JP6791460B2 - Antenna device and electronic equipment - Google Patents

Description

The present invention relates to an electronic device having a communication function and an antenna device provided in the electronic device.

In recent years, with the widening of the communication band used for communication, the demand for a wide band antenna device for covering the communication band is increasing.

As one of the methods for widening the antenna device, a feeding radiation element connected to the feeding circuit and a non-feeding radiation element physically separated from the power feeding circuit are provided, and the non-feeding radiation element is used as the feeding radiation element. Conventionally, a method of imparting the characteristics of a non-feeding radiating element to the characteristics of a feeding radiating element by coupling with an electromagnetic field has been used (Patent Document 1).

International Publication No. 2012/153690

In the antenna device as described in Patent Document 1, a plurality of antennas used in a plurality of systems may be arranged in the same electronic device (housing). FIG. 22 is a circuit diagram of an antenna device showing an example. The antenna device 100 shown in FIG. 22 includes a first antenna 1 and a second antenna 2. The first antenna 1 includes a first radiating element 11 on the first antenna side and a second radiating element 12 on the first antenna side. Further, the second antenna 2 includes a second antenna side radiating element 29. A power feeding circuit 10 is connected to the first radiating element 11 on the first antenna side. The first radiating element 11 on the first antenna side and the second radiating element 12 on the first antenna side are coupled via a transformer circuit composed of the first coil L1 and the second coil L2. As in the example shown in FIG. 22, by providing the first antenna-side second radiating element 12 coupled to the first antenna-side first radiating element 11, the applicable frequency band can be widened.

In the example shown in FIG. 22, the first antenna side second radiating element 12 has the transformer circuit and the first antenna side second radiating element 12 at a resonance frequency determined by the first antenna side first radiating element 11 and the first coil L1 constituting the transformer circuit. By adding the resonance frequency determined by the second radiating element 12 on the first antenna side, the first antenna 1 can be widened in a certain applicable frequency region. However, in a plurality of communication bands formed by a plurality of resonance frequencies determined by the first radiation element 11 on the first antenna side and the first coil L1 constituting the transformer circuit, the communication band that can be widened is limited. Be done. This is because the resonance frequency added as described above is a value determined by the transformer circuit and the second radiating element 12 on the first antenna side.

Therefore, in order to widen the band of the first antenna 1 in yet another frequency region, for example, a configuration including a variable reactance circuit capable of switching the reactance between the second coil L2 and the ground is considered. This makes it possible to add the resonance frequency determined by the transformer circuit, the second radiating element 12 on the first antenna side, and the variable reactance circuit, resulting in a configuration as shown in FIG. 22 without the variable reactance circuit. In comparison, it becomes easier to widen the bandwidth in a plurality of communication bands.

On the other hand, when a plurality of antennas are arranged in the same housing as in the case of the first antenna 1 and the second antenna 2 in FIG. 22, the variable reactance circuit as described above of the first antenna 1 is further used. When trying to widen the bandwidth, isolation from other antennas such as the second antenna becomes a problem. That is, for example, depending on the reactance of the variable reactance circuit, one of the plurality of resonance frequencies of the first antenna 1 is in the communication band of the second antenna 2, and is in a state of matching or close to one resonance frequency ( A "substantial match") may occur. In such a state, the isolation between the first antenna 1 and the second antenna 2 may decrease, and the communication characteristics using the first antenna 1 and the second antenna 2 may deteriorate.

FIG. 23 is a diagram showing an example in which the above-mentioned inconvenience occurs. In FIG. 23, the vertical axis represents the dB notation (S11) of the reflectance coefficient of the antenna, and the horizontal axis represents the frequency. Further, in FIG. 23, A1 shows the frequency characteristic of the reflection coefficient of the first antenna 1, and A2 shows the frequency characteristic of the reflection coefficient of the second antenna 2. The first antenna 1 has resonance points at frequencies f11, f12, and f13, and the second antenna 2 has resonance points at frequencies f21 and f22. FIG. 23 shows that when the reactance of the variable reactance circuit of the first antenna is switched, the resonance frequency f13 of the first antenna 1 substantially coincides with the resonance frequency f22 of the second antenna 2 in a certain reactance. ing. In such a state, the isolation between the first antenna 1 and the second antenna 2 is lowered in the frequency region near the frequency f13 and the frequency f22, and the communication characteristics of the antenna device are deteriorated.

In this way, when the resonance frequency of one of the plurality of resonance frequencies of the first antenna 1 matches or is close to the resonance frequency of the second antenna 2 by switching the reactors of the variable reactorance circuit, the frequency band is used. , The resonance between the first antenna 1 and the second antenna 2 is lowered, and the communication characteristics using the first antenna 1 and the second antenna 2 are deteriorated.

Therefore, an object of the present invention is to provide an antenna device and an electronic device that facilitates widening the bandwidth in a plurality of communication bands over a wide frequency domain even in an electronic device provided with a plurality of antennas.

(1) The antenna device as an example of the present disclosure first includes a first antenna including a first antenna-side first radiation element and a first antenna-side second radiation element, and a second antenna including a second antenna-side radiation element. And a self-resonant circuit connected between the first antenna-side first radiation element and the feeding circuit connection portion and between the first antenna-side second radiation element and the ground. .. Then, the self-resonant circuit includes a first coil, a second coil electromagnetically coupled to the first coil, and a coupling element having a capacitance formed between the first coil and the second coil. The first coil is connected between the first antenna-side first radiation element and the power supply circuit connection portion, and the second coil is the first antenna-side second radiation element. The variable reactorance circuit is connected between the first coil and the feeding circuit connection portion, or between the second coil and the ground, and the self-resonant circuit is connected. It has a plurality of resonance frequencies that change depending on the reactivity of the variable reactorance circuit, and at least one of the resonance frequencies of the self-resonance circuit is a frequency within the communication band of the second antenna.

