Antenna device and electronic apparatus

Abstract

Provided are an antenna device and an electronic apparatus making it possible to reduce the impact that a filter circuit makes on antenna characteristics, in a case where a radiating element and the filter circuit are not connected. An antenna device (100) of the present disclosure comprises: a radiating element (11) to which a power supply circuit (30) is connected; and an impedance adjustment circuit (10) connected to the radiating element (11). The impedance adjustment circuit (10) includes: a switching circuit for switching the path, among a plurality of paths that include a first path (10a) and a second path (10b), for connecting to the radiating element (11); a filter circuit (20) provided to the first path (10a); and an impedance adjustment element (40) provided to the second path (10b). The filter circuit (20) is a parallel resonance circuit including at least two magnetically coupled inductance elements.

Description

Antenna equipment and electronic equipment

[0001] This disclosure relates to antenna devices and electronic equipment technology.

[0002] An antenna device equipped with a filter circuit to broaden the usable frequency band is disclosed in International Publication No. 2023 / 120075 (Patent Document 1). The antenna device disclosed in Patent Document 1 has a filter circuit between the radiating element and the ground, and is provided with a switch to switch connections with multiple types of frequency adjustment elements to change the position of the frequency band to be broadened.

[0003] International Publication No. 2023 / 120075

[0004] When a filter circuit is used in an antenna device, depending on the connection configuration between the radiating element and the filter circuit, there was a risk that the filter circuit could affect the antenna characteristics even if the radiating element and the filter circuit were not connected.

[0005] This disclosure was made to solve these problems, and its purpose is to provide an antenna device and electronic equipment that can reduce the influence of a filter circuit on antenna characteristics when the radiating element and the filter circuit are not connected.

[0006] An antenna device according to this disclosure comprises a radiating element to which a feed circuit is connected, and an impedance adjustment circuit connected to the radiating element. The impedance adjustment circuit includes a switching circuit that switches the path connected to the radiating element from among a plurality of paths, including a first path and a second path, a filter circuit provided in the first path, and an impedance adjustment element provided in the second path. The filter circuit is a parallel resonant circuit including at least two magnetically coupled inductance elements.

[0007] The electronic device according to this disclosure comprises the above-described antenna device and a power supply circuit.

[0008] In the antenna device according to this disclosure, by using a filter circuit of a parallel resonant circuit that includes at least two inductance elements magnetically coupled to an impedance adjustment circuit, the influence of the filter circuit on the antenna characteristics when the radiating element and the filter circuit are not connected can be reduced.

[0009] This is a schematic diagram of an electronic device including an antenna device in Embodiment 1. This is a diagram for explaining the equivalent circuit of the filter circuit in Embodiment 1. This is a diagram for explaining the equivalent circuit of a filter circuit to be compared. This is a diagram for explaining the change in reactance of a filter circuit to be compared. This is a diagram for explaining the change in reactance of the filter circuit in Embodiment 1. This is a schematic diagram of an electronic device including an antenna device in Embodiment 2. This is a diagram for explaining the equivalent circuit of the filter circuit in Embodiment 2. This is a diagram for explaining the change in reactance of the filter circuit in Embodiment 2. This is a schematic diagram of an electronic device including an antenna device in Modification 1. This is a schematic diagram of an electronic device including an antenna device in Modification 2. This is a schematic diagram of an electronic device including an antenna device in Modification 3. This is a schematic diagram of an electronic device including an antenna device in Modification 4.

[0010] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0011] [Embodiment 1] Figure 1 is a schematic diagram of an electronic device 200 including an antenna device 100 in Embodiment 1. The antenna device 100 includes a radiating element 11 to which a power supply circuit 30 is connected, and an impedance adjustment circuit 10 is provided between the radiating element 11 and the power supply circuit 30. The power supply circuit 30 supplies power to the radiating element 11 and radiates a high-frequency signal from the radiating element 11. The antenna device 100 broadens the usable frequency band by adjusting the impedance with the impedance adjustment circuit 10.

[0012] The antenna device 100 branches off from the radiating element 11 midway, and the branched portion 11a is grounded to GND (ground electrode). Therefore, the antenna device 100 is an inverted F antenna. However, the antenna device 100 is not limited to an inverted F antenna; any fed antenna, such as a monopole antenna or a loop antenna, may also be used.

