WO2022259308A1

WO2022259308A1 - Antenna device and wireless terminal

Info

Publication number: WO2022259308A1
Application number: PCT/JP2021/021560
Authority: WO
Inventors: 洋平古賀; 学吉川; 旅人殿岡; 実櫻井; 聡史 ▲崎▼田; 貴裕篠島
Original assignee: Ｆｃｎｔ株式会社
Priority date: 2021-06-07
Filing date: 2021-06-07
Publication date: 2022-12-15
Also published as: JPWO2022259308A1

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

Antenna device and wireless terminal

The present invention relates to an antenna device and a wireless terminal.

In a wireless terminal exemplified by a smartphone, a conductor provided inside the terminal is used as an antenna ground (see Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 2017-085540 JP 2013-074361 A

In a wireless terminal such as a smartphone, a ground as large as possible is established by electrically connecting a first ground formed on a substrate having a feeding point and a second ground formed by a conductor on the rear surface of the display. was secured to the antenna. If such a configuration is adopted, the current flowing through the first ground and the second ground cannot be controlled, so there is a limit to improving the radiation efficiency of the antenna.

One aspect of the disclosed technique aims to provide an antenna device with higher radiation efficiency and a wireless terminal including the antenna device.

One aspect of the disclosed technique is exemplified by the following antenna device. The present antenna device includes an antenna operating at a first frequency and a second frequency higher than the first frequency, a feeding point for feeding power to the antenna, a first conductor plate formed in a plate shape, a second conductor plate formed in the second conductor plate, a connecting portion electrically connecting the first conductor plate and the second conductor plate, and the first conductor plate and the second conductor plate and a circuit element disposed therebetween. A first distance from a nearby portion of the first conductor plate closest to the antenna to a first spaced portion of the first conductor plate furthest from the antenna is a distance from the vicinity portion to the second distance. is set shorter than a second distance from the antenna to a second spaced portion of the conductor plate, and the circuit element is positioned between the first conductor plate and the second distance at the first frequency. The conductor plate is electrically connected, and the first conductor plate and the second conductor plate are electrically disconnected at the second frequency.

According to the disclosed technology, it is possible to provide an antenna device with higher radiation efficiency and a wireless terminal equipped with the antenna device.

FIG. 1 is a diagram showing an example of an antenna device 1 according to an embodiment. FIG. 2 is a diagram illustrating the configuration adopted in the simulation. FIG. 3 is a first diagram showing the results of the first simulation. FIG. 4 is a second diagram showing the results of the first simulation. FIG. 5 is a third diagram showing the results of the first simulation. FIG. 6 is a first diagram illustrating the results of the second simulation. FIG. 7 is a second diagram illustrating the results of the second simulation. FIG. 8 is a diagram illustrating the results of the third simulation. FIG. 9 is a diagram illustrating results of the fourth simulation. FIG. 10 is a diagram illustrating a circuit employed as contact P2. FIG. 11 is a diagram illustrating the results of the fifth simulation; FIG. 12 is a diagram explaining the configuration of the antenna device in the sixth simulation. FIG. 13 is a diagram illustrating the configuration of an antenna device according to a comparative example prepared in the sixth simulation; FIG. 14 is a diagram illustrating the result of the sixth simulation; FIG. 15 is a diagram illustrating an appearance of a smartphone according to an implementation example; FIG. 16 is a diagram illustrating an example of an internal configuration of a smartphone according to an implementation example; FIG. 17 is a first diagram illustrating variations in the shape of the first ground substrate. FIG. 18 is a second diagram illustrating variations in the shape of the first ground substrate. FIG. 19 is a diagram illustrating a configuration in which the first ground substrate and the second ground substrate do not overlap in plan view. FIG. 20 is a diagram illustrating a configuration in which a feeding point is connected to the center of an antenna.

