Antenna device and electronic apparatus

Abstract

The present disclosure provides: an antenna device capable of obtaining necessary radiation efficiency while enabling miniaturization; and an electronic apparatus. This antenna device (100) according to the present disclosure comprises a substrate (20) and a first antenna and a second antenna that are formed on the substrate (20). A ground region (20b) includes a region (20b1) having a length (D2) in a Y direction orthogonal to an X direction and a region (20b2) having a length (D3) longer than the length (D2). When the substrate (20) is divided in the X direction, with an electromagnetic field coupling element (10) serving as a boundary, into a first side (20c) on which a first antenna element (41) and a second antenna element (42) are formed and a second side (20d) on the opposite side to the first side (20c), the region (20b2) is provided on the second side (20d) of the substrate (20), and a cable (40) for connecting a power supply circuit (30) to the first antenna or the second antenna is fixed.

Description

Antenna device and electronic device

[0001] The present disclosure relates to an antenna device and an electronic device.

[0002] In recent years, electronic devices used for communication are sometimes required to operate in multiple frequency bands. To this end, such electronic devices are equipped with antenna devices that combine two antennas (radiating elements) to broaden the available frequency band. For example, Patent Document 1 discloses an antenna device in which two antennas, a powered antenna and a parasitic antenna, are combined by an electromagnetic coupling element.

[0003] Patent No. 6614363

[0004] However, when forming an antenna device with two antennas on a substrate, there is a risk of the radiation efficiency being degraded depending on the positional relationship between the two radiating elements and the ground area. On the other hand, since the antenna device is used by being incorporated into an electronic device, the specifications of the electronic device require miniaturization, but the placement of the two radiating elements and the ground area may be restricted by the cable connecting the power supply circuit.

[0005] Therefore, an object of the present disclosure is to provide an antenna device and electronic device that can achieve necessary radiation efficiency while enabling miniaturization.

[0006] An antenna device according to one embodiment of the present disclosure includes a substrate and a first antenna and a second antenna formed on the substrate. The first antenna includes a first radiating element formed by extending in a first direction of the substrate and a first coil connected in series to the first radiating element. The second antenna includes a second radiating element formed by extending in the first direction and a second coil connected in series to the second radiating element and magnetically coupled to the first coil. The first coil and the second coil form an electromagnetic coupling element. The substrate includes an antenna region in which the first radiating element and the second radiating element are formed, and a ground region formed in the first direction along the antenna region. The ground region includes a first region having a first length in a second direction orthogonal to the first direction, and a second region having a second length longer than the first length. When the substrate is divided into a first side on which the first radiating element and the second radiating element are formed in a first direction, and a second side opposite the first side, the second region is provided on the second side of the substrate, and a cable connecting the power supply circuit to the first antenna or the second antenna is fixed thereto.

[0007] An electronic device according to an embodiment of the present disclosure includes the antenna device described above and a power supply circuit connected to the first antenna or the second antenna via a cable.

[0008] According to one embodiment of the present disclosure, the antenna device has a ground area that includes a second area having a second length in a second direction that is longer than the first area, and the cable is fixed in the second area, thereby enabling miniaturization while achieving the required radiation efficiency.

[0009] 1 is a schematic diagram of an electronic device including an antenna device according to an embodiment; 2 is a perspective view of an electromagnetic field coupling element according to an embodiment; 3 is a plan view of the electromagnetic field coupling element according to an embodiment; 4 is a side view of the electromagnetic field coupling element according to an embodiment; 5 is an equivalent circuit diagram of the antenna device according to an embodiment; 6 is a diagram showing frequency characteristics of radiation efficiency of the antenna device according to an embodiment; 7 is a schematic diagram of an electronic device including an antenna device according to a first modification; 8 is a schematic diagram of an electronic device including an antenna device according to a second modification; 9 is a schematic diagram of an electronic device including an antenna device according to a third modification; 10 is a schematic diagram of an electronic device including an antenna device according to a fourth modification; 11 is a schematic diagram of an electronic device including an antenna device according to a fifth modification; and 12 is a schematic diagram of an electronic device including an antenna device according to a sixth modification.

[0010] Hereinafter, an antenna device and an electronic device according to the present embodiment will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0011] First, an electronic device including an antenna device will be described. Fig. 1 is a schematic diagram of an electronic device 200 including an antenna device 100 according to an embodiment. As shown in Fig. 1, the electronic device 200 includes the antenna device 100 and a power supply circuit 30 that supplies power to a first antenna element 41 (first radiating element). The electronic device 200 is, for example, a laptop computer, a mobile phone, a smartphone, or a tablet that incorporates the antenna device 100 that is capable of communication in frequency bands including the 2.4 GHz band and the 5 GHz to 7 GHz band.

