Antenna device and wireless terminal

Abstract

Provided are an antenna device having higher radiation efficiency, and a wireless terminal provided with said antenna device. This antenna device is provided with an antenna that operates at a first frequency and a second frequency that is higher than the first frequency, a first conductor plate having a feeding point for supplying electric power to the antenna, a second conductor plate, a connection part that electrically connects the first conductor plate and the second conductor plate, and a circuit element provided between the first conductor plate and the second conductor plate. A first distance from a proximate location of the first conductor that is closest to the antenna to a first distant location of the first conductor plate that is farthest from the antenna is set to be less than a second distance from the proximate location to a second distant location of the second conductor plate that is farthest from the antenna, and the circuit element electrically connects the first conductor plate and the second conductor plate at the first frequency, and electrically disconnects the first conductor plate and the second conductor plate at the second frequency.

Description

[Technical field]

[0001] The present invention relates to an antenna device and a wireless terminal. [Background technology]

[0002] In wireless terminals such as smartphones, a conductor provided inside the terminal is used as an antenna ground (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP2017-085540A [Patent Document 2] JP 2013-074361 A Summary of the Invention [Problem to be solved by the invention]

[0004] In wireless terminals such as smartphones, the first ground formed on the substrate with the power supply point is electrically connected to the second ground formed by a conductor on the back surface of the display, thereby securing the largest possible ground for the antenna. When this type of configuration is adopted, the current flowing through the first ground and the second ground cannot be controlled, so there is a limit to how much the radiation efficiency of the antenna can be improved.

[0005] An object of one aspect of the disclosed technology is to provide an antenna device with higher radiation efficiency and a wireless terminal including the antenna device. [Means for solving the problem]

[0006] One aspect of the disclosed technology is exemplified by an antenna device as follows. The antenna device includes an antenna that operates at a first frequency and a second frequency higher than the first frequency, a first conductor plate having a power supply point for supplying power to the antenna and formed in a plate shape, a second conductor plate formed in a plate shape, a connection portion that electrically connects the first conductor plate and the second conductor plate, and a circuit element provided between the first conductor plate and the second conductor plate. A first distance from a nearby portion of the first conductor plate that is closest to the antenna to a first remote portion of the first conductor plate that is farthest from the antenna is set shorter than a second distance from the nearby portion to a second remote portion of the second conductor plate that is farthest from the antenna, and the circuit element electrically connects the first conductor plate and the second conductor plate at the first frequency and electrically separates the first conductor plate and the second conductor plate at the second frequency. Effect of the Invention

[0007] According to the disclosed technique, it is possible to provide an antenna device with higher radiation efficiency and a wireless terminal equipped with the antenna device. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an example of an antenna device 1 according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating the configuration employed in the simulation. [Diagram 3] FIG. 3 is a first diagram showing the results of the first simulation. [Figure 4] FIG. 4 is a second diagram showing the results of the first simulation. [Diagram 5] FIG. 5 is a third diagram showing the results of the first simulation. [Figure 6] FIG. 6 is a first diagram illustrating the results of the second simulation. [Figure 7] FIG. 7 is a second diagram illustrating the results of the second simulation. [Figure 8] FIG. 8 is a diagram illustrating the results of the third simulation. [Figure 9] FIG. 9 is a diagram illustrating the results of the fourth simulation. [Figure 10] FIG. 10 is a diagram illustrating a circuit that is employed as the contact P2. [Figure 11] FIG. 11 is a diagram illustrating the results of the fifth simulation. [Figure 12] FIG. 12 is a diagram illustrating the configuration of the antenna device in the sixth simulation. [Figure 13] FIG. 13 is a diagram illustrating the configuration of an antenna device according to a comparative example prepared in the sixth simulation. [Figure 14] FIG. 14 is a diagram illustrating the results of the sixth simulation. [Figure 15] FIG. 15 is a diagram showing the appearance of a smartphone according to an implementation example. [Figure 16] FIG. 16 is a diagram illustrating an example of an internal configuration of a smartphone according to an implementation example. [Figure 17] FIG. 17 is a first diagram illustrating variations in the shape of the first ground substrate. [Figure 18] FIG. 18 is a second diagram illustrating variations in the shape of the first ground substrate. [Figure 19] FIG. 19 is a diagram illustrating a configuration in which the first ground substrate and the second ground substrate do not overlap in a plan view. [Figure 20] FIG. 20 is a diagram illustrating a configuration in which a feed point is connected to the center of the antenna. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] <Embodiment> The configurations of the embodiments described below are examples, and the disclosed technology is not limited to the configurations of the embodiments. The antenna device according to the embodiment has, for example, the following configuration. The antenna device according to the embodiment has an antenna that operates at a first frequency and a second frequency higher than the first frequency, a first conductor plate formed in a plate shape having a power supply point that supplies power to the antenna, a second conductor plate formed in a plate shape, a connection portion that electrically connects the first conductor plate and the second conductor plate, and a circuit element provided between the first conductor plate and the second conductor plate. A first distance from a nearby portion of the first conductor plate that is closest to the antenna to a first remote portion of the first conductor plate that is farthest from the antenna is set shorter than a second distance from the nearby portion to a second remote portion of the second conductor plate that is farthest from the antenna, and the circuit element electrically connects the first conductor plate and the second conductor plate at the first frequency and electrically disconnects the first conductor plate and the second conductor plate at the second frequency.

