adjusting only the width.

[0026] The antenna device 10 according to this embodiment has a simple configuration and allows the resonant frequency to be easily adjusted.

[0027] (Details of the antenna device 10) Fig. 6A is a diagram showing an example of the configuration of the antenna device 10 according to this embodiment. In the example shown in Fig. 6A, the second element portion 102 and the third element portion 103 are configured in the shape of a trapezoid with the upper base located on the second side S2 and the lower base located on the fifth side S5.

[0028] Moreover, Fig. 6B is a diagram showing another configuration of the antenna device 10 according to this embodiment. In the example shown in Fig. 6B, the second element portion 102 and the third element portion 103 are configured in a triangular shape.

[0029] Moreover, Fig. 6C is a diagram showing another configuration of the antenna device 10 according to this embodiment. In the example shown in Fig. 6C, the second element portion 102 and the third element portion 103 are configured in a rectangular shape.

[0030] 6A to 6C, the second element portion 102 and the third element portion 103 are configured to be symmetrical with respect to the central axis of the antenna device 10 in the second direction. Also, by adjusting the angle θ of the second element portion 102 and the third element portion 103, it is possible to adjust the element length LE formed by the first element portion 101, the second element portion 102, and the third element portion 103.

[0031] In this embodiment, the predetermined length of the fifth side S5 where the first element portion 101 does not contact the second element portion 102 and the third element portion 103 is 8 mm. In this embodiment, the length of the portion where the second element portion 102 is located on the third side S3 and the length of the portion where the third element portion 103 is located on the fourth side S4 are 5 mm. The length of the first element portion 101 in the short side direction is 6 mm.

[0032] Fig. 7 is a diagram showing the relationship between each configuration of the antenna device 10 according to this embodiment and the VSWR characteristics. The example shown in Fig. 7 shows an example of waveforms when the angle θ is changed from the configuration in Fig. 6B to the configuration in Fig. 6A to 90 degrees in Fig. 6C.

[0033] 7, by increasing the element length LE, it is possible to lower the antenna resonant frequency. That is, in the antenna device 10 according to this embodiment, the width direction of the antenna device 10 itself is fixed at, for example, 24 mm, and the resonant frequency can be precisely adjusted by adjusting the element length LE.

[0034] As described above, the antenna device 10 according to this embodiment includes a rectangular substrate 100. The substrate 100 is defined by a first side S1 and a second side S2 that are parallel to each other in a first direction, and a third side S3 and a fourth side S4 that are parallel to each other in a second direction perpendicular to the first direction and have lengths longer than the lengths of the first side S1 and the second side S2. The antenna device 10 also includes a first element portion 101 that is an antenna element made of metal foil and located on the surface of the substrate 100. The first element portion 101 has a rectangular shape with both ends located on the third side S3 and the fourth side S4 and a longitudinal direction that is the first direction. The antenna device 10 also includes a second element portion 102 that is an antenna element made of metal foil and located on the surface of the substrate 100. The second element portion 102 is in contact with the third side S3 and a fifth side S5, which is one side of the first element portion 101, in a region different from the first element portion 101. The antenna device 10 also includes a third element portion 103, which is an antenna element made of metal foil on the surface of the substrate 100 and contacts the fourth side S4 and the fifth side S5 in an area different from the first element portion 101 and the second element portion 102. The fifth side S5 has a side of a predetermined length between the side where the first element portion 101 and the second element portion 102 contact and the side where the first element portion 101 and the third element portion 103 contact. Note that the side of the predetermined length exists in a position where the first element portion 101 does not contact the second element portion 102 or the third element portion 103.

[0035] As a result, the antenna device 10 according to this embodiment can easily adjust the resonant frequency with a simple configuration in a communication environment that supports the resonant frequency of a predetermined frequency band.

[0036] Furthermore, the second element portion 102 and the third element portion 103 of the antenna device 10 may be configured in a triangular shape, which allows the antenna device 10 to achieve a higher antenna resonance frequency.

[0037] Furthermore, the second element portion 102 and the third element portion 103 of the antenna device 10 may be configured in a rectangular shape, which allows the antenna device 10 to lower the resonant frequency of the antenna.

[0038] Furthermore, the second element portion 102 and the third element portion 103 of the antenna device 10 may be configured in a trapezoidal shape with the upper base located on the second side S2 and the lower base located on the fifth side S5. This allows the antenna device 10 to appropriately adjust the resonant frequency of the antenna corresponding to a desired frequency.

[0039] (Other embodiments) Although the embodiments have been described in detail with reference to the drawings, the present embodiments are not limited to the contents described in the above embodiments. Furthermore, the components described above include those that can be easily imagined by a person skilled in the art and those that are substantially the same. Furthermore, the configurations described above can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the spirit of the embodiments.

[0040] For example, the antenna device 10 according to this embodiment can reduce the effect on the antenna characteristics even when metal or dielectrics are placed close to the antenna. Fig. 8A is a diagram showing a configuration in which the antenna device 10 according to this embodiment is sandwiched between metal plates 400. Fig. 8B is a side view of the configuration in which the antenna device 10 according to this embodiment is sandwiched between metal plates 400, taken along the line AA in Fig. 8A.

[0041] In the example shown in Fig. 8A, metal plate 400 is a square with one side measuring 500 mm. In the example shown in Fig. 8B, length L5 is 10.5 mm, and length L6 is 4 mm.