[0013] The impedance adjustment circuit 10 includes a switch 50 for switching the path connected to the radiating element 11 from among a plurality of paths (first path 10a, second path 10b), a filter circuit 20 provided in the first path 10a, and an impedance adjustment element 40 provided in the second path 10b. Although the impedance adjustment circuit 10 shown in Figure 1 illustrates two paths, the first path 10a and the second path 10b, as an example of a plurality of paths, it may have three or more paths. The impedance adjustment circuit 10 only needs to include at least the first path 10a and the second path 10b, and be able to switch the path connected to the radiating element 11 using the switch 50.

[0014] The filter circuit 20 includes a first wiring 21 having a series resonant circuit in which a first coil L1 (first inductance element) and a capacitor C1 (capacitor element) are connected in series, and a second wiring 22 provided in parallel with the first wiring 21. Furthermore, the filter circuit 20 further includes a third wiring 23 having a second coil L2 (second inductance element) in the second wiring 22 and connected in series with the first wiring 21 and the second wiring 22.

[0015] In the filter circuit 20, the first coil L1 and the second coil L2 are magnetically coupled, generating a mutual inductance M. The coupling coefficient between the first coil L1 and the second coil L2 is denoted as k. Figure 2 is a diagram illustrating the equivalent circuit of the filter circuit 20 in Embodiment 1. In the filter circuit 20, the magnetic field coupling of the first coil L1 and the second coil L2 generates a positive mutual inductance +M in the first coil L1 and the second coil L2, and a negative mutual inductance -M in the third wiring 23. Therefore, the filter circuit 20 functions as a parallel resonant circuit as shown in the equivalent circuit in Figure 2.

[0016] Although not shown in the diagram, the filter circuit 20 is, for example, a rectangular parallelepiped chip component. The filter circuit 20 is constructed by forming conductor patterns for the first coil L1, the second coil L2, and the capacitor C1 on each insulating substrate (for example, liquid crystal polymer, low-temperature co-fired ceramics, etc.) and then stacking the insulating substrates. The filter circuit 20 is not limited to chip components, and each element or some of the elements may be composed of different components.

[0017] The antenna device 100 is implemented in mobile devices such as smartphones and adjusts its impedance to broaden the frequency band or to support multiple frequency bands. The impedance adjustment of the antenna device 100 is performed by switching the path connecting the radiating element 11 to the impedance adjustment circuit 10 using a switch 50. Figure 2 shows the equivalent circuit when the radiating element 11 and the impedance adjustment element 40 are connected by the switch 50, but even though the radiating element 11 and the filter circuit 20 are not connected, there is a C-type reactance (C) between the radiating element 11 and the filter circuit 20. ｏｆｆ ) has.

[0018] Here, the C-type reactance (C) that occurs between the radiating element and the filter circuit when disconnected. ｏｆｆ The problems caused by the above will be explained. Figure 3 is a diagram illustrating the equivalent circuit of the comparison filter circuit 20Z. As shown in Figure 3, the comparison filter circuit 20Z is a parallel resonant circuit in which the first coil L1 and the third coil L3 are not magnetically coupled. The filter circuit 20Z has a capacitor C1 on the first wiring 21, a first coil L1 on the second wiring 22, and a second coil L2 on the third wiring 23.

[0019] The comparative antenna device, which is not shown in the figures, is configured in the same way as the antenna device 100 shown in Figure 1, but with the impedance adjustment circuit 10 replaced by the impedance adjustment circuit 10Z shown in Figure 3. The impedance of the comparative antenna device is also adjusted using the impedance adjustment circuit 10Z.

[0020] In the comparative filter circuit 20Z, as mentioned above, even though the radiating element 11 and the filter circuit 20Z are not connected, there is a C-type reactance (C) between the radiating element 11 and the filter circuit 20Z. ｏｆｆ ) has. The comparative filter circuit 20Z has an inductive reactance at frequencies higher than the parallel resonance frequency, but the C-reactive reactance (C ｏｆｆ This cancels out the effect, resulting in a lower impedance. In other words, the filter circuit 20Z being compared can be considered connected to the radiating element 11 even when it is not connected to the radiating element 11. As a result, in the antenna device being compared, the filter circuit 20Z will affect the antenna characteristics when the radiating element 11 and the filter circuit 20Z are not connected.