(2) The antenna device as an example of the present disclosure first includes a first antenna having a first antenna-side first radiating element having a feeding circuit connection portion, a first antenna having a first antenna-side second radiating element, and a second antenna side. A second antenna provided with a radiating element, and a self-resonant circuit connected between the first radiating element on the first antenna side and the ground and connected between the second radiating element on the first antenna side and the ground. , Equipped with. Then, the self-resonant circuit includes a first coil, a second coil electromagnetically coupled to the first coil, and a coupling element having a capacitance formed between the first coil and the second coil. The first coil is connected between the first radiation element on the first antenna side and the ground, and the second coil is composed of a variable resonant circuit connected between the second coil and the ground. Connected to the variable reactorance circuit, the resonance frequency of the self-resonant circuit changes depending on the reactivity of the variable reactorance circuit, and at least one of the resonance frequencies of the self-resonant circuit is a frequency within the communication band by the second antenna. It is characterized by being.

(3) As an example of the present disclosure, an electronic device includes the antenna device, a power supply circuit connected to the power supply circuit connection portion, and a control circuit for controlling the variable reactance circuit.

According to the present invention, the resonance frequency of the self-resonant circuit of the first antenna can be adjusted according to the switching of the reactance of the variable reactance circuit. Then, when the resonance frequency outside the communication band of the first antenna substantially matches any resonance frequency within the communication band of the second antenna, the self-resonance frequency can be adjusted to be close to the substantially matched resonance frequency. By having the structure, the isolation between the first antenna and the second antenna can be ensured, and the bandwidth can be easily widened in a plurality of communication bands over a wide frequency region.

FIG. 1 is a circuit diagram of the antenna device 101A according to the first embodiment. FIG. 2 is a circuit diagram of the antenna device 101B according to the first embodiment. FIG. 3 is a circuit diagram of the antenna device 101C according to the first embodiment. FIG. 4 is a diagram showing an example of a resonance current flowing through the self-resonant circuit SR in the first antenna 1. 5 (A) and 5 (B) are diagrams showing the frequency characteristics of the reflection coefficients of the first antenna 1 and the second antenna 2 of the antenna device 101A shown in FIG. FIG. 5C is a diagram showing the frequency characteristics of the radiation efficiency of the first antenna 1. 6 (A) and 6 (B) are diagrams showing the frequency characteristics of the reflection coefficients of the first antenna 1 and the second antenna 2 of the antenna device 101A shown in FIG. 7 (A), 7 (B), and 7 (C) are diagrams showing the frequency characteristics of the reflection coefficients of the first antenna 1 and the second antenna 2 of the antenna device 101C shown in FIG. FIG. 7D is a diagram showing the frequency characteristics of the radiation efficiency of the first antenna 1. 8 (A) and 8 (B) are diagrams showing a communication band of communication performed by the first antenna 1 and a reception band of one of the communication bands of communication performed by the second antenna 2. .. FIG. 9 is a diagram showing another configuration example of the first antenna 1 included in the antenna device of the first embodiment. 10 (A) and 10 (B) are diagrams showing another configuration example of the first antenna 1 included in the antenna device of the first embodiment. FIG. 11 is an external perspective view of the coupling element 3. FIG. 12 is a perspective view showing the internal structure of the coupling element 3. FIG. 13A is a cross-sectional view taken along the YZ plane passing through the center of the coupling element 3 in FIG. FIG. 13B is a cross-sectional view taken along the line XX passing through the center of the coupling element 3 in FIG. FIG. 14 is a plan view showing conductor patterns formed on the plurality of insulating substrates. FIG. 15 is a plan view showing an example of the structure of an electronic device including the first antenna 1 and the second antenna 2. FIG. 16 is a circuit diagram of the first antenna 1 and the second antenna 2 included in the antenna device 102 of the second embodiment. 17 (A) and 17 (B) are diagrams showing the frequency characteristics of the reflection coefficients of the first antenna 1 and the second antenna 2 of the second embodiment. FIG. 17C is a diagram showing a state when the resonance frequency fsr of the self-resonant circuit SR included in the first antenna 1 is set to be substantially equal to the resonance frequency f13p of the first antenna 1. 18 (A) and 18 (B) are circuit diagrams of the first antenna 1 included in the antenna device according to the third embodiment. 19 (A) and 19 (B) are circuit diagrams of the first antenna 1 included in another antenna device according to the third embodiment. 20 (A) and 20 (B) are circuit diagrams of the first antenna 1 included in the antenna device according to the fourth embodiment. FIG. 21 is a block diagram showing a configuration of a main part of the communication circuit connected to the first antenna 1 and a main part of the communication circuit connected to the second antenna 2. FIG. 22 is a circuit diagram of an antenna device in which the characteristics of the non-feeding radiation element are switched by adding reactance. In FIG. 23, a state occurs in which one resonance frequency of the plurality of resonance frequencies of the first antenna 1 matches one resonance frequency of the second antenna 2 according to the reactances of the variable reactance circuits 13 and 23 in FIG. 22. It is a figure which shows an example.

Hereinafter, a plurality of embodiments for carrying out the present invention will be shown with reference to the drawings with reference to some specific examples. The same reference numerals are given to the same parts in each figure. Although the embodiments are shown separately for convenience of explanation in consideration of the explanation of the main points or the ease of understanding, partial replacement or combination of the configurations shown in different embodiments is possible. In the second and subsequent embodiments, the description of matters common to those of the first embodiment will be omitted, and only the differences will be described. In particular, similar actions and effects with the same configuration will not be mentioned sequentially for each embodiment.

