Antenna device and communication device

Abstract

Provided are: an antenna device having a smaller number of frequency adjustment elements as compared to the number of antennas; and a communication apparatus using the antenna device. The antenna device (100) according to the present disclosure comprises: a first radiation element (11); a second radiation element (21); a frequency adjustment element (23); a first power feeder circuit (12); and a second power feeder circuit (22). The second radiation element (21) is disposed at a position that allows electric field coupling and / or magnetic field coupling with the first radiation element (11). The frequency adjustment element (23) is connected to the first radiation element (11) or a second radiation element (21, 21A). The first power feeder circuit (12) supplies a high-frequency signal to the first radiation element (11). The second power feeder circuit (22) supplies a high-frequency signal to the second radiation element (21, 21A).

Description

[Technical field]

[0001] The present disclosure relates to a technique for an antenna device and a communication device using the antenna device. [Background technology]

[0002] In recent years, technological advances have created a demand for communication devices (e.g., smartphones, mobile phones, etc.) that support multiple communication systems, and the number of frequency bands that such communication devices can support is increasing. In order to support multiple frequency bands, Japanese Patent Laid-Open Publication No. 2011-071597 (Patent Document 1) discloses a communication device that provides a frequency switching circuit (frequency adjustment element) in an antenna to adjust the supported frequency band. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-071597 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a communication device adopts MIMO (multiple-input and multiple-output) using multiple antennas, it is necessary to provide frequency adjustment elements according to the number of antennas. Therefore, as the number of frequency bands supported by a single communication device increases, the number of antennas increases, and the same number of frequency adjustment elements as the antennas must be provided. As a result, there is a problem that the cost of the frequency adjustment elements per communication device increases.

[0005] The present disclosure has been made to solve such problems, and has as its object to provide an antenna device in which the number of frequency adjustment elements is small relative to the number of antennas, and a communication device using the antenna device. [Means for solving the problem]

[0006] An antenna device according to the present disclosure comprises a first radiating element, a second radiating element arranged at a position relative to the first radiating element allowing at least one of electric field coupling and magnetic field coupling, a frequency adjustment element connected to the first radiating element or the second radiating element, a first feed circuit that supplies a high-frequency signal to the first radiating element, and a second feed circuit that supplies a high-frequency signal to the second radiating element, wherein the first radiating element and the second radiating element are arranged such that the first radiating element is coupled to the second radiating element at a first point where the electric field is maximum at the resonant frequency, and the second radiating element is coupled to the first radiating element at a second point where the electric field is maximum at the resonant frequency.

[0007] A communication device according to the present disclosure includes the above antenna device and a communication circuit that transmits and receives signals using the antenna device. Effect of the Invention

[0008] The antenna device according to the present disclosure arranges a second radiating element at a position where at least one of electric field coupling and magnetic field coupling is possible with respect to a first radiating element, and connects a frequency adjustment element to the first radiating element or the second radiating element, thereby making it possible to control the operating frequency band with a small number of frequency adjustment elements compared to the number of antennas. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of an antenna device according to a first embodiment. [Diagram 2] 3 is a schematic diagram of a frequency adjustment element in the first embodiment. FIG. [Diagram 3] 5 is a diagram showing the reflection characteristics of the antenna device in the first embodiment. FIG. [Figure 4] 5 is a diagram showing reflection characteristics when an inductance value is changed in a frequency adjustment element of the antenna device in the first embodiment. FIG. [Diagram 5] 5 is a diagram showing reflection characteristics when a capacitance value is changed in a frequency adjustment element of the antenna device in the first embodiment. FIG. [Figure 6]1 is a schematic diagram of a communication device according to a first embodiment. [Figure 7] FIG. 4 is a schematic diagram of an antenna device according to a modified example of the first embodiment. [Figure 8] FIG. 11 is a schematic diagram of an antenna device according to a second embodiment. [Figure 9] 13 is a diagram showing reflection characteristics when a frequency adjustment element is provided in a second antenna in the antenna device according to the second embodiment. FIG. [Figure 10] 13 is a diagram showing reflection characteristics when a frequency adjustment element is provided in a first antenna in the antenna device according to the second embodiment. FIG. [Figure 11] FIG. 11 is a schematic diagram of an antenna device according to a third embodiment. [Figure 12] 13 is a diagram illustrating the reflection characteristics of the antenna device according to the third embodiment. [Figure 13] FIG. 13 is a schematic diagram of an antenna device according to a modified example of the third embodiment. [Figure 14] FIG. 13 is a diagram showing the reflection characteristics of an antenna device according to a modification of the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and their description will not be repeated.