[0010] According to the antenna device, at the first frequency, the circuit element electrically connects the first conductive plate and the second conductive plate, so that the antenna, the first conductive plate, and the second conductive plate can be operated as radiators, and the radiation efficiency of the antenna device at the first frequency can be improved. Also, at the second frequency higher than the first frequency, it is considered that a strong current distribution occurs in the antenna and the first conductive plate connected to the antenna by the feeding point. Therefore, at the second frequency, the circuit element electrically disconnects the first conductive plate and the second conductive plate, so that the first conductive plate can be operated as a radiator and the effect of the second conductive plate on the radiation efficiency can be reduced. Therefore, according to the antenna device, the radiation efficiency of the antenna can be further improved.

[0011] The antenna device will be further described below with reference to the drawings. FIG. 1 is a diagram showing an example of an antenna device 1 according to an embodiment. FIG. 1(A) is a diagram showing the antenna device 1 as viewed from the front. FIG. 1(B) is a diagram showing the antenna device 1 as viewed from the side in the direction of the arrow in FIG. 1(A). The antenna device 1 includes a first ground substrate 11, a feeding point 12, a second ground substrate 13, an antenna 15, a contact P2, a contact P3, a contact P4, and a contact P5. The X direction in FIG. 1 is the width direction, the Y direction is the height direction, and the Z direction is the thickness direction. The view from the Z direction is also referred to as a plan view.

[0012] The first ground substrate 11 is a grounded substrate. The first ground substrate 11 is, for example, a printed circuit board on which various electronic components are mounted. The first ground substrate 11 is provided with, for example, a plate-shaped conductor, and is used, for example, as a ground for the antenna 15. Various electronic components may be mounted on the first ground substrate 11. The first ground substrate 11 is formed, for example, in a rectangular plate shape in a plan view. For example, a power feeding point 12 that feeds power to the antenna 15 is provided at one end of the first ground substrate 11 in the width direction. The first ground substrate 11 is an example of a "first conductor plate."

[0013] The antenna 15 is a monopole antenna having one end connected to the power feed point 12 and the other end open. For example, the antenna 15 receives power from the power feed point 12 and emits radio waves in the microwave band. For example, the antenna 15 resonates at two frequencies in the microwave band (a first frequency f1 and a second frequency f2 higher than the first frequency f1). The length of the antenna 15 is a quarter wavelength, and is, for example, approximately equal to the width of the first ground substrate 11. The antenna 15 is disposed along an end surface 111 on the short side of the first ground substrate 11 formed in a plate shape. The longitudinal direction of the antenna 15 coincides with, for example, the width direction of the antenna device 1. In other words, the antenna 15 is parallel to the end surface 111 on the short side of the first ground substrate 11 formed in a rectangular plate shape. Moreover, the end surface 111 forms a straight line parallel to the antenna 15 in a plan view.