[0021] Specifically, Figure 4 is a diagram illustrating the change in reactance of the filter circuit 20Z being compared. Figure 4(a) is a graph showing the change in reactance of only the filter circuit 20Z, and Figure 4(b) is a graph showing the C-type reactance (C ｏｆｆ This is a graph showing the change in reactance of ). Figure 4(c) shows the filter circuit 20Z and the C-type reactance (C ｏｆｆ This graph shows the change in reactance when combined with ). In Figures 4(a) to 4(c), the horizontal axis is frequency and the vertical axis is reactance.

[0022] The change in reactance shown in Figure 4 is the result of a simulation performed under the following conditions. The filter circuit 20Z has a first coil L1 = 1 nH, a third coil L3 = 1.8 nH, and a capacitor C1 = 1.57 pF. C-type reactance (C ｏｆｆ The capacitance is 0.3 pF. Also, the parallel resonant frequency of the 20Z filter circuit is approximately 4 GHz.

[0023] As shown in Figure 4(a), the filter circuit 20Z has an inductive reactance of approximately +j40Ω at around 6GHz (mark m2), indicating a large positive inductive reactance at frequencies higher than the parallel resonance frequency. On the other hand, the capacitive reactance (C ｏｆｆ As shown in Figure 4(b), it has a large negative reactance of approximately -j90Ω around 6GHz (mark m2).

[0024] Therefore, when the filter circuit 20Z is not connected to the radiating element 11, a large positive L reactance on the higher frequency side than the parallel resonance frequency is canceled by a large negative C reactance (C ｏｆｆ ), resulting in a reduced reactance. The filter circuit 20Z not connected to the radiating element 11 has an absolute value of reactance less than j50Ω on the higher frequency side from around approximately 6 GHz (mark m2) as shown in FIG. 4(c), indicating a low reactance. Note that series resonance occurs in the filter circuit 20Z not connected to the radiating element 11 at around 7.6 GHz.

[0025] Thus, in the antenna device 100 of Embodiment 1, a filter circuit 20 including the first coil L1 and the second coil L2 that are magnetically coupled and function as a parallel resonance circuit is used. As described above, a positive mutual inductance +M is generated in the first coil L1 and the second coil L2 of the filter circuit 20, and a negative mutual inductance -M is generated in the third wiring 23. Therefore, the filter circuit 20 does not have a large positive L reactance on the higher frequency side than the parallel resonance frequency.

[0026] Specifically, FIG. 5 is a diagram for explaining the change in reactance of the filter circuit 20 in Embodiment 1. FIG. 5(a) is a graph showing the change in reactance of only the filter circuit 20, and FIG. 5(b) is a graph showing the change in reactance of the C reactance (C ｏｆｆ ). FIG. 5(c) is a graph showing the change in reactance when the filter circuit 20 and the C reactance (C ｏｆｆ ) are combined. In FIGS. 5(a) to 5(c), the horizontal axis represents frequency, and the vertical axis represents reactance.

[0027] Note that the change in reactance shown in FIG. 5 is the result of simulation under the following conditions. The filter circuit 20 has a first coil L1 = 3.5 nH, a second coil L2 = 1 nH, a capacitor C1 = 0.3 pF, and a coupling coefficient k = 0.2. The parallel resonance frequency of the filter circuit 20 is approximately 4 GHz. Here, the mutual inductance M is the coupling coefficient k×((the first coil L1×the second coil L2)) 1 / 2It is calculated by the C-type reactance (C ｏｆｆ ) = 0.3pF.

[0028] As shown in Figure 5(a), the filter circuit 20 has an inductive reactance of approximately +j10Ω around 6GHz (mark m2), and the inductive reactance at frequencies higher than the parallel resonance frequency is kept low. On the other hand, the capacitive reactance (C ｏｆｆ As shown in Figure 5(b), it has a large negative reactance of approximately -j90Ω around 6GHz (mark m2).

[0029] Therefore, when the filter circuit 20 is not connected to the radiating element 11, the inductive reactance and the capacitive reactance (C) are measured at frequencies higher than the parallel resonant frequency. ｏｆｆ ) do not cancel each other out, and a large reactance can be maintained. As shown in Figure 5(c), the filter circuit 20, which is not connected to the radiating element 11, has an absolute value of reactance of j50Ω or more up to about 7.5GHz, and exhibits high reactance in the range of about 5GHz to about 7.5GHz.

