Antenna device

Abstract

To provide an antenna device capable of switching directivity.SOLUTION: An antenna device comprises a bottom board 2, a first antenna 10 configured to operate as a zero-order resonant antenna including first conductor 11 and shorting element 13, a second antenna 20 including a second conductor 21, which is a conductor arranged to surround the first conductor, and a switching unit 3 for switching the antenna to be operated. The second antenna is configured to operate in the same frequency band as the first antenna.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The disclosure herein relates to an antenna device. [Background technology]

[0002] Patent Document 1 discloses an antenna device capable of switching directivity by using two patch antennas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-36780 A Summary of the Invention [Problem to be solved by the invention]

[0004] As disclosed in Patent Document 1, there is a demand for an antenna device capable of switching directivity from the viewpoint of diversity, MIMO (Multiple Input Multiple Output), etc. On the other hand, there is also a demand for a compact antenna device.

[0005] One object of the present disclosure is to provide an antenna that is capable of switching directivity and being miniaturized. [Means for solving the problem]

[0006] The antenna device disclosed herein includes a first antenna (10) configured to operate as a zero-order resonant antenna, the first antenna (10) including a ground plate (2), a first conductor (11) which is a flat conductor arranged opposite the ground plate, and a short-circuit element (13) which electrically connects the first conductor and the ground plate, a second antenna (20) including a second conductor (21) which is a conductor arranged to surround the first conductor, and a switching unit (3) for switching which of the first antenna and the second antenna is to be operated, the second antenna being configured to operate in the same frequency band as the first antenna.

[0007] In one aspect, the disclosed antenna device can be understood as an antenna device in which a zero-order resonant antenna operating at the same frequency is formed inside a second antenna formed using a second conductor. With a zero-order resonant antenna, the size of the plate-shaped conductor (i.e., the first conductor) arranged opposite the ground plane can be made smaller than the patch antenna disclosed in Patent Document 1. This allows the size of the device as a whole to be reduced. In addition, the above antenna device is configured so that the antenna to be operated can be switched by the switching unit. Since the first antenna and the second antenna have different configurations, their directivities can also be different. Therefore, the directivity also changes with the switching of the antenna to be operated. In other words, with the above configuration, it is possible to switch the directivity while reducing the size.

[0008] The various aspects disclosed in this specification adopt different technical means to achieve their respective objectives. The claims and the parenthetical symbols described in this section are merely illustrative of the corresponding relationship with the embodiments described below, and are not intended to limit the technical scope. The objectives, features, and effects disclosed in this specification will become clearer with reference to the following detailed description and the accompanying drawings. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is an external perspective view of the antenna device. [Diagram 2] FIG. 3 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] 1 is a block diagram showing a schematic configuration of an antenna device. [Figure 4] FIG. 11 is a diagram showing a current distribution when the first antenna is activated. [Diagram 5] FIG. 11 is a diagram showing the directivity in the XY plane when the first antenna is activated. [Figure 6] FIG. 11 is a diagram showing the directivity in the XZ plane when the first antenna is activated. [Figure 7]13 is a diagram showing the directivity in the YZ plane when the first antenna is activated. FIG. [Figure 8] FIG. 13 is a diagram showing a current distribution when the second antenna is activated. [Figure 9] FIG. 13 is a diagram showing the directivity in the XY plane when the second antenna is activated. [Figure 10] FIG. 13 is a diagram showing the directivity in the XZ plane when the second antenna is activated. [Figure 11] FIG. 13 is a diagram showing the directivity in the YZ plane when the second antenna is activated. [Figure 12] FIG. 4 is a diagram showing reflection characteristics for each frequency of a first antenna and a second antenna. [Figure 13] FIG. 11 is an external perspective view of an antenna device according to a second embodiment. [Figure 14] FIG. 11 is a diagram showing a current distribution when the first antenna is activated in the second embodiment. [Figure 15] FIG. 11 is a diagram showing directivity in the XY plane when the first antenna in the second embodiment is activated. [Figure 16] 13 is a diagram showing the directivity in the XZ plane when the first antenna in the second embodiment is activated. FIG. [Figure 17] 13 is a diagram showing the directivity in the YZ plane when the first antenna in the second embodiment is activated. FIG. [Figure 18] FIG. 11 is a diagram showing a current distribution in the second embodiment. [Figure 19] FIG. 11 is a diagram showing directivity in the XY plane when the second antenna in the second embodiment is activated. [Figure 20] FIG. 11 is a diagram showing the directivity in the XZ plane when the second antenna in the second embodiment is activated. [Figure 21] FIG. 11 is a diagram showing the directivity in the YZ plane when the second antenna in the second embodiment is activated. [Figure 22] FIG. 11 is a diagram showing reflection characteristics for each frequency of the first antenna and the second antenna in the second embodiment. [Figure 23] FIG. 11 is an external perspective view of an antenna device according to a third embodiment. [Figure 24] FIG. 13 is an external perspective view of an antenna device according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiment, and various modified examples described below are also included in the technical scope of the present disclosure. In addition, various modifications other than those described below can be implemented within the scope of the gist. Various supplements and modified examples can be implemented in appropriate combinations within the scope of no technical contradiction. Members having the same function may be assigned the same reference numerals and their description may be omitted. In addition, when only a part of the configuration is mentioned, the description described elsewhere can be applied to the other parts.

[0011] In the present disclosure, "parallel" is not limited to a completely parallel state. The "parallel" state also includes a state inclined by several degrees to about 15 degrees. In other words, the expression "parallel" may include a state in which the two are generally parallel (so-called substantially parallel state). The expression "vertical" in the present disclosure is also not limited to a completely vertical state, but also includes a state inclined by several degrees to about 15 degrees. In the present disclosure, "facing" refers to a state in which the two members face each other with a predetermined distance between them. The facing state also includes a state in which the two members face each other approximately, such as a state in which the two members face each other with an inclination of about 15 degrees. In addition, "facing" in the present disclosure may include a state in which the two members are shifted laterally and are parallel to each other.