[0011] [Embodiment 1] <Basic configuration of antenna device> 1 is a schematic diagram of an antenna device 100 according to the first embodiment. The antenna device 100 includes a first antenna 10 and a second antenna 20. The first antenna 10 includes a first radiating element 11 and a first feed circuit 12. The second antenna 20 includes a second radiating element 21, a second feed circuit 22, and a frequency adjustment element 23. The antenna device 100 is mounted on a communication device such as a mobile terminal such as a mobile phone, a smartphone, or a tablet, or a personal computer with a communication function.

[0012] Due to the need for MIMO and an increase in the number of supported frequency bands, antenna devices used in communication devices such as smartphones include multiple antennas such as a first antenna 10 and a second antenna 20, as in the antenna device 100. However, in an antenna device in which the first antenna and the second antenna are provided independently, it is necessary to provide a frequency adjustment element for each of the first antenna and the second antenna in order to adjust the operating frequency band of each antenna.

[0013] Therefore, in the antenna device 100, the first radiating element 11 of the first antenna 10 and the second radiating element 21 of the second antenna 20 are arranged to be electric field coupled or magnetic field coupled, or to be electric field coupled and magnetic field coupled (hereinafter also simply referred to as coupling), and a frequency adjustment element 23 is provided only on the second antenna 20. In other words, in the antenna device 100, by coupling the first antenna 10 and the second antenna 20, a plurality of desired operating frequency bands can be obtained, and at least one of the operating frequency bands can be adjusted by one frequency adjustment element 23. Of course, the antenna device 100 may be provided with a frequency adjustment element only on the first antenna 10, not on the second antenna 20.

[0014] The configuration of the antenna device 100 will be described more specifically. The first antenna 10 and the second antenna 20 are inverted-F antennas. Furthermore, in order to enable at least one of electric field coupling and magnetic field coupling between the first radiating element 11 and the second radiating element 21, the first antenna 10 of the inverted-F antenna and the second antenna 20 of the inverted-F antenna are arranged to face each other as shown in Fig. 1. Therefore, the first radiating element 11 and the second radiating element 21 are arranged such that the orientation of the open end A (radiating end) of the first radiating element 11 and the orientation of the open end A (radiating end) of the second radiating element 21 are opposite to each other, and the first radiating element 11 and the second radiating element 21 are arranged in parallel.

[0015] The position for electric field coupling or magnetic field coupling, or electric field coupling and magnetic field coupling, of the second radiating element 21 with respect to the first radiating element 11 is not limited to the position shown in Fig. 1. It is sufficient that the second radiating element 21 is disposed with respect to the first radiating element 11 at a position where at least the open end A (radiating end) of the first radiating element 11 is coupled to the second radiating element 21 at any position, and the open end B (radiating end) of the second radiating element 21 is coupled to the first radiating element 11 at any position.

[0016] The open end A of the first radiating element 11 is a point (first point) where the electric field is maximum at the resonant frequency. The open end B of the second radiating element 21 is a point (second point) where the electric field is maximum at the resonant frequency. That is, the antenna device 100 is arranged so that the first radiating element 11 is coupled to the second radiating element 21 at the open end A (first point) where the electric field is maximum at the resonant frequency, and the second radiating element 21 is coupled to the first radiating element 11 at the open end B (second point) where the electric field is maximum at the resonant frequency, thereby making it possible to couple the second radiating element 21 to the first radiating element 11 by electric field coupling or magnetic field coupling, or by electric field coupling and magnetic field coupling.

[0017] The antenna device 100 can eliminate the coupling between the open end A of the first radiating element 11 and the open end B of the second radiating element 21 by arranging the first radiating element 11 and the second radiating element 21 such that the open end A (first point) of the first radiating element 11 is coupled to a point other than the open end B (second point) of the second radiating element 21, and the open end B (second point) of the second radiating element 21 is coupled to a point other than the open end A (first point) of the first radiating element 11.

[0018] The first feeding circuit 12 supplies a high-frequency signal to the first radiating element 11, and the second feeding circuit 22 supplies a high-frequency signal to the second radiating element 21. The first radiating element 11 is not provided with a frequency adjustment element, but the second radiating element 21 is provided with a frequency adjustment element 23.