<< First Embodiment >>
FIG. 1 is a circuit diagram of the antenna device 101A according to the first embodiment, FIG. 2 is a circuit diagram of another antenna device 101B according to the first embodiment, and FIG. 3 is a circuit diagram according to the first embodiment. It is a circuit diagram of yet another antenna device 101C.

The antenna devices 101A, 101B, and 101C all include a first antenna 1 and a second antenna 2. Further, the configuration of the first antenna 1 in the antenna devices 101A, 101B, 101C is the same. The first antenna 1 includes a first radiating element 11 on the first antenna side and a second radiating element 12 on the first antenna side. The first radiating element 11 on the first antenna side and the second radiating element 12 on the first antenna side are, for example, monopole type radiating elements.

The first antenna 1 includes a self-resonant circuit SR connected between the first antenna-side first radiation element 11 and the feeding circuit connection portion, and between the first antenna-side second radiation element 12 and the ground.

The self-resonant circuit SR is composed of a coupling element 3 and a variable reactance circuit 13. The coupling element 3 is integrally formed with the first coil L1, the second coil L2 electromagnetically coupled to the first coil L1, and the capacitance C formed between the first coil L1 and the second coil L2. It is a chip type element. The coupling element 3 is not limited to the one integrally formed by the chip type element, and for example, the capacitance C and the first coil L1 and the second coil L2 may be formed separately.

The coupling element 3 includes a first radiation element connection terminal PA, a second radiation element connection terminal PS, a power supply circuit connection terminal PF, and a ground connection terminal (connection terminal of the variable reactance circuit 13) PG. The first coil L1 is connected between the first radiating element 11 on the first antenna side and the feeding circuit connection portion. That is, the first coil L1 is connected between the first radiating element 11 on the first antenna side and the feeding circuit 10.

The variable reactance circuit 13 is connected between the second coil L2 and the ground, and the second coil L2 is connected between the second radiation element 12 on the first antenna side and the variable reactance circuit 13. The variable reactance circuit 13 may be composed of a plurality of reactance elements 14 and a switch 15 for selecting them, or may be composed of a variable capacitor, a variable inductor, or the like, as will be described later.

The second antenna 2 shown in FIG. 1 includes a second antenna side radiating element 29. The second antenna side radiating element 29 is, for example, a monopole type radiating element. A feeding circuit 20 is connected to the radiating element 29 on the second antenna side.

The second antenna 2 shown in FIG. 2 includes a first radiating element 21 on the second antenna side and a second radiating element 22 on the second antenna side. The first radiating element 21 on the second antenna side and the second radiating element 22 on the second antenna side are, for example, monopole type radiating elements. A power feeding circuit 20 is connected to the first radiating element 21 on the second antenna side. The first radiating element 21 on the second antenna side and the second radiating element 22 on the second antenna side are electromagnetically coupled. The first radiating element 21 on the second antenna side and the second radiating element 22 on the second antenna side may be electromagnetically coupled using a chip-type element such as the coupling element 3 included in the first antenna 1. ..

The second antenna 2 shown in FIG. 3 includes a first radiating element 21 on the second antenna side and a second radiating element 22 on the second antenna side. The first radiating element 21 on the second antenna side and the second radiating element 22 on the second antenna side are, for example, monopole type radiating elements. A power feeding circuit 20 is connected to the first radiating element 21 on the second antenna side. A variable reactance circuit 23 is provided between the second radiating element 22 on the second antenna side and the ground. The variable reactance circuit 23 is composed of a plurality of reactance elements 24 and a switch 25 for selecting them. The first radiating element 21 on the second antenna side and the second radiating element 22 on the second antenna side are electromagnetically coupled. The first radiating element 21 on the second antenna side and the second radiating element 22 on the second antenna side are electromagnetically coupled using a chip-type element such as the coupling element 3 like the first antenna 1. May be good.

In the antenna devices 101A, 101B, and 101C, the first antenna 1 and the second antenna 2 are antennas used in different communication systems, or antennas used in the same communication system. As an example of different communication systems, the first antenna 1 is an LTE communication antenna, and the second antenna 2 is an antenna for WiFi, GPS, Bluetooth (registered trademark), or the like. Further, as an example of the same communication system, for example, the first antenna 1 is the main antenna of the diversity antenna, and the second antenna 2 is the sub-antenna. Alternatively, the first antenna 1 and the second antenna 2 are antennas for performing communication by, for example, a MIMO (Multi-Input Multi-Output) method.

FIG. 4 is a diagram showing an example of a resonance current flowing through the self-resonant circuit SR in the first antenna 1. The self-resonant circuit SR is composed of the first coil L1 of the coupling element 3, the capacitance C of the coupling element 3, the second coil L2 of the coupling element 3, and the variable reactance circuit 13, and the resonance current RC flows through this path. Therefore, the resonance frequency of the self-resonant circuit SR changes depending on the reactance of the variable reactance circuit 13. In other words, the resonance frequency of the self-resonant circuit SR can be arbitrarily changed by setting the reactance of the variable reactance circuit 13. At least one of the resonance frequencies of the self-resonant circuit SR is a frequency within the communication band of the second antenna 2.

In the present invention, the "communication band by the second antenna" refers to the case where the frequency band (communication frequency band) handled by the communication system using the second antenna 2 (matched by the second antenna 2) is one in the embodiment. , In the frequency range from the lower limit frequency to the upper limit frequency of the frequency band, and when there are a plurality of frequency bands (communication frequency bands) handled by the communication system using the second antenna 2 (matched by the second antenna 2), It is a frequency region from the lower limit frequency to the upper limit frequency in the entire frequency band (communication frequency band). Further, in the present embodiment, the "frequency within the communication band by the second antenna" is a frequency included in the above frequency domain.

In the present embodiment, due to the presence of the variable reactance circuit 13, such a self-resonant circuit SR is maintained while maintaining the electromagnetic field coupling between the first antenna-side first radiation element 11 and the first antenna-side second radiation element 12. Resonance frequency can be set.