[0012] The antenna device 1 of the present disclosure is used by being attached to a moving body such as a vehicle. The antenna device 1 may be attached to the roof of the vehicle, the upper end of the windshield, a dashboard, a pillar, a door panel, a bumper, or the like. The antenna device 1 can be used by being connected to an ECU (Electronic Control Unit) for communication mounted on the vehicle. The ECU can use a signal received by the antenna device 1 and can input a transmission signal to the antenna device 1.

[0013] The antenna device 1 includes a first antenna 10 and a second antenna 20, as described below. The first antenna 10 and the second antenna 20 are configured to operate at the same frequency. The antenna device 1 may be used for only one of transmission and reception. Since radio wave transmission and reception is reversible, a configuration capable of transmitting radio waves of a certain frequency is also a configuration capable of receiving radio waves of the same frequency. In the following, the term "transmission and reception" refers to at least one of transmission and reception. In the following, a frequency that the antenna device 1 targets for transmission or reception is referred to as a target frequency. The target frequency may be referred to as an operating frequency. The antenna device 1 is capable of transmitting and receiving not only the target frequency but also radio waves of a frequency within a predetermined range determined based on the target frequency. In the present disclosure, a frequency band that the antenna device 1 can transmit or receive is also referred to as a target frequency band.

[0014] The antenna device 1 of this embodiment is configured to be capable of transmitting and receiving radio waves in a frequency band used in cellular communication. In other words, the antenna device 1 is configured as an antenna for performing data communication with a wireless base station constituting a 4G or 5G mobile communication system. The target frequency is assumed to be 3.75 GHz as an example here.

[0015] In another embodiment, the antenna device 1 may be configured to transmit and receive radio waves in a frequency band used in short-range wireless communication, such as Bluetooth Low Energy (Bluetooth is a registered trademark), Wi-Fi (registered trademark), ZigBee (registered trademark), UWB (Ultra Wide Band), etc. Of course, the target frequency may be appropriately designed, and may be, for example, 300 MHz, 760 MHz, 850 MHz, 900 MHz, 1.17 GHz, 1.28 GHz, 1.55 GHz, 2.45 GHz, 5.9 GHz, etc. in other embodiments.

[0016] The antenna device 1 may be applied to Virtual MIMO. Virtual MIMO is a technology for simultaneously transmitting data by switching the directivity of an antenna at high speed and performing high-speed sampling at a sampling rate twice or more faster than that of conventional MIMO. Of course, the antenna device 1 of the present disclosure may be applied to various uses, not limited to Virtual MIMO.

[0017] Hereinafter, "λ" represents the wavelength of the radio wave of the target frequency (hereinafter, also referred to as the target wavelength). For example, "λ / 2" and "0.5λ" mean half the length of the target wavelength, and "λ / 4" and "0.25λ" mean a quarter of the length of the target wavelength. In the examples of the dimensions of the members constituting the antenna device 1, the expression using λ can be understood as the electrical length. The electrical length here is the effective length taking into consideration the fringing electric field and the wavelength shortening effect due to the dielectric. The electrical length is sometimes called the effective length. Of course, for the part not affected by the wavelength shortening effect, λ can be understood as the length in a vacuum or in air. In the present disclosure, the description of approximately λ / 2 may be understood as a length within λ / 2±20%. The description of approximately λ / 4 may be understood as a length within λ / 4±20%. The descriptions of λ / 2 and λ / 4 may also be interpreted as meaning approximately λ / 2 and approximately λ / 4, unless otherwise specified, such as "exactly."

[0018] The antenna device 1 is connected to the radio device 50 via a communication cable, and signals received by the antenna device 1 are sequentially output to the radio device 50. The radio device 50 uses the signals received by the antenna device 1 and supplies high-frequency power corresponding to the transmission signal to the antenna device 1. The communication cable may be, for example, a coaxial cable. Of course, other power supply lines such as a feeder line may also be used as the communication cable.

[0019] (First embodiment) The following describes a schematic configuration of the antenna device 1. As shown in Fig. 3, the antenna device 1 includes a circuit module 60, an antenna section 100, and a substrate 5. The circuit module 60 includes a switching section 3. The circuit module 60 is connected to a wireless device 50 via a communication cable.

[0020] The circuit module 60 is a circuit that performs signal processing related to at least one of signal transmission and signal reception. The circuit module 60 is configured to perform at least one of modulation, demodulation, frequency conversion, amplification, digital-to-analog conversion, and detection. The circuit module 60 processes a signal received by the antenna unit 100 and transmits the signal to the wireless device 50. The circuit module 60 may be configured to be capable of performing signal / data processing related to Virtual MIMO.

[0021] The antenna section 100, the circuit module 60, and the switching section 3 are mounted on a substrate 5. Note that the circuit module 60 and the switching section 3 may be mounted on the substrate 5 of the antenna section 100.

[0022] The antenna section 100 has an electrical configuration as an antenna. The antenna section 100 includes a ground plane 2, a first antenna 10, and a second antenna 20. The first antenna 10 includes a first conductor 11, a first feeding point 12, and a short element 13. The second antenna 20 includes a second conductor 21 and a second feeding point 22.

[0023] The substrate 5 is a plate-like member made of an electrically insulating material such as resin and having a predetermined thickness h. The substrate 5 is a member for arranging the first conductor 11 and the second conductor 21 so as to face the ground plate 2 with a predetermined distance h therebetween. Therefore, the shape of the substrate 5 is not limited to a plate shape, and may be another shape.

[0024] The substrate 5 has a first surface 5a and a second surface 5b. The first surface 5a is the surface to which the first conductor 11 and the second conductor 21 are attached. The second surface 5b is the surface to which the ground plate 2 is attached. The first surface 5a may be referred to as the top surface. The second surface 5b is the surface opposite to the first surface 5a. The second surface 5b may be referred to as the back surface or the bottom surface. The direction perpendicular to the substrate 5 is the up-down direction for the antenna device 1. The up-down direction is the direction from the second surface 5b to the first surface 5a of the two surfaces of the substrate 5.

[0025] The ground plate 2 is a rectangular plate (including foil) made of a conductor such as copper. The ground plate 2 provides a ground potential (earth potential) for the first antenna 10 and the second antenna 20. The ground plate 2 may be electrically connected to a ground pattern (not shown) that supplies a ground potential in a printed circuit board. Note that the ground plate 2 may be any shape as long as it is larger than the first conductor 11 and the second conductor 21, and its shape is not limited to a rectangular shape.