[0019] The frequency adjustment element 23 is an element that adjusts the operating frequency band of the coupled first antenna 10 and second antenna 20. Fig. 2 is a schematic diagram of the frequency adjustment element 23 in the first embodiment. As shown in Fig. 2, the frequency adjustment element 23 has a plurality of elements that are each grounded, and a switch 231 that electrically connects to one element from among the plurality of elements. The plurality of elements includes, for example, a coil 232, a capacitor 233, a short wiring 234, a coil 235, a capacitor 236, and an open wiring 237.

[0020] Coil 232 has an inductance value of, for example, 5 nH, and coil 235 has an inductance value of, for example, 10 nH. Capacitor 233 has a capacitance value of, for example, 0.5 pF, and capacitor 236 has a capacitance value of, for example, 1 pF. Frequency adjustment element 23 can be connected to second radiating element 21 by switching between different inductance values ​​and different capacitance values, and can adjust the operating frequency band of antenna device 100 according to the connected inductance value and capacitance value.

[0021] <Antenna device characteristics> FIG. 3 is a diagram showing the reflection characteristic of the antenna device 100 in the first embodiment. In FIG. 3, the horizontal axis is frequency, the vertical axis is return loss, the solid line is the reflection characteristic of the first antenna 10, and the dashed line is the reflection characteristic of the second antenna 20. The return loss indicates the ratio of the power returned from the radiating element to the power output from the power feed circuit to the radiating element, and therefore means that power is radiated from the radiating element at a frequency where the return loss is low. By coupling the first antenna 10 and the second antenna 20, the antenna device 100 has two operating frequency bands, one with a center frequency of about 3.1 GHz and the other with a center frequency of about 4.1 GHz, as shown in FIG. 3. Here, the frequency adjustment element 23 is in an open state not connected to the ground, that is, connected to 237 in FIG. 2.

[0022] Antenna device 100 can adjust these two operating frequency bands collectively by using frequency adjustment element 23. Fig. 4 is a diagram showing the reflection characteristics when the inductance value is changed by frequency adjustment element 23 of antenna device 100 in the first embodiment. Fig. 5 is a diagram showing the reflection characteristics when the capacitance value is changed by frequency adjustment element 23 of antenna device 100 in the first embodiment. In Figs. 4 and 5, the horizontal axis is frequency, the vertical axis is return loss, the solid line is the reflection characteristic of first antenna 10, and the dashed line is the reflection characteristic of second antenna 20.

[0023] Fig. 4(a) shows the reflection characteristic when switch 231 is connected to coil 232 with an inductance value of 5 nH in frequency adjustment element 23. In the reflection characteristic shown in Fig. 4(a), the frequency band having a center frequency of about 3.1 GHz in Fig. 3 changes to a frequency band having a center frequency of about 2.8 GHz, and the frequency band having a center frequency of about 4.1 GHz changes to a frequency band having a center frequency of about 4.2 GHz.

[0024] Fig. 4(b) shows the reflection characteristic when the switch 231 in the frequency adjustment element 23 is connected to the coil 235 having an inductance value of 10 nH. In the reflection characteristic shown in Fig. 4(b), the frequency band having a center frequency of about 3.1 GHz in Fig. 3 changes to a frequency band having a center frequency of about 2.9 GHz, and the frequency band having a center frequency of about 4.1 GHz changes to a frequency band having a center frequency of about 4.2 GHz. Compared with the reflection characteristic shown in Fig. 4(a), the reflection characteristic shown in Fig. 4(b) has a smaller return loss of the second antenna 20 in the frequency band having a center frequency of about 4.2 GHz, and the power that can be radiated from the second antenna 20 is larger.

[0025] Fig. 5(a) shows the reflection characteristics when switch 231 is connected to capacitor 233 with a capacitance value of 0.5 pF in frequency adjustment element 23. In the reflection characteristics shown in Fig. 5(a), the frequency band having a center frequency of about 3.1 GHz in Fig. 3 changes to a frequency band having a center frequency of about 3.2 GHz, and the frequency band having a center frequency of about 4.1 GHz changes to a frequency band having a center frequency of about 4.9 GHz.

[0026] Fig. 5(b) shows the reflection characteristic when switch 231 in frequency adjustment element 23 is connected to capacitor 236 with a capacitance value of 1 pF. In the reflection characteristic shown in Fig. 5(b), the frequency band having a center frequency of about 3.1 GHz in Fig. 3 does not change, and the frequency band having a center frequency of about 4.1 GHz changes to a frequency band having a center frequency of about 4.7 GHz. Compared to the reflection characteristic shown in Fig. 5(a), the reflection characteristic shown in Fig. 5(b) has a larger return loss of second antenna 20 in the frequency band having a center frequency of about 4.7 GHz.