[0012] [Configuration of Antenna Device] The antenna device 100 includes a first antenna element 41 (first radiating element) and a second antenna element 42 (second radiating element) extending in the X direction (first direction) of a plate-shaped substrate 20. Here, the substrate 20 is a printed wiring board (PWB), for example, a board with a base material of FR4 (Flame Retardant Type 4) to which copper foil is attached. Therefore, the first antenna element 41 and the second antenna element 42 are formed by patterning the copper foil on the substrate 20 and then etching it.

[0013] The substrate 20 includes an antenna region 20a in which a first antenna element 41 and a second antenna element 42 are formed, and a ground region 20b formed in the X direction along the antenna region 20a. The ground region 20b is an area where copper foil serving as a reference potential is attached, and is formed from one end of the substrate 20 to the other end in the X direction. Furthermore, the ground region 20b has a step along its length in the Y direction (second direction). The ground region 20b is electrically connected to the ground electrode of the electronic device 200 by a conductive material (not shown) such as copper tape. On the other hand, the antenna region 20a does not include copper foil serving as a reference potential because the copper foil, which serves as a reference potential, would degrade the antenna radiation efficiency, as will be described later.

[0014] The antenna device 100 has an electromagnetic coupling element 10 mounted on a substrate 20. As will be described later, the electromagnetic coupling element 10 includes a coil L1 (first coil) and a coil L2 (second coil), which are magnetically coupled to each other. One end of the coil L1 is connected to a first external electrode 11, and the other end is connected to a second external electrode 12. Furthermore, one end of the coil L2 is connected to a third external electrode 13, and the other end is connected to a fourth external electrode 14.

[0015] 1 , the first antenna element 41 is connected to the first external electrode 11 of the electromagnetic coupling element 10 and is electrically connected to the coil L1 of the electromagnetic coupling element 10. The second external electrode 12 of the coil L1 is connected to a wiring 43, and the wiring 43 is electrically connected to the power feed circuit 30 via the cable 40. Specifically, the antenna elements and wiring formed on the substrate 20 are electrically connected to the external electrode of the electromagnetic coupling element 10 with solder or a conductive adhesive. Therefore, the first antenna 41 and the coil L1 of the electromagnetic coupling element 10 together constitute a first antenna, which functions as a power feed antenna when power is supplied from the power feed circuit 30.

[0016] The first antenna is electrically connected to the ground region 20b via the wiring 41a of the first antenna element 41 and functions as an inverted-F antenna (IFA). The first antenna is capable of communication in a frequency band including, for example, approximately 5 GHz.

[0017] 1 , the second antenna element 42 is connected to the fourth external electrode 14 of the electromagnetic field coupling element 10, and is electrically connected to the coil L2 of the electromagnetic field coupling element 10. The third external electrode 13 of the coil L2 is connected to the wiring 44, and is electrically connected to the ground region 20b. Therefore, the second antenna element 42 and the coil L2 of the electromagnetic field coupling element 10 together constitute a second antenna, and the second antenna functions as a parasitic antenna.

[0018] The second antenna functions as a branched monopole antenna, and the second antenna element 42 includes a first portion 42a extending in the positive X direction (the direction of the arrow) and a second portion 42b extending in the negative X direction (the direction opposite to the arrow). Since the length of the first portion 42a of the second antenna is longer than the length of the second portion 42b, the first portion 42a is capable of communication in a frequency band including, for example, approximately 2.4 GHz, and the second portion 42b is capable of communication in a frequency band including, for example, approximately 6 GHz.

[0019] As shown in FIG. 1 , the antenna device 100 has a first antenna and a second antenna formed on a substrate 20 and is mounted on an electronic device 200. Therefore, along with the demand for miniaturization of the electronic device 200, the antenna device 100 itself is also required to be miniaturized. However, in the antenna device 100, the first antenna element 41, which is a powered antenna, and the second antenna element 42, which is a parasitic antenna, are arranged close to each other to electromagnetically couple the first antenna element 41 and the second antenna element 42 in order to broaden the communication band. However, if the first antenna element 41 and the second antenna element 42 are not arranged at a certain distance from the ground area 20b, there is a risk that the electromagnetic coupling will be impaired. Therefore, it is preferable that the Y-direction distance from the first antenna element 41 or the second antenna element 42 to the ground area 20b be longer than the Y-direction distance from the first antenna element 41 to the second antenna element 42.

[0020] On the other hand, it was necessary to reduce the size of the antenna device 100 by shortening the length D1 in the Y direction of the antenna region 20a in which the first antenna element 41 and the second antenna element 42 are formed. Also, if the first antenna element 41 and the second antenna element 42 themselves were arranged close to the ground region 20b, the respective antenna elements would be affected by the ground region 20b, which could degrade the radiation efficiency of the antenna device 100.