[0026] In the following, the concept of a right-handed three-dimensional coordinate system having X-axis, Y-axis, and Z-axis is introduced as appropriate, and the configuration of the antenna device 1 is described. The X-axis and Y-axis are set so that the XY plane is parallel to the ground plane and perpendicular to each other. The Z-axis is an axis perpendicular to the substrate / ground plane, and is set so that the upward direction of the substrate / ground plane is the positive direction. In this embodiment, the X-axis is parallel to the short side of the ground plane or substrate, and the Y-axis is parallel to the long side. The X-axis direction corresponds to the second direction recited in the claims, and the Y-axis direction corresponds to the first direction.

[0027] <First Antenna 10> The first antenna 10 is configured to operate as a zero-order resonant antenna at a target frequency. The first conductor 11 is a rectangular plate (including foil) made of a conductor such as copper. The first conductor 11 has four sides. The first conductor 11 is arranged to face the ground plate 2 in parallel via the substrate 5. Here, the shape of the first conductor 11 is a square. In other embodiments, the planar shape of the first conductor 11 may be a circle, a regular octagon, a regular hexagon, or the like. The first conductor 11 may also be a rectangle, an elongated ellipse, or the like. It is more preferable that the opposing conductor plate 30 is a point-symmetric figure such as a circle, a square, a rectangle, or a parallelogram.

[0028] The dimensions of the first conductor 11 are designed so that it operates as a zero-order resonant antenna at the target frequency in cooperation with the short element 13. That is, the area of ​​the first conductor 11 is set to an area that forms a capacitance that resonates in parallel with the inductance component of the short element 13 described later at the target frequency. Therefore, the area of ​​the first conductor 11, that is, the first horizontal length L1x, which is the length of the side of the first conductor 11 in the X-axis direction, and the first vertical length L1y, which is the length of the side of the first conductor 11 in the Y-axis direction, are appropriately set based on the inductance component of the short element 13 and the target frequency. The first vertical length L1y corresponds to the length of the first conductor 11 in the first direction, and the first horizontal length L1x corresponds to the length of the first conductor 11 in the second direction.

[0029] For example, the first horizontal length L1x of the first conductor 11 is set to be shorter than λ / 2 of a predetermined frequency. The first horizontal length L1x may be set to 8 mm, 10 mm, or the like. The first vertical length L1y is set to be shorter than the length L2y of a side in the Y-axis direction of the second conductor 21 of the second antenna 20 described later. The first vertical length L1y is set to be, for example, 8 mm, 10 mm, or the like.

[0030] As shown in FIG. 1, the short element 13 is a portion that electrically connects the first conductor 11 and the ground plate 2. The short element 13 is provided in the center of the first conductor 11. The center here may be a region that is within a predetermined distance (e.g., 3 mm) from the center of the first conductor 11. The center may be interpreted as a region that is closer to the center of the first conductor 11 than the edges of the first conductor 11. The center of the first conductor 11 may be the intersection of the diagonals of the first conductor 11. Hereinafter, the center of the first conductor 11 is also referred to as the conductor plate center.

[0031] 2 is a cross-section of the antenna device 1 taken along a line II-II that passes through the short-circuit element 13 and is parallel to the X-axis direction, as viewed from the direction of the arrow 200. The short-circuit element 13 may be realized by a conductive pin (hereinafter also referred to as a short pin). The inductance of the short-circuit element 13 can be adjusted by adjusting the thickness and length of the short-circuit element 13. Note that the position at which the short-circuit element 13 is formed does not need to strictly coincide with the center of the conductor plate. The short-circuit element 13 may be offset from the center of the conductor plate.

[0032] A first feed point 12 is formed at an arbitrary position of the first conductor 11. The first feed point 12 is a portion where the inner conductor of the coaxial cable and the first conductor 11 are electrically connected. The distance between the first feed point 12 and the short element 13 should be a distance that allows impedance matching between the feed line and the antenna device 1 at the target frequency, and the first feed point 12 may be installed at any position within a range that satisfies this condition.

[0033] As a method of feeding power to the first conductor 11, various methods can be adopted, such as a direct feeding method and an electromagnetic coupling method. The direct feeding method is a method in which a feeding line is directly connected to the first conductor 11. The feeding line means a conductive member electrically connected to the inner conductor of a coaxial cable or a signal input / output terminal of a transmitting / receiving circuit. The feeding line may be a microstrip line. The feeding line may include a conductor pin, a via, etc. In the direct feeding method, the connection point between the feeding line and the first conductor 11 corresponds to the first feeding point 12. The electromagnetic coupling method means a feeding method that utilizes electromagnetic coupling between a microstrip line or the like for feeding power and the first conductor 11.

[0034] Additionally, the first antenna 10 may have an impedance matching element (not shown) that electrically connects the first feeding point 12 and the ground plane 2. Here, impedance matching means that the impedance value of the signal sending side and the impedance value of the signal receiving side are made substantially the same. If the impedance is not matched, the gain may decrease due to reflection, etc., and the practicality of the antenna may decrease.

[0035] <Second antenna 20> The second antenna 20 is a conductor member configured to operate as a patch antenna. The second conductor 21 is realized by using a conductor such as copper. The second conductor 21 has a frame shape surrounding the first conductor 11 with a predetermined distance D. The predetermined distance D is set to a distance at which no current flows from the first conductor 11 to the second conductor 21 when power is fed to the first feeding point 12 to operate the first antenna 10. Alternatively, the distance D is set to a value at which, even if a current flows from the first conductor 11 to the second conductor 21, the amount of the current does not affect the operation of the first antenna 10. The predetermined distance D may be set to, for example, 1 mm, 2 mm, or 3 mm. Such a second conductor 21 may be interpreted as a conductor plate (conductor film) with a cutout in the center. The second conductor 21 is disposed opposite the ground plate 2 via the substrate 5.

[0036] The outer shape (in other words, the outline shape) of the second conductor 21 is rectangular. In this embodiment, it is rectangular. Note that in other embodiments, the outer shape of the second conductor 21 may be a shape other than a rectangle, such as an elongated oval. The outer shape of the second conductor 21 may be a square, as described later. The outer shape of the second conductor 21 may be a circle, a regular octagon, a regular hexagon, or the like.