[0027] In the antenna device 100, the center frequencies of two frequency bands can be controlled collectively for two antennas (first antenna 10, second antenna 20) by one frequency adjustment element 23, as shown in the reflection characteristics shown in Fig. 4 and Fig. 5. In the frequency adjustment element 23, the coils 232, 235 and the capacitors 233, 236 are switched by the switch 231 to adjust the frequency, but an element combining a coil and a capacitor may be switched by the switch 231 to adjust the frequency, or a variable capacitor element or a variable inductance element may be used instead of the switch and these passive elements.

[0028] <Communication equipment using antenna devices> Fig. 6 is a schematic diagram of a communication device according to the first embodiment. The communication device shown in Fig. 6 is a mobile terminal 200 capable of communication in a plurality of frequency bands (e.g., n78 (3.3-3.8 GHz), n79 (4.4-5.0 GHz), etc.). For this reason, the mobile terminal 200 is provided with an antenna device 100 including a first antenna 10 and a second antenna 20. The mobile terminal 200 is, for example, a mobile phone, a smartphone, or a tablet.

[0029] In the antenna device 100, the first radiating element 11 and the second radiating element 21 are arranged on the substrate 31 so that they face each other in order to couple the second radiating element 21 to the first radiating element 11 through electric field coupling or magnetic field coupling, or through electric field coupling and magnetic field coupling. The first radiating element 11 is provided with a connection terminal 12a for connection to the first power feed circuit 12 shown in FIG. 1, and the second radiating element 21 is provided with a connection terminal 22a for connection to the second power feed circuit 22 shown in FIG. 1 and a connection terminal 23a for connection to the frequency adjustment element 23 shown in FIG. 1. In FIG. 6, the first power feed circuit 12, the second power feed circuit 22, and the frequency adjustment element 23 are provided on the back side of the surface of the substrate 31 on which the first radiating element 11 and the second radiating element 21 are provided, and are therefore not shown. Furthermore, the mobile terminal 200 is provided with an RFIC 32 (semiconductor IC) connected to the first power feed circuit 12 and the second power feed circuit 22 of the antenna device 100. The area 33 other than where the substrate 31 is provided includes a conductor connected to the ground potential.

[0030] <Modifications of the Antenna Device> FIG. 7 is a schematic diagram of an antenna device 100A according to a modification of the first embodiment. The antenna device 100A includes a first antenna 10 and a second antenna 20A. The first antenna 10 includes a first radiating element 11 and a first feeding circuit 12. The second antenna 20A includes a second radiating element 21A, a second feeding circuit 22, and a frequency adjustment element 23. Unlike the second radiating element 21 shown in FIG. 1, the second radiating element 21A is not grounded via the frequency adjustment element 23, and the frequency adjustment element 23 is provided on the feeding circuit side. Therefore, the second antenna 20A is a monopole antenna. Of course, the first antenna 10, which is an inverted F antenna, may be a monopole antenna.

[0031] In order for the first radiating element 11 and the second radiating element 21A to be electric field coupled or magnetic field coupled, or electric field coupled and magnetic field coupled, the first antenna 10, which is an inverted-F antenna, and the second antenna 20A, which is a monopole antenna, are arranged to face each other as shown in Fig. 7. Therefore, the first radiating element 11 and the second radiating element 21A are arranged such that the orientation of the open end A of the first radiating element 11 and the orientation of the open end B of the second radiating element 21A are opposite, and the first radiating element 11 and the second radiating element 21A are arranged in parallel.

[0032] The antenna device 100A can adjust two operating frequency bands at once by the frequency adjustment element 23 provided in the second antenna 20A. In the antenna device 100A shown in FIG. 7, the frequency adjustment element 23 is provided in the second antenna 20A of the monopole antenna, but the frequency adjustment element 23 may be provided in the first antenna 10 of the inverted F antenna. In addition, when the frequency adjustment element 23 is provided in the second antenna 20A of the monopole antenna, it is also possible to connect the frequency adjustment element 23 in series to the second radiating element 21A. However, when the frequency adjustment element 23 is connected in series to the second radiating element 21A, the elements included in the frequency adjustment element 23 affect the characteristics of the second antenna 20A, so it is preferable to provide the frequency adjustment element 23 in a shunt connection on the power supply circuit side as shown in FIG. 7.