[0030] Thus, in the filter circuit 20, the inductive reactance is greater than the capacitive reactance (C) at frequencies higher than the parallel resonant frequency. ｏｆｆ ) cancels out, and the impedance does not become low. In other words, even when the radiating element 11 and the filter circuit 20 are not connected, the antenna device 100 cannot be considered as if the radiating element 11 and the filter circuit 20 were connected. As a result, the antenna device 100 can reduce the influence of the filter circuit 20 on the antenna characteristics when the radiating element 11 and the filter circuit 20 are not connected.

[0031] As described above, the antenna device 100 in the first embodiment includes a radiating element 11 to which a power supply circuit 30 is connected, and an impedance adjustment circuit 10 connected to the radiating element 11. The impedance adjustment circuit 10 includes a switch 50 (switching circuit) that switches a path connected to the radiating element 11 from among a plurality of paths including a first path 10a and a second path 10b, a filter circuit 20 provided in the first path 10a, and an impedance adjustment element 40 provided in the second path 10b. The filter circuit 20 is a parallel resonance circuit including at least two inductance elements that magnetically couple.

[0032] Specifically, the filter circuit 20 includes a first wiring 21 and a second wiring 22 provided in parallel, and a third wiring 23 connected in series to the first wiring 21 and the second wiring 22. The first wiring 21 has a series resonance circuit in which a first coil L1 (first inductance element) and a capacitor C1 (capacitor element) are connected in series. The second wiring 22 has a second coil L2 (second inductance element) that magnetically couples with the first coil L1.

[0033] In the filter circuit 20, a positive mutual inductance +M occurs between the first coil L1 and the second coil L2, and a negative mutual inductance -M occurs in the third wiring 23, so that there is no large positive L reactance on the higher frequency side than the parallel resonance frequency. By using the filter circuit 20 having no large positive L reactance on the higher frequency side than the parallel resonance frequency, the antenna device 100 can reduce the influence of the filter circuit 20 on the antenna characteristics when the radiating element 11 and the filter circuit 20 are not connected.

[0034] Note that the first path 10a and the second path 10b of the antenna device 100 are provided between the radiating element 11 and the power supply circuit 30. The switching circuit that switches the path includes a switch 50 that switches the path connected to the radiating element 11. The switch 50 may be a semiconductor switch such as a MOSFET or a physical switch.

[0035] [Embodiment 2] In the above-described embodiment, the filter circuit 20 is described as having a series resonance circuit in which the first wiring 21 has the first coil L1 (first inductance element) and the capacitor C1 (capacitor element) connected in series, and the second wiring 22 has the second coil L2 (second inductance element) that magnetically couples with the first coil L1. However, the filter circuit used in the antenna device is not limited to this, and any parallel resonance circuit including at least two inductance elements that magnetically couple may be used.

[0036] FIG. 6 is a schematic diagram of an electronic device 200A including the antenna device 100A in Embodiment 2. FIG. 7 is a diagram for explaining the equivalent circuit of the filter circuit 20A in Embodiment 2. In the antenna device 100A shown in FIG. 6, the same components as those of the antenna device 100 shown in FIG. 1 are denoted by the same reference numerals, and detailed descriptions thereof will not be repeated. Also, in the filter circuit 20A shown in FIGS. 6 and 7, the same components as those of the filter circuit 20 shown in FIGS. 1 and 2 are denoted by the same reference numerals, and detailed descriptions thereof will not be repeated.

[0037] The antenna device 100A includes a radiation element 11 to which a power supply circuit 30 is connected, and an impedance adjustment circuit 10A is provided between the radiation element 11 and the power supply circuit 30. The antenna device 100A broadens the usable frequency band by adjusting the impedance with the impedance adjustment circuit 10A.

[0038] The impedance adjustment circuit 10A includes a switch 50 that switches the path connected to the radiation element 11 from among a plurality of paths (first path 10a, second path 10b), a filter circuit 20A provided in the first path 10a, and an impedance adjustment element 40 provided in the second path 10b. In the impedance adjustment circuit 10A shown in FIG. 6, two paths, the first path 10a and the second path 10b, are illustrated as examples of the plurality of paths, but it may have three or more paths. The impedance adjustment circuit 10A may include at least the first path 10a and the second path 10b, as long as the path connected to the radiation element 11 can be switched by the switch 50.

