JP6724429B2 - Antenna device and electronic device - Google Patents

Description

The present invention relates to an antenna device that is also used in a communication system that uses communication signals having different frequency bands, and an electronic device that includes the antenna device.

With the recent sophistication of communication devices, for example, mobile phone terminals and so-called smartphones need not only an antenna for communication with a base station but also near field communication such as NFC (Near field communication). ..

For example, Patent Document 1 discloses a small antenna device that is commonly used by a plurality of systems having different frequency bands. This antenna device includes a radiating element, a power feeding circuit of the first frequency band connected to the radiating element, a ground conductor arranged to face the radiating element, and a reactance element connecting the radiating element and the ground conductor. The power feeding coil and a power feeding circuit for the second frequency band connected to the power feeding coil. The radiating element functions, for example, as a field emission antenna for communication with a base station in the first frequency band and as a part of the NFC antenna in the second frequency band.

International Publication 2014/098024

For example, a radiating element that acts as an electromagnetic radiation antenna (far-field transmission antenna) in the first frequency band, which is the UHF/SHF band, and a magnetic field radiation antenna (near the magnetic field coupling type, in the second frequency band, which is the HF band, for example) In order to be used also as a part of the field transmission antenna), it is important to achieve impedance matching so that power can be sufficiently fed from the feeding circuit in the second frequency band to the magnetic field radiation antenna. Therefore, it is effective to provide a winding transformer that performs impedance conversion and strongly couples the feeding circuit in the second frequency band and the magnetic field radiation antenna.

Alternatively, in the NFC power supply circuit that uses the second frequency band, the output section that connects the coil antenna is often configured by a differential circuit (balanced circuit) in order to increase the practical output. On the other hand, many radiating elements that utilize the above-mentioned first frequency band, for example, for communication with a base station, are modifications of a monopole antenna, and are equivalently unbalanced circuits. Therefore, when the NFC power supply circuit is connected to the radiating element, there arises a problem that an unnecessary leak current flows between the balanced circuit and the unbalanced circuit. Therefore, it is effective to provide a balanced/unbalanced conversion circuit (balun) and electrically connect the radiating element and the NFC power supply circuit through the balanced/unbalanced conversion circuit.

However, since the frequencies of the first frequency band and the second frequency band are significantly different, the loss required for the transformer is different depending on whether the antenna device acts as an electromagnetic radiation antenna or a magnetic field radiation antenna. The characteristics of are very different. Therefore, when the dual-purpose radiating element is used as an electromagnetic wave radiating antenna or a magnetic field radiating antenna, adverse effects due to a transformer or a balun are likely to occur.

The above is not limited to the case where one radiating element is used for two communication in different frequency bands, and the same applies when one radiating element is used for communication and wireless power transmission in different frequency bands. Occur in.

Therefore, an object of the present invention is to provide an antenna device capable of effectively utilizing the radiating element in the two frequency bands when the radiating element is also used in the two frequency bands having different frequencies, and an electronic apparatus including the antenna device. To provide.

(1) The antenna device of the present invention is
A first insulator,
A second insulator fixed to the first insulator and having a magnetic permeability higher than that of the first insulator;
A first coupling conductor formed on the first insulator and connected to a first feeding circuit and a radiating element in a first frequency band;
A second coupling conductor formed on the second insulator, coupled to the first coupling conductor, and coupled to a second power supply circuit in a second frequency band lower than the frequency of the first frequency band;
Equipped with.

With the above configuration, a signal in the first frequency band, which is a relatively high frequency band, is applied (energized) to the first coupling conductor formed in the first insulator having a relatively low magnetic permeability such as non-magnetic ferrite. Therefore, the hysteresis loss generated in the first insulator is small. Since the signal in the second frequency band, which is a relatively low frequency band, is applied (energized) to the second coupling conductor formed in the second insulator having high magnetic permeability such as magnetic ferrite, at least Strongly couple via magnetic field. Further, due to the high magnetic permeability of the second insulator, the second coupling conductor required for obtaining the predetermined inductance can be short, so that the conductor loss due to the second coupling conductor is small. Due to these effects, when the radiating element is also used in the two frequency bands having different frequencies, the adverse effect due to the transformer or balun being connected to the radiating element is reduced.

(2) The first coupling conductor has a coil shape, the second coupling conductor has a coil shape, and the first coupling conductor and the second coupling conductor are wound around the same winding axis. It is preferable that the first coupling conductor, the second coupling conductor, the first insulator, and the second insulator are configured as one element. As a result, the positional relationship between the first insulator and the second insulator and the positional relationship between the first coupling conductor and the second coupling conductor become constant, so that the first feeding circuit and the second feeding circuit viewed from each other. The characteristics of the radiating element are stabilized.

(3) In the above (1) or (2), at least a part of the second coupling conductor may be exposed from the second insulator. Thereby, the second coupling conductor can be used as a part of the radiating element in the second frequency band.

(4) In any one of (1) to (3) above, it is preferable that the first insulator and the second insulator are ceramics that are integrally sintered. Thereby, the first insulator and the second insulator are easily integrated.

(5) In any one of (1) to (4) above, the inductance of the second coupling conductor is preferably larger than the inductance of the first coupling conductor.