[0033] As described above, the antenna device 100, 100A of embodiment 1 comprises the first radiating element 11, the second radiating element 21, 21A arranged at a position where at least one of electric field coupling and magnetic field coupling is possible with the first radiating element 11, a frequency adjustment element 23 connected to the first radiating element 11 or the second radiating element 21, 21A, a first power feed circuit 12 that supplies a high-frequency signal to the first radiating element 11, and a second power feed circuit 22 that supplies a high-frequency signal to the second radiating elements 21, 21A.

[0034] As a result, in the antenna device 100, 100A of embodiment 1, the second radiating element 21, 21A is arranged at a position where at least one of electric field coupling and magnetic field coupling is possible with the first radiating element 11, and the frequency adjustment element 23 is connected to the first radiating element 11 or the second radiating element 21, 21A, so that the operating frequency band can be controlled with a small number of frequency adjustment elements compared to the number of antennas.

[0035] The first radiating element 11 and the second radiating elements 21, 21A are preferably arranged such that the first radiating element 11 is electric field coupled to the second radiating element 21, 21A at an open end A (first point) where the electric field is maximum at the resonant frequency, and the second radiating elements 21, 21A are electric field coupled to the first radiating element 11 at an open end B (second point) where the electric field is maximum at the resonant frequency. This allows the second radiating elements 21, 21A to be electric field coupled or magnetic field coupled, or electric field coupled and magnetic field coupled, to the first radiating element 11.

[0036] The first radiating element 11 and the second radiating elements 21, 21A are preferably arranged such that the open end A (first point) of the first radiating element 11 is electric field coupled at a point other than the open end B (second point) of the second radiating element 21, 21A, and the open end B (second point) of the second radiating element 21, 21A is electric field coupled at a point other than the open end A (first point) of the first radiating element 11. This results in the second radiating elements 21, 21A being electric field coupled or magnetic field coupled, or electric field coupled and magnetic field coupled, to the first radiating element 11.

[0037] Specifically, the first radiating element 11 and the second radiating elements 21, 21A are preferably arranged such that the orientation of the open end A of the first radiating element 11 is opposite to the orientation of the open end B of the second radiating elements 21, 21A. Also, the first radiating element 11 and the second radiating elements 21, 21A are preferably arranged in parallel.

[0038] The mobile terminal 200 (communication device) includes the antenna device 100, 100A, and an RFIC 32 (semiconductor IC) connected to the first power supply circuit 12 and the second power supply circuit 22 of the antenna device 100, 100A. This allows the mobile terminal 200 (communication device) to communicate in a wider frequency band by adjusting multiple operating frequency bands.

[0039] [Embodiment 2] In the first embodiment, an antenna device 100 has been described in which a first antenna 10 of an inverted-F antenna and a second antenna 20 of an inverted-F antenna are arranged to face each other as shown in Fig. 1. In the second embodiment, an antenna device will be described in which the first antenna and the second antenna are arranged to face the same direction.

[0040] <Basic configuration of antenna device> 8 is a schematic diagram of an antenna device 100B according to the second embodiment. The antenna device 100B includes a first antenna 10 and a second antenna 20. The first antenna 10 includes a first radiating element 11 and a first feed circuit 12. The second antenna 20 includes a second radiating element 21, a second feed circuit 22, and a frequency adjustment element 23.

[0041] The configuration of the antenna device 100B will be described more specifically. The first antenna 10 and the second antenna 20 are inverted-F antennas. Furthermore, in order for the first radiating element 11 and the second radiating element 21 to be electric field-coupled or magnetic field-coupled, or electric field-coupled and magnetic field-coupled, the first antenna 10 of the inverted-F antenna and the second antenna 20 of the inverted-F antenna are arranged facing the same direction as shown in FIG. 8. Therefore, the first radiating element 11 and the second radiating element 21 are arranged such that the direction of the open end A of the first radiating element 11 is the same as the direction of the open end B of the second radiating element 21, and the first radiating element 11 and the second radiating element 21 are arranged in parallel.

[0042] <Antenna device characteristics> 9 is a diagram showing the reflection characteristics when a frequency adjustment element 23 is provided in the second antenna 20 in the antenna device 100B according to the second embodiment. In FIG. 9, the horizontal axis represents frequency, the vertical axis represents return loss, the solid line represents the reflection characteristics of the first antenna 10, and the dashed line represents the reflection characteristics of the second antenna 20.