5 (A) and 5 (B) are diagrams showing the frequency characteristics of the reflection coefficients of the first antenna 1 and the second antenna 2 shown in FIG. 1, and the vertical axis is the reflection coefficient (S11) of the antenna. , The horizontal axis is the frequency. Further, FIG. 5C is a diagram showing the frequency characteristics of the radiation efficiency of the first antenna 1, where the vertical axis represents the radiation efficiency and the horizontal axis represents the frequency.

The characteristics of the antenna device 101B shown in FIG. 2 are almost the same as those shown in FIG. 1 except that the resonance point of the second radiating element 22 on the second antenna side is added.

In FIGS. 5 (A) and 5 (B), A1 shows the frequency characteristic of the reflection coefficient of the first antenna 1, and A2 shows the frequency characteristic of the reflection coefficient of the second antenna 2. In the state shown in FIG. 5A, the first antenna 1 has resonance points at frequencies f11, f12, and f13, respectively, and the second antenna 2 has resonance points at frequencies f21 and f22, respectively. For example, the frequency f11 is the basic resonance frequency of the first radiating element 11 on the first antenna side, and the frequency f13 is the third-order resonance frequency of the first radiating element 11 on the first antenna side. Further, the frequency f12 is a resonance frequency by the second radiation element 12 on the first antenna side, the coupling element 3, and the variable reactance circuit 13. In other words, the resonance frequency given to the first antenna-side first radiation element 11 by the first antenna-side second radiation element 12 and the self-resonant circuit is f12. Similarly, for example, the frequency f21 is the basic resonance frequency of the radiation element 29 of the second antenna 2, and the frequency f22 is the third-order resonance frequency of the radiation element 29. The frequencies f11 and f12 are resonance points within the communication band of the first antenna 1, and the frequencies f13 are outside the communication band of the first antenna 1 and are one of the resonance points not used by the first antenna 1. is there.

In the example shown in FIG. 5A, when the third-order resonance frequency f13 of the resonance frequencies of the first radiation element 11 on the first antenna side substantially matches the resonance frequency f22 used by one of the second antennas 2. Indicates the state. That is, since the frequency f13 is a resonance point due to the harmonics of the frequency f11, it is in a state where it unintentionally overlaps with the resonance frequency f22 used in the second antenna. In the present invention, in such a case, the above-mentioned state can be avoided by switching the reactance of the variable reactance circuit.

6 (A) and 6 (B) are diagrams showing the frequency characteristics of the reflection coefficients of the first antenna 1 and the second antenna 2 of the antenna device 101A shown in FIG. FIG. 6A shows an example of “substantially matching a certain resonance frequency” described above. FIG. 6B is an example of a state in which the situation of “substantially matching a certain resonance frequency” is avoided (a state in which the frequency is different from a certain resonance frequency). For example, as shown in FIG. 6A, the region A in which the reflection coefficient of the first antenna 1 near the resonance point A of the first antenna is -6 dB or less and the vicinity of the resonance point B of the second antenna 2 When the regions B in which the reflection coefficient of the antenna is −6 dB or less overlap, the resonance point A of the first antenna 1 and the resonance point B of the second antenna 2 substantially coincide with each other. Also, since the reflectance coefficient of -6.021 corresponds to 3.0 in VSWR (voltage standing wave ratio), VSWR (voltage standing wave ratio) is used instead of the index that the reflection coefficient of the antenna is -6 dB or less. An index of 3 or less may be used.

FIG. 5B shows a state when the resonance frequency fsr of the self-resonant circuit SR included in the first antenna 1 is set to be substantially equal to the resonance frequency f13 of the first antenna 1 as described above. By doing so, the self-resonant circuit SR can resonate at the resonance frequency f13 of the first antenna 1. Then, as shown in FIG. 5B, the reflectance coefficient A1 of the first antenna 1 becomes higher at the frequency f13. That is, the self-resonant circuit SR self-resonates at this frequency f13 (fsr) to form a closed current path between the two grounds and the self-resonant circuit, so that the first antenna side first radiation element 11 and the first 1 The current flowing into the second radiating element 12 on the antenna side is suppressed. As a result, the radiation of the first radiation element 11 on the first antenna side and the second radiation element 12 on the first antenna side is suppressed. Therefore, as shown in FIG. 5C, the radiation efficiency of the first antenna 1 decreases at the frequency f13. As a result, isolation between the first antenna 1 and the second antenna 2 can be ensured.

Since the resonance frequency of the self-resonant circuit SR shown in FIG. 1 can be switched by selecting the reactance element 14 of the variable reactance circuit 13, the resonance frequency f12 of the first antenna 1 accompanies the switching of the reactance of the variable reactance circuit 13. (The resonance frequency of the second radiation element 12, the coupling element 3, and the variable reactance circuit 13 on the first antenna side) are also displaced. As a result, as shown in FIG. 5C, the radiation efficiency is increased between the resonance frequencies f11 and f12 of the first antenna 1.

7 (A), 7 (B), and 7 (C) are diagrams showing the frequency characteristics of the reflection coefficients of the first antenna 1 and the second antenna 2 shown in FIG. 3, and the vertical axis is the antenna. The reflectance coefficient and the horizontal axis are frequencies. Further, FIG. 7D is a diagram showing the frequency characteristics of the radiation efficiency of the first antenna 1, where the vertical axis represents the radiation efficiency and the horizontal axis represents the frequency.