<Embodiment>
The configuration of the embodiment shown below is an example, and the disclosed technology is not limited to the configuration of the embodiment. An antenna device according to an embodiment has, for example, the following configuration. An antenna device according to the present embodiment includes an antenna that operates at a first frequency and a second frequency that is higher than the first frequency, and a feeding point that feeds power to the antenna, and a first conductive plate formed in a plate shape. a second conductor plate formed in a plate shape; a connecting portion electrically connecting the first conductor plate and the second conductor plate; and a circuit element provided between the conductor plate. A first distance from a nearby portion of the first conductor plate closest to the antenna to a first spaced portion of the first conductor plate furthest from the antenna is a distance from the vicinity portion to the second distance. is set shorter than a second distance from the antenna to a second spaced portion of the conductor plate, and the circuit element is positioned between the first conductor plate and the second distance at the first frequency. The conductor plate is electrically connected, and the first conductor plate and the second conductor plate are electrically disconnected at the second frequency.

According to the antenna device, the circuit element electrically connects the first conductor plate and the second conductor plate at the first frequency, thereby connecting the antenna, the first conductor plate, and the second conductor plate. can operate as a radiator, and the radiation efficiency of the antenna device at the first frequency can be increased. Also, at a second frequency higher than the first frequency, it is considered that a strong current distribution occurs in the antenna and the first conductor plate connected to the antenna by the feeding point. Therefore, at the second frequency, the circuit element electrically disconnects the first conductor plate and the second conductor plate so that the first conductor plate operates as a radiator and the second conductor The effect of the plate on radiation efficiency can be reduced. Therefore, according to this antenna device, the radiation efficiency of the antenna can be further improved.

The above 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. 1A is a front view of the antenna device 1. FIG. FIG. 1(B) is a side view of the antenna device 1 from 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, contacts P2, contacts P3, contacts P4, and contacts 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. A direction view from the Z direction is also referred to as a planar view.

The first ground substrate 11 is a grounded substrate. The first ground board 11 is, for example, a printed 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 as, for example, the ground of the antenna 15 . Various electronic components may be mounted on the first ground substrate 11 . The first ground substrate 11 is formed in, for example, a rectangular plate shape in plan view. At one end of the first ground substrate 11 in the width direction, for example, a feeding point 12 that feeds an antenna 15 is provided. The first ground substrate 11 is an example of a "first conductor plate".

Antenna 15 is a monopole antenna having one end connected to feeding point 12 and the other end being an open end. The antenna 15 receives power from, for example, the feeding point 12 and emits radio waves in the microwave band. The antenna 15 resonates, for example, at two frequencies in the microwave band (a first frequency f ₁ and a second frequency f ₂ higher than the first frequency f ₁ ). The length of the antenna 15 is a quarter wavelength, and is approximately equal to the width of the first ground substrate 11, for example. The antenna 15 is arranged along the 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 the width direction of the antenna device 1, for example. 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. Further, the end face 111 forms a straight line parallel to the antenna 15 in plan view.

The second ground board 13 is a grounded board. The second ground substrate 13 is, for example, a plate-shaped conductor. The second ground board 13 is used as a ground for the antenna 15, for example. The second ground substrate 13 is formed in a rectangular plate shape in plan view. The length of the short side of the second ground board 13 is substantially equal to the length of the short side of the first ground board 11 . Also, 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 board 13 overlaps the short side of the first ground board 11 on the antenna 15 side in plan view. Therefore, one of the two short sides of second ground substrate 13 is parallel to antenna 15 . The second ground board 13 is an example of a "second conductor plate".

The third ground board 14 is a grounded board. 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 plan view. The length of the short side of the third ground board 14 is substantially equal to the length of the short side of the first ground board 11 . Also, the length of the long side of the third ground board 14 is substantially equal to the length of the long side of the second ground board 13 . That is, the size of the third ground board 14 is substantially the same as that of the second ground board 13 . The third ground board 14 is an example of a "third conductor plate".

The third ground substrate 14 is arranged 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 plan view. Then, 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 board 13 is provided between the first ground board 11 and the third ground board 14 . When the antenna device 1 is mounted on a wireless terminal exemplified by a smart phone, the third ground substrate 14 may be, for example, an organic electroluminescence (organic EL) display.