(6) In any one of (1) to (5) above, it is preferable that the first frequency band is the UHF band or the SHF band, and the first frequency band is the HF band.

(7) The electronic device of the present invention is
A first power supply circuit in a first frequency band, a second power supply circuit in a second frequency band lower than the frequency of the first frequency band, and an antenna device,
The antenna device is
A first insulator,
A second insulator fixed to the first insulator and having a magnetic permeability higher than that of the first insulator;
A first coupling conductor formed on the first insulator and connected to the first feeding circuit and the radiating element;
A second coupling conductor formed on the second insulator, coupled to the first coupling conductor, and coupled to the second feeding circuit;
It is characterized by including.

With the above configuration, loss during communication using the first frequency band or during power transmission can be reduced, and the radiation element can also be used to reduce the size and reduce the loss.

(8) In the above (7), it is preferable to include a housing including the radiating element in at least a part thereof.

According to the present invention, when a radiation element is also used in two frequency bands having different frequencies, an antenna device that can effectively utilize the radiation element in the two frequency bands, and an electronic device including the antenna device can be obtained. ..

1A is a plan view of the antenna device 101 according to the first embodiment, FIG. 1B is a cross-sectional view taken along the line AA in FIG. 1A, and FIG. It is a BB sectional view in FIG. FIG. 2 is a perspective view showing a metal housing portion of an electronic device such as a smartphone including the antenna device 101. FIG. 3 is a circuit diagram of the antenna device 101. FIG. 4 is an exploded perspective view of the balun 3. FIG. 5 is a sectional view of the balun 3 taken along the line CC in FIG. FIG. 6 is an equivalent circuit diagram of the antenna device 101 using lumped constant elements. 7A is an equivalent circuit diagram of the antenna device 101 in the UHF band or the SHF band, and FIG. 7B is an equivalent circuit diagram of the antenna device 101 in the HF band. FIG. 8 is a sectional view of the balun 3 according to the second embodiment. FIG. 9 is a diagram showing a circuit diagram of a main part of the antenna device 103 according to the third embodiment, and particularly a diagram showing a circuit connection relationship with the transformer 2. FIG. 10 is an equivalent circuit diagram of the antenna device 104 according to the fourth embodiment using lumped constant elements.

The “antenna device” shown in each embodiment can be applied to both the transmission (power transmission) side and the reception (power reception) side of a signal (or power). Even when the "antenna device" is described as an antenna that radiates a magnetic flux, the antenna device is not limited to the source of the magnetic flux. Even when receiving (linking) the magnetic flux generated by the transmission partner antenna device, that is, even if the transmission/reception relationship between the “antenna device” and the communication partner antenna device shown in each embodiment is opposite, The "antenna device" shown in the form has the same effect.

The “antenna device” shown in each of the following embodiments is an antenna device used for near-field communication using a magnetic field coupling with a communication partner antenna device, or a proximity using magnetic field coupling with a power transmission partner antenna device. It is an antenna device used for power transmission in the field. In the case of communication, it is applied to a communication system such as NFC (Near field communication). In the case of power transmission, it is applied to a power transmission system such as an electromagnetic induction system or a magnetic field resonance system.

The second frequency band shown in each embodiment is, for example, the HF band, particularly 13.56 MHz, 6.78 MHz, or a frequency band in the vicinity thereof. The size of the antenna device in the second frequency band is sufficiently smaller than the wavelength λ ₂ in the second frequency band, and the radiation efficiency of electromagnetic waves is low in the used frequency band. The size of the antenna device is λ ₂ /10 or less. The first frequency band shown in each embodiment is, for example, a UHF band, an SHF band, or a higher frequency band. The size of the antenna device in the first frequency band is the same as or larger than the wavelength λ ₁ of the first frequency band, and the radiation efficiency of electromagnetic waves is high in the used frequency band. The size of the antenna device is lambda _1/10 or more. The second frequency band is a frequency that is 1/10 or less of the first frequency band. The wavelength here is an effective wavelength in consideration of the wavelength shortening effect due to the dielectric properties and magnetic permeability of the base material on which the coil antenna conductor is formed.

In each embodiment, the "electronic device" includes mobile phone terminals such as smartphones and feature phones, wearable terminals such as smart watches and smart glasses, mobile PCs such as notebook PCs and tablet PCs, cameras, game machines, toys, and the like. It refers to various electronic devices such as information devices, IC tags, SD cards, SIM cards, and information media such as IC cards.

<<First Embodiment>>
1A is a plan view of the antenna device 101 according to the first embodiment, FIG. 1B is a cross-sectional view taken along the line AA in FIG. 1A, and FIG. It is a BB sectional view in FIG. FIG. 2 is a perspective view showing a metal housing portion of an electronic device such as a smartphone including the antenna device 101. FIG. 3 is a circuit diagram of the antenna device 101.

The antenna device 101 includes a radiating element 1, substrates 6A and 6B, a battery pack 8, a capacitor C1, a first feeding circuit 81, a second feeding circuit 82, a balun 3, reactance elements 61 and 62 and capacitors C41, C42, C43 and C44. Equipped with. The housing of the electronic device accommodates the first power supply circuit 81, the second power supply circuit 82, other circuits, and other components.