In FIGS. 7 (A), 7 (B), and 7 (C), A1 shows the frequency characteristic of the reflection coefficient of the first antenna 1, and A2 shows the frequency characteristic of the reflection coefficient of the second antenna 2. As described above, the first antenna 1 has resonance points at frequencies f11, f12, and f13, respectively. The second antenna 2 has resonance points at frequencies f21, f22, and f23, respectively. For example, the frequency f21 is the basic resonance frequency of the first radiation element 21 on the second antenna side, and the frequency f23 is the third resonance frequency of the first radiation element 21 on the second antenna side. Further, the frequency f22 is a resonance frequency by the second radiating element 22 on the second antenna side and the variable reactance circuit 23. The frequencies f11 and f12 are resonance points within the communication band of the first antenna 1, and the frequencies f13 are outside the communication band of the first antenna 1 and are one of the resonance points not used by the first antenna 1. is there.

In the example shown in FIG. 7B, the resonance frequency f22 used in the second antenna by the second antenna side second radiating element 22 and the variable reactance circuit 23 depends on the reactance selection of the variable reactance circuit 23. The state when it substantially matches f13 is shown.

FIG. 7C shows a state when the resonance frequency fsr of the self-resonant circuit SR included in the first antenna 1 is set to be substantially equal to the resonance frequency f13 of the first antenna 1. In this way, when the self-resonant circuit SR resonates at the resonance frequency f13 of the first antenna 1, the reflection coefficient A1 of the first antenna 1 becomes higher at the frequency f13, as shown in FIG. 7C. That is, the self-resonant circuit SR self-resonates at this frequency f13 (fsr), and the first antenna-side first radiating element 11 and the first antenna-side second radiating element 12 do not radiate at the frequency f13. Therefore, as shown in FIG. 7D, the radiation efficiency of the first antenna 1 decreases at the frequency f13. As a result, isolation between the first antenna 1 and the second antenna 2 can be ensured.

Since the resonance frequency of the self-resonant circuit SR shown in FIG. 1 can be switched by selecting the reactance element 14 of the variable reactance circuit 13, the resonance frequency f12 of the first antenna 1 accompanies the switching of the reactance of the variable reactance circuit 13. (The resonance frequency of the second radiation element 12, the coupling element 3, and the variable reactance circuit 13 on the first antenna side) are also displaced. As a result, as shown in FIG. 7D, the radiation efficiency is increased between the resonance frequencies f11 and f12 of the first antenna 1.

FIG. 5A shows an example in which the resonance frequency of the radiating element 29 of the second antenna 2 substantially matches one resonance frequency of the first antenna 1, and FIG. 7B shows the second radiation on the second antenna side. An example is shown in which the resonance frequency of the element 22 and the variable reactorance circuit 23 substantially matches the resonance frequency of one of the first antennas 1, but in any case, at least one of the resonance frequencies of the self-resonance circuit SR is the second antenna. If the frequency is within the communication band of 2, the radiation efficiency of the first antenna 1 can be reduced at the resonance frequency of the specific first antenna 1, thereby between the first antenna 1 and the second antenna 2. Isolation can be secured.

8 (A) and 8 (B) are diagrams showing a communication band of communication performed by the first antenna 1 and a reception band of one of the communication bands of communication performed by the second antenna 2. .. In FIGS. 8A and 8B, A1 shows the frequency characteristic of the reflection coefficient of the first antenna 1, and A2 shows the frequency characteristic of a part of the reflection coefficient of the second antenna 2, respectively. The first antenna 1 has resonance points at frequencies fa, fb, and fc, respectively. The band including the resonance point of the frequency fa is used for communication in the communication frequency bands FB1 and FB2, and the band including the resonance point of the frequency fb is used for communication in the communication frequency band FB3, and the band including the resonance point of the frequency fc. Is used for communication in the communication frequency band FB4.

In the example shown in FIG. 8A, the resonance frequency f1 of the second antenna 2 is used as the reception band (Rx) in the predetermined communication system, and this frequency f1 is the communication frequency band in the communication system using the first antenna 1. It matches the transmission band (Tx) of FB2. The reception band and transmission band shown in FIG. 8 (A) are shown by simplifying a part of the band of the 3GPP (Third Generation Partnership Project) standard, and 1 GHz or more for the frequency band lower than 1 GHz. It shows that a plurality of reception bands and transmission bands are denser than the frequency band of. In this case, the communication band is from 700 MHz, which is the lower limit frequency (LLF), to 2700 MHz, which is the upper limit frequency (ULF), in the communication frequency band shown in FIG. 8 (A). Further, as shown in FIG. 8A, each reception band and transmission band have a lower limit frequency and an upper limit frequency, and have a certain width. One communication frequency band is composed of one transmission band and one reception band, and is a frequency region that is equal to or higher than the lower limit frequency of the transmission band and lower than or lower than the upper limit frequency of the reception band.

In such a state, the reactance of the variable reactance circuit 13 is determined so that the resonance frequency of the self-resonant circuit SR of the first antenna 1 is close to or equal to the resonance frequency f1 of the second antenna 2. As a result, as shown in FIG. 8B, the reflection coefficient of the first antenna 1 becomes higher at the frequency f1, and the isolation between the first antenna 1 and the second antenna 2 at the frequency f1 is ensured. Further, as a result, the resonance point of the second radiating element 12 on the first antenna side is added to the frequency region lower than Tx of the frequency f1, and for example, Rx of the frequency fa is widened. Further, as shown in FIG. 8A, many bands may be densely packed in a low frequency region. However, even in such a case, the radiation of the first antenna can be suppressed by focusing on a specific band. For example, the radiation of the first antenna 1 at Tx is suppressed with almost no effect on Rx included in the communication frequency band FB2 in FIG. 8A.

FIG. 9 is a diagram showing another configuration example of the first antenna 1 included in the antenna device of the present embodiment. The configuration of the variable reactance circuit 13 is different from that of the first antenna 1 shown in FIG. In the example of FIG. 1, the reactance element 14 is provided on the ground side of the switch 15, but as shown in FIG. 9, the switch 15 may be provided on the ground side of the reactance element 14.