[0037] The second horizontal length L2x, which is the length of the side of the second conductor 21 in the X-axis direction, is set to a value longer than the first horizontal length L1x. The second horizontal length L2x is set to, for example, 20 mm or 22 mm. The second vertical length L2y, which is the length of the side of the second conductor 21 in the Y-axis direction, is a value equivalent to the length of λ / 2 of a radio wave at a predetermined frequency. The second vertical length L2y is set to a value longer than the first vertical length L1y. The second vertical length L2y is set to, for example, 18 mm or 20 mm. The second vertical length L2y corresponds to the length of the second conductor 21 in the first direction, and the second horizontal length L2x is the length of the second conductor 21 in the second direction.

[0038] The second conductor 21 has four sides, a first frame portion 21a, a second frame portion 21b, a third frame portion 21c, and a fourth frame portion 21d. The first frame portion 21a is one of two sides parallel to the X-axis that is located relatively closer to the positive direction of the Y-axis, and the third frame portion 21c is one of two sides parallel to the Y-axis that is located relatively closer to the positive direction of the X-axis, and the second frame portion 21b is one of two sides parallel to the Y-axis that is located relatively closer to the positive direction of the X-axis.

[0039] For convenience, the four corners of the second conductor 21 are referred to as a first corner C1, a second corner C2, a third corner C3, and a fourth corner C4. The first corner C1 is a corner where the first frame portion 21a and the second frame portion 21b are connected. The second corner C2 is a corner where the second frame portion 21b and the third frame portion 21c are connected. The third corner C3 is a corner where the third frame portion 21c and the fourth frame portion 21d are connected. The fourth corner C4 is a corner where the fourth frame portion 21d and the first frame portion 21a are connected.

[0040] The second feeding point 22 is provided near the center of the first frame portion 21a in the X-axis direction. The second feeding point 22 is a portion where the inner conductor of the coaxial cable and the second conductor 21 are electrically connected.

[0041] <Switching section 3> The switching unit 3 is configured to switch the antenna to be operated between the first antenna 10 and the second antenna 20. The switching unit 3 includes a switch for switching the feed point to be fed (in other words, enabled) between the first feed point 12 and the second feed point 22, and a controller 31 for controlling the on / off of the switch. The controller 31 may be an integrated circuit (IC), a field programmable gate array (FPGA), or a central processing unit (CPU). Switching the feed point corresponds to switching the antenna to be operated between the first antenna 10 and the second antenna 20. The controller 31 selectively enables (feeds) either the first feed point 12 or the second feed point 22. Since there is a distance D between the first conductor 11 and the second conductor 21, when power is fed to the first feed point 12, only the first antenna 10 operates, and when power is fed to the second feed point 22, only the second antenna 20 operates. The switching unit 3 does not necessarily have to be provided in the circuit module 60. It may be provided independently on the substrate 5.

[0042] <Zero-order resonant antenna and its operation> Here, the operation of the first antenna 10 will be described first. The first antenna 10 is configured as a zero-order resonant antenna at the target frequency. A zero-order resonant antenna is also called a metamaterial antenna. A zero-order resonant antenna is an antenna that utilizes zero-order resonance, which is a phenomenon in which a metamaterial resonates at a frequency where the phase constant β becomes zero, among the dispersion characteristics of the metamaterial. A zero-order resonant antenna is characterized by operating by LC parallel resonance between the capacitance (C) formed between the ground plate 2 and the first conductor 11 and the inductance (L) of the short element 13. The resonant frequency corresponds to the operating frequency as an antenna.

[0043] In the zero-order resonant antenna, when power of an operating frequency is fed from a feeding point to the first conductor 11, parallel resonance occurs due to energy exchange between the inductor and the capacitor, and an electric field perpendicular to the ground plate 2 is generated between the ground plate 2 and the first conductor 11. That is, an electric field in the Z-axis direction is generated. This perpendicular electric field propagates from the short element 13 toward the edge of the first conductor 11. The perpendicular electric field becomes a vertically polarized wave at the edge of the first conductor 11 and is radiated into space. Note that the vertically polarized wave in this disclosure refers to radio waves whose electric field vibration direction is perpendicular to the ground plate 2 and the first conductor 11, and can also be called a ground-vertically polarized wave or simply a vertically polarized wave.

[0044] The propagation direction of the vertical electric field generated by the above-mentioned LC parallel resonance (in other words, zero-order resonance) is symmetrical with respect to the short element 13, and therefore has the same gain in all directions in the antenna horizontal plane. In other words, one metamaterial antenna has directivity in all directions (360°) from the center of the first conductor 11 toward its edge. The antenna horizontal plane in this disclosure means a plane parallel to the ground plate 2 and the first conductor 11. In this disclosure, the direction from the center of the first conductor 11 toward its edge is also referred to as the antenna horizontal direction. From another perspective, the antenna horizontal direction is a direction perpendicular to the Z-axis direction and includes the X-axis direction and the Y-axis direction. In short, the antenna horizontal direction corresponds to the lateral direction (in other words, the side) of the antenna device 1.

[0045] In addition, the operation of the antenna when it transmits (radiates) radio waves and the operation when it receives radio waves are mutually reversible. Although the above description has been given taking the example of radiating radio waves, the above configuration allows the antenna to receive vertically polarized waves arriving from the horizontal direction.

[0046] By the way, in addition to the zero-order resonant antenna, there is a patch antenna as an antenna using a metal plate facing the ground plate. The patch antenna is an antenna that utilizes a resonance phenomenon that occurs when the path length of the current is λ / 2, and is different from the zero-order resonant antenna in terms of its operating principle. In addition, the patch antenna needs to have a dimension where the radiating element is λ / 2 in terms of its operating principle, while the zero-order resonant antenna does not need the first conductor 11 to have a length of λ / 2. Furthermore, the zero-order resonant antenna is different from the patch antenna in terms of directivity. That is, the patch antenna and the plate-shaped inverted F antenna form a beam in a direction perpendicular to the ground plate (i.e., upward), while the zero-order resonant antenna basically forms a beam in the horizontal direction of the antenna, not in the upward direction of the antenna. In addition, the patch antenna is an antenna that does not require a short circuit, while the zero-order resonant antenna requires a short circuit. Thus, in terms of the operating principle, directivity, configuration, etc., the zero-order resonant antenna is different from the patch antenna.