[0021] Furthermore, since the antenna device 100 requires power to be supplied from the feed circuit 30 to the first antenna element 41 of the feed antenna, it is necessary to connect a cable 40 to the electromagnetic coupling element 10. The cable 40 is a coaxial cable, and the inner conductor 40b is electrically connected to the wiring 43. Furthermore, to prevent problems such as disconnection of the inner conductor 40b and the wiring 43 due to movement of the cable 40, the cable 40 is fixed to the ground area 20b by a fixing means 40c such as soldering, while the outer conductor 40a is electrically connected to the ground area 20b. The cable 40 includes an insulator 40d between the outer conductor 40a and the inner conductor 40b. However, the cable 40 needs to have a certain thickness for mechanical strength, and the length D3 (second length) of the ground area 20b in the Y direction must also be long enough to match the thickness of the cable 40. Therefore, the ground area has been a bottleneck in miniaturizing the antenna device.

[0022] Therefore, the antenna device 100 employs a ground area 20b having a step in the length in the Y direction. Specifically, as shown in Fig. 1 , the ground area 20b includes an area 20b1 (first area) having a length D2 (first length) in the Y direction and an area 20b2 (second area) having a length D3 (>D2) in the Y direction. Of the ground area 20b, the area 20b1 is disposed in the area where the first antenna element 41 and the second antenna element 42 are formed, and the area 20b2 is disposed in the area where the cable 40 is fixed.

[0023] In other words, when the substrate 20 is divided in the X direction by the electromagnetic coupling element 10 into a first side 20c on which the first antenna element 41 and the second antenna element 42 are formed and a second side 20d opposite the first side 20c, at least the region 20b2 needs to be provided on the second side 20d. This allows the length D2 of the region 20b1 of the ground region 20b to be shortened, thereby enabling the antenna device 100 to be miniaturized while maintaining the length D1 of the antenna region 20a in the Y direction. For example, if the length D1 of the antenna region 20a in the Y direction is 3 mm and the length D2 of the region 20b1 is 1 mm, the length of the antenna device 100 in the Y direction can be reduced to 4 mm. The length D3 of the region 20b2 is 2 mm, so the cable 40 can be sufficiently fixed in the region 20b2.

[0024] On the other hand, an antenna device having a ground area with a length D3 in the Y direction and no step in the Y direction length requires a length in the Y direction of 5 mm, which is the sum of the Y direction length D1 (3 mm) of the antenna area and the length D3 (2 mm) of the ground area, making it difficult to miniaturize.

[0025] [Structure of Electromagnetic Coupling Element] Next, an electromagnetic field coupling element according to an embodiment will be described with reference to the drawings. FIG. 2 is a perspective view of an electromagnetic field coupling element 10 according to an embodiment. FIG. 3 is a plan view of the electromagnetic field coupling element 10 according to an embodiment. FIG. 4 is a side view of the electromagnetic field coupling element 10 according to an embodiment. Here, in FIGS. 2 to 4, the short side direction of the electromagnetic field coupling element 10 is the X direction, the long side direction is the Y direction, and the height direction is the Z direction. The stacking direction of the substrates is the Z direction, and the arrow indicates the direction toward the upper layer.

[0026] The electromagnetic field coupling element 10 is a rectangular parallelepiped chip component that is an antenna coupling element that couples two antennas (radiating elements). A first external electrode 11, a second external electrode 12, a third external electrode 13, and a fourth external electrode 14 are formed on the outer surface of the electromagnetic field coupling element 10, as shown in Fig. 2. The electromagnetic field coupling element 10 has a pair of opposing main surfaces, with the lower main surface in Fig. 2 being the mounting surface that faces the circuit board.

[0027] The electromagnetic coupling element 10 includes two coils L1 and L2 to magnetically couple two antennas (radiating elements), and the coils L1 and L2 form a transformer that is magnetically coupled.

[0028] The specific configuration of the electromagnetic coupling element 10 will be described. As shown in Figures 2 to 4, the electromagnetic coupling element 10 is composed of an insulator 1 (ceramic element body) made of ceramic layers in which multiple substrates (ceramic green sheets) on which coil wiring is formed are stacked. The insulator 1 has a pair of opposing main surfaces and a side surface connecting the main surfaces. A plurality of first conductor patterns 21, a second conductor pattern 22, a plurality of third conductor patterns 23, and a fourth conductor pattern 24 are stacked parallel to the main surface of the insulator 1 to form the electromagnetic coupling element 10 containing the coil L1 and the coil L2.