The radiating element 1 is a conductive flat plate having a rectangular planar shape. The radiating element 1 has its longitudinal direction aligned with the lateral direction (X direction in FIG. 1A) and has a first end E1 and a second end E2 at both ends in the longitudinal direction. As shown in FIG. 2, this radiating element 1 is a part of a metal housing of an electronic device. That is, the housing of the electronic device partially includes the radiating element 1. The radiating element 1 has the longest length of the shortest length between only two points of the radiating element 1 that passes through only the surface or the inside of the radiating element 1, and a wavelength of a first frequency band described later is λ. ₁ lambda _1/10 or more when expressed, is lambda _2/10 or less when expressed the wavelength of the second frequency band later in lambda _2.

The portion of the housing of the electronic device that also serves as the radiating element is not limited to metal, and may be graphite or the like as long as it has conductivity.

The substrates 6A and 6B are flat plates of an insulator having a rectangular planar shape. The board 6A is provided with the flat ground conductor 4 inside. The substrates 6A and 6B are arranged side by side in the vertical direction (Y direction in FIG. 1A) with the battery pack 8 interposed therebetween, and are also arranged on the same plane. The board 6A and the board 6B are connected by a not-shown coaxial cable or the like.

The capacitor C1, the first feeding circuit 81, the second feeding circuit 82, the balun 3, the reactance elements 61 and 62, and the capacitors C41 to C44 are on one main surface of the substrate 6A (the front surface of the substrate 6A in FIG. 1A). Implemented in. The configuration of the balun 3 will be described later in detail. The capacitors C1 and C41 to C44 are electronic components such as chip capacitors. The choke inductor CHC is an electronic component such as a chip coil.

FIG. 3 is a circuit diagram showing a main part of the antenna device 101 shown in FIG. 1A, and in particular, is a diagram showing a circuit connection relationship with the balun 3.

The first coil (“first coupling conductor”) 31 of the balun 3 is connected between the radiating element 1 and the ground conductor 4 (see FIGS. 1(A)(B)(C) and FIG. 3). Specifically, the terminal P22 of the balun 3 is connected near the first end E1 of the radiating element 1 via the connection conductor 71A and the connection pin 7, and the terminal P21 of the balun 3 is connected to the connection conductor 72A and the interlayer connection conductor. It is connected to the ground conductor 4 via 52A. The connection of the second coil (“second coupling conductor”) 32 of the balun 3 will be described later.

The connection conductors 71A and 72A are linear conductor patterns formed on one main surface of the substrate 6A. The connection pin 7 is, for example, a movable probe pin, and the interlayer connection conductor 52A is, for example, a via conductor.

The capacitor C1 is connected between the radiating element 1 and the ground conductor 4. Specifically, one end of the capacitor C1 is connected to the vicinity of the second end E2 of the radiating element 1 via the connection conductor 73A and the connection pin 7, and the other end of the capacitor C1 is connected to the connection conductor 74A and the interlayer connection conductor ( It is connected to the ground conductor 4 via (not shown). The connection conductors 73A and 74A are linear conductor patterns formed on the one main surface of the substrate 6A.

Therefore, as shown in FIG. 1A, a loop including the radiating element 1, the ground conductor 4, the first coil 31 of the balun 3 and the capacitor C1 is formed.

The first power supply circuit 81 is an IC for the UHF band or the SHF band (first frequency band). The input/output portion of the first feeding circuit 81 is connected to the vicinity of the second end portion E2 in the longitudinal direction of the radiating element 1 via the connecting conductor formed on the one main surface of the substrate 6A, the connecting pin 7, and the reactance element 61. To be done. The reactance element 61 is, for example, an electronic component such as a chip capacitor, and the first feeding circuit 81 is, for example, a feeding circuit of a 2.4 GHz band wireless LAN communication system.

The connecting portion between the radiating element 1 including the reactance element 62 and the ground conductor 4 is a stub provided for matching the antenna including the radiating element 1 and the first feeding circuit 81, and the reactance element 62 is one main component of the substrate 6A. It is connected to the vicinity of the second end E2 of the radiating element 1 via the connecting conductor and the connecting pin 7 formed on the surface. The reactance element 62 is an electronic component such as a chip capacitor. In addition, the reactance element 62 may be configured to include a plurality of elements as necessary. However, the reactance element 62 is not an indispensable structure, and may be a structure without a stub. Further, the connecting portion may directly connect the radiating element 1 and the ground conductor 4 without the reactance element 62.

The second power supply circuit 82 is a balanced input/output type HF band (second frequency band) IC. The input/output unit of the second feeding circuit 82 is connected to the second coil (“second coupling conductor”) 32 of the balun 3 via the capacitors C41 to C44 (see FIG. 3). A series circuit of capacitors C41 and C42 is connected in parallel to the second coil 32 of the balun 3, and an LC resonance circuit is formed by the second coil 32 of the balun 3 and the capacitors C41 and C42. The second power feeding circuit 82 feeds a communication signal in the HF band (second frequency band) to the LC resonance circuit via the capacitors C43 and C44. The second power supply circuit 82 is, for example, a 13.56 MHz RFIC element for RFID.