[0047] Fig. 4 is a diagram showing the current distribution when power is fed to the first feeding point 12 and the first antenna 10 is operated. As shown in Fig. 4, it can be seen that the current is distributed point-symmetrically with the short element 13, which is the center of the first conductor 11, as the center. Note that P1 in Fig. 4 represents a value such as 10 dBA / m, 15 dBA / m, or 20 dBA / m. P2 is a value 20 dBA / m larger than P1. The same applies to P1 and P2 shown in Figs. 8 and 14 described later.

[0048] 5, 6, and 7 are diagrams showing the directivity when the first antenna 10 is operated. FIG. 5 shows the directivity in the XY plane, in other words, the antenna horizontal direction. FIG. 6 shows the directivity in the XZ plane. Furthermore, FIG. 7 shows the directivity in the YZ plane. As shown in FIG. 5, 6, and 7, the first antenna 10 has directivity in the horizontal direction, and a null occurs in the upward direction. That is, the directivity of the first antenna 10 is a direction perpendicular to the direction from the ground plate 2 to the first conductor 11. In this disclosure, the direction perpendicular to the direction from the ground plate 2 to the first conductor 11 is also referred to as the antenna horizontal direction. The antenna horizontal direction means the direction from the center of the first conductor 11 to the side, or simply the lateral direction for the antenna device 1. Note that 0° in FIG. 6 and FIG. 7 corresponds to the antenna upward direction, and 90° corresponds to the antenna horizontal direction. The same applies to FIG. 10, FIG. 11, FIG. 16, FIG. 17, FIG. 20, and FIG. 21.

[0049] <Operation of the second antenna 20> Here, the operation of the second antenna 20 will be described. In this embodiment, the second antenna 20 operates when the switching unit 3 switches the feeding point for feeding power to the second feeding point 22. Since the length of the second antenna 20 in the Y-axis direction (i.e., the second vertical length L2y) is set to λ / 2, standing waves of current and voltage are formed in the second frame portion 21b and the third frame portion 21c during feeding, and it is expected that the second antenna 20 operates as a patch antenna. The radio waves at that time may be polarized waves whose electric field vibration direction is parallel to the Y-axis. In addition, since the second antenna 20 operates as a patch antenna, it is expected that a beam is formed in the positive direction of the Z-axis.

[0050] FIG. 8 is a diagram showing the current distribution when power is fed to the second feeding point 22 and the second antenna 20 is operated. As shown in FIG. 8, the current is distributed along the direction of the second vertical length L2y, whose electrical length is a half wavelength of a predetermined frequency. In other words, a current standing wave is generated in the Y-axis direction near the first frame portion 21a and the second frame portion 21b. This is the same as the current distribution of a general patch antenna. In other words, it can be seen from the simulation that the operation is as expected.

[0051] 9, 10, and 11 are diagrams showing the directivity when the second antenna 20 is operated. FIG. 9 shows the directivity in the XY plane, in other words, in the horizontal direction of the antenna. FIG. 10 shows the directivity in the XZ plane. Furthermore, FIG. 11 shows the directivity in the YZ plane. As shown in FIG. 9, 10, and 11, the second antenna 20 has directivity in the upward direction. In other words, the directivity of the second antenna 20 is in the direction from the ground plate to the second conductor 21.

[0052] Fig. 12 shows the results of simulating the S parameters (reflection characteristics) of the first antenna 10 and the second antenna 20. The horizontal axis of the graph shown in Fig. 12 represents frequency, and the vertical axis represents S11. The solid line represents S11 when the first antenna 10 is operated, and the solid line represents S11 when the second antenna 20 is operated.

[0053] As shown by the simulation results of the reflection characteristics in FIG. 12, in the first antenna 10, S11 drops to -10 dB near the target frequency of 3.75 GHz. This graph also indirectly shows that the first antenna 10 has LC resonance (in other words, zero-order resonance) at the target frequency. Also, S11 of the second antenna 20 at 3.75 GHz is -8.5 dB. In general, an input reflection coefficient of -5 dB or less is often considered to be a practical configuration. As shown in the graph in FIG. 12, both the first antenna 10 and the second antenna 20 are fully practical as antennas for transmitting and receiving the target frequency.

[0054] In addition, it was also confirmed by analysis that the correlation coefficient between the first antenna 10 and the second antenna 20 was 0.072. This value is sufficient for use as MIMO. In addition, when the bit error rate (BER) was tested while the vehicle was traveling at a speed of 60 km / h, it was confirmed that the BER was about 0.05. In other words, according to the configuration of this embodiment, it is expected that sufficient communication quality can be obtained even in a traveling environment.

[0055] <Summary of the First Embodiment> According to the above configuration, the first antenna 10 has directivity in the horizontal direction, and the second antenna 20 has directivity in the upward direction. That is, the directivity can be changed by 90° by switching the power supply point to be supplied by the switching unit 3. Therefore, if the substrate 5 is attached in a position parallel to the roof of the vehicle, it may be possible to communicate well with each of the devices located above the vehicle and the devices located on the sides of the vehicle. In addition, when this embodiment is applied to Virtual MIMO, the antenna unit 100, which is an antenna module provided in the antenna device 1, is substantially equivalent in size to one patch antenna, so that MIMO can be performed in a smaller size.

[0056] <Second embodiment> This embodiment is a modification based on the previous embodiment, and the description of the previous embodiment can be used. In the previous embodiment, the outer shape of the second conductor 21 is rectangular, but in this embodiment, it is square. The second horizontal length L2x and the second vertical length L2y are values ​​equivalent to the length of λ / 2 of the radio wave at the target frequency.