[0029] The coil L1 has two layers of first conductor patterns 21a and 21b stacked on top of one layer of a second conductor pattern 22, with the conductor patterns electrically connected to each other by via conductors 31. Specifically, the coil L1 connects the two layers of first conductor patterns 21a and 21b, i.e., the first conductor patterns 21a and 21b, in parallel by the via conductors 31, and connects the second conductor pattern 22 to the first conductor pattern 21 on the second layer in series by the via conductors 31. Therefore, the coil L1 can reduce the inductance component compared to when the first conductor pattern 21a and the second conductor pattern 22 are connected in series. Note that the first conductor pattern 21 may be a conductor pattern having two or more layers.

[0030] The coil L2 has two layers of third conductor patterns 23a, 23b stacked on top of one layer of a fourth conductor pattern 24, with the conductor patterns electrically connected to each other by via conductors 32. Specifically, the coil L2 connects the third conductor patterns 23a, 23a, of the two layers in parallel by the via conductors 32, and connects the fourth conductor pattern 24 to the third conductor pattern 23 of the second layer in series by the via conductors 32. Therefore, the coil L2 can reduce the inductance component compared to when the third conductor pattern 23a and the fourth conductor pattern 24 are connected in series. Note that the third conductor pattern 23 may be a conductor pattern of two or more layers.

[0031] The coils L1 and L2 are disposed within the insulator 1 such that, when viewed from the stacking direction of the insulator 1, the opening of the coil L1 overlaps the opening of the coil L2. As shown in FIG. 3 , when viewed from the stacking direction of the insulator 1, the openings of the coils L1 and L2 are disposed such that they are offset in the long-side direction relative to the center of the electromagnetic coupling element 10 and are disposed in a direction approaching the second external electrode 12 provided on the short side of the electromagnetic coupling element 10. However, the arrangement of the coils L1 and L2 shown in FIG. 3 is merely an example, and other arrangements may be used. Specifically, the coils L1 and L2 are disposed within the insulator 1 such that the second conductor pattern 22 and the fourth conductor pattern 24 face each other. Because the coils L1 and L2 are configured such that the second conductor pattern 22 of one layer and the fourth conductor pattern 24 of the first layer face each other across an insulating layer, the capacitance component is smaller than in a configuration in which conductor patterns of three layers face each other across an insulating layer.

[0032] Furthermore, when the coils L1 and L2 are arranged so that the second conductor pattern 22 and the fourth conductor pattern 24 face each other, the coupling coefficient between the coils L1 and L2 can be maintained high compared to when the coils L1 and L2 are arranged so that the first conductor pattern 21 of the second layer and the third conductor pattern 23 of the second layer face each other. Therefore, by arranging the coils L1 and L2 so that the second conductor pattern 22 and the fourth conductor pattern 24 face each other, the mutual inductance M between the coils L1 and L2 does not decrease in the electromagnetic field coupling element 10.

[0033] As shown in Figure 2, a first external electrode 11 is provided on one of the short sides of the side of the insulator 1, a second external electrode 12 is provided on the other short side, a third external electrode 13 is provided on one of the long sides, and a fourth external electrode 14 is provided on the other long side.

[0034] Each of the multiple first conductor patterns 21 is electrically connected to the first external electrode 11. Of the multiple first conductor patterns 21, only the lower-layer first conductor pattern 21b may be electrically connected to the first external electrode 11, and the upper-layer first conductor pattern 21a may be electrically connected to the first conductor pattern 21b via a via conductor. The second conductor pattern 22 is electrically connected to the second external electrode 12.

[0035] Each of the plurality of third conductor patterns 23 is electrically connected to the third external electrode 13. Of the plurality of third conductor patterns 23, only the lower-layer third conductor pattern 23b may be electrically connected to the third external electrode 13, and the upper-layer third conductor pattern 23a may be electrically connected to the third conductor pattern 23b via a via conductor. The fourth conductor pattern 24 is electrically connected to the fourth external electrode 14.

[0036] [Equivalent Circuit of Antenna Device] An equivalent circuit of the antenna device 100 employing the electromagnetic field coupling element 10 shown in Figures 2 and 3 will be described. Figure 5 is an equivalent circuit diagram of the antenna device 100 according to the embodiment. The antenna device 100 uses the electromagnetic field coupling element 10 to couple a first antenna element 41, which is a powered antenna connected to the power feed circuit 30, and a second antenna element 42, which is a parasitic antenna that is not fed by the power feed circuit 30.

[0037] Specifically, the first antenna element 41 is electrically connected to the first external electrode 11 of the electromagnetic field coupling element 10, and the power feed circuit 30 is electrically connected to the second external electrode 12 of the electromagnetic field coupling element 10. In other words, the coil L1 of the electromagnetic field coupling element 10 is connected between the first antenna element 41 and the power feed circuit 30.

[0038] 5 , the coil L1 has a coil portion formed by the first conductor pattern 21 a and a coil portion formed by the first conductor pattern 21 b connected in parallel, and a coil portion formed by the second conductor pattern 22 connected in series to these portions. In the coil L1, the side of the coil portion formed by the second conductor pattern 22 is connected to the power supply circuit 30.