[0039] The filter circuit 20A includes a first wiring 21 having a series resonant circuit in which a first coil L1 (first inductance element) and a capacitor C1 (capacitor element) are connected in series, and a second wiring 22 provided in parallel with the first wiring 21. Furthermore, the filter circuit 20A includes a third wiring 23 connected in series with the first wiring 21 and the second wiring 22, and the third wiring 23 has a second coil L2 (second inductance element).

[0040] In the filter circuit 20A, the first coil L1 and the second coil L2 are magnetically coupled, generating a mutual inductance M. The coupling coefficient between the first coil L1 and the second coil L2 is denoted as k. As shown in Figure 7, the magnetic field coupling of the first coil L1 and the second coil L2 in the filter circuit 20A generates a negative mutual inductance -M in the first coil L1 and the second coil L2, and a positive mutual inductance +M in the second wiring 22. Therefore, the filter circuit 20A functions as a parallel resonant circuit as shown in the equivalent circuit in Figure 7, and does not have a large positive inductance reactance at frequencies higher than the parallel resonant frequency.

[0041] Specifically, Figure 8 is a diagram illustrating the change in reactance of the filter circuit 20A in Embodiment 2. Figure 8(a) is a graph showing the change in reactance of only the filter circuit 20A, and Figure 8(b) is a graph showing the C-type reactance (C ｏｆｆ This is a graph showing the change in reactance of the filter circuit 20A and the C-type reactance (C). Figure 8(c) shows the filter circuit 20A and the C-type reactance (C ｏｆｆ This graph shows the change in reactance when combined with ). In Figures 8(a) to 8(c), the horizontal axis is frequency and the vertical axis is reactance.

[0042] The change in reactance shown in Figure 8 is the result of a simulation performed under the following conditions. The filter circuit 20A has a first coil L1 = 1.0 nH, a second coil L2 = 0.5 nH, a capacitor C1 = 1.57 pF, and a coupling coefficient k = 0.6. C-type reactance (C ｏｆｆ The capacitance is 0.3 pF. Also, the parallel resonant frequency of the filter circuit 20A is approximately 4 GHz.

[0043] As shown in Figure 8(a), the filter circuit 20A has an inductive reactance of approximately +j5Ω at around 6GHz (mark m2), and the inductive reactance at frequencies higher than the parallel resonance frequency is kept low. On the other hand, the capacitive reactance (C ｏｆｆ As shown in Figure 8(b), it has a large negative reactance of approximately -j90Ω around 6GHz (mark m2).

[0044] Therefore, when the filter circuit 20A is not connected to the radiating element 11, the inductive reactance and the capacitive reactance (C) are measured at frequencies higher than the parallel resonant frequency. ｏｆｆ ) do not cancel each other out, and a large reactance can be maintained. As shown in Figure 8(c), the filter circuit 20A, which is not connected to the radiating element 11, has an absolute reactance of j50Ω or more up to about 8.0GHz, and exhibits high reactance in the range of about 5GHz to about 8GHz.

[0045] As described above, the antenna device 100A in Embodiment 2 includes a radiating element 11 to which a power supply circuit 30 is connected, and an impedance adjustment circuit 10A connected to the radiating element 11. The impedance adjustment circuit 10A includes a switch 50 (switching circuit) that switches the path connected to the radiating element 11 from among a plurality of paths including a first path 10a and a second path 10b, a filter circuit 20A provided in the first path 10a, and an impedance adjustment element 40 provided in the second path 10b. The filter circuit 20A is a parallel resonant circuit including at least two magnetically coupled inductance elements.

[0046] Specifically, the filter circuit 20A includes a first wiring 21 and a second wiring 22 arranged in parallel, and a third wiring 23 connected in series to the first wiring 21 and the second wiring 22. The first wiring 21 has a series resonant circuit in which a first coil L1 (first inductance element) and a capacitor C1 (capacitor element) are connected in series. The third wiring 23 has a second coil L2 (second inductance element) that is magnetically coupled to the first coil L1.

[0047] The filter circuit 20A does not have a large positive inductance at frequencies higher than the parallel resonant frequency because a negative mutual inductance -M is generated in the first coil L1 and the second coil L2, and a positive mutual inductance +M is generated in the second wiring 22. By using the filter circuit 20A, which does not have a large positive inductance at frequencies higher than the parallel resonant frequency, the antenna device 100A can reduce the influence of the filter circuit 20A on the antenna characteristics when the radiating element 11 and the filter circuit 20A are not connected.