[0057] In the previous embodiment, the switching unit 3 is configured to switch the antenna to be operated by switching the feeding point to be fed, but the antenna to be operated may be switched by other methods. In this embodiment, as shown in FIG. 13, the switching unit 3 is configured to switch the antenna to be operated by using a switch 3a, which is a switch, instead of the second feeding point 22. That is, the switching unit 3 includes a switch 3a that electrically connects the first conductor 11 and the second conductor 21, and a controller 31 that controls the on / off of the switch 3a. For convenience, one side portion facing the first frame portion 21a among the four sides of the first conductor 11 is referred to as the first side portion 11a. The first side portion 11a is a side portion located relatively closer to the Y-axis positive side among two sides of the first conductor 11 parallel to the X-axis. Hereinafter, the sides of the first conductor 11 facing the second frame portion 21b, the third frame portion 21c, and the fourth frame portion 21d will also be referred to as the second side portion, the third side portion, and the fourth side portion, respectively.

[0058] The switch 3a may be disposed so as to connect the first frame portion 21a and the first side portion 11a. For example, the switch 3a connects the central portions of the first side portion 11a and the first frame portion 21a in the X-axis direction. Thus, in this embodiment, the connection point of the switch 3a to the second conductor 21 is near the center of the first frame portion 21a in the X-axis direction.

[0059] The switch 3a may be a simple switch, or may be one that turns on and off the electrical connection by other methods. For example, the first side portion 11a and the second conductor 21 may be electrically connected by a diode. In this case, a DC power supply is connected in parallel to the diode. The controller 31 may turn on and off the DC power supply to turn on and off the electrical connection between the first conductor 11 and the second conductor 21.

[0060] When the switch 3a is off, the first conductor 11 and the second conductor 21 are not conductive, so the current flowing from the first feed point 12 into the first conductor 11 does not flow into the second conductor 21, but is consumed in the first antenna 10. That is, when the switch 3a is off, the first antenna 10 operates, and the second antenna 20 does not operate. On the other hand, when the switch 3a is on, the current from the first feed point 12 can flow into the second antenna 20 via the first conductor 11. Due to impedance relationships or other reasons, the patch antenna is easier to operate electrically than the metamaterial antenna. Therefore, when the switch 3a is on, the current flowing from the first feed point 12 into the first conductor 11 flows into the first frame portion 21a of the second conductor 21, and the second antenna 20 operates independently.

[0061] Specifically, when the switch 3a is on, a current that flows from the switch 3a to the first frame portion 21a propagates toward the second frame portion 21b and the fourth frame portion 21d. Here, when the second frame portion 21b and the fourth frame portion 21d are λ / 2, standing waves are formed in the second frame portion 21b and the fourth frame portion 21d, and these portions can operate as a patch antenna.

[0062] <Verification of the operation of the second embodiment> As described above, in this embodiment, it is expected that when the switching unit 3 is off, the first antenna 10 operates, and when the switching unit 3 is on, the second antenna 20 operates.

[0063] FIG. 14 is a diagram showing the current distribution when the switch 3a is turned off. As shown in FIG. 14, it can be seen that the current is distributed point-symmetrically with the short element 13, which is the center of the first conductor 11, as the center. Also, FIG. 15, FIG. 16, and FIG. 17 are diagrams showing the directivity when the switch 3a is turned off. FIG. 15 shows the directivity in the XY plane, in other words, in the horizontal direction of the antenna. Also, FIG. 16 shows the directivity in the XZ plane. Furthermore, FIG. 17 shows the directivity in the YZ plane. As shown in FIG. 15, FIG. 16, and FIG. 17, the first antenna 10 has directivity in the horizontal direction, and a null occurs in the upward direction. In other words, the directivity of the first antenna 10 is the horizontal direction of the antenna. From these current distributions and directivities, it can be seen that when the switch 3a is turned off, the first antenna 10 operates as a zero-order resonant antenna.

[0064] On the other hand, Fig. 18 is a diagram showing the current distribution when the switch 3a is turned on. As shown in Fig. 18, the current is distributed along the direction of the second vertical length L2y, whose electrical length is a half-tone of a predetermined frequency. That is, a current standing wave is generated in the Y-axis direction near the first frame portion 21a and the second frame portion 21b. This is because the current flows from the first conductor 11 through the switch 3a to the first frame portion 21a, and then flows from the first frame portion 21a to the second frame portion 21b and the fourth frame portion 21d.

[0065] 19, 20, and 21 are diagrams showing the directivity when the switch 3a is turned on. FIG. 19 shows the directivity in the XY plane, in other words, in the horizontal direction of the antenna. FIG. 20 shows the directivity in the XZ plane. Furthermore, FIG. 21 shows the directivity in the YZ plane. As shown in FIG. 19, 20, and 21, the second antenna 20 has directivity in the upward direction. It can be seen that by turning on the switch 3a in this way, the second conductor 21 operates as a patch antenna.

[0066] FIG. 22 shows the results of simulating S parameters (reflection characteristics) when the switch 3a is on and off. In this simulation, for convenience, the on / off of the switch 3a was reproduced by changing the magnitude of the resistance value between the first conductor 11 and the second conductor 21. Specifically, the resistance value was set to 0.1 ohms when the switching unit 3 was on and 5M ohms when it was off. The horizontal axis of the graph shown in FIG. 22 represents frequency, and the vertical axis represents S11. The solid line in FIG. 22 represents S11 when the first antenna 10 is activated, and the solid line represents S11 when the second antenna 20 is activated.

[0067] As shown in the simulation results of the reflection characteristics in Fig. 22, it is understood that the first antenna 10 has an LC resonance (in other words, a zero-order resonance) at a predetermined frequency of about 3.75 GHz. The S11 of the first antenna 10 at 3.75 GHz is -18 dB, which is sufficiently practical as an antenna for transmitting and receiving a predetermined frequency. The S11 of the second antenna 20 is -8 dB, which is also sufficiently practical as an antenna for transmitting and receiving a predetermined frequency.

[0068] In the simulation, the correlation coefficient between the first antenna 10 and the second antenna 20 was 0.415. In addition, when the bit error rate (BER) was tested while traveling at a speed of 60 km / h, it was confirmed that the BER was about 0.05, similar to the first embodiment. In this embodiment as well, it is expected that sufficient communication quality can be obtained while traveling.

[0069] <Summary of the second embodiment> According to this embodiment, as in the preceding embodiment, the directivity can be changed by 90°. Furthermore, compared to the configuration of the first embodiment, the number of feeding points provided in the antenna device 1 can be reduced, and the circuit configuration can be further simplified.

