JP2012085305A - Antenna device and communication terminal unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an antenna device which matches impedance with a feeder circuit in a wide frequency band and a communication terminal unit including the antenna device.SOLUTION: An antenna device 106 includes an antenna element 11 and an impedance conversion circuit 25 connecting to the antenna element 11. The impedance conversion circuit 25 connects with a feeding end of the antenna element 11. The impedance conversion circuit 25 is disposed between the antenna element 11 and a feeder circuit 30. The impedance conversion circuit 25 includes a first inductance element L1 connecting to the feeder circuit 30 and a second inductance element L2 connecting to the first inductance element L1, and a first end and a second end of the first inductance element L1 are respectively connected to the feeder circuit 30 and an antenna. A first end and a second end of the second inductance element L2 are respectively connected to the antenna element 11 and a ground.

Description

  The present invention relates to an antenna device and a communication terminal device using the antenna device, and more particularly to an antenna device capable of matching in a wide frequency band.

  In recent years, communication terminals such as mobile phones have been developed for communication systems such as GSM (Global System for mobile Communication) (registered trademark), DCS (Digital Communication System), PCS (Personal Communication Services), UMTS (Universal Mobile Telecommunications System), and the like. May be required to support GPS (Global Positioning System), wireless LAN, Bluetooth (registered trademark), and the like. Therefore, the antenna device in such a communication terminal device is required to cover a wide frequency band from 800 MHz to 2.4 GHz.

  As an antenna device corresponding to a wide frequency band, as disclosed in Patent Literature 1 and Patent Literature 2, an antenna device having a broadband matching circuit constituted by an LC parallel resonance circuit or an LC series resonance circuit is generally used. Is. Further, as an antenna device corresponding to a wide frequency band, for example, tunable antennas disclosed in Patent Document 3 and Patent Document 4 are known.

JP 2004-336250 A JP 2006-173697 A JP 2000-124728 A JP2008-035065

  However, since the matching circuits shown in Patent Documents 1 and 2 include a plurality of resonance circuits, insertion loss in the matching circuit tends to increase, and a sufficient gain may not be obtained.

  On the other hand, the tunable antennas disclosed in Patent Documents 3 and 4 require a circuit for controlling the variable capacitance element, that is, a switching circuit for switching the frequency band, so that the circuit configuration tends to be complicated. In addition, since a loss and distortion in the switching circuit are large, a sufficient gain may not be obtained.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide an antenna device impedance-matched with a power feeding circuit in a wide frequency band, and a communication terminal device including the antenna device.

(1) The antenna device of the present invention includes an antenna element and an impedance conversion circuit connected to the antenna element,
The impedance conversion circuit includes a transformer type circuit in which a first inductance element and a second inductance element are coupled via a mutual inductance M;
A first end of the first inductance element is connected to a power feeding circuit, a second end of the first inductance element is connected to a ground, a first end of the second inductance element is connected to the antenna element, and the second The second end of the inductance element is connected to ground,
The mutual inductance M is larger than the inductance of the second inductance element.

(2) In (1), the first inductance element (L1) includes a first coil element (L1a) and a second coil element (L1b), and the first coil element and the second coil element are in series with each other. It is preferable that the winding pattern of the conductor is formed so as to form a closed magnetic circuit.

(3) In (1) or (2), the second inductance element (L2) includes a third coil element (L2a) and a fourth coil element (L2b), and the third coil element and the fourth coil element Are preferably connected in series with each other and have a conductor winding pattern formed so as to form a closed magnetic circuit.

(4) In any one of (1) to (3), the first inductance element and the second inductance element are coupled via a magnetic field and an electric field,
When an alternating current flows through the first inductance element, a direction of a current flowing through the second inductance element due to coupling via the magnetic field and a direction of a current flowing through the second inductance element due to coupling via the electric field are determined. Preferably they are the same.

(5) In any one of (1) to (4), when an alternating current flows through the first inductance element, the direction of the current flowing through the second inductance element depends on the first inductance element and the second inductance element. It is preferable that the magnetic barrier be oriented between the two.

(6) In any one of (1) to (5), the first inductance element and the second inductance element are in a multilayer body (multilayer substrate) in which a plurality of dielectric layers or magnetic layers are laminated. Preferably, the first inductance element and the second inductance element are coupled to each other inside the multilayer body.