[0039] On the other hand, the second antenna element 42 is electrically connected to the fourth external electrode 14 of the electromagnetic field coupling element 10, and the third external electrode 13 of the electromagnetic field coupling element 10 is connected to GND (earthed). In other words, the coil L2 of the electromagnetic field coupling element 10 is connected between the second antenna element 42 and GND.

[0040] As shown in FIG. 5 , the coil L2 has a coil portion formed by the third conductor pattern 23 a and a coil portion formed by the third conductor pattern 23 b connected in parallel, and a coil portion formed by the fourth conductor pattern 24 connected in series to these portions. In the coil L2, the side of the coil portion formed by the third conductor pattern 23 a and the coil portion formed by the third conductor pattern 23 b, which are connected in parallel, is connected to GND. Since more current flows on the GND side than on the second antenna element 42 side, the Q value of the coil L2 can be improved by connecting the coil portions connected in parallel to the GND side. Note that by using the third external electrode 13 of the electromagnetic coupling element 10 as a GND electrode (ground electrode), the coil portions connected in parallel can be connected to the GND side.

[0041] 5, in the antenna device 100, the frequency band available for the first antenna element 41 and the second antenna element 42 can be broadened by magnetically coupling the coil L1 and the coil L2. Note that a mutual inductance M occurs between the coil L1 and the coil L2.

[0042] Note that the electromagnetic field coupling element 10 shown in Figures 2 to 4 is just an example, and is not limited to the electromagnetic field coupling element of this structure, and any structure may be used as long as it is an electromagnetic field coupling element that magnetically couples coil L1 and coil L2 to form a transformer.

[0043] [Radiation Efficiency of Antenna Device] It has been explained that the radiation efficiency of the antenna device 100 shown in FIG. 1 is improved by employing a ground region 20b with a step in the Y-direction length. Specifically, it will be explained how the radiation efficiency of the antenna device 100 is improved compared to a comparative example. FIG. 6 is a diagram showing the frequency characteristics of the radiation efficiency of the antenna device 100 according to the embodiment. In FIG. 6, the horizontal axis represents frequency and the vertical axis represents antenna efficiency (radiation efficiency). The solid line graph A3 in FIG. 6 shows the frequency characteristics of the radiation efficiency of the antenna device 100. In the antenna device 100, a step is provided in the Y-direction length of the ground region 20b, with the length D2 of region 20b1 being 1 mm and the length D3 of region 20b2 being 2 mm.

[0044] On the other hand, the frequency characteristics of the radiation efficiency of the antenna device of comparison A are shown by the dashed line graph A1. The antenna device of comparison A has no step in the Y-direction length of the ground region, and the Y-direction length of the ground region is 1.5 mm. However, to make the Y-direction length of the antenna device of comparison A the same as that of antenna device 100, it is set to 4 mm, and the Y-direction length of the antenna region is set to 2.5 mm.

[0045] The frequency characteristics of the radiation efficiency of the antenna device of comparison B are shown by the dashed-dotted line graph A2. The antenna device of comparison B has no step in the Y-direction length of the ground region, and the Y-direction length of the ground region is 1.8 mm. However, to make the Y-direction length of the antenna device of comparison B the same as that of antenna device 100, it is set to 4 mm, and the Y-direction length of the antenna region is set to 2.2 mm.

[0046] 6 shows that the antenna efficiency is higher in all frequency bands than the graphs A1 and A2 of the comparison targets A and B. Therefore, the antenna device 100 can obtain the required radiation efficiency by employing the ground region 20b having a step in the length in the Y direction.

[0047] [Modifications of the Antenna Device] The antenna device 100 shown in Fig. 1 is one example, and is not limited to this configuration. Modifications of the antenna device will be described below with reference to the drawings. Note that the modifications described below and the configuration of the antenna device 100 shown in Fig. 1 can be combined as appropriate, provided there are no technical impediments.

[0048] (Variation 1) In the antenna device 100, the first antenna element 41 and the feed circuit 30 are electrically connected, and the second antenna element 42 is used as a parasitic antenna. However, the present invention is not limited to this, and the second antenna element and the feed circuit may be electrically connected, and the first antenna element may be used as a parasitic antenna.

[0049] Fig. 7 is a schematic diagram of an electronic device 200a including an antenna device 100a according to Modification 1. In the antenna device 100a shown in Fig. 9, the same components as those in the antenna device 100 shown in Fig. 1 are denoted by the same reference numerals, and detailed description thereof will not be repeated.