In the antenna device 1, by arranging the first ground substrate 11 and the second ground substrate 13 in this manner, the length of the first ground substrate 11 to the furthest point from the end surface 111 (D1 in FIG. 1) It can be understood that the length (D2 in FIG. 1) from the end surface 111 of the second ground substrate 13 to the furthest point is longer than the length. Preferably, the length of D1 is λ ₁ /2 (λ ₁ is the effective wavelength of radio waves of the first frequency f ₁ ), and the length of D2 is λ ₂ /2 (λ ₂ is the second frequency f ₂ effective wavelength of radio waves). Here, the effective wavelength is the wavelength shorter than the free space wavelength due to the surrounding dielectric constant.

The first ground substrate 11 and the second ground substrate 13 are separated 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 contacts P2, P3, P4, and P5 are provided near four corners of the first ground substrate 11, for example. The contacts P2, P3, P4, and 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 contact P2, the contact P3, the contact P4, and the contact P5 may be provided at the edge of the first ground substrate 11 (near each side forming the rectangle of the first ground substrate 11). Of the contact P2, the contact P3, the contact P4, and the contact P5, the contact P2 is provided at a position closest to the feeding point 12. FIG. Contact point P2 is preferably provided within a range of λ ₁ /8 from feed point 12 . Moreover, the contact P3, the contact P4, and the contact P5 are preferably provided at positions separated from the feeding point 12 by λ ₁ /8 or more. Contact points P2, P3, contact point P4, and contact point P5 electrically connect, for example, the first ground substrate 11 and the second ground substrate 13 via spring contacts.

The contact P2 has a low impedance at the _first frequency f1 and a high impedance at the _second frequency f2. That is, when the feeding point 12 operates at the first frequency f1, the contact P2 has a low impedance, so that the first ground substrate 11 and the second ground substrate 13 are also electrically connected by the contact P2. When the feeding point 12 operates at the second frequency f2, the electrical connection between the first ground substrate 11 and the second ground substrate 13 through the contact P2 is cut off because the contact P2 becomes high impedance. The contact P2 may be implemented by, for example, a parallel resonant circuit including a capacitor and an inductor, or a switch.

<Simulation>
A simulation was performed to verify the performance of the antenna device 1 and will 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 distance between the antenna 15 and the end surface 111 of the first ground substrate 11 was set to 1 mm. Also, the distance between the antenna 15 and the end face 111 was set to 1.0 mm. Furthermore, the conductivity of the antenna 15 is 1×10 ⁶ (S/m), 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 was set to 5.8×10 ⁴ (S/m).

FIG. 2 is a diagram illustrating the configuration adopted in the simulation. In this simulation, a conduction model (FIG. 2A) in which the first ground substrate 11 and the second ground substrate 13 are electrically connected, and a conduction model in which the first ground substrate 11 and the second ground substrate 13 are electrically connected A non-conducting model (FIG. 2(B)) that is non-conducting at the same time was verified.

<First simulation>
In the first simulation, the radiation efficiency of the antenna device 1 was verified for each of the conducting model and the non-conducting model. 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 in FIG. 3 indicates radiation efficiency (dB), and the horizontal axis indicates frequency (GHz). The dotted line in FIG. 3 indicates the simulation result of the non-conducting model, and the solid line in FIG. 3 indicates the simulation result of the conducting model. FIG. 4 is a Smith chart showing simulation results of a non-conducting model. FIG. 5 is a Smith chart showing simulation results of the conduction model.

As can be understood by referring to FIGS. 3 to 5, the conduction model has higher radiation efficiency in the low frequency range (for example, frequency 0.7 GHz). Also, in a high frequency region (for example, frequencies of 2.6 GHz or higher), the non-conducting model has higher radiation efficiency. According to the results of this simulation, the radiation efficiency of the antenna device 1 is higher when the first ground substrate 11 and the second ground substrate 13 are electrically connected in the low frequency region, and the radiation efficiency of the antenna device 1 is higher in the high frequency region. It can be understood that the radiation efficiency of the antenna device 1 is higher when the ground substrate 11 and the second ground substrate 13 are electrically non-conductive.

<Second simulation>
Next, a second simulation was performed to verify the current distribution for each of the conducting model and the non-conducting model. 6 and 7 are diagrams illustrating the results of the second simulation. FIG. 6 illustrates the current distribution when the frequency is low (when the frequency is 0.75 GHz), and FIG. 7 illustrates the current distribution when the frequency is high (when the frequency is 4.0 GHz). Also, FIGS. 6A and 7B illustrate the current distribution in the conduction model, and FIGS. 6B and 7B illustrate the current distribution in the non-conduction model. Note that in FIGS. 6 and 7, a stronger current is distributed in a dark-colored region (region with dense dots) than in a light-colored region (region with sparse dots). Here is an example.