[0042] Fig. 9 is a diagram showing the VSWR characteristics in a configuration in which the antenna device 10 according to this embodiment is sandwiched between metal plates 400. As shown in Fig. 9, there is no significant difference in the VSWR characteristics of the antenna device 10 according to this embodiment between a state in free space where the antenna device 10 is not sandwiched between metal plates 400 and a state in which the antenna device 10 is sandwiched between metal plates 400 and is in proximity to metal. In other words, the antenna device 10 according to this embodiment can reduce the effect on the antenna characteristics even when metal is in proximity.

[0043] In the above embodiment, an example in which the length of the first element portion 101 in the short-side direction is 6 mm has been described, but the configuration of the embodiment is not limited to this. For example, as shown in FIG. 10A, the resonant frequency can be changed by changing the length of the first element portion 101 in the short-side direction. FIG. 10B is a diagram showing the change in resonant frequency when the length of FIG. 10A is extended by 0.3 mm, 0.6 mm, and 0.9 mm, respectively. As shown in FIG. 10B, the frequency tends to become lower as the length of the short-side direction of the first element portion 101 extends further in the second direction. Therefore, the antenna device 10 can appropriately adjust the resonant frequency depending on conditions such as the space available in the antenna device 10.

[0044] 6A to 6C, a configuration in which the length L11 is 8 mm has been described. In this embodiment, the length L11 is not limited to 8 mm. For example, as shown in FIG. 11A, the length L11 may be smaller than 8 mm. As shown in FIG. 11A, the resonant frequency can be changed by changing the length L11, which corresponds to a side of a predetermined length. FIG. 11B is a diagram showing the change in resonant frequency when the length L11 in FIG. 11A is set to 8 mm, 4 mm, and 0 mm, respectively. As shown in FIG. 11B, the frequency tends to increase as the length L11 decreases. Therefore, by adjusting the length L11, the antenna device 10 can appropriately adjust the resonant frequency depending on conditions such as the space available in the antenna device 10.

[0045] The features of the antenna device 10 will be described below.

[0046] The antenna device 10 according to the first aspect includes a rectangular substrate 100. The substrate 100 is defined by a first side S1 and a second side S2 that are parallel to each other in a first direction, and a third side S3 and a fourth side S4 that are parallel to each other in a second direction perpendicular to the first direction and have lengths longer than the lengths of the first side S1 and the second side S2. The antenna device 10 also includes a first element portion 101 that is an antenna element made of metal foil and located on the surface of the substrate 100. The first element portion 101 has a rectangular shape with both ends located on the third side S3 and the fourth side S4 and a longitudinal direction that is the first direction. The antenna device 10 also includes a second element portion 102 that is an antenna element made of metal foil and located on the surface of the substrate 100. The second element portion 102 is in contact with the third side S3 and a fifth side S5, which is one side of the first element portion 101, in a region different from the first element portion 101. The antenna device 10 also includes a third element portion 103, which is an antenna element made of metal foil on the surface of the substrate 100 and contacts the fourth side S4 and the fifth side S5 in an area different from the first element portion 101 and the second element portion 102. The fifth side S5 has a side of a predetermined length between the side where the first element portion 101 and the second element portion 102 contact and the side where the first element portion 101 and the third element portion 103 contact. Note that the side of the predetermined length exists in a position where the first element portion 101 does not contact the second element portion 102 or the third element portion 103.

[0047] According to the above configuration, the antenna device 10 can easily adjust the resonant frequency with a simple configuration in a communication environment that supports the resonant frequency of a predetermined frequency band.

[0048] The second element section 102 and the third element section 103 of the antenna device 10 according to the second aspect may be configured in a triangular shape.

[0049] According to the above configuration, the antenna device 10 can increase the resonant frequency of the antenna.

[0050] The second element section 102 and the third element section 103 of the antenna device 10 according to the third embodiment may be configured in a rectangular shape.

[0051] According to the above configuration, the antenna device 10 can lower the resonant frequency of the antenna.

[0052] The second element portion 102 and the third element portion 103 of the antenna device 10 according to the fourth aspect may be configured in the shape of a trapezoid with its upper base located on the second side S2 and its lower base located on the fifth side S5.

[0053] According to the above configuration, the antenna device 10 can appropriately adjust the resonant frequency of the antenna corresponding to a desired frequency. [Explanation of symbols]

[0054] 10, 11 Antenna device 100 boards 101 First element section 102 Second element section 103 Third Element Section 111, 112 Power supply unit 121, 122 Short section 201, 202 Ground Section 211, 212 through holes 400 metal plate S1 First side S2 Second side S3 Third side S4 Fourth side S5 5th side

Claims

1. a rectangular substrate defined by a first side and a second side parallel to each other in a first direction, and a third side and a fourth side parallel to each other in a second direction perpendicular to the first direction, the third side and the fourth side being longer than the first side and the second side; a first element portion formed in a rectangular shape, the first element portion being an antenna element made of a metal foil on the surface of the substrate, the first element portion having both ends provided on the third side and the fourth side, and the first direction being a longitudinal direction; the antenna element made of the metal foil on the surface of the substrate, a second element portion that is in contact with the third side and a fifth side that is one side of the first element portion in a region different from the first element portion; the antenna element is made of the metal foil on the surface of the substrate, and includes a third element portion that contacts the fourth side and the fifth side in a region different from the first element portion and the second element portion; The fifth side has a side of a predetermined length between the side where the first element part and the second element part contact and the side where the first element part and the third element part contact, along which the first element part does not contact the second element part and the third element part.

2. The antenna device according to claim 1 , wherein the second element portion and the third element portion are configured in a triangular shape.

3. The antenna device according to claim 1 , wherein the second element portion and the third element portion are configured in a rectangular shape.

4. The antenna device according to claim 1 , wherein the second element portion and the third element portion are configured in a trapezoidal shape with an upper base provided on the second side and a lower base provided on the fifth side.

Images