The second coil 32 of the balun 3 is magnetically or electromagnetically coupled (magnetic field coupling and electric field coupling) with the loop including the radiating element 1, the ground conductor 4, the first coil 31 of the balun 3 and the capacitor C1.

FIG. 4 is an exploded perspective view of the balun 3. FIG. 5 is a sectional view of the balun 3 taken along the line CC in FIG.

The balun 3 includes base material layers S1, S2, S3, S4 on which coil patterns 32a, 32b, 32c, 32d are formed, and base material layers S5, S6, S7, on which coil patterns 31a, 31b, 31c, 31d are formed. S8 and base material layers S9, S10, S11 and S12 on which the coil patterns 32e, 32f, 32g and 32h are formed are provided.

The coil patterns 31a, 31b, 31c, 31d constitute a rectangular helical first coil 31. Further, the coil patterns 32a, 32b, 32c, 32d configure a rectangular helical coil 32A, and the coil patterns 32e, 32f, 32g, 32h configure a rectangular helical coil 32B. The second coil 32 is configured by the coils 32A and 32B. The first coil 31 and the second coil 32 are coil openings of the first coil 31 and coils of the second coil 32 when viewed in plan in the winding axis direction of the first coil 31 or the winding axis direction of the second coil 32. It overlaps with the opening. Furthermore, the first coil 31 and the second coil 32 are coaxial. That is, the first coil 31 and the second coil 32 are wound around the same winding axis. Input/output terminals P11, P12, P21, P22 are formed on the outer surface of the laminated body of the base material layers S1 to S12, but they are not shown in FIG.

Of the plurality of base material layers, the base material layers S1, S2, S3, S9, S10, S11 are magnetic ferrite layers, and the base material layers S4, S5, S6, S7, S8, S12 are non-magnetic ferrite layers. It is a layer. The base material layers S4, S5, S6, S7 and S8 correspond to the "first insulator" according to the present invention, and the base material layers S1, S2, S3, S9, S10 and S11 correspond to the "first insulating material" according to the present invention. 2 insulators”. That is, the first coil 31 is formed of a first insulator having a relatively low effective magnetic permeability, and the second coil 32 is formed of a second insulator having a high effective magnetic permeability. More specifically, in the length along the coil conductor (the length of the current path of the current flowing through the coil conductor), the first coil 31 is longer than the second insulator in the first insulator. The length of the second coil 32 is higher than that of the first insulator in the length along the coil conductor (the length of the current path of the current flowing through the coil conductor). It is formed so that the ratio of the height is high.

The balun 3 is manufactured by printing and forming a predetermined coil pattern on a magnetic ferrite green sheet and a non-magnetic ferrite green sheet, stacking and pressure bonding, separating into individual pieces, and firing each. That is, the "second insulator" is fixed to the "first insulator", and both are integrated.

In this way, the first coil 31 and the second coil 32 are wound around the same winding axis, and the first coil 31 (first coupling conductor), the second coil 32 (second coupling conductor), the non-coil The magnetic layer (first insulator) and the magnetic layer (second insulator) are configured as one element. As a result, the positional relationship between the non-magnetic layer and the magnetic layer and the positional relationship between the first coil 31 and the second coil 32 become constant.

As shown in FIGS. 4 and 5, the second coil 32 is exposed from the magnetic body (second insulator) in a plane perpendicular to the winding axis of the second coil 32 (embedded in the magnetic body). Since the magnetic layer does not form a closed magnetic circuit for the second coil 32, the magnetic flux generated by the current flowing through the second coil 32 spreads to the outside of the balun 3. Therefore, the second coil 32 can also be used as a part of the radiating element in the second frequency band. Furthermore, since the magnetic layer does not form a closed magnetic circuit with respect to the second coil 32, the magnetic flux generated by the current flowing through the second coil 32 easily interlinks with the first coil 31 and the first coil 31 and the second coil 32. The coupling coefficient between them increases, and the efficiency of transmission between the first coil 31 and the second coil 32 increases.

FIG. 6 is an equivalent circuit diagram of the antenna device 101 using lumped constant elements. In FIG. 6, the radiating element 1 is represented by an inductor L0, the first coil 31 of the balun 3 is represented by an inductor L1, and the second coil 32 of the balun 3 is represented by an inductor L2. In FIG. 6, the mutual inductance between the second coil 32 and the radiating element 1 is represented by M02, and the mutual inductance between the first coil 31 and the second coil 32 is represented by M12. The magnetic field coupling between the second coil 32 and the radiating element 1 is due to the fact that the magnetic path of the second coil of the balun 3 is an open magnetic path, as described above.

It is not necessary that the conductor forming the second coil 32 and the conductor forming the radiating element 1 are magnetically coupled to each other, and the second coil 32 electrically connected to the second feeding circuit 82 and the radiating element 1 are included. At least the first coil 31 included in the loop may be electrically connected by magnetic field coupling.

7A is an equivalent circuit diagram of the antenna device 101 in the UHF band or the SHF band, and FIG. 7B is an equivalent circuit diagram of the antenna device 101 in the HF band. In FIG. 7A, the reactance elements 61 and 62 are represented by capacitors C61 and C62.