First, the case where the frequency is low will be considered with reference to FIG. At low frequencies, the conduction model produces a strong current distribution over a wider area. Since a strong current distribution also occurs in the first ground substrate 11 and the second ground substrate 13, it is assumed that the first ground substrate 11 and the second ground substrate 13 operate as radiators when the frequency is low. Conceivable. Therefore, when the frequency is low, the radiation efficiency of the antenna device 1 is considered to be higher in the conduction model.

Next, with reference to FIG. 7, the case where the frequency is high will be considered. At high frequencies, the non-conducting model produces a strong current distribution over a wider area. Since a strong current distribution occurs in the first ground substrate 11, it is considered that the first ground substrate 11 operates as a radiator when the frequency is high. Also, when the frequency is high, a strong current distribution occurs near the antenna 15, so it is considered preferable to suppress the influence of the third ground substrate 14 on the current distribution. Therefore, when the frequency is high, the radiation efficiency of the antenna device 1 is considered to be higher in the non-conducting model.

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

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

With reference to FIG. 8, it can be understood that the radiation efficiency indicated by the thin solid line is high in the low frequency region. Also, it can be understood that the radiation efficiency indicated by the thick solid line increases in the high frequency region. 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 understood that connection and disconnection of the contacts P4 and P5 have little effect on the radiation efficiency. 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 understood that it is preferable to connect the contact point P3.

It can be understood that the radiation efficiency indicated by the dotted line has low radiation efficiency in the low frequency range, and high radiation efficiency in the high frequency range. That is, it can be understood that the radiation efficiency of the antenna device 1 can be improved by connecting the contact P2 in the low frequency region and disconnecting the contact P2 in the high frequency region.

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

With reference to FIG. 9, it can be understood 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 region of the antenna device 1 . As for the radiation efficiency indicated by the thick solid line, it can be understood that the radiation efficiency of the antenna device 1 is low in the low frequency range, while the radiation efficiency of the antenna device 1 is high in the high frequency range. That is, by providing an inductor having an inductance of 1 nH or less as the contact point P2, the radiation efficiency of the antenna device 1 can be increased in a low frequency region.

<Fifth simulation>
Next, a fifth simulation for verifying the radiation efficiency of the antenna device 1 when a trap circuit or a switch is provided as the contact P2 with the contacts P3, P4, and P5 connected will be described. FIG. 10 is a diagram illustrating a circuit employed as contact P2. 10(A) and 10(B) are views of the antenna device 1 viewed from the side (from the direction of the arrow in FIG. 1(A)) near the contact point P2. FIG. 10A is a diagram showing an example of the trap circuit 16 employed 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 .

FIG. 10(B) 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 opening and closing according to the frequency. Examples of the switch circuit 17 include a diode switch, a field effect transistor (FET) switch, or a Micro Electro Mechanical Systems (MEMS) switch. The switch circuit 17 is in a closed state (switch-on) in a low frequency range (for example, a frequency of 0.7 GHz), and electrically connects the first ground substrate 11 and the second ground substrate 13 . Also, the switch circuit 17 is in an open state (switch is off) in a high frequency range (for example, a frequency of 2.6 GHz or higher), and the first ground substrate 11 and the second ground substrate 13 are electrically disconnected.

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 with the inductance of the inductor 161 of 1 nH and the capacitance of the capacitor 162 of 2 pF is provided as the contact P2 (in the legend in the figure, "p2 -1n-2p_p3S_p4O_p5O”). A thin solid line indicates the radiation efficiency when the contact P2 is disconnected (denoted as "p2O_p3S_p4O_p5O" in the legend in the drawing). A two-dot chain line indicates the radiation efficiency with the contact P2 connected (denoted as "p2S_p3S_p4O_p5O" in the legend in the drawing). Note that in each of the radiation efficiencies illustrated in FIG. 11, contact P3 is connected and contact P4 and contact P5 are disconnected.