[0014] The second ground substrate 13 is a grounded substrate. The second ground substrate 13 is, for example, a plate-shaped conductor. The second ground substrate 13 is used, for example, as a ground for the antenna 15. The second ground substrate 13 is formed in a rectangular plate shape in a plan view. The length of the short side of the second ground substrate 13 is approximately equal to the length of the short side of the first ground substrate 11. The length of the long side of the second ground substrate 13 is longer than the length of the long side of the first ground substrate 11. One of the two short sides of the second ground substrate 13 overlaps with the short side of the first ground substrate 11 on the antenna 15 side in a plan view. Therefore, one of the two short sides of the second ground substrate 13 is parallel to the antenna 15. The second ground substrate 13 is an example of a "second conductor plate."

[0015] The third ground substrate 14 is a grounded substrate. The third ground substrate 14 is, for example, a plate-shaped conductor. The conductivity of the third ground substrate 14 is preferably lower than the conductivity of the second ground substrate 13. The second ground substrate 13 is formed in a rectangular plate shape in a plan view. The length of the short side of the third ground substrate 14 is approximately equal to the length of the short side of the first ground substrate 11. Moreover, the length of the long side of the third ground substrate 14 is approximately equal to the length of the long side of the second ground substrate 13. In other words, the size of the third ground substrate 14 is approximately the same as that of the second ground substrate 13. The third ground substrate 14 is an example of a "third conductor plate."

[0016] The third ground substrate 14 is disposed so as to be in contact with the second ground substrate 13 over its entire surface so as to overlap with the second ground substrate 13 in a plan view. In the thickness direction, the second ground substrate 13 is provided on the third ground substrate 14, and the feeding point 12 is provided on the second ground substrate 13. In other words, the second ground substrate 13 is provided between the first ground substrate 11 and the third ground substrate 14. When the antenna device 1 is implemented in a wireless terminal such as a smartphone, the third ground substrate 14 may be, for example, an organic electroluminescence (organic EL) display.

[0017] In the antenna device 1, by arranging the first ground substrate 11 and the second ground substrate 13 in this manner, it can be seen that the length (D2 in FIG. 1) of the second ground substrate 13 from the end face 111 to the farthest point is longer than the length (D1 in FIG. 1) of the first ground substrate 11 from the end face 111 to the farthest point. Preferably, the length of D1 is λ1 / 2 (λ1 is the effective wavelength of the radio wave of the first frequency f1) and the length of D2 is λ2 / 2 (λ2 is the effective wavelength of the radio wave of the second frequency f2). Here, the effective wavelength is a wavelength that is shorter than the wavelength in free space due to the surrounding dielectric constant.

[0018] The first ground substrate 11 and the second ground substrate 13 are separated from each other in the thickness direction. That is, a gap is formed between the first ground substrate 11 and the second ground substrate 13. A contact P2, a contact P3, a contact P4, and a contact P5 are provided in the gap. The contact P2, the contact P3, the contact P4, and the contact P5 are provided, for example, near the four corners of the first ground substrate 11. The contacts P2, the contact P3, the contact P4, and the contact P5 are not limited to being provided near the four corners of the first ground substrate 11, and may be provided at other locations on the first ground substrate 11. The number of contacts is not limited to four, and may be more than four. The contacts P2, the contact P3, the contact P4, and the contact P5 may be provided on the edge of the first ground substrate 11 (near each side forming a rectangle of the first ground substrate 11). Of the contacts P2, the contact P3, the contact P4, and the contact P5, the contact P2 is provided at a position closest to the power supply point 12. Contact P2 is preferably provided within a range of λ1 / 8 from feed point 12. Contacts P3, P4, and P5 are preferably provided at positions that are λ1 / 8 or more away from feed point 12. Contacts P2, P3, P4, and P5 electrically connect first ground substrate 11 and second ground substrate 13 via spring contacts, for example.

[0019] Contact P2 is a contact that has a low impedance at the first frequency f1 and a high impedance at the second frequency f2. That is, when feeding point 12 operates at first frequency f1, contact P2 has a low impedance, and first ground substrate 11 and second ground substrate 13 are electrically connected by contact P2 as well. When feeding point 12 operates at second frequency f2, contact P2 has a high impedance, and the electrical connection between first ground substrate 11 and second ground substrate 13 by contact P2 is cut off. Contact P2 may be realized by, for example, a parallel resonant circuit including a capacitor and an inductor, or a switch.