[0043] 9(a) shows the reflection characteristic when the switch 231 in the frequency adjustment element 23 is connected to the short circuit wiring 234 shown in FIG. 2. That is, the inductance value connected to the second radiating element 21 is 0 nH, and the capacitance value is 0 pF. The reflection characteristic shown in FIG. 9(a) has two operating frequency bands, a frequency band with a center frequency of about 4.5 GHz and a frequency band with a center frequency of about 5.2 GHz.

[0044] 9(b) shows the reflection characteristic when switch 231 in frequency adjustment element 23 is connected to coil 232 having an inductance value of 5 nH shown in FIG. 2. In the reflection characteristic shown in FIG. 9(b), the frequency band having a center frequency of about 4.5 GHz in FIG. 9(a) changes to a frequency band having a center frequency of about 3.7 GHz, and the frequency band having a center frequency of about 5.2 GHz hardly changes. In antenna device 100B, by providing frequency adjustment element 23 in second antenna 20, it is possible to adjust the frequency band having a center frequency mainly of about 4.5 GHz.

[0045] On the other hand, although not shown, a case will be described in which a frequency adjustment element is provided in the first antenna 10 instead of the second antenna 20 in the antenna device 100B. Fig. 10 is a diagram showing the reflection characteristics when a frequency adjustment element is provided in the first antenna 10 in the antenna device 100B according to the second embodiment. In Fig. 10, the horizontal axis is frequency, the vertical axis is return loss, the solid line is the reflection characteristic of the first antenna 10, and the dashed line is the reflection characteristic of the second antenna 20.

[0046] FIG. 10(a) shows the reflection characteristic when the switch in the frequency adjustment element is connected to the short wiring. That is, the inductance value connected to the first radiating element 11 is 0 nH, and the capacitance value is 0 pF. The reflection characteristic shown in FIG. 10(a) has two operating frequency bands, one with a center frequency of about 4.5 GHz and the other with a center frequency of about 5.2 GHz. The reflection characteristic shown in FIG. 10(a) is almost the same as the reflection characteristic shown in FIG. 9(a).

[0047] Fig. 10(b) shows the reflection characteristic when the switch in the frequency adjustment element is connected to a capacitor with a capacitance value of 2 pF. In the reflection characteristic shown in Fig. 10(b), the frequency band having a center frequency of about 4.5 GHz in Fig. 10(a) hardly changes, and the frequency band having a center frequency of about 5.2 GHz changes to a frequency band having a center frequency of about 5.5 GHz. In the antenna device 100B, by providing a frequency adjustment element in the first antenna 10, it is possible to adjust the frequency band having a center frequency of mainly about 5.2 GHz.

[0048] In the antenna device 100B, the first antenna 10 and the second antenna 20 are arranged facing in the same direction and coupled, resulting in two operating frequency bands, but one of the two operating frequency bands can be primarily adjusted by an antenna having a frequency adjustment element.

[0049] [Embodiment 3] In the modification of the first embodiment, an antenna device 100A has been described in which a first antenna 10, which is an inverted-F antenna, and a second antenna 20A, which is a pole antenna, are arranged to face each other as shown in Fig. 7. In the third embodiment, an antenna device using not only an inverted-F antenna or a pole antenna, but also a loop antenna will be described.

[0050] <Basic configuration of antenna device> 11 is a schematic diagram of an antenna device 100C according to the third embodiment. The antenna device 100C includes a first antenna 10 and a second antenna 20C. The first antenna 10 includes a first radiating element 11 and a first feed circuit 12. The second antenna 20C includes a second radiating element 21C, a second feed circuit 22, and a frequency adjustment element 23.

[0051] The configuration of the antenna device 100C will be described more specifically. The first antenna 10 is an inverted F antenna, and the second antenna 20C is a loop antenna. The second antenna 20C, which is a loop antenna, has one end of a second radiating element 21C connected to a second feed circuit 22, and the other end of the second radiating element 21C connected to a frequency adjustment element 23. The frequency adjustment element 23 may be provided in the first antenna 10, not in the second antenna 20C.

[0052] 11, in order for the first radiating element 11 and the second radiating element 21C to be electric field coupled or magnetic field coupled, or electric field coupled and magnetic field coupled, the first antenna 10 of the inverted-F antenna as seen from the first feed circuit 12 and the second antenna 20C of the loop antenna as seen from the second feed circuit 22 are arranged to face each other. Therefore, the first radiating element 11 and the second radiating element 21C are arranged such that the orientation of the open end A of the first radiating element 11 is opposite to the orientation of the side of the second radiating element 21C to which the frequency adjustment element 23 is connected, and the first radiating element 11 and the second radiating element 21C have a portion in parallel.