As described with reference to FIGS. 8 and 9, the contact P2 is connected in the low frequency region and disconnected in the high frequency region, so that the radiation efficiency of the antenna device 1 can be increased. . Referring to FIG. 11, the radiation efficiency indicated by the thick solid line shows a high radiation efficiency in the low frequency region as in the state where the contact P2 is connected (thin solid line), and in the high frequency region when the contact P2 is disconnected. It can be understood that high radiation efficiency is exhibited similarly to the state (two-dot chain line). That is, the radiation efficiency of the antenna device 1 can be improved by providing the trap circuit 16 at the position of the contact point P2. Moreover, it is preferable to set the inductance of the inductor 161 included in the trap circuit 16 to 1 nH and the capacitance of the capacitor 162 to 2 pF.

<Sixth simulation>
According to the above simulation, it is preferable to connect the contact P2 in the low frequency region and disconnect the contact P2 in the high frequency region while the contact P3 is connected, in order to realize high radiation efficiency of the antenna device 1. be able to. A sixth simulation for examining the position of the contact point P3 will now be described.

FIG. 12 is a diagram illustrating the configuration of the antenna device 1 in the sixth simulation. In the sixth simulation, the radiation efficiency of the antenna device 1 was simulated when the distance D3 from the end face 111 to the contact P3 was changed while the contacts P2, P4, and P5 were disconnected. FIG. 13 is a diagram illustrating 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 is set to λ ₂ /8, and the distance D5 from the end face 111 to the contact P3 is set to 3λ ₂ /8. Incidentally, in the antenna device 500, the contacts P4 and P5 are omitted.

FIG. 14 is a diagram illustrating the result of the sixth simulation; In FIG. 14, the vertical axis indicates the radiation efficiency (dB) and indicates the distance (mm) from the antenna 15 to the contact point P3. 14, the solid line indicates the radiation efficiency of the antenna device 1, and the dotted line indicates the radiation efficiency of the antenna device 500. In FIG. Referring to FIG. 14, the radiation efficiency of the antenna device 1 can be made higher than that of the antenna device 500 by setting the distance D3 from the end face 111 to the contact point P3 in a range of 10 mm or more (λ ₂ /8 or more). I understand what you can do.

According to the results of the first to fifth simulations, in both the low frequency region (for example, the frequency region near 0.7 GHz) and the high frequency region (for example, the frequency region near 2.6 GHz), the contact P3 is connected. However, it can be understood that the radiation efficiency of the antenna device 1 can be increased. Further, by connecting the contact P2 in a low frequency region and disconnecting the contact P2 in a high frequency region, the radiation efficiency of the antenna device 1 can be increased from a low frequency region to a high frequency region.

Further, according to the result of the sixth simulation, the position of the contact point P3 is determined so that the distance D3 from the end surface 111 to the contact point P3 is in the range of 10 mm or more (the range of λ ₂ /8 or more). can increase the radiation efficiency of

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

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 housing 210 of smartphone 200 is removed. FIG. 16A is a front view of the smartphone 200 with the housing 210 removed. FIG. 16B is a side view of smartphone 200 with housing 210 removed from the direction of the arrow in FIG. 16A. In the smartphone 200 , for example, electronic components that perform various controls of the smartphone 200 are mounted on the first ground substrate 11 . A second ground substrate 13 is provided on the back surface of the display 213 . That is, it can be said that the internal configuration of the smartphone 200 is obtained by replacing the third ground substrate 14 of the antenna device 1 with the display 213 . The display of the smart phone includes electrodes for touch sensors and the like, but the equivalent conductivity of the display 213 is approximately the same as that of the third ground substrate 14 .

By mounting the antenna device 1 on the smartphone 200, high radiation efficiency can be achieved from a low frequency range to a high frequency range, and the communication performance of the smart phone 200 can be improved.

<Modification>
In the embodiment described above, the first ground substrate 11 is formed in a rectangular shape, 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. FIG. 17 illustrates a triangular first ground substrate 11a. The first ground substrate 11 a is arranged with the side 112 , which is one side of the triangle, 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 employed, the length D1a from the side 112 to the vertex 113 facing the side 112 is λ ₁ /2, and the length D2 is λ ₂ / 2 is preferable for increasing the radiation efficiency of the antenna device 1 .