[0050] In the electromagnetic field coupling element 10a, one end of the coil L1 is connected to the first external electrode 11 and the other end is connected to the third external electrode 13, and one end of the coil L2 is connected to the second external electrode 12 and the other end is connected to the fourth external electrode 14.

[0051] 7, the first antenna element 41 is connected to the first external electrode 11 of the electromagnetic field coupling element 10a and is electrically connected to the coil L1 of the electromagnetic field coupling element 10a. The third external electrode 13 of the coil L1 is connected to the wiring 44 and is electrically connected to the ground region 20b. Therefore, the first antenna element 41 and the coil L1 of the electromagnetic field coupling element 10a together constitute a first antenna, which functions as a parasitic antenna.

[0052] 1 , the second antenna element 42 is connected to the fourth external electrode 14 of the electromagnetic coupling element 10a and is electrically connected to the coil L2 of the electromagnetic coupling element 10a. The second external electrode 12 of the coil L2 is connected to a wiring 43, and the wiring 43 is electrically connected to the power supply circuit 30 via the cable 40. Therefore, the second antenna element 42 and the coil L2 of the electromagnetic coupling element 10a together constitute a second antenna, and the second antenna functions as a power supply antenna when power is supplied from the power supply circuit 30.

[0053] In the antenna device 100a, the second antenna element 42 functions as a powered antenna and the first antenna element 41 functions as a non-powered antenna, but since it uses a ground area 20b with a step in the Y-direction length, it is possible to achieve the required radiation efficiency while making it possible to reduce the size.

[0054] The second antenna element 42 is formed farther from the ground area 20b than the first antenna element 41. This is because the frequency band of the second antenna element 42 is lower than the frequency band of the first antenna element 41, and therefore the second antenna element 42 is more susceptible to the influence of the ground area 20b. The frequency band of the first portion 42a of the second antenna element 42 is, for example, approximately 2.4 GHz, and the frequency band of the first antenna element 41 is, for example, approximately 5 GHz. If the frequency band of the second antenna element 42 is higher than the frequency band of the first antenna element 41, the second antenna element 42 may be formed closer to the ground area 20b than the first antenna element 41. Furthermore, since the second portion 42b of the second antenna element 42 is formed on the second side 20d, it is positioned near the region 20b2 of the ground region 20b. However, since the length of the second portion 42b is shorter than the length of the first portion 42a, the frequency band is high, for example, about 6 GHz, and it is less susceptible to the influence of the ground region 20b than the first portion 42a of the second antenna element 42.

[0055] (Variation 2) In the antenna device 100, the second antenna element 42 includes two parts, the first part 42 a and the second part 42 b, each of which has its own frequency band. However, this is not limited to this, and the second antenna element may be configured as a simple monopole antenna.

[0056] Fig. 8 is a schematic diagram of an electronic device 200b including an antenna device 100b according to Modification 2. In antenna device 100b shown in Fig. 8, the same components as those in antenna device 100 shown in Fig. 1 are denoted by the same reference numerals, and detailed description thereof will not be repeated.

[0057] The second antenna element 42B has a shape that extends only in the positive X direction from the portion connected to the fourth external electrode 14 of the electromagnetic field coupling element 10. Therefore, the second antenna including the second antenna element 42B and the coil L2 of the electromagnetic field coupling element 10 functions as a simple monopole antenna.

[0058] The antenna device 100b has a shape in which only the second antenna element 42B extends in the positive X direction, but it uses a ground area 20b with a step in the length in the Y direction, so it can be made smaller while still achieving the required radiation efficiency.

[0059] The second antenna including the second antenna element and the coil L2 of the electromagnetic field coupling element 10 may be configured not only as a monopole antenna, but also as an inverted F-type antenna or a loop antenna.

[0060] (Variation 3) In the antenna device 100, the first antenna element 41 is electrically connected to the ground region 20b via the wiring 41a and functions as an inverted-F antenna. However, this is not limiting, and the first antenna element may be configured as a monopole antenna.

[0061] Fig. 9 is a schematic diagram of an electronic device 200c including an antenna device 100c according to Modification 3. In antenna device 100c shown in Fig. 9, the same components as those in antenna device 100 shown in Fig. 1 are denoted by the same reference numerals, and detailed description thereof will not be repeated.

[0062] The first antenna element 41C has a shape that extends only in the positive X direction from the portion connected to the first external electrode 11 of the electromagnetic field coupling element 10. Therefore, the first antenna including the first antenna element 41C and the coil L1 of the electromagnetic field coupling element 10 functions as a monopole antenna.

[0063] The antenna device 100c has a shape in which only the first antenna element 41C extends in the positive X direction, but it uses a ground area 20b with a step in the length in the Y direction, so it can be made smaller while still achieving the required radiation efficiency.

[0064] The first antenna including the first antenna element and the coil L1 of the electromagnetic field coupling element 10 may be configured as a loop antenna, in addition to a monopole antenna or an inverted F antenna.