[0020] <Simulation> A simulation was performed to verify the performance of the antenna device 1, which will now be described. In this simulation, the length of D1 was set to 45.0 mm, and the length of D2 was set to 137.0 mm. The length of the antenna 15 and the widths of the first ground substrate 11, the second ground substrate 13, and the third ground substrate 14 were set to 66.0 mm. The gap between the antenna 15 and the end surface 111 of the first ground substrate 11 was set to 1 mm. In addition, the distance between the antenna 15 and the end surface 111 was set to 1.0 mm. Furthermore, the conductivity of the antenna 15 was set to 1×10 6 (S / m), and the conductivity of the first ground substrate 11 is 1×10 6 (S / m), and the conductivity of the second ground substrate 13 is 1×10 6 (S / m), and the conductivity of the third ground substrate 14 is 5.8×10 4 (S / m).

[0021] 2 is a diagram illustrating a configuration used in the simulation. In this simulation, a conductive model (FIG. 2(A)) in which the first ground substrate 11 and the second ground substrate 13 are electrically conductive, and a non-conductive model (FIG. 2(B)) in which the first ground substrate 11 and the second ground substrate 13 are electrically non-conductive were verified.

[0022] <First Simulation> In the first simulation, the radiation efficiency of the antenna device 1 was verified for each of the conductive model and the non-conductive model. Figs. 3 to 5 are diagrams showing the results of the first simulation. Fig. 3 is a diagram illustrating the radiation efficiency of the antenna device 1 verified by simulation. The vertical axis of Fig. 3 indicates the radiation efficiency (dB), and the horizontal axis indicates the frequency (GHz). The dotted line in Fig. 3 indicates the simulation result of the non-conductive model, and the solid line in Fig. 3 indicates the simulation result of the conductive model. Fig. 4 is a Smith chart showing the simulation result of the non-conductive model. Fig. 5 is a Smith chart showing the simulation result of the conductive model.

[0023] 3 to 5, in the low-frequency region (e.g., a frequency of 0.7 GHz), the conductive model has a higher radiation efficiency. In the high-frequency region (e.g., a frequency of 2.6 GHz or higher), the non-conductive model has a higher radiation efficiency. From the results of this simulation, it can be seen that in the low-frequency region, the radiation efficiency of the antenna device 1 is higher when the first ground substrate 11 and the second ground substrate 13 are electrically conductive, and in the high-frequency region, the radiation efficiency of the antenna device 1 is higher when the first ground substrate 11 and the second ground substrate 13 are electrically non-conductive.

[0024] <Second Simulation> Next, a second simulation was performed to verify the current distribution for each of the conductive model and the non-conductive model. Figures 6 and 7 are diagrams illustrating the results of the second simulation. Figure 6 illustrates the current distribution when the frequency is low (when the frequency is 0.75 GHz), and Figure 7 illustrates the current distribution when the frequency is high (when the frequency is 4.0 GHz). Figures 6(A) and 7(B) illustrate the current distribution in the conductive model, and Figures 6(B) and 7(B) illustrate the current distribution in the non-conductive model. Note that Figures 6 and 7 illustrate that a stronger current is distributed in the darker areas (areas where dots are dense) than in the lighter areas (areas where dots are sparse).

[0025] First, let us consider the case of low frequency with reference to Fig. 6. When the frequency is low, the conductive model has a stronger current distribution over a wider area. Since the stronger current distribution also occurs in the first ground substrate 11 and the second ground substrate 13, it is considered that the first ground substrate 11 and the second ground substrate 13 act as radiators when the frequency is low. Therefore, it is considered that the conductive model has a higher radiation efficiency of the antenna device 1 when the frequency is low.

[0026] Next, with reference to Fig. 7, the case of high frequency will be considered. At high frequency, strong current distribution occurs in a wider area in the non-conductive model. Since the strong current distribution occurs in the first ground substrate 11, it is considered that the first ground substrate 11 operates as a radiator at high frequency. Furthermore, since strong current distribution occurs near the antenna 15 at high frequency, it is considered preferable to suppress the influence of the third ground substrate 14 on the current distribution. Therefore, it is considered that the radiation efficiency of the antenna device 1 is higher in the non-conductive model at high frequency.