18A and 18B are second diagrams illustrating variations in the shape of the first ground substrate 11. FIG. FIG. 18 illustrates the first ground substrate 11b formed in a shape combining two rectangles. The first ground substrate 11 b is arranged with a side 114 , which is one side, 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 employed, the length D1b from the side 114 to the farthest point from the first ground substrate 114 on the first ground substrate 11b is λ ₁ /2, It is preferable that the length of D2 is λ ₂ /2 in order to improve the radiation efficiency of the antenna device 1 .

In the embodiment described above, the first ground substrate 11 and the second ground substrate 13 are arranged to overlap each other in plan view. However, the first ground substrate 11 and the second ground substrate 13 do not have to overlap in 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 in plan view. 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 way, the length D1 between the end surface 111 and the farthest point between the end surface 111 and the first ground substrate 11 is λ ₁ /2. In order to increase the radiation efficiency of the antenna device 1, it is preferable that the length D2 from the end face 111 to the farthest point of the second ground substrate 13 from the end face 111 is λ ₂ /2.

In the embodiment described above, the feeding point 12 was provided at the end of the antenna 15, but the feeding point 12 may be provided at a position other than the end of the antenna 15. FIG. 20 is a diagram illustrating a configuration in which the feeding point 12 is connected to the center of the antenna 15. As shown in FIG. The feed point 12 may be connected to the center of the antenna 15, as illustrated in FIG.

In the embodiment described above, the antenna provided in the antenna device 1 was a monopole antenna. However, the antenna provided in the antenna device 1 is not limited to the monopole antenna. The antenna provided in the antenna device 1 may be an inverted F antenna or a loop antenna.

The embodiments and modifications disclosed above can be combined.

Reference Signs List 1 Antenna device 11 First ground substrate 11a First ground substrate 11b First ground substrate 12 Feeding point 13 Second ground substrate 14 Third ground substrate 15 Antenna 16 Trap circuit 161 Inductor 162 Capacitor 111 End face 112 Side 113 Vertex 200 Smartphone 210 Case 211 Speaker 212 Microphone 213 Display 500 Antenna device P2...contact P3...contact P4...contact P5...contact

Claims

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 conductor plate formed in a plate shape;
a connection portion that electrically connects the first conductor plate and the second conductor 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 closest to the antenna to a first spaced portion of the first conductor plate furthest from the antenna is a distance from the vicinity portion to the second distance. is set shorter than a second distance to a second distance farthest from the antenna among the conductor plates of
The circuit element is
electrically connecting the first conductor plate and the second conductor plate at the first frequency;
At the second frequency, the first conductor plate and the second conductor plate are electrically separated;
antenna device.
the first distance is approximately 1/2 of the effective wavelength of the radio wave of the first frequency;
The second distance is approximately 1/2 of the effective wavelength of the radio wave of the second frequency,
The antenna device according to claim 1.
A third conductor plate is provided superimposed on the surface of the second conductor plate,
The conductivity of the third conductor plate is lower than the conductivity of the second conductor plate,
The antenna device according to claim 1 or 2.
the antenna-side end of the first conductor plate forms a straight line parallel to the antenna in plan view,
The feed point is provided at the end of the straight line,
The antenna device according to any one of claims 1 to 3.
The connecting portion is provided at the edge of the first conductor plate,
The antenna device according to any one of claims 1 to 4.
The connecting portion is provided within a range of 1/8 or less of the effective wavelength of the first frequency from the feeding point.
The antenna device according to any one of claims 1 to 5.
wherein the circuit element is a trap circuit including an inductor and a capacitor;
The antenna device according to any one of claims 1 to 6.
The circuit element is a high frequency switch,
The antenna device according to any one of claims 1 to 6.
wherein the antenna is one of a monopole antenna, an inverted F antenna and a loop antenna;
The antenna device according to any one of claims 1 to 8.
An antenna device according to any one of claims 1 to 9,
wireless terminal.
The antenna device according to claim 3,
wherein the third conductive plate comprises a display panel;
wireless terminal.