[0065] (Variation 4) In the antenna device 100, the ground area 20b is formed from one end to the other end of the substrate 20 in the X direction. However, this is not limited to this, and a configuration may be adopted in which a ground area is not formed from one end to the other end of the substrate in the X direction.

[0066] Fig. 10 is a schematic diagram of an electronic device 200d including an antenna device 100d according to Modification 4. In antenna device 100d shown in Fig. 10, the same components as those in antenna device 100 shown in Fig. 1 are denoted by the same reference numerals, and detailed description thereof will not be repeated.

[0067] The substrate 20 includes an antenna region 20a in which the first antenna element 41 and the second antenna element 42 are formed, and a ground region 20D formed in the X direction along the antenna region 20a. The ground region 20D is not formed from one end to the other end of the substrate 20 in the X direction, but is formed up to a position where it connects to the wiring 41a of the first antenna element 41, as shown in Fig. 10, and is not formed from that position in the positive X direction.

[0068] The ground region 20D has a step in its length in the Y direction. Specifically, as shown in FIG. 10 , the ground region 20D has a region 20D1 with a length D2 in the Y direction and a region 20D2 with a length D3 (>D2) in the Y direction. The region 20D1 is disposed in the region where the first antenna element 41 and the second antenna element 42 are formed, and the region 20D2 is disposed in the region where the cable 40 is fixed. The ground region 20D is electrically connected to the ground electrode of the electronic device 200d by a conductive material (not shown) such as copper tape.

[0069] In the antenna device 100d, the ground area 20D is not formed from one end of the substrate 20 to the other end in the X direction, but a ground area 20D having a step in the length in the Y direction is adopted, thereby enabling miniaturization while obtaining the required radiation efficiency.

[0070] (Variation 5) In the antenna device 100, the ground area 20b has been described as having the area 20b1 with the length D2 in the Y direction and the area 20b2 with the length D3 (>D2) in the Y direction. However, this is not limited thereto, and the antenna device may employ a ground area including an area in which the length D2 in the Y direction is 0 (zero).

[0071] Fig. 11 is a schematic diagram of an electronic device 200e including an antenna device 100e according to Modification 5. In antenna device 100e shown in Fig. 11, the same components as those in antenna device 100 shown in Fig. 1 are denoted by the same reference numerals, and detailed description thereof will not be repeated.

[0072] The substrate 20 includes an antenna region 20a in which the first antenna element 41 and the second antenna element 42 are formed, and a ground region 20E formed in the X direction along the antenna region 20a.

[0073] 11 , the ground region 20E has a region with a length D3 in the Y direction extending up to a position where the ground region 20E is connected to the wiring 41a of the first antenna element 41, and a region with a length of 0 (zero) in the Y direction extending from the region in the positive X direction. In other words, the ground region 20E includes a region with a length of 0 (zero) in the Y direction and a region with a length D3 in the Y direction, and has a step in the length in the Y direction. The ground region 20E is electrically connected to the ground electrode of the electronic device 200e by a conductive material (not shown) such as copper tape.

[0074] In the region in the positive X-direction from the position where the first antenna element 41 is connected to the wiring 41a, the length of the ground region 20E in the Y-direction is 0 (zero). Therefore, the first antenna element 41 and the second antenna element 42 in this region are not affected by the ground region 20E. Therefore, the antenna device 100e can also achieve the required radiation efficiency while enabling miniaturization. Note that the cable 40 is fixed by the ground region 20E with a length D3 in the Y-direction. In this example, the ground region 20E is formed only in the region where the cable 40 is fixed. However, another ground region may also be formed on the tip side of the second antenna element 42.

[0075] (Variation 6) In the antenna device 100, it has been described that the ground area 20b is electrically connected to the ground electrode of the electronic device 200 by a conductive material (not shown) such as copper tape. However, the present invention is not limited to this, and the entire ground area may be covered with a conductive material such as copper tape or copper foil.

[0076] Fig. 12 is a schematic diagram of an electronic device 200f including an antenna device 100f according to Modification 6. In antenna device 100f shown in Fig. 12, the same components as those in antenna device 100 shown in Fig. 1 are denoted by the same reference numerals, and detailed description thereof will not be repeated.

[0077] As shown in Figure 12, the ground region 20E is formed such that an area with a length D3 in the Y direction extends up to the position where it connects to the wiring 41a of the first antenna element 41, and an area with a length of 0 (zero) in the Y direction is formed from that position in the positive X direction.

[0078] Furthermore, a copper foil 60 is provided so as to cover the entire ground area 20E. The copper foil 60 is provided not only on the ground area 20E but also protrudes from the substrate 20. However, the copper foil 60 does not cover the antenna area 20a other than the ground area 20E.