In the UHF band or the SHF band (first frequency band), the capacitor C1 has a low impedance and is equivalently in a short state. Therefore, the radiating element 1 is grounded at a predetermined position as shown by the grounding end SP in FIG. 7(A). The series circuit of the choke inductor CHC and the first coil 31 of the balun 3 has a high impedance in the UHF band or the SHF band (first frequency band) and is equivalently open. Therefore, as shown by the open end OP in FIG. 7A, one end of the radiating element 1 is open.

The first feeding circuit 81 feeds voltage by using the connection point of the radiating element 1 as a feeding point. In the UHF band or the SHF band (first frequency band), the open end OP of the radiating element 1 resonates so that the current intensity is zero and the ground end SP has a voltage intensity of zero. In other words, the length and the like of the radiating element 1 are set so as to resonate in the UHF band or the SHF band. However, the radiating element 1 resonates in the fundamental mode in the low band and in the higher mode in the high band in the frequency band of 700 MHz to 2.4 GHz. Therefore, in the UHF band or the SHF band (first frequency band), current flows in the region shown by the solid arrow in FIG.

In the UHF band or the SHF band (first frequency band), when the capacitor C1 is used alone without forming a resonance circuit, the capacitor C1 does not become a short circuit completely, so the ground end SP of the radiating element 1 is used. There will be some voltage strength at. Similarly, in the UHF band or the SHF band (first frequency band), when the first coil 31 is used alone without being an anti-resonance circuit, the series circuit of the choke inductor CHC and the first coil 31 of the balun 3 is Since it is not completely in the open state, some current intensity is generated in the open end OP of the radiating element 1.

In this way, in the UHF band or SHF band (first frequency band), standing waves of current intensity and voltage intensity are generated in the radiating element 1, and the radiating element 1 acts as an inverted F-type antenna. Although an inverted F-type antenna is illustrated here, a patch antenna such as a monopole antenna, a one-wavelength loop antenna, an inverted L-type antenna, a plate-shaped inverted F antenna (PIFA), a slot antenna, a notch antenna, etc. The same applies to other standing wave type antennas in which standing waves of current strength and voltage strength are generated on the radiating element due to resonance.

On the other hand, in the HF band (second frequency band), as shown in FIG. 7B, a loop including the radiating element 1 (inductor L1), the ground conductor 4, the first coil 31 of the balun 3 and the capacitor C1 is Configure an LC resonant circuit. As described above, the second coil 32 of the balun 3 is mainly magnetically coupled to the loop that constitutes the LC resonance circuit.

The loop causes LC resonance in the HF band and a resonance current flows. In other words, the circuit constants such as the length of the radiating element 1 and the reactance components of the first coil 31 of the balun 3 and the capacitor C1 are set so as to resonate in the HF band. Therefore, in the HF band (second frequency band), a current flows in the region shown by the dashed arrow in FIG.

Thus, in the HF band (second frequency band), the loop including the radiating element 1, the ground conductor 4, the first coil 31 of the balun 3, and the capacitor C1 acts as a magnetic field radiation antenna that contributes to magnetic field radiation. .. Here, in the HF band (second frequency band), since the length of the loop is sufficiently short with respect to the wavelength, the loop is a small loop antenna for communication by magnetic field coupling.

The reactance elements 61 and 62 have high impedance in the HF band (second frequency band), and the first power feeding circuit 81 is not equivalently connected. Therefore, the first power feeding circuit 81 is in the HF band. Does not affect the communication of. Further, the first coil 31 of the balun 3 has high impedance in the UHF band or the SHF band (first frequency band), and the first coil 31 of the balun 3 is not equivalently connected. Therefore, since the loop including the first coil 31 of the balun 3 is in the open state, the communication signal in the UHF band or the SHF band does not flow in the second power supply circuit 82, and the second power supply circuit 82 is in the UHF band or the SHF band. Does not affect band communication.

According to this embodiment, the following operational effects are achieved.

(1) A signal in the UHF/SHF band (first frequency band) is applied to the first coil (first coupling conductor) 31 formed in a non-magnetic body (first insulator having a relatively low effective magnetic permeability). Although (energized), the first insulator has a small hysteresis loop for the same magnetic field strength, so that the hysteresis loss that appears remarkably as the frequency increases can be suppressed. Further, the signal in the HF band (second frequency band) is applied (energized) to the second coil (second coupling conductor) 32 formed in the magnetic body (second insulator having high effective magnetic permeability). , Coupled strongly via at least a magnetic field. Further, due to the high effective magnetic permeability of the magnetic body (second insulator) 32, the second coil (second coupling conductor) 32 required to obtain a predetermined inductance may be short, so that the conductor loss due to the second coil 32 does not occur. small. Due to these effects, when the radiating element is also used in the two frequency bands whose frequencies are separated from each other, the adverse effect due to the connection of the balun to the radiating element is reduced. That is, loss during communication or power transmission using the first frequency band and during communication or power transmission using the second frequency band is reduced, and the radiation element is also used to reduce the size and reduce the loss. ..