(7) In any one of (1) to (6), the first inductance element includes at least two inductance elements electrically connected in parallel, and the two inductance elements sandwich the second inductance element. It is preferable that they are arranged in a positional relationship.

(8) In any one of (1) to (7), the second inductance element includes at least two inductance elements electrically connected in parallel, and the two inductance elements sandwich the first inductance element. It is preferable that they are arranged in a positional relationship.

(9) A communication terminal device according to the present invention includes an antenna device including an antenna element, a power feeding circuit, and an impedance conversion circuit connected between the antenna element and the power feeding circuit.
The impedance conversion circuit includes a transformer type circuit in which a first inductance element and a second inductance element are coupled via a mutual inductance M;
The first end of the first inductance element is connected to the power supply circuit, the second end of the first inductance element is connected to the ground, the first end of the second inductance element is connected to the antenna element, and The second end of the two-inductance element is connected to ground,
The mutual inductance M is larger than the inductance of the second inductance element.

  According to the antenna device of the present invention, a pseudo negative inductance component is generated in the impedance conversion circuit, so that the effective inductance component of the antenna element is suppressed by the negative inductance component, that is, the appearance of the antenna element is apparent. As a result, the impedance frequency characteristic of the antenna device is reduced. Therefore, the impedance change of the antenna device can be suppressed over a wide band, and impedance matching with the feeding circuit can be achieved over a wide frequency band.

  Moreover, according to the communication terminal device of the present invention, since the antenna device is provided, the communication terminal device can support various communication systems having different frequency bands.

FIG. 1A is a circuit diagram of the antenna device 101 according to the first embodiment, and FIG. 1B is an equivalent circuit diagram thereof. FIG. 2 is a diagram illustrating the action of a negative inductance component that is artificially generated in the impedance conversion circuit 45 and the action of the impedance conversion circuit 45. FIG. 3A is a circuit diagram of the antenna device 102 of the second embodiment, and FIG. 3B is a diagram showing a specific arrangement of each coil element. FIG. 4 is a diagram in which various arrows indicating states of magnetic field coupling and electric field coupling are entered in the circuit illustrated in FIG. FIG. 5 is a circuit diagram of the antenna device 102 corresponding to multiband. FIG. 6A is a perspective view of the impedance conversion circuit 35 of the third embodiment, and FIG. 6B is a perspective view of the impedance conversion circuit 35 as viewed from the lower surface side. FIG. 7 is an exploded perspective view of the laminated body 40 constituting the impedance conversion circuit 35. FIG. 8 is a diagram illustrating the operating principle of the impedance conversion circuit 35. FIG. 9 is a circuit diagram of the antenna device of the fourth embodiment. FIG. 10 is an exploded perspective view of the laminate 40 that constitutes the impedance conversion circuit 34. FIG. 11A is a perspective view of the impedance conversion circuit 135 of the fifth embodiment, and FIG. 11B is a perspective view of the impedance conversion circuit 135 viewed from the lower surface side. FIG. 12 is an exploded perspective view of the laminated body 40 constituting the impedance conversion circuit 135. FIG. 13 is a circuit diagram of the antenna device 106 according to the sixth embodiment, and FIG. 13B is an equivalent circuit diagram thereof. FIG. 14A is a circuit diagram of the antenna device 107 of the seventh embodiment, and FIG. 14B is a diagram showing a specific arrangement of each coil element. FIG. 15A is a diagram showing the transformer ratio of the impedance conversion circuit based on the equivalent circuit shown in FIG. FIG. 16 is a circuit diagram of the antenna device 107 corresponding to the multiband. FIG. 17 is a diagram illustrating an example of a conductor pattern of each layer when the impedance conversion circuit 25 according to the eighth embodiment is configured on a multilayer substrate. FIG. 18 shows the main magnetic flux passing through the coil element by the conductor pattern formed in each layer of the multilayer substrate shown in FIG. FIG. 19 is a diagram showing the magnetic coupling relationship of the four coil elements L1a, L1b, L2a, and L2b of the impedance conversion circuit 25 according to the eighth embodiment. FIG. 20 is a diagram illustrating a configuration of an impedance conversion circuit according to the ninth embodiment, and is a diagram illustrating an example of a conductor pattern of each layer when the impedance conversion circuit is configured on a multilayer substrate. FIG. 21 is a diagram showing main magnetic fluxes passing through the coil element by the conductor pattern formed in each layer of the multilayer substrate shown in FIG. FIG. 22 is a diagram showing the magnetic coupling relationship of the four coil elements L1a, L1b, L2a, and L2b of the impedance conversion circuit according to the ninth embodiment. FIG. 23 is a diagram illustrating an example of a conductor pattern of each layer of the impedance conversion circuit according to the tenth embodiment configured on a multilayer substrate. FIG. 24 is a diagram showing main magnetic fluxes passing through the coil element by the conductor pattern formed in each layer of the multilayer substrate shown in FIG. FIG. 25 is a diagram showing the magnetic coupling relationship of the four coil elements L1a, L1b, L2a, and L2b of the impedance conversion circuit according to the ninth embodiment. FIG. 26 is a diagram illustrating an example of a conductor pattern of each layer when the impedance conversion circuit according to the eleventh embodiment is configured on a multilayer substrate. FIG. 27 is a circuit diagram of an impedance conversion circuit according to the twelfth embodiment. FIG. 28 is a diagram illustrating an example of a conductor pattern of each layer when the impedance conversion circuit according to the twelfth embodiment is configured on a multilayer substrate. FIG. 29 is a circuit diagram of an impedance conversion circuit according to the thirteenth embodiment. FIG. 30 is a diagram illustrating an example of a conductor pattern of each layer when the impedance conversion circuit according to the thirteenth embodiment is configured on a multilayer substrate. FIG. 31A is a configuration diagram of a communication terminal apparatus as a first example of the fourteenth embodiment, and FIG. 31B is a configuration diagram of a communication terminal apparatus as a second example.