[0070] <Third embodiment> This embodiment may be understood as a modification based on the preceding embodiment. The description of the preceding embodiment may be used in this embodiment. In the second embodiment, the switching unit 3 includes one switch for electrically connecting the first side portion 11a and the second conductor 21, but may include multiple switches. In this embodiment, as shown in FIG. 23, the switching unit 3 includes a second switch 3b in addition to the first switch 3a, which is the switch 3a in the second embodiment.

[0071] The first switch 3a is configured to electrically connect the first conductor 11 and the second conductor 21 at a predetermined position. The second switch 3b is configured to electrically connect the first conductor 11 and the second conductor 21 at a position different from that of the first switch 3a.

[0072] The first switch 3a connects the first side 11a and the first frame 21a, as in the second embodiment. The second switch 3b is configured to electrically connect the second side 11b facing the second frame 21b to the second frame 21b. The second side 11b is the side located relatively closer to the negative X-axis direction of the two sides of the first conductor 11 parallel to the Y-axis.

[0073] The first switch 3a connects the first side 11a and the first frame 21a at roughly the center in the X-axis direction, and the second switch 3b connects the second side 11b and the second frame 21b at roughly the center in the Y-axis direction.

[0074] The first switch 3a and the second switch 3b may be simple switches as in the second embodiment, or may be switches that turn on and off electrical connection in other ways.

[0075] In this embodiment, the second antenna 20 does not have the second feeding point 22. Instead, power is fed from the first feeding point 12 to the second antenna 20 via the first conductor 11 by turning on the first switch 3a and the second switch 3b.

[0076] When both the first switch 3a and the second switch 3b are off, the first conductor 11 and the second conductor 21 are not conductive, so that the current that flows from the first feeding point 12 into the first conductor 11 does not flow into the second conductor 21 and is consumed in the first antenna 10. In other words, when the first switch 3a and the second switch 3b are off, the first antenna 10 operates and the second antenna 20 is inoperative.

[0077] When at least one of the first switch 3a and the second switch 3b is on, a current from the first feeding point 12 can flow into the second antenna 20 via the first conductor 11. As in the second embodiment, when at least one of the first switch 3a and the second switch 3b is on, a current from the first feeding point 12 flows mainly to the second conductor 21, and the second antenna 20 operates mainly. Details are as follows.

[0078] <Operation characteristics of the third embodiment> In this embodiment, when both the first switch 3a and the second switch 3b are off, the first antenna 10 operates. When at least one of the first switch 3a or the second switch 3b is on, the second antenna 20 operates.

[0079] When both the first switch 3a and the second switch 3b are off, the operation of the first antenna 10 is the same as that of the second embodiment. Also, when only the first switch 3a is on, the operation of the second antenna 20 is the same as that of the second embodiment. That is, when the first switch 3a is on and the second switch 3b is off, standing waves are generated in the second frame portion 21b and the fourth frame portion 21d, and the antenna operates as a patch antenna. When only the first switch 3a is on, the polarization is polarized in the Y-axis direction, as shown in FIG.

[0080] Moreover, the current distribution when only the second switch 3b is on is a distribution obtained by rotating the current distribution (FIG. 18) in the second embodiment 90 degrees counterclockwise in the XY coordinate system. That is, when the first switch 3a is off and the second switch 3b is on, standing waves are generated in the first frame portion 21a and the third frame portion 21c, and the second antenna 20 operates as a patch antenna. The polarization at this time is a polarization in the X-axis direction. Similarly, the directivity is a directivity obtained by rotating the directions in FIGS. 19, 20, and 21 90 degrees counterclockwise in the XY coordinate system.

[0081] The current distribution when both the first switch 3a and the second switch 3b are on is the average of the current distribution when only the first switch 3a is on and when only the second switch 3b is on. As a result, the directivity when both the first switch 3a and the second switch 3b are on is the average of the directivity when only the first switch 3a is on and when only the second switch 3b is on. In other words, the directivity at this time is upward.

[0082] In the simulation, the correlation coefficient between the antenna model corresponding to a state where only the first switch 3a is on and the antenna model corresponding to a state where only the second switch 3b is on was 0.175. The correlation coefficient between the model corresponding to a state where only the first switch 3a is on and the model corresponding to a state where both the first switch 3a and the second switch 3b are on was 0.61.

[0083] <Modification> Although the second antenna 20 is configured to operate as a patch antenna in this example, the present invention is not limited to this. The second antenna 20 may be any antenna having a larger size than the first antenna 10. For example, the second antenna 20 may be a loop antenna.

[0084] Although the first antenna 10 is shown as being rectangular in shape, the shape is not limited to this and may be polygonal, or may be hexagonal as shown in FIG.

[0085] (Other embodiments) The disclosure in this specification and drawings, etc. is not limited to the exemplified embodiments. The disclosure includes the exemplified embodiments and modifications by those skilled in the art based thereon. For example, the disclosure is not limited to the combination of parts and / or elements shown in the embodiments. The disclosure can be implemented by various combinations. The disclosure can have additional parts that can be added to the embodiments. The disclosure includes the omission of parts and / or elements of the embodiments. The disclosure includes the substitution or combination of parts and / or elements between a certain embodiment and another embodiment. The disclosed technical scope is not limited to the description of the embodiments. Some disclosed technical scopes are indicated by the description of the claims, and should be interpreted as including all modifications within the meaning and scope equivalent to the description of the claims.

[0086] The disclosure in the specification and drawings is not limited by the claims. The disclosure in the specification and drawings includes the technical ideas described in the claims, and extends to more diverse and broader technical ideas than the technical ideas described in the claims. Therefore, various technical ideas can be extracted from the disclosure in the specification and drawings without being bound by the claims.