[0027] <Third Simulation> Next, a third simulation will be described to verify the characteristics of antenna 15 when the connection state between first ground substrate 11 and second ground substrate 13 is switched by contacts. In the third simulation, the radiation efficiency of antenna 15 was simulated by switching between connection and disconnection at each of contacts P2, P3, P4, and P5 illustrated in FIG.

[0028] FIG. 8 is a diagram illustrating the results of the third simulation. The vertical axis of FIG. 8 indicates radiation efficiency (dB), and the horizontal axis indicates frequency (GHz). In FIG. 8, the thin solid line indicates the radiation efficiency when the contacts P2, P3, P4, and P5 are cut (in the legend in the figure, it is written as "p2O_p3O_p4O_p5O"). The dotted line indicates the radiation efficiency when the contact P3 is connected and the contacts P2, P4, and P5 are cut (in the legend in the figure, it is written as "p2O_p3S_p4O_p5O"). The dashed and dotted line indicates the radiation efficiency when the contact P2 is connected and the contacts P3, P4, and P5 are cut (in the legend in the figure, it is written as "p2S_p3O_p4O_p5O"). The two-dot chain line indicates the radiation efficiency when contacts P2 and P3 are connected and contacts P4 and P5 are disconnected (in the figure legend, this is indicated as "p2S_p3S_p4O_p5O"). The thick solid line indicates the radiation efficiency when contacts P2, P3, P4, and P5 are connected (in the figure legend, this is indicated as "p2S_p3S_p4S_p5S").

[0029] 8, it can be seen that the radiation efficiency indicated by the thin solid line is high in the low frequency range. Also, it can be seen that the radiation efficiency indicated by the thick solid line is high in the high frequency range. Since there is no significant difference between the radiation efficiency indicated by the two-dot chain line and the radiation efficiency indicated by the thick solid line, it can be seen that the effect on the radiation efficiency due to the connection and disconnection of the contacts P4 and P5 is small. On the other hand, since the radiation efficiency indicated by the one-dot chain line is lower than the radiation efficiency indicated by the two-dot chain line, it can be seen that it is preferable to connect the contact P3.

[0030] It can be seen that the radiation efficiency indicated by the dotted line is low in the low frequency range, but high in the high frequency range. In other words, it can be seen that the radiation efficiency of the antenna device 1 can be increased by connecting the contact P2 in the low frequency range and disconnecting the contact P2 in the high frequency range.

[0031] <Fourth Simulation> Next, a fourth simulation will be described to verify the radiation efficiency of the antenna device 1 when an inductor is provided as the contact P2 while the contacts P3, P4, and P5 are connected. FIG. 9 is a diagram illustrating the results of the fourth simulation. In FIG. 9, the vertical axis indicates the radiation efficiency (dB), and the horizontal axis indicates the frequency (GHz). In FIG. 9, the dashed line indicates the radiation efficiency when an inductor with an inductance of 1nH is provided as the contact P2 (in the legend in the figure, it is written as "p2-1n_p3S_p4O_p5O"). The dotted line indicates the radiation efficiency when an inductor with an inductance of 2nH is provided as the contact P2 (in the legend in the figure, it is written as "p2-2n_p3S_p4O_p5O"). The thick solid line indicates the radiation efficiency when an inductor with an inductance of 10nH is provided as the contact P2 (in the legend in the figure, it is written as "p2-10n_p3S_p4O_p5O"). The two-dot chain line indicates the radiation efficiency when contact P2 is disconnected (in the figure's legend, this is written as "p2O_p3S_p4O_p5O"). The thin solid line indicates the radiation efficiency when contact P2 is connected (in the figure's legend, this is written as "p2S_p3S_p4O_p5O"). In the case of the two-dot chain line and the thin solid line, no inductor is provided as contact P2. Note that in each of the radiation efficiencies illustrated in FIG. 9, contact P3 is connected, and contacts P4 and P5 are disconnected.

[0032] 9, it can be seen that the radiation efficiency indicated by the dashed dotted line and the radiation efficiency indicated by the thin solid line are equally good in the low frequency range of the antenna device 1. It can be seen that the radiation efficiency indicated by the thick solid line is low in the low frequency range, while the radiation efficiency of the antenna device 1 is high in the high frequency range. In other words, by providing an inductor with an inductance of 1 nH or less as the contact point P2, it is possible to increase the radiation efficiency of the antenna device 1 in the low frequency range.