It should be noted that the first coil L1 and the second coil L2 having the same winding axis of the coupling element 3 allow the first antenna side first radiation element 11 and the first antenna side second radiation element 12 to have a small space. Since the electromagnetic field coupling can be performed relatively strongly, an antenna device in which the resonance by the first antenna side second radiating element 12, the coupling element 3 and the variable reactance circuit 13 is widened can be obtained.

10 (A) and 10 (B) are views showing another configuration example of the first antenna 1 included in the antenna device of the present embodiment. The configuration of the variable reactance circuit 13 is different from that of the first antenna 1 shown in FIG. In the example shown in FIG. 10A, the variable reactance circuit 13 is composed of a variable inductor whose inductance changes depending on a control signal and a control voltage. In the example shown in FIG. 10B, the variable reactance circuit 13 is composed of a variable capacitor whose capacitance changes depending on a control signal and a control voltage. The variable reactance circuit 13 may be a combination of a variable capacitor and a variable inductor.

As described above, the variable reactance circuit 13 may be composed of a variable capacitor, a variable inductor, or the like.

FIG. 11 is an external perspective view of the coupling element 3. FIG. 12 is a perspective view showing the internal structure of the coupling element 3. A first radiation element connection terminal PA, a second radiation element connection terminal PS, a power supply circuit connection terminal PF, and a ground connection terminal (connection terminal of the variable reactance circuit 13) PG are formed on the outer surface of the coupling element 3.

FIG. 13A is a cross-sectional view taken along the YZ plane passing through the center of the coupling element 3 in FIG. FIG. 13B is a cross-sectional view taken along the line XX passing through the center of the coupling element 3 in FIG.

The main part of the coupling element 3 is a laminate of a plurality of insulating base materials in which a conductor pattern is formed on a predetermined insulating base material. The first coil L1, the second coil L2, and the capacitance C are formed by conductor patterns formed on the plurality of insulating substrates.

FIG. 14 is a plan view showing conductor patterns formed on the plurality of insulating substrates. Conductor patterns CP1, CP2, CP3, and CP4 for forming capacitance C are formed in the four layers above the bottom layer. Conductor patterns L11, L12, L13, L14, and L15 for forming the first coil L1 are formed on the five layers above it. Further, conductor patterns L21, L22, L23, L24, and L25 for forming the second coil L2 are formed on the five layers above it. When the conductor pattern L15 and the conductor pattern L21 face each other, the first coil L1 and the second coil L2 are electromagnetically coupled.

The structure of the coupling element 3 is not limited to that shown in FIGS. 11 to 14. For example, as the capacitance component of the capacitance C, the parasitic capacitance component generated by the first coil L1 and the second coil L2 facing each other may be used. That is, the capacitance C may be composed of a parasitic capacitance component generated between the first coil L1 and the second coil L2, or may be composed of a combined capacitance of this parasitic capacitance component and the capacitance of other capacitors. It may be.

FIG. 15 is a plan view showing an example of the structure of the electronic device 201 including the first antenna 1 and the second antenna 2. A dielectric chip antenna in which the first radiating element 11 on the first antenna side and the second radiating element 12 on the first antenna side are formed is mounted in one region of the circuit board 4 where the ground pattern is not formed. Similarly, a dielectric chip antenna in which the first radiating element 21 on the second antenna side and the second radiating element 22 on the second antenna side are formed is mounted in the other region where the ground pattern is not formed. The coupling element 3 shown in FIG. 1 is mounted on the circuit board 4. Further, the circuit board 4 is provided with the power feeding circuits 10 and 20 and the variable reactance circuits 13 and 23 shown in FIG. The circuit board 4 is housed in the housing of the electronic device 201.

In the example shown above, the resonance frequency of the self-resonant circuit SR of the first antenna 1 is approximated or equal to the resonance frequency f1 of the second antenna 2, so that the first antenna 1 and the second antenna 2 at the frequency f1 Isolation was ensured, but for example, if the resonance frequency of the self-resonant circuit SR shown in FIG. 1 is set to a predetermined unnecessary frequency in the band of the transmission signal transmitted from the feeding circuit 10. It is also possible to suppress the transmission of the signal of the unnecessary frequency from the first antenna 1.

<< Second Embodiment >>
In the second embodiment, an example of an antenna device provided with a variable reactance circuit on the power feeding radiation element side will be shown.

FIG. 16 is a circuit diagram of the first antenna 1 and the second antenna 2 included in the antenna device 102 of the second embodiment. The first antenna 1 is the same as the first antenna 1 shown in the first embodiment, between the first antenna side first radiation element 11 and the feeding circuit connection portion, and the first antenna side second radiation element 12 It is provided with a self-resonant circuit SR connected between the ground and the ground. However, the variable reactance circuit 13 is connected between the first coil L1 of the coupling element 3 and the feeding circuit 10 to which the first radiating element 11 on the first antenna side is connected. Further, the second coil L2 of the coupling element 3 to which the second radiating element 12 on the first antenna side is connected is connected to the ground. The configuration of the second antenna 2 is the same as that shown in the first embodiment.

17 (A) and 17 (B) are diagrams showing the frequency characteristics of the reflection coefficients of the first antenna 1 and the second antenna 2 of the present embodiment, the vertical axis is the reflection coefficient of the antenna, and the horizontal axis is the frequency. Is.

In FIGS. 17 (A) and 17 (B), A1 shows the frequency characteristic of the reflection coefficient of the first antenna 1, and A2 shows the frequency characteristic of the reflection coefficient of the second antenna 2. The first antenna 1 has resonance points at frequencies f11, f12, and f13, respectively. For example, the frequency f11 is the basic resonance frequency of the first antenna-side first radiating element 11 including the variable reactance circuit 13, and the frequency f13 is the third order of the first antenna-side first radiating element 11 including the variable reactance circuit 13. Resonance frequency. Further, the frequency f12 is a resonance frequency by the second radiating element 12 on the first antenna side. The second antenna 2 has a resonance point at a frequency f22. This frequency f22 is the resonance frequency of the second radiating element 22 on the second antenna side and the variable reactance circuit 23.