(2) Since the positional relationship between the non-magnetic material layer and the magnetic material layer and the positional relationship between the first coil 31 and the second coil 32 are constant, they are viewed from the first feeding circuit 81 and the second feeding circuit 82. The characteristics of the radiating element 1 (characteristics as a field emission antenna) and the second coil 32 of the balun 3 include a loop (magnetic field radiation) including the radiating element 1, the ground conductor 4, the first coil 31 of the balun 3 and the capacitor C1. Characteristics as a type antenna) are stabilized.

(3) Since the second coil 32 is exposed from the magnetic body (second insulator) (not embedded in the magnetic body), the second coil 32 is also used as a part of the radiating element in the second frequency band. it can.

(4) Since the second coil 32 is exposed from the magnetic body (second insulator) (not embedded in the magnetic body), the magnetic flux generated by the current flowing through the second coil 32 is linked with the first coil 31. The coupling coefficient between the first coil 31 and the second coil 32 is increased.

(5) Since the first insulator and the second insulator are integrally sintered ceramics, the first insulator and the second insulator can be easily integrated.

(6) Since the effective magnetic permeability of the second insulator is high (because it is higher than the effective magnetic permeability of the first insulator in comparison with the effective magnetic permeability of the first insulator), the self-inductance of the second coil 32 is easy. Can be greatly increased. Since the self-inductance of the second coil 32 is large as described above, the current flowing through the second coil 32 can be suppressed. Therefore, it is possible to prevent the second coil 32 that causes a large hysteresis loss from consuming the electric power of the signal in the UHF/SHF band (first frequency band).

(7) Since the effective magnetic permeability of the first insulator is low (because it is lower than the effective magnetic permeability of the second insulator in comparison with the effective magnetic permeability of the second insulator), the self-inductance of the first coil 31 is easy. Can be made very small. In this way, if the self-inductance of the first coil 31 is small, the leakage inductance of the loop that is magnetically or electromagnetically coupled to the transmission partner antenna device in the antenna device of this embodiment can be suppressed.

(8) The hysteresis coefficient of the first insulator in the so-called Steinmetz empirical formula can be made smaller (compared to the second insulator, the hysteresis coefficient of the first insulator can be made smaller than that of the second insulator). As described above, since the hysteresis coefficient of the first insulator is small, the hysteresis loss in the first insulator can be further suppressed.

(9) The electric insulation of the first insulator can be made higher (compared to the second insulator, the electric insulation can be made higher than that of the second insulator). As described above, the high electrical insulation of the first insulator can suppress the eddy current loss in the first insulator (the eddy current loss becomes more remarkable as the frequency increases).

Note that, in the present embodiment, an example in which the radiating element 1 is included in a part of the housing of the electronic device has been shown, but the entire housing of the electronic device may be the radiating element, and similar operational effects are obtained.

<<Second Embodiment>>
In the second embodiment, a balun in which the magnetic layer, the non-magnetic layer, the first coil, and the second coil have a positional relationship different from that of the balun of the first embodiment will be described.

FIG. 8 is a sectional view of the balun 3 according to the second embodiment. The balun 3 includes base material layers S0 to S12, and the rectangular helical second coil 32 is formed on the base material layers S5, S6, S7, and S8. Further, a rectangular helical coil 31A is formed on the base material layers S1, S2, S3, S4, and a rectangular helical coil 31B is formed on the base material layers S9, S10, S11, S12. The first coil 31 is configured by the coils 31A and 31B. The first coil 31 and the second coil 32 are coil openings of the first coil 31 and coils of the second coil 32 when viewed in plan in the winding axis direction of the first coil 31 or the winding axis direction of the second coil 32. The openings overlap. Furthermore, the first coil 31 and the second coil 32 are coaxial. That is, the first coil 31 and the second coil 32 are wound around the same winding axis. Input/output terminals are formed on the outer surface of the laminated body of the base material layers S0 to S12.

Of the plurality of base material layers, the base material layers S0 to S4 and S8 to S12 are nonmagnetic ferrite layers, and the base material layers S5 to S7 are magnetic ferrite layers. The nonmagnetic ferrite layer corresponds to the "first insulator" according to the present invention, and the magnetic ferrite layer corresponds to the "second insulator" according to the present invention.

Contrary to the balun shown in FIG. 5, the balun 3 of the present embodiment has a structure in which the second coil 32 is sandwiched by the first coils 31A and 31B in the stacking direction. Further, it has a structure in which the magnetic layer is sandwiched between the non-magnetic layers.

The antenna device having the balun and the electronic device including the balun shown in this embodiment also have the same effects as the first embodiment.

<<Third Embodiment>>
The third embodiment shows a case where unbalanced power feeding is performed in both the first power feeding circuit and the second power feeding circuit.

FIG. 9 is a diagram showing, as a circuit diagram, a main part of the antenna device 103 according to the third embodiment, and particularly shows a circuit connection relationship with the transformer 2. As is clear from comparison with the circuit shown in FIG. 3 in the first embodiment, the second power feeding circuit 82 is a power feeding circuit in the second frequency band, and feeds the second coil 22 of the transformer 2 unbalancedly. The first coil 21 of the transformer 2 is connected between the radiating element 1 and the ground conductor. The first coil 21 is formed of a first insulator having a low effective magnetic permeability, and the second coil 22 is formed of a second insulator having a high effective magnetic permeability. The configurations of the first insulator and the second insulator are as shown in FIG. 4, FIG. 5, FIG.