[0033] <5th Simulation> Next, a fifth simulation will be described to verify the radiation efficiency of the antenna device 1 in a case where a trap circuit or a switch is provided as the contact P2 while the contacts P3, P4, and P5 are connected. FIG. 10 is a diagram illustrating a circuit used as the contact P2. FIGS. 10(A) and 10(B) are diagrams illustrating the antenna device 1 viewed from the side (from the direction of the arrow in FIG. 1(A)) near the contact P2. FIG. 10(A) is a diagram illustrating an example of a trap circuit 16 used as the contact P2. The trap circuit 16 is a circuit in which an inductor 161 and a capacitor 162 are connected in parallel, and is also called a parallel resonant circuit. The trap circuit 16 is provided to connect the first ground substrate 11 and the second ground substrate 13.

[0034] 10B is a diagram showing an example of the switch circuit 17 employed as the contact P2. The switch circuit 17 is, for example, a high-frequency switch that is switched between open and closed according to the frequency. Examples of the switch circuit 17 include a diode switch, a field effect transistor (FET) switch, and a micro electro mechanical systems (MEMS) switch. The switch circuit 17 is in a closed state (switched on) in a low-frequency region (for example, a frequency of 0.7 GHz) and electrically connects the first ground substrate 11 and the second ground substrate 13. The switch circuit 17 is in an open state (switched off) in a high-frequency region (for example, a frequency of 2.6 GHz or higher) and electrically disconnects the first ground substrate 11 and the second ground substrate 13.

[0035] FIG. 11 is a diagram illustrating the results of the fifth simulation. In FIG. 11, the vertical axis indicates radiation efficiency (dB), and the horizontal axis indicates frequency (GHz). In FIG. 11, the thick solid line illustrates the radiation efficiency when the trap circuit 16, in which the inductor 161 has an inductance of 1 nH and the capacitor 162 has a capacitance of 2 pF, is provided as the contact P2 (in the legend in the figure, it is written as "p2-1n-2p_p3S_p4O_p5O"). The thin solid line illustrates the radiation efficiency in a state in which the contact P2 is disconnected (in the legend in the figure, it is written as "p2O_p3S_p4O_p5O"). The two-dot chain line illustrates the radiation efficiency in a state in which the contact P2 is connected (in the legend in the figure, it is written as "p2S_p3S_p4O_p5O"). In each of the radiation efficiencies illustrated in FIG. 11, the contact P3 is connected, and the contacts P4 and P5 are disconnected.

[0036] As described with reference to Fig. 8 and Fig. 9, the contact P2 is connected in the low frequency region and disconnected in the high frequency region, thereby increasing the radiation efficiency of the antenna device 1. With reference to Fig. 11, it can be seen that the radiation efficiency indicated by the thick solid line is as high as the state in which the contact P2 is connected (thin solid line) in the low frequency region, and is as high as the state in which the contact P2 is disconnected (two-dot chain line) in the high frequency region. That is, the radiation efficiency of the antenna device 1 can be increased by providing the trap circuit 16 at the position of the contact P2. It is also preferable that the inductor 161 included in the trap circuit 16 has an inductance of 1 nH and the capacitance of the capacitor 162 has a capacitance of 2 pF.

[0037] <Sixth Simulation> From the above simulations, it can be said that in a state where the contact P3 is connected, connecting the contact P2 in a low frequency region and disconnecting the contact P2 in a high frequency region is preferable for realizing high radiation efficiency of the antenna device 1. Here, a sixth simulation in which the position of the contact P3 is considered will be described.

[0038] FIG. 12 is a diagram for explaining the configuration of the antenna device 1 in the sixth simulation. In the sixth simulation, a simulation was performed on the radiation efficiency of the antenna device 1 when the distance D3 from the end face 111 to the contact P3 was changed with the contacts P2, P4, and P5 cut off. FIG. 13 is a diagram for explaining the configuration of an antenna device 500 according to a comparative example prepared in the sixth simulation. In the antenna device 500 according to the comparative example, the distance D4 from the end face 111 to the contact P2 was set to λ2 / 8, and the distance D5 from the end face 111 to the contact P3 was set to 3λ2 / 8. Note that the contacts P4 and P5 are omitted in the antenna device 500.