[0048] (Modification 1) In the antenna device 100, as shown in Figure 1, an impedance adjustment circuit 10 is provided between the radiating element 11 and the power supply circuit 30. However, the location of the impedance adjustment circuit 10 is not limited to this. Figure 9 is a schematic diagram of the electronic equipment 200B including the antenna device 100B of Modification 1. In the antenna device 100B shown in Figure 9, the same reference numerals are used for components that are the same as those in the antenna device 100 shown in Figure 1, and detailed explanations are not repeated.

[0049] As shown in Figure 9, the antenna device 100B has an impedance adjustment circuit 10 installed between the radiating element 11 and GND (ground electrode), and on wiring branched from the wiring connecting the radiating element 11 and the feed circuit 30. Even when the impedance adjustment circuit 10 is installed in a position like that of the antenna device 100B, it is necessary to reduce the influence of the filter circuit 20 on the antenna characteristics when the radiating element 11 and the filter circuit 20 are not connected. Therefore, the antenna device 100B makes the filter circuit 20 a parallel resonant circuit including a first coil L1 and a second coil L2 that are magnetically coupled, thereby reducing the influence of the filter circuit 20 on the antenna characteristics when the radiating element 11 and the filter circuit 20 are not connected. Note that the configuration of Modification 1 may also be applied to the antenna device 100A in the embodiment.

[0050] (Modification 2) Furthermore, Figure 10 is a schematic diagram of the electronic equipment 200C including the antenna device 100C of Modification 2. In the antenna device 100C shown in Figure 10, the same reference numerals are used for components that are the same as those in the antenna device 100 shown in Figure 1, and detailed explanations are not repeated.

[0051] As shown in Figure 10, the antenna device 100C has an impedance adjustment circuit 10 provided between the branched portion 11a of the radiating element 11 and GND (ground electrode). Even when the impedance adjustment circuit 10 is provided in a position like that of the antenna device 100C, it is necessary to reduce the influence of the filter circuit 20 on the antenna characteristics when the radiating element 11 and the filter circuit 20 are not connected. Therefore, the antenna device 100C makes the filter circuit 20 a parallel resonant circuit including a first coil L1 and a second coil L2 that are magnetically coupled, thereby reducing the influence of the filter circuit 20 on the antenna characteristics when the radiating element 11 and the filter circuit 20 are not connected. Note that the configuration of Modification 2 may also be applied to the antenna device 100A in the embodiment.

[0052] (Modification 3) In the antenna device 100, as shown in Figure 1, a switch 50 was described to switch the path connected to the radiating element 11 from among multiple paths (first path 10a, second path 10b), but the configuration for switching paths is not limited to this. Figure 11 is a schematic diagram of the electronic equipment 200D including the antenna device 100D of Modification 3. In the antenna device 100D shown in Figure 11, the same reference numerals are used for components that are the same as those in the antenna device 100 shown in Figure 1, and detailed explanations are not repeated.

[0053] As shown in Figure 11, the antenna device 100D has an impedance adjustment circuit 10D between the radiating element 11 and the power supply circuit 30. The impedance adjustment circuit 10D includes a third path 10c and a fourth path 10d, with an impedance adjustment element 40 provided in the third path 10c and a filter circuit 20 and a Pin diode 60 provided in the fourth path 10d. The Pin diode 60 is connected in series with the filter circuit 20.

[0054] Furthermore, the impedance adjustment circuit 10D includes inductance elements 61 and 62 for switching the voltage applied to the filter circuit 20 and the Pin diode 60. One end of inductance element 61 is connected to the third path 10c, and a predetermined voltage can be applied to the other end. One end of inductance element 62 is connected to the third path 10c, and the other end is grounded to GND (ground electrode).

[0055] In the impedance adjustment circuit 10D, when no predetermined voltage is applied to the other end of the inductance element 61 (voltage OFF), no voltage is applied to the filter circuit 20 and the Pin diode 60, so only the third path 10c connects to the radiating element 11. On the other hand, in the impedance adjustment circuit 10D, when a predetermined voltage is applied to the other end of the inductance element 61 (voltage ON), voltage is applied to the filter circuit 20 and the Pin diode 60, so the third path 10c and the fourth path 10d connect to the radiating element 11.