A loop including the radiating element 1, the ground conductor, the first coil 21 of the transformer 2, and the capacitor C1 is configured. This loop acts as a magnetic field radiation type antenna. The connection structure of the first feeding circuit 81 to the radiating element 1 is the same as that of the first embodiment.

According to this embodiment, the magnetic field radiation antenna including the radiation element 1 and the second feeding circuit 82 are impedance-matched by the transformer 2. Further, the coupling between the second power feeding circuit 82 and the magnetic field radiation type antenna can be enhanced, and power can be fed from the second power feeding circuit 82 to the magnetic field radiation type antenna with high efficiency.

<<Fourth Embodiment>>
In the fourth embodiment, an example of unbalanced power feeding to a magnetic field radiation antenna by a balanced power feeding circuit is shown.

FIG. 10 is an equivalent circuit diagram of the antenna device 104 according to the fourth embodiment using lumped constant elements. The antenna device 104 includes a balun 3 and a transformer 2. The first coil 33 of the balun 3 is connected to the second coil 22 of the transformer 2 via the capacitor C3, and the first coil 21 of the transformer 2 is connected as a part of the loop of the magnetic field emission antenna. Other configurations are the same as those of the antenna device 101 shown in the first embodiment.

An LC resonance circuit is configured by the first coil 33 of the balun 3, the second coil 22 of the transformer 2, and the capacitor C3. The second power supply circuit 82 supplies balanced power to the second coil 34 of the balun 3. This signal (power) is unbalancedly fed to the loop of the magnetic field radiation type antenna including the first coil 21 of the transformer 2 via the LC resonance circuit.

Similar to the antenna device 103 shown in the third embodiment, the first coil 21 of the transformer 2 is formed of an insulator having a low effective magnetic permeability, and the second coil 22 of the transformer 2 is an insulator having a high effective magnetic permeability. Formed on the body.

In the present embodiment, since the signal current in the first frequency band fed from the first feeding circuit 81 does not flow in either the first coil 33 or the second coil 34 of the balun 3, the first coil of the balun 3 does not flow. Both 33 and the second coil 34 are formed of an insulator having a high effective magnetic permeability. Therefore, according to the present embodiment, the first coil 33 and the second coil 34 are magnetically coupled via the insulator having a high effective magnetic permeability, so that the coupling coefficient between the first coil 33 and the second coil 34 is large. And the transmission efficiency between the first coil 33 and the second coil 34 increases.

<<Other Embodiments>>
In the balun shown in FIGS. 5 and 8, the structure in which the second coil is sandwiched by the first coil in the stacking direction or the first coil is sandwiched by the second coil in the stacking direction is shown. Instead of such a sandwich structure, the first coil 31 and the second coil 32 may be simply laminated. Further, the first coil 31 and the second coil 32 may be alternately and repeatedly arranged. This applies not only to the balun but also to the transformer.

Further, the portion corresponding to the magnetic core or the air core of the balun or transformer is not limited to the structure in which the magnetic layer and the non-magnetic layer are linearly arranged, and may be a toroidal shape as a whole. For example, it is composed of a magnetic body having a gap like a C shape and a non-magnetic body arranged at the gap position, the first coil is formed in the non-magnetic body portion, and the first coil is formed in the magnetic body portion. Two coils may be formed.

In addition, the balun or transformer according to the present invention is not formed by the laminated body of the base material but by winding the first coil and the second coil around the bobbin formed by the non-magnetic material and the magnetic material. It may be configured.

In the balun shown in FIGS. 5 and 8, an example in which a magnetic ferrite layer and a non-magnetic ferrite layer are laminated is shown, but the first coupling conductor is formed on the first insulator having a relatively low magnetic permeability. The second coupling conductor may be formed on the second insulator having a relatively high magnetic permeability.

In addition, the base material layer on which the first coil is formed does not have to immediately correspond to the first insulator, and in the stacked state of the base material, there is a non-magnetic material near the first coil and the vicinity of the second coil. It suffices if there is a magnetic substance in

Moreover, the magnetic permeability in a certain layer may be non-uniform. For example, the magnetic material may be inside the coil opening of the second coil, and the outside of the coil pattern of the second coil may be a non-magnetic material.

Further, the boundary between the first insulator and the second insulator does not have to be a definite boundary surface between the non-magnetic material and the magnetic material. One or both of the first insulator and the second insulator may be a mixture of a magnetic substance and a non-magnetic substance. Further, the ratio of the magnetic substance to the non-magnetic substance may be unevenly distributed, and the magnetic permeability may have a gradient.

Further, the first coupling conductor (first coil) and the second coupling conductor (second coil) are not limited to being rectangular as viewed from the winding axis, and may be circular, elliptical, or any other shape.