  The following first to fifth and fourteenth embodiments (FIGS. 1 to 12 and 31) are embodiments of the antenna device and the communication terminal device included in the present invention.

<< First Embodiment >>
FIG. 1A is a circuit diagram of the antenna device 101 according to the first embodiment, and FIG. 1B is an equivalent circuit diagram thereof.
As illustrated in FIG. 1A, the antenna device 101 includes an antenna element 11 and an impedance conversion circuit 45 connected to the antenna element 11. The antenna element 11 is a monopole antenna, and an impedance conversion circuit 45 is connected to the feeding end of the antenna element 11. The impedance conversion circuit 45 is inserted between the antenna element 11 and the power feeding circuit 30. The power feeding circuit 30 is a power feeding circuit for feeding a high frequency signal to the antenna element 11 and generates and processes a high frequency signal, but may include a circuit that combines and demultiplexes the high frequency signal.

  The impedance conversion circuit 45 includes a first inductance element L1 connected to the power feeding circuit 30 and a second inductance element L2 coupled to the first inductance element L1. More specifically, the first end of the first inductance element L1 is connected to the feeder circuit 30, the second end is connected to the ground, the first end of the second inductance element L2 is connected to the antenna element 11, and the second end. Each end is connected to ground.

  The first inductance element L1 and the second inductance element L2 are tightly coupled. As a result, a pseudo negative inductance component is generated. The negative inductance component cancels out the inductance component of the antenna element 11 itself, so that the inductance component of the antenna element 11 is apparently small. That is, since the effective inductive reactance component of the antenna element 11 is reduced, the antenna element 11 is less dependent on the frequency of the high frequency signal.

  The impedance conversion circuit 45 includes a transformer type circuit in which the first inductance element L1 and the second inductance element L2 are tightly coupled via the mutual inductance M. As shown in FIG. 1B, this transformer type circuit can be equivalently converted into a T type circuit including three inductance elements Z1, Z2, and Z3. That is, the T-type circuit includes a first port P1 connected to the power feeding circuit, a second port P2 connected to the antenna element 11, a third port P3 connected to the ground, the first port P1 and the branch point. A first inductance element Z1 connected between them, a second inductance element Z2 connected between the second port P2 and the branch point A, and a third terminal connected between the third port P3 and the branch point A. It consists of an inductance element Z3.

  When the inductance of the first inductance element L1 shown in FIG. 1A is L1, the inductance of the second inductance element L2 is L2, and the mutual inductance is M, the inductance of the first inductance element Z1 of FIG. , L1-M, the inductance of the second inductance element Z2 is L2-M, and the inductance of the third inductance element Z3 is + M. If L2 <M, the inductance of the second inductance element Z2 is a negative value. That is, a pseudo negative composite inductance component is formed here.