[0053] In the first antenna 10, which is an inverted F antenna, the open end A of the first radiating element 11 is the point (first point) where the electric field is maximum at the resonant frequency. However, in the second antenna 20C, which is a loop antenna, the electric field is maximum at the center (second point) of the second radiating element 21C at the resonant frequency. Therefore, in order to couple the second radiating element 21C to the first radiating element 11 by electric field coupling or magnetic field coupling, or by electric field coupling and magnetic field coupling, it is preferable that in the antenna device 100C, the open end A (first point) of the first radiating element 11 is coupled to a point other than the center (second point) of the second radiating element 21C, and the center (second point) of the second radiating element 21C is coupled to a point other than the open end A (first point) of the first radiating element 11.

[0054] <Antenna device characteristics> Fig. 12 is a diagram showing the reflection characteristics of the antenna device 100C in the third embodiment. In Fig. 12, the horizontal axis is frequency, the vertical axis is return loss, the solid line is the reflection characteristics of the first antenna 10, and the dashed line is the reflection characteristics of the second antenna 20C. The antenna device 100C has two operating frequency bands by coupling the first antenna 10 and the second antenna 20C, and the two operating frequency bands can be adjusted collectively by the frequency adjustment element 23 provided in the second antenna 20C.

[0055] Fig. 12(a) shows the reflection characteristic when switch 231 in frequency adjustment element 23 is connected to coil 232 having an inductance value of 5 nH shown in Fig. 2. The reflection characteristic shown in Fig. 12(a) has two operating frequency bands: a frequency band with a center frequency of about 3.2 GHz and a frequency band with a center frequency of about 4.7 GHz.

[0056] Fig. 12(b) shows the reflection characteristic when switch 231 in frequency adjustment element 23 is connected to coil 235 having an inductance value of 10 nH shown in Fig. 2. In the reflection characteristic shown in Fig. 12(b), the frequency band having a center frequency of about 3.2 GHz in Fig. 12(a) changes to a frequency band having a center frequency of about 2.9 GHz, and the frequency band having a center frequency of about 4.7 GHz changes to a frequency band having a center frequency of about 4.3 GHz.

[0057] <Modifications of the Antenna Device> 13 is a schematic diagram of an antenna device 100D according to a modification of the third embodiment. The antenna device 100D includes a first antenna 10D and a second antenna 20C. The first antenna 10D includes a first radiating element 11D and a first feed circuit 12. The second antenna 20C includes a second radiating element 21C, a second feed circuit 22, and a frequency adjustment element 23.

[0058] The configuration of the antenna device 100D will be described more specifically. The first antenna 10D and the second antenna 20C are loop antennas. The first antenna 10D, which is a loop antenna, has one end of a first radiating element 11D connected to a first feed circuit 12, and the other end of the first radiating element 11D grounded. The second antenna 20C, which is a loop antenna, has one end of a second radiating element 21C connected to a second feed circuit 22, and the other end of the second radiating element 21C connected to a frequency adjustment element 23. The frequency adjustment element 23 may be provided in the first antenna 10D, not in the second antenna 20C.

[0059] 13, in order for the first radiating element 11D and the second radiating element 21C to be electric field coupled or magnetic field coupled, the first antenna 10D of the loop antenna as viewed from the first feed circuit 12 and the second antenna 20C of the loop antenna as viewed from the second feed circuit 22 are arranged to face each other. Therefore, the first radiating element 11D and the second radiating element 21C are arranged such that the grounded side of the first radiating element 11D faces the side of the second radiating element 21C to which the frequency adjustment element 23 is connected, and the first radiating element 11D and the second radiating element 21C have a portion where they are parallel to each other.

[0060] The first antenna 10D, which is a loop antenna, has a maximum electric field at the center (first point) of the first radiating element 11D at the resonant frequency. Similarly, the second antenna 20C, which is a loop antenna, has a maximum electric field at the center (second point) of the second radiating element 21C at the resonant frequency. Therefore, in order to couple the second radiating element 21C to the first radiating element 11D by electric field coupling or magnetic field coupling, or by electric field coupling and magnetic field coupling, it is preferable that in the antenna device 100D, the center (first point) of the first radiating element 11D is coupled to a point other than the center (second point) of the second radiating element 21C, and the center (second point) of the second radiating element 21C is coupled to a point other than the center (first point) of the first radiating element 11D.