FIG. 17 (B) shows that the reactance frequency of the first antenna 1 is shifted from the resonance frequency f11 to f11p from the state shown in FIG. 17 (A) according to the selection of the reactance of the variable reactance circuit 13 of the first antenna 1. The state when f13 is displaced to f13p and the reactance frequency f13p substantially coincides with the reactance frequency f22 of the second antenna 2 is shown. In this case as well, the resonance point of the frequency f13 due to the harmonic of the fundamental wave of the first radiating element is displaced together with the frequency f11, so that the resonance frequency f22 used in the second antenna 2 is unintentionally overlapped. Is.

FIG. 17C shows a state when the resonance frequency fsr of the self-resonant circuit SR included in the first antenna 1 is set to be substantially equal to the resonance frequency f13p of the first antenna 1. In this way, when the self-resonant circuit SR resonates at the resonance frequency f13p of the first antenna 1, the reflection coefficient A1 of the first antenna 1 becomes higher at the frequency f13p, as shown in FIG. 17C. That is, the self-resonant circuit SR self-resonates at this frequency f13p (fsr), and the radiation of the first antenna-side first radiation element 11 and the first antenna-side second radiation element 12 is suppressed.

<< Third Embodiment >>
In the third embodiment, the first antenna in which the configurations of the first radiating element and the second radiating element in the first antenna are different from the example shown in the first embodiment is shown.

18 (A) and 18 (B) are circuit diagrams of the first antenna 1 included in the antenna device according to the third embodiment. The first antenna-side first radiating element 11 shown in FIGS. 18A and 18B is a loop-type radiating element, and the first antenna-side second radiating element 12 is a monopole-type radiating element.

The configuration of the self-resonant circuit SR connected to the first antenna-side first radiation element 11 and the first antenna-side second radiation element 12 shown in FIG. 18A is the same as that shown in FIG. Further, the configuration of the self-resonant circuit SR connected to the first antenna-side first radiation element 11 and the first antenna-side second radiation element 12 shown in FIG. 18B is the same as that shown in FIG.

19 (A) and 19 (B) are circuit diagrams of the first antenna 1 included in another antenna device according to the third embodiment. The first antenna-side first radiating element 11 shown in FIGS. 19A and 19B is a loop-type radiating element, and the first antenna-side second radiating element 12 is a monopole-type radiating element. In the examples shown in FIGS. 19A and 19B, the power feeding circuit 10 is connected between one end of the first radiating element 11 on the first antenna side and the ground. Other configurations are the same as the examples shown in FIGS. 18 (A) and 18 (B).

According to the configurations shown in FIGS. 18 (A) and 19 (A), the effects are exhibited in the same manner as the antenna device shown in the first embodiment. Further, according to the configurations shown in FIGS. 18 (B) and 19 (B), the effects are exhibited in the same manner as the antenna device shown in the first embodiment.

<< Fourth Embodiment >>
The fourth embodiment shows an antenna device including a PIFA (planar inverted-F antenna).

20 (A) and 20 (B) are circuit diagrams of the first antenna 1 included in the antenna device according to the fourth embodiment. In the first antenna 1 shown in FIGS. 20A and 20B, a feeding circuit 10 is connected to a predetermined feeding point of the first radiating element 11 on the first antenna side, and a predetermined grounding point (PIFA). The first coil L1 of the coupling element 3 is connected between the position of the short pin) and the ground. A variable reactance circuit 13 is connected between the second coil L2 of the coupling element 3 and the ground.

In this way, the ground side of the first coil L1 of the coupling element 3 connected to the grounding point of the first radiating element 11 on the first antenna side becomes the maximum point of the current flowing through the first radiating element 11 on the first antenna side.

As shown in FIGS. 20A and 20B, the first coil L1 of the coupling element 3 may be provided between the grounding point of the first radiating element 11 on the first antenna side and the ground. , The first coil L1 of the coupling element 3 is inserted between a predetermined feeding point of the first radiating element 11 on the first antenna side and the feeding circuit 10, and the grounding point of the first radiating element 11 on the first antenna side is grounded. You may connect directly.

As shown in this embodiment, the first radiating element 11 on the first antenna side may be a PIFA. Further, the first radiating element 11 on the first antenna side is not limited to PIFA, and may be a general inverted-F antenna.

<< Fifth Embodiment >>
In the fifth embodiment, a configuration example of a communication circuit included in the electronic device according to the present invention will be shown.

FIG. 21 is a block diagram showing a configuration of a main part of the communication circuit connected to the first antenna 1 and a main part of the communication circuit connected to the second antenna 2. The communication circuit connected to the first antenna 1 includes an RFIC, a power amplifier RFPA, switches SW1 and SW2, a duplexer DUP, a control circuit CNT, and a low noise amplifier LNA. The same applies to the communication circuit connected to the second antenna 2.

The power amplifier RFPA amplifies the transmission signal output from the RFIC. The switches SW1 and SW2 select one of a plurality of duplexer DUPs. The control circuit CNT selects switches SW1 and SW2, respectively. The control circuit CNT of the communication circuit connected to the first antenna 1 selects the switch (switch 15 in FIG. 1) of the variable reactance circuit 13 of the first antenna 1. Further, the control circuit CNT of the communication circuit connected to the second antenna 2 selects the switch (switch 25 in FIG. 1) of the variable reactance circuit 23 of the second antenna 2.