[0079] The copper foil 60 is joined to the ground area 20E with a conductive adhesive, solder, etc. The cable 40 is fixed to the ground area 20E covered with the copper foil 60. In other words, the cable 40 is fixed to the ground area 20E with the copper foil 60 sandwiched between them. The cable 40 is joined to the copper foil 60 with a conductive adhesive, solder, etc.

[0080] (Aspects) (1) An antenna device according to the present disclosure is an antenna device including a substrate, and a first antenna and a second antenna formed on the substrate, wherein the first antenna includes a first radiating element formed by extending in a first direction of the substrate, and a first coil connected in series with the first radiating element, the second antenna includes a second radiating element formed by extending in the first direction, and a second coil connected in series with the second radiating element and magnetically coupled with the first coil, the first coil and the second coil forming an electromagnetic field coupling element, the substrate includes an antenna region in which the first radiating element and the second radiating element are formed, and a ground region formed in the first direction along the antenna region, the ground region including: a first region having a first length in a second direction orthogonal to the first direction, and a second region having a second length longer than the first length, When the substrate is divided into a first side on which the first radiating element and the second radiating element are formed in a first direction, and a second side opposite the first side, the second region is provided on the second side of the substrate, and a cable connecting the power supply circuit to the first antenna or the second antenna is fixed thereto.

[0081] (2) In the antenna device described in (1), a part of the first radiating element of the first antenna is electrically connected to the ground region.

[0082] (3) In the antenna device according to (1) or (2), the second radiating element is formed farther from the ground region than the first radiating element.

[0083] (4) In the antenna device described in (3), the second radiating element includes a first portion extending in the positive direction of the first direction and a second portion extending in the negative direction of the first direction.

[0084] (5) In the antenna device according to (4), the second radiating element has a second portion whose length is shorter than the first portion.

[0085] (6) In the antenna device described in any one of (1) to (5), the distance in the second direction from the first radiating element or the second radiating element to the ground region is longer than the distance in the second direction from the first radiating element to the second radiating element.

[0086] (7) In the antenna device according to any one of (1) to (6), the ground area is formed from one end to the other end of the substrate in the first direction.

[0087] (8) An antenna device according to the present disclosure includes the antenna device according to any one of (1) to (7) and a power supply circuit connected to the first antenna or the second antenna via a cable.

[0088] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0089] 1 Insulator, 10, 10a Electromagnetic field coupling element, 11 First external electrode, 12 Second external electrode, 13 Third external electrode, 14 Fourth external electrode, 20 Substrate, 20a Antenna area, 20b, 20D, 20E Ground area, 30 Power supply circuit, 40 Cable, 40a Outer conductor, 40b Inner conductor, 40c Fixing means, 41, 41C First antenna element, 42, 42B Second antenna element, 100, 100a to 100f Antenna device, 200, 200a to 200f Electronic device.

Claims

1. An antenna device comprising a substrate, and a first antenna and a second antenna formed on the substrate, wherein the first antenna includes a first radiating element formed by extending in a first direction of the substrate, and a first coil connected in series with the first radiating element, the second antenna includes a second radiating element formed by extending in the first direction, and a second coil connected in series with the second radiating element and magnetically coupled with the first coil, the first coil and the second coil constituting an electromagnetic field coupling element, the substrate includes an antenna region in which the first radiating element and the second radiating element are formed, and a ground region formed in the first direction along the antenna region, the ground region includes a first region having a first length in a second direction perpendicular to the first direction, and a second region having a second length longer than the first length, an antenna device in which, when the substrate is divided in the first direction into a first side on which the first radiating element and the second radiating element are formed, and a second side opposite the first side, the second region is provided on the second side of the substrate, and a cable connecting a power supply circuit to the first antenna or the second antenna is fixed.

2. The antenna device according to claim 1, wherein the first antenna has a portion of the first radiating element electrically connected to the ground region.

3. The antenna device according to claim 1 or 2, wherein the second radiating element is formed on a side farther from the ground region than the first radiating element.

4. The antenna device according to claim 3, wherein the second radiating element includes a first portion extending in a positive direction of the first direction and a second portion extending in a negative direction of the first direction.

5. The antenna device according to claim 4, wherein the second portion of the second radiating element has a length shorter than the length of the first portion.

6. An antenna device described in any one of claims 1 to 5, wherein the distance in the second direction from the first radiating element or the second radiating element to the ground area is longer than the distance in the second direction from the first radiating element to the second radiating element.

7. The antenna device according to any one of claims 1 to 6, wherein the ground area is formed from one end to the other end of the substrate in the first direction.

8. An electronic device comprising: the antenna device according to any one of claims 1 to 7; and the power supply circuit connected to the first antenna or the second antenna via the cable.

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