[0056] The impedance adjustment circuit 10D includes a Pin diode 60 connected in series with the filter circuit 20, rather than a switch 50. The switching circuit is configured to switch the path connected to the radiating element 11 by switching the voltage applied to the filter circuit 20 and the Pin diode 60.

[0057] Even when a switching circuit is configured as in antenna device 100D, it is necessary to reduce the influence of the filter circuit 20 on the antenna characteristics when the radiating element 11 and the filter circuit 20 are not connected. Therefore, antenna device 100D reduces the influence of the filter circuit 20 on the antenna characteristics when the radiating element 11 and the filter circuit 20 are not connected by making the filter circuit 20 a parallel resonant circuit including a first coil L1 and a second coil L2 that magnetically couple the filter circuit 20. Note that the configuration of modified example 3 may also be applied to antenna device 100A in the embodiment.

[0058] (Modification 4) The impedance adjustment circuit included in the antenna device is not limited to the configuration described above. Figure 12 is a schematic diagram of the electronic equipment 200E including the antenna device 100E of Modification 4. In the antenna device 100E shown in Figure 12, the same reference numerals are used for components that are the same as those in the antenna device 100 shown in Figure 1, and detailed explanations are not repeated.

[0059] As shown in Figure 12, the antenna device 100E has an impedance adjustment circuit 10E between the radiating element 11 and the power supply circuit 30. The impedance adjustment circuit 10E includes a switch 50 that switches the path connected to the radiating element 11 from among a plurality of paths (fifth path 10e, sixth path 10f), an impedance adjustment element 41 provided in the fifth path 10e, an impedance adjustment element 42 provided in the sixth path 10f, and a filter circuit 20 provided in the seventh path 10g which is connected in series with the fifth path 10e and the sixth path 10f. In the impedance adjustment circuit 10E shown in Figure 12, two paths, the fifth path 10e and the sixth path 10f, are shown as examples of the plurality of paths that can be switched by the switch 50, but there may be three or more paths.

[0060] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope of the claims are intended to be included.

[0061] 10, 10A, 10D, 10E, 10Z Impedance adjustment circuits, 11 Radiating elements, 20, 20A, 20Z Filter circuits, 30 Power supply circuits, 40, 41, 42 Impedance adjustment elements, 50 Switches, 60 Pin diodes, 61, 62 Inductance elements, 100, 100A to 100E Antenna devices, 200, 200A to 200E Electronic equipment.

Claims

1. An antenna device comprising: a radiating element to which a power supply circuit is connected; and an impedance adjustment circuit connected to the radiating element, wherein the impedance adjustment circuit includes: a switching circuit that switches the path to which the radiating element is connected from among a plurality of paths including a first path and a second path; a filter circuit provided in the first path; and an impedance adjustment element provided in the second path, wherein the filter circuit is a parallel resonant circuit including at least two magnetically coupled inductance elements.

2. The antenna device according to claim 1, wherein the filter circuit includes a first wiring and a second wiring provided in parallel, and a third wiring connected in series with respect to the first wiring and the second wiring, the first wiring having a series resonant circuit including a first inductance element, and either the second wiring or the third wiring having a second inductance element that is magnetically coupled with the first inductance element.

3. The antenna device according to claim 2, wherein the first wiring has a series resonant circuit in which the first inductance element and the capacitor element are connected in series, and the second wiring has the second inductance element.

4. The antenna device according to claim 2, wherein the first wiring has a series resonant circuit in which the first inductance element and the capacitor element are connected in series, and the third wiring has the second inductance element.

5. The antenna device according to any one of claims 1 to 4, wherein the impedance adjustment circuit is provided between the radiating element and the power supply circuit.

6. The antenna device according to any one of claims 1 to 4, wherein the impedance adjustment circuit is provided between the radiating element and the ground electrode.

7. The antenna device according to claim 6, wherein the impedance adjustment circuit is provided in wiring branched from the wiring connecting the radiating element and the power supply circuit.

8. The antenna device according to any one of claims 1 to 7, wherein the switching circuit includes a switch for switching the path connected to the radiating element.

9. The antenna device according to any one of claims 1 to 7, wherein the switching circuit includes a Pin diode connected in series with the filter circuit, and switches the voltage applied to the filter circuit and the Pin diode, and switches the path connected to the radiating element.

10. An electronic device comprising the antenna device according to any one of claims 1 to 9, and a power supply circuit for supplying power to the radiating element.

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