[0087] (Disclosure of technical ideas) This specification discloses multiple technical ideas described in the following multiple dependent claims. Some of the claims may be described in a multiple dependent form, where the subsequent claim alternatively refers to the preceding claim. Furthermore, some of the claims may be described in a multiple dependent form, where the subsequent claim alternatively refers to the preceding claim. The claims described in these multiple dependent forms define multiple technical ideas. (Technical thought 1) The main plate (2) and a first antenna (10) including a first conductor (11) which is a flat conductor arranged opposite to the ground plane, and a short element (13) which electrically connects the first conductor and the ground plane, the first antenna (10) being configured to operate as a zero-order resonant antenna; A second antenna (20) including a second conductor (21) that is a conductor arranged to surround the first conductor; a switching unit (3) for switching between the first antenna and the second antenna, The antenna device, wherein the second antenna is configured to operate in the same frequency band as the first antenna. (Technical thought 2) The first conductor is provided with a first feeding point (12) which is a feeding point, The second conductor is provided with a second feeding point (22) which is a feeding point separate from the first feeding point, The antenna device according to Technical Idea 1, wherein the switching unit is configured to switch the feed point to be fed with power between the first feed point and the second feed point. (Technical Thought 3) The first conductor is provided with a first feeding point (12) which is a feeding point, The switching unit is a switch (3a) that electrically connects the first conductor and the second conductor; A controller (31) that switches the connection state of the switch, The antenna device according to Technical Idea 1 is configured so that the operating antenna is switched by switching the connection state of the switch. (Technical Thought 4) The switching unit is a first switch (3a) that electrically connects the first conductor and the second conductor; a second switch (3b) that electrically connects the first conductor and the second conductor and is different from the first switch; a controller (31) that switches the connection states of the first and second switches, the first switch is configured to electrically connect the first conductor and the second conductor at a predetermined position; The antenna device described in Technical Idea 1, wherein the second switch is configured to electrically connect the first conductor and the second conductor at a position different from that of the first switch. (Technical Thought 5) The first conductor is rectangular and has four sides. The switching unit is a first switch (3a) that electrically connects the first conductor and the second conductor; a second switch (3b) that electrically connects the first conductor and the second conductor and is different from the first switch; a controller (31) that switches the connection states of the first and second switches, the first switch is configured to electrically connect a first side portion (11a) that is one of the four sides and the second conductor; The antenna device described in Technical Idea 1, wherein the second switch is configured to electrically connect a second side portion (11b), which is a side of the first conductor perpendicular to the first side, to the second conductor. (Technical Thought 6) The antenna device described in any one of Technical Ideas 1 to 5, wherein the first antenna is configured to resonate in parallel in the frequency band using an inductance provided by the short-circuit element and a capacitance formed by the ground plate and the first conductor. (Technical Thought 7) the second conductor is configured so that a length (L2y) in a first direction, which is a predetermined direction, is a half wavelength of the frequency band, The antenna device described in any one of Technical Ideas 1 to 6, wherein the first conductor is configured so that its length (L1y) in the first direction is shorter than half the wavelength of the frequency band, and its length (L1x) in a second direction perpendicular to the first direction is shorter than the length (L2x) of the second conductor in the second direction. (Technical Thought 8) the first antenna has directivity in a direction perpendicular to a direction from the ground plane to the first conductor, The antenna device according to any one of Technical Ideas 1 to 7, wherein the second antenna is an antenna having directivity in a direction from the ground plane to the second conductor. [Explanation of symbols]

[0088] REFERENCE SIGNS LIST 1 antenna device, 2 ground plate, 3 switching section, 3a switch (first switch), 3b second switch, 10 first antenna, 11 first conductor, 11a first side section, 11b second side section, 12 first feeding point, 13 shorting element, 20 second antenna, 21 second conductor, 22 second feeding point, 31 controller

Claims

1. A main plate (2), a first antenna (10) including a first conductor (11) which is a flat conductor arranged opposite to the ground plane, and a short element (13) which electrically connects the first conductor and the ground plane, the first antenna (10) being configured to operate as a zero-order resonant antenna; A second antenna (20) including a second conductor (21) that is a conductor arranged so as to surround the first conductor; A switching unit (3) for switching an antenna to be operated between the first antenna and the second antenna, The second antenna is configured to operate in the same frequency band as the first antenna.

2. The first conductor is provided with a first feeding point (12) which is a feeding point, The second conductor is provided with a second feeding point (22) which is a feeding point separate from the first feeding point, The antenna device according to claim 1 , wherein the switching unit is configured to switch between the first feed point and the second feed point to feed power.

3. The first conductor is provided with a first feeding point (12) which is a feeding point, The switching unit is a switch (3a) that electrically connects the first conductor and the second conductor; A controller (31) that switches the connection state of the switch, The antenna device according to claim 1 , wherein an operating antenna is switched by changing a connection state of the switch.

4. The switching unit is A first switch (3a) that electrically connects the first conductor and the second conductor; a second switch (3b) that electrically connects the first conductor and the second conductor and is different from the first switch; A controller (31) that switches the connection states of the first and second switches, the first switch is configured to electrically connect the first conductor and the second conductor at a predetermined position; The antenna device according to claim 1 , wherein the second switch is configured to electrically connect the first conductor and the second conductor at a position different from that of the first switch.

5. The first conductor is rectangular and has four sides. The switching unit is A first switch (3a) that electrically connects the first conductor and the second conductor; a second switch (3b) that electrically connects the first conductor and the second conductor and is different from the first switch; A controller (31) that switches the connection states of the first and second switches, The first switch is configured to electrically connect a first side portion (11a) that is one of the four sides and the second conductor, 2. The antenna device according to claim 1, wherein the second switch is configured to electrically connect a second side portion (11b) of the first conductor that is perpendicular to the first side and the second conductor.

6. The antenna device according to claim 1 , wherein the first antenna is configured to resonate in parallel in the frequency band using an inductance provided by the short-circuit element and a capacitance formed between the ground plane and the first conductor.

7. the second conductor is configured so that a length in a first direction, which is a predetermined direction, is a half wavelength of the frequency band; 2. The antenna device according to claim 1, wherein the first conductor is configured so that its length in the first direction is shorter than half a wavelength of the frequency band, and its length in a second direction perpendicular to the first direction is shorter than the length of the second conductor in the second direction.

8. the first antenna has directivity in a direction perpendicular to a direction from the ground plane to the first conductor, The antenna device according to claim 7 , wherein the second antenna has directivity in a direction from the ground plane to the second conductor.

Images