Further, the first coupling conductor and the second coupling conductor are viewed from the winding axis as long as the second coupling conductor is magnetically or electromagnetically coupled (magnetic field coupling and electric field coupling) to the first coupling conductor. You don't have to go around. That is, for example, the first coupling conductor and the second coupling conductor may be linear.

Although the antenna device and the electronic device in the communication system mainly using magnetic field coupling such as NFC have been described in the above-described embodiments, the antenna device and the electronic device in the above-described embodiment are non-contact using magnetic field coupling. The power transmission system (electromagnetic induction method, magnetic field resonance method, etc.) can be used in the same manner. For example, the antenna device according to the above-described embodiment can be applied as a power receiving antenna device to a power receiving device of a magnetic field resonance type non-contact power transmission system used in the HF band, particularly at a frequency of 6.78 MHz or near 6.78 MHz. Even in this case, the antenna device functions as a power receiving antenna device. In the contactless power transmission system, the “power feeding circuit” described in the above embodiment corresponds to the power receiving circuit or the power transmitting circuit. In the case of a power receiving circuit, it is connected to a power receiving antenna device and supplies power to a load (for example, a secondary battery). In the case of a power transmission circuit, the power transmission circuit is connected to the power transmission antenna device and supplies power to the power transmission antenna device.

The "effective magnetic permeability" described above is an expression in the sense of magnetic permeability that effectively affects the coupling conductor. For example, the effective permeability of the first insulator is the permeability of the first insulator that affects the first coupling conductor, and the effective permeability of the second insulator is the second permeability that affects the second coupling conductor. It is the magnetic permeability of the insulator. When the magnetic permeability changes depending on the magnetic field strength, the time-average magnetic permeability per current cycle is the effective magnetic permeability in the UHF/SHF band (first frequency band) signal. Furthermore, when at least one of the first insulator and the second insulator has inhomogeneity or anisotropy, the inductance generated in the first coupling conductor including the first insulator is reduced to that of the first coupling conductor. The value obtained by dividing the inductance determined only by the conductor shape is the effective magnetic permeability of the first insulator. Similarly, the effective magnetic permeability of the second insulator is a value obtained by dividing the inductance generated in the second coupling conductor including the second insulator by the inductance determined only by the conductor shape of the second coupling conductor.

Finally, the above description of the embodiments is illustrative in all respects and not restrictive. Those skilled in the art can appropriately make modifications and changes. The scope of the invention is indicated by the claims rather than by the embodiments described above. Further, the scope of the present invention includes modifications from the embodiments within the scope equivalent to the claims.

C1, C3... Capacitors C41, C42, C43, C44... Capacitor C61, C62... Capacitor CHC... Choke inductor E1... First end E2... Second end L0, L1, L2... Inductor OP... Open ends P11, P12, P21, P22... Input/output terminals S0 to S12... Base material layer SP... Grounding end 1... Radiating element 2... Transformer 3... Balun 4... Ground conductors 6A, 6B... Board 7... Connection pin 8... Battery pack 21... First coil 22... 2nd coil 31... 1st coil (1st coupling conductor)
31A, 31B... 1st coil 31a-31d... Coil pattern 32... 2nd coil (2nd coupling conductor)
32A, 32B... Coils 32a to 32h... Coil pattern 33... First coil 34... Second coil 52A... Interlayer connection conductors 61, 62... Reactance elements 71A, 72A... Connection conductors 73A, 74A... Connection conductor 81... First feeding circuit 82... 2nd electric power feeding circuits 101, 103, 104... Antenna device

Claims (8)

A first insulator,
A second insulator fixed to the first insulator and having a magnetic permeability higher than that of the first insulator;
A first coupling conductor formed on the first insulator and connected to a first feeding circuit and a radiating element in a first frequency band;
A second coupling conductor formed in the second insulator, magnetically coupled to the first coupling conductor at least, and connected to a second power supply circuit in a second frequency band lower than the frequency of the first frequency band;
An antenna device provided with. The first coupling conductor has a coil shape, the second coupling conductor has a coil shape, and the first coupling conductor and the second coupling conductor have respective coils when viewed in plan from one winding axis. The antenna device according to claim 1, wherein the openings are overlapped, and the first coupling conductor, the second coupling conductor, the first insulator, and the second insulator are configured as one element. The antenna device according to claim 1, wherein at least a part of the second coupling conductor is exposed from the second insulator. The antenna device according to claim 1, wherein the first insulator and the second insulator are integrally sintered ceramics. The antenna device according to claim 1, wherein the inductance of the second coupling conductor is larger than the inductance of the first coupling conductor. The antenna device according to claim 1, wherein the first frequency band is the UHF band or the SHF band, and the first frequency band is the HF band. An electronic device comprising a first power supply circuit in a first frequency band, a second power supply circuit in a second frequency band lower than the frequency of the first frequency band, and an antenna device,
The antenna device is
A first insulator,
A second insulator fixed to the first insulator and having a magnetic permeability higher than that of the first insulator;
A first coupling conductor formed on the first insulator and connected to the first feeding circuit and the radiating element;
A second coupling conductor formed on the second insulator, coupled to the first coupling conductor, and coupled to the second feeding circuit;
An electronic device comprising: The electronic device according to claim 7, further comprising a housing including at least a part of the radiating element.

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