[0039] Fig. 14 is a diagram illustrating the results of the sixth simulation. In Fig. 14, the vertical axis indicates radiation efficiency (dB), and indicates the distance (mm) from antenna 15 to contact point P3. In Fig. 14, the solid line indicates the radiation efficiency of antenna device 1, and the dotted line indicates the radiation efficiency of antenna device 500. With reference to Fig. 14, it can be seen that the radiation efficiency of antenna device 1 can be made higher than that of antenna device 500 by setting distance D3 from end face 111 to contact point P3 to a range of 10 mm or more (a range of λ2 / 8 or more).

[0040] From the results of the first to fifth simulations, it can be seen that in both low-frequency ranges (for example, a frequency range around 0.7 GHz) and high-frequency ranges (for example, a frequency range around 2.6 GHz), the radiation efficiency of the antenna device 1 can be increased by connecting the contact P3. Also, by connecting the contact P2 in the low-frequency range and disconnecting the contact P2 in the high-frequency range, the radiation efficiency of the antenna device 1 can be increased from the low-frequency range to the high-frequency range.

[0041] Furthermore, the results of the sixth simulation show that the radiation efficiency of the antenna device 1 can be improved by determining the position of the junction P3 so that the distance D3 from the end face 111 to the junction P3 is in the range of 10 mm or more (in the range of λ2 / 8 or more).

[0042] <Implementation example> A case where the above-described antenna device 1 is mounted on a smartphone will be described. Fig. 15 is a diagram showing the appearance of a smartphone 200 according to an implementation example. The smartphone 200 is a portable wireless terminal. A speaker 211, a microphone 212, and a display 213 are provided on the front side of a housing 210 of the smartphone 200. The display 213 is, for example, an organic electroluminescence (organic EL) display panel. The display 213 is an example of a "display panel".

[0043] FIG. 16 is a diagram showing an example of the internal configuration of the smartphone 200 according to the implementation example. FIG. 16 illustrates a state in which the housing 210 of the smartphone 200 is removed. FIG. 16(A) is a diagram showing the smartphone 200 from the front with the housing 210 removed. FIG. 16(B) is a diagram showing the smartphone 200 from the side with the housing 210 removed from the direction of the arrow in FIG. 16(A). In the smartphone 200, for example, electronic components that execute various controls of the smartphone 200 are mounted on the first ground substrate 11. In addition, the second ground substrate 13 is provided on the back surface of the display 213. That is, the internal configuration of the smartphone 200 can be said to be a configuration in which the third ground substrate 14 of the antenna device 1 is replaced with the display 213. Note that the inside of the display of the smartphone includes electrodes for a touch sensor, but the equivalent conductivity of the display 213 is approximately the same as that of the third ground substrate 14.

[0044] By mounting the antenna device 1 on the smartphone 200, high radiation efficiency can be achieved from low to high frequency ranges, and the communication performance of the smartphone 200 can be improved.

[0045] <Modification> In the above-described embodiment, the first ground substrate 11 is formed into a rectangle, but the shape of the first ground substrate 11 is not limited to a rectangle. FIG. 17 is a first diagram illustrating variations in the shape of the first ground substrate 11. FIG. 17 illustrates a first ground substrate 11a formed into a triangle. The first ground substrate 11a is disposed such that a side 112, which is one side of the triangle, is parallel to the antenna 15. For reference, FIG. 17 also illustrates an example of the position of the contact point P2. Even when such a first ground substrate 11a is used, it is preferable that the length D1a from the side 112 to the vertex 113 opposite the side 112 is λ1 / 2 and the length D2 is λ2 / 2 in terms of improving the radiation efficiency of the antenna device 1.

[0046] FIG. 18 is a second diagram illustrating variations in the shape of the first ground substrate 11. FIG. 18 illustrates a first ground substrate 11b formed in a shape obtained by combining two rectangles. The first ground substrate 11b is disposed with one side 114 parallel to the antenna 15. For reference, FIG. 18 also illustrates an example of the position of the contact point P2. Even when such a first ground substrate 11b is used, it is preferable in terms of improving the radiation efficiency of the antenna device 1 that the length D1b from the side 114 to the point on the first ground substrate 11b farthest from the first ground substrate 114 is λ1 / 2 and the length D2 is λ2 / 2.