The control circuit CNT of the communication circuit connected to the first antenna 1 controls the resonance point of the first antenna 1 by selecting the switch (switch 15 in FIG. 1) of the variable reactance circuit 13 of the first antenna 1. Also, the resonance frequency of the self-resonant circuit SR is controlled.

The control circuit CNT of the communication circuit connected to the second antenna 2 controls the resonance point of the second antenna 2 by selecting the switch (switch 25 in FIG. 1) of the variable reactance circuit 23 of the second antenna 2. To do.

Finally, the description of the embodiments described above is exemplary in all respects and not restrictive. Modifications and changes can be made as appropriate for those skilled in the art. The scope of the present invention is indicated by the scope of claims, not by the above-described embodiment. Further, the scope of the present invention includes modifications from the embodiment within the scope of the claims and within the scope of the claims.

For example, in each of the above embodiments, an antenna device including two antennas (first antenna 1 and second antenna 2) has been illustrated, but the same applies to the case where three or more antennas are provided.

C ... Capacitive CNT ... Control circuit CP1, CP2, CP3, CP4 ... Capacitive forming conductor pattern DUP ... Duplexer L1 ... First coil L11, L12, L13, L14, L15 ... First coil forming conductor pattern L2 ... Second coil L21, L22, L23, L24, L25 ... 2nd coil forming conductor pattern LNA ... Low noise amplifier PF ... Feeding circuit connection terminal PS ... 2nd radiation element connection terminal RC ... Resonant current RFPA ... Power amplifier SR ... Self-resonant circuit SW1, SW2 ... Switch PA ... 1st radiation element connection terminal 1 ... 1st antenna 2 ... 2nd antenna 3 ... Coupling element 4 ... Circuit boards 10, 20 ... Power supply circuit 11 ... 1st antenna side 1st radiation element 12 ... 1st antenna Side second radiating elements 13, 23 ... Variable reactors circuit 14 ... Reacting element 15 ... Switch 20 ... Feeding circuit 21 ... Second antenna side first radiating element 22 ... Second antenna side second radiating element 24 ... Reacting element 25 ... Switch 29 ... Second antenna side radiating element 100, 101A, 101B, 101C, 102 ... Antenna device 201 ... Electronic device

Claims (10)

A first antenna including a first radiating element on the first antenna side and a second radiating element on the first antenna side,
A second antenna having a radiating element on the second antenna side and
A self-resonant circuit that is connected between the first antenna-side first radiating element and the power feeding circuit connection portion and is connected between the first antenna-side second radiating element and the ground is provided.
The self-resonant circuit is variable with a first coil, a second coil electromagnetically coupled to the first coil, and a coupling element having a capacitance formed between the first coil and the second coil. Consists of a reactance circuit
The first coil is connected between the first radiating element on the first antenna side and the feeding circuit connection portion.
The second coil is connected between the second radiating element on the first antenna side and the ground.
The variable reactance circuit is connected between the first coil and the feeding circuit connection portion, or between the second coil and the ground.
The self-resonant circuit has a plurality of resonance frequencies that change depending on the reactance of the variable reactance circuit.
At least one of the resonance frequencies of the self-resonant circuit is a frequency within the communication band of the second antenna.
An antenna device characterized by that. A first antenna having a first antenna-side first radiating element having a feeding circuit connection portion and a first antenna having a first antenna-side second radiating element,
A second antenna having a radiating element on the second antenna side and
A self-resonant circuit connected between the first antenna-side first radiating element and the ground and connected between the first antenna-side second radiating element and the ground is provided.
The self-resonant circuit includes a coupling element having a first coil, a second coil electromagnetically coupled to the first coil, and a capacitance formed between the first coil and the second coil. It consists of a variable reactance circuit connected between the second coil and the ground.
The first coil is connected between the first radiating element on the first antenna side and the ground.
The second coil is connected to the variable reactance circuit and
The resonance frequency of the self-resonant circuit changes depending on the reactance of the variable reactance circuit.
At least one of the resonance frequencies of the self-resonant circuit is a frequency within the communication band of the second antenna.
An antenna device characterized by that. The antenna device according to claim 1 or 2, wherein the variable reactance circuit includes a plurality of reactance elements and a switch for selecting a connection between the plurality of reactance elements. The antenna device according to claim 1 or 2, wherein the variable reactance circuit is composed of at least one variable inductor or at least one variable capacitor. The antenna device according to any one of claims 1 to 4, wherein the second antenna side radiating element has two or more resonance frequencies within the communication band of the second antenna. The resonance frequency given to the first antenna-side first radiation element by the first antenna-side second radiation element and the self-resonance circuit changes depending on the reactance of the variable reactance circuit, and the first antenna-side first radiation element is changed. The antenna device according to any one of claims 1 to 5, wherein at least one of the resonance frequencies applied to the radiating element is within the communication band by the first antenna. The resonance frequency given to the first antenna-side first radiating element by the first antenna-side second radiating element and the self-resonant circuit changes depending on the reactor of the variable reactorance circuit, and the first antenna-side first radiating element is changed. One of claims 1 to 5, wherein at least one of the resonance frequencies given to the radiating element is different from all the resonance frequencies of the second antenna within the communication band of the second antenna. The antenna device described. The second antenna includes a variable reactance circuit connected to the radiating element on the second antenna side.
The antenna device according to any one of claims 1 to 7, wherein the variable reactance circuit connected to the second antenna-side radiating element includes a switch and a plurality of reactance elements. The second antenna includes a variable reactance circuit connected to the radiating element on the second antenna side.
The antenna device according to any one of claims 1 to 7, wherein the variable reactance circuit connected to the second antenna-side radiating element is composed of at least one variable inductor or variable capacitor. An electronic device comprising the antenna device according to any one of claims 1 to 9, a feeding circuit connected to the feeding circuit connection portion, and a control circuit for controlling the variable reactance circuit.

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