[0061] <Antenna device characteristics> Fig. 14 is a diagram showing the reflection characteristics of antenna device 100D in a variation of embodiment 3. In Fig. 14, the horizontal axis is frequency, the vertical axis is return loss, the solid line is the reflection characteristics of first antenna 10D, and the dashed line is the reflection characteristics of second antenna 20C. By coupling first antenna 10D and second antenna 20C, antenna device 100D has two operating frequency bands, and these two operating frequency bands can be adjusted by frequency adjustment element 23 provided in second antenna 20C.

[0062] Fig. 14(a) shows the reflection characteristic when switch 231 in frequency adjustment element 23 is connected to coil 232 having an inductance value of 5 nH shown in Fig. 2. The reflection characteristic shown in Fig. 14(a) has two operating frequency bands, a frequency band having a center frequency of about 3.7 GHz and a frequency band having a center frequency of about 5.3 GHz. Note that a coil (for example, a 5 nH coil) may be connected to first radiating element 11D to adjust the inductance value.

[0063] Fig. 14(b) shows the reflection characteristic when switch 231 in frequency adjustment element 23 is connected to coil 235 having an inductance value of 10 nH shown in Fig. 2. In the reflection characteristic shown in Fig. 14(b), the frequency band having a center frequency of about 3.7 GHz in Fig. 14(a) hardly changes, but the frequency band having a center frequency of about 5.3 GHz changes to a frequency band having a center frequency of about 4.6 GHz. Note that a coil (for example, a 5 nH coil) may be connected to first radiating element 11D to adjust the inductance value.

[0064] In the antenna device 100D, by coupling the first antenna 10D, which is a loop antenna, and the second antenna 20C, which is also a loop antenna, the antenna device 100D has two operating frequency bands, but the frequency adjustment element 23 makes it possible to mainly adjust one of the two operating frequency bands.

[0065] As described above, the first antenna including the first radiating element and the first feeding circuit may be any one of a monopole antenna, an inverted-F antenna, and a loop antenna, and the second antenna including the second radiating element and the second feeding circuit may be any one of a monopole antenna, an inverted-F antenna, and a loop antenna. Also, the frequency adjustment element may be connected to the first radiating element or the second radiating element.

[0066] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0067] 10, 10D first antenna, 11, 11D first radiating element, 12 first power supply circuit, 20, 20A, 20C second antenna, 21, 21A, 21C second radiating element, 22 second power supply circuit, 23 frequency adjustment element, 31 substrate, 32 communication circuit, 100, 100A to 100D antenna device, 200 mobile terminal.

Claims

1. A first radiating element; A second radiating element disposed at a position capable of at least one of electric field coupling and magnetic field coupling with respect to the first radiating element; A frequency adjustment element connected to the first radiating element or the second radiating element; a first feeding circuit that supplies a high frequency signal to the first radiating element; a second feeding circuit that supplies a high-frequency signal to the second radiating element; The arrangement of the first radiating element and the second radiating element is as follows: An antenna device, wherein the first radiating element is coupled to the second radiating element at a first point where the electric field is maximum at a resonant frequency, and the second radiating element is coupled to the first radiating element at a second point where the electric field is maximum at a resonant frequency.

2. The arrangement of the first radiating element and the second radiating element is as follows:

2. The antenna device according to claim 1, wherein the first point of the first radiating element is coupled to a point other than the second point of the second radiating element, and the second point of the second radiating element is coupled to a point other than the first point of the first radiating element.

3. a first antenna including the first radiating element and the first feeding circuit is any one of a monopole antenna, an inverted F antenna, and a loop antenna; 3. The antenna device according to claim 1, wherein a second antenna including the second radiating element and the second feeding circuit is any one of a monopole antenna, an inverted F antenna, and a loop antenna.

4. The arrangement of the first radiating element and the second radiating element is as follows:

4. The antenna device according to claim 3, wherein, when the first antenna and the second antenna are a monopole antenna or an inverted-F antenna, the first antenna and the second antenna are arranged such that a direction of an open end of the first radiating element and a direction of an open end of the second radiating element are opposite to each other.

5. 3. The antenna device according to claim 1, wherein the first radiating element and the second radiating element are arranged in parallel.

6. The antenna device according to claim 1 or 2; a semiconductor IC connected to the first power supply circuit and the second power supply circuit of the antenna device.

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