[0047] In the above-described embodiment, the first ground substrate 11 and the second ground substrate 13 are arranged to overlap each other in a plan view. However, the first ground substrate 11 and the second ground substrate 13 do not have to overlap each other in a plan view. FIG. 19 is a diagram illustrating a configuration in which the first ground substrate 11 and the second ground substrate 13 do not overlap each other in a plan view. In addition, for reference, FIG. 19 also illustrates an example of the position of the contact point P2. Even when the first ground substrate 11 and the second ground substrate 13 are arranged in this manner, it is preferable in terms of improving the radiation efficiency of the antenna device 1 that the length D1 from the end surface 111 to the location of the first ground substrate 11 that is farthest from the end surface 111 is λ1 / 2 and the length D2 from the end surface 111 to the location of the second ground substrate 13 that is farthest from the end surface 111 is λ2 / 2.

[0048] In the embodiment described above, the feed point 12 is provided at the end of the antenna 15, but the feed point 12 may be provided at a location other than the end of the antenna 15. Fig. 20 is a diagram illustrating a configuration in which the feed point 12 is connected to the center of the antenna 15. As illustrated in Fig. 20, the feed point 12 may be connected to the center of the antenna 15.

[0049] In the above-described embodiment, the antenna included in the antenna device 1 is a monopole antenna. However, the antenna included in the antenna device 1 is not limited to a monopole antenna. The antenna included in the antenna device 1 may be an inverted-F antenna or a loop antenna.

[0050] The embodiments and modifications disclosed above can be combined with each other. [Explanation of symbols]

[0051] 1. Antenna device 11 First ground substrate 11a First ground substrate 11b First ground substrate 12. Power supply point 13 Second ground board 14 Third ground board 15 Antenna 16. Trap Circuit 161··Inductor 162 Capacitor 111...end face 112 sides 113 Vertex 200·Smartphone 210··Housing 211··Speaker 212 Microphone 213··Display 500 Antenna device P2 Contact P3 Contact P4 Contact P5 Contact

Claims

1. an antenna operating at a first frequency and a second frequency higher than the first frequency; a first conductor plate having a feeding point for feeding power to the antenna and formed in a plate shape; a second conductive plate formed in a plate shape; a connection portion that electrically connects the first conductive plate and the second conductive plate; a circuit element provided between the first conductor plate and the second conductor plate, a first distance from a nearby portion of the first conductor plate that is closest to the antenna to a first remote portion of the first conductor plate that is farthest from the antenna is set shorter than a second distance from the nearby portion to a second remote portion of the second conductor plate that is farthest from the antenna; The circuit element includes: the first conductor plate and the second conductor plate are electrically connected at the first frequency; At the second frequency, the first conductor plate and the second conductor plate are electrically separated. Antenna device.

2. the first distance is approximately ½ of an effective wavelength of the radio wave of the first frequency; The second distance is approximately ½ of an effective wavelength of radio waves of the second frequency.

2. The antenna device according to claim 1.

3. a third conductor plate is provided on a surface of the second conductor plate so as to overlap the third conductor plate; The conductivity of the third conductive plate is lower than the conductivity of the second conductive plate.

3. The antenna device according to claim 1 or 2.

4. an end portion of the first conductor plate on the antenna side forms a straight line parallel to the antenna in a plan view; The power supply point is provided at an end of the straight line. An antenna device according to any one of claims 1 to 3.

5. The connection portion is provided on an edge portion of the first conductor plate. An antenna device according to any one of claims 1 to 4.

6. The connection portion is provided at a distance from the power supply point within a range of 1 / 8 of an effective wavelength of the first frequency. An antenna device according to any one of claims 1 to 5.

7. The circuit element is a trap circuit including an inductor and a capacitor.

7. An antenna device according to claim 1.

8. The circuit element is a high frequency switch.

7. An antenna device according to claim 1.

9. The antenna is any one of a monopole antenna, an inverted F antenna, and a loop antenna. An antenna device according to any one of claims 1 to 8.

10. Equipped with an antenna device according to any one of claims 1 to 9, Wireless terminal.

11. The antenna device according to claim 3, the third conductive plate includes a display panel; Wireless terminal.

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