  On the other hand, the antenna element 11 is equivalently composed of an inductance component LANT, a radiation resistance component Rr, and a capacitance component CANT as shown in FIG. The inductance component LANT of the antenna element 11 alone acts so as to be canceled out by the negative combined inductance component (L2-M) in the impedance conversion circuit 45. That is, when the antenna element 11 side is viewed from the point A of the impedance conversion circuit, the inductance component (of the antenna element 11 including the second inductance element Z2) is small (ideally zero). The impedance frequency characteristic of 101 becomes small.

  In order to generate such a negative inductance component, it is important to couple the first inductance element and the second inductance element with a high degree of coupling. Specifically, the degree of coupling may be 1 or more.

  The impedance conversion ratio by the transformer circuit is a ratio (L1: L2) of the inductance L2 of the second inductance element L2 to the inductance L1 of the first inductance element L1.

  FIG. 2 is a diagram schematically showing the action of a negative inductance component that is artificially generated in the impedance conversion circuit 45 and the action of the impedance conversion circuit 45. In FIG. 2, a curve S0 represents an impedance locus on the Smith chart when the frequency is swept over the use frequency band of the antenna element 11. Since the antenna element 11 alone has a relatively large inductance component LANT, the impedance changes greatly as shown in FIG.

  In FIG. 2, a curve S1 is an impedance locus when the antenna element 11 side is viewed from the point A of the impedance conversion circuit. In this way, the inductance component LANT of the antenna element is canceled by the pseudo negative inductance component of the impedance conversion circuit, and the locus of the impedance viewed from the point A toward the antenna element side is greatly reduced.

  In FIG. 2, a curve S <b> 2 is an impedance locus of the antenna device 101 as viewed from the power feeding circuit 30. Thus, the impedance of the antenna device 101 approaches 50Ω (the center of the Smith chart) by the impedance conversion ratio (L1: L2) by the transformer type circuit. This fine adjustment of the impedance may be performed by adding a separate inductance element or capacitance element to the transformer type circuit.

  In this manner, the impedance change of the antenna device can be suppressed over a wide band. Therefore, impedance matching with the feeder circuit can be achieved over a wide frequency band.

<< Second Embodiment >>
FIG. 3A is a circuit diagram of the antenna device 102 of the second embodiment, and FIG. 3B is a diagram showing a specific arrangement of each coil element.
The basic configuration of the second embodiment is the same as that of the first embodiment, but a more specific configuration for coupling (tight coupling) the first inductance element and the second inductance element with an extremely high degree of coupling. Is shown.

  As shown in FIG. 3A, the first inductance element L1 is composed of a first coil element L1a and a second coil element L1b, and these coil elements are connected in series with each other, and a closed magnetic circuit Is wound to constitute. The second inductance element L2 includes a third coil element L2a and a fourth coil element L2b, and these coil elements are connected in series with each other and wound so as to form a closed magnetic circuit. . In other words, the first coil element L1a and the second coil element L1b are coupled in opposite phases (polarity coupling), and the third coil element L2a and the fourth coil element L2b are coupled in opposite phases (polarity coupling). .

  Further, the first coil element L1a and the third coil element L2a can be coupled in phase (depolarized coupling), and the second coil element L1b and the fourth coil element L2b can be coupled in phase (depolarized coupling). preferable.

  FIG. 4 is a diagram in which various arrows indicating states of magnetic field coupling and electric field coupling are entered in the circuit illustrated in FIG. As shown in FIG. 4, when a current is supplied from the power feeding circuit in the direction of arrow a in the figure, a current flows in the direction of arrow b in the figure through the first coil element L1a, and the arrow in the figure is drawn in the second coil element L1b. Current flows in the direction c. Then, as indicated by an arrow A in the figure, a magnetic flux passing through the closed magnetic path is formed by these currents.

  Since the coil element L1a and the coil element L2a are parallel to each other, the magnetic field generated by the current b flowing through the coil element L1a is coupled to the coil element L2a, and the induced current d flows through the coil element L2a in the reverse direction. Similarly, since the coil element L1b and the coil element L2b are parallel to each other, the magnetic field generated by the current c flowing through the coil element L1b is coupled to the coil element L2b, and the induced current e is applied to the coil element L2b in the reverse direction. Flowing. Then, as indicated by an arrow B in the figure, a magnetic flux passing through the closed magnetic path is formed by these currents.

  Since the closed magnetic circuit of the magnetic flux A generated in the first inductance element L1 by the coil elements L1a and L1b and the closed magnetic circuit of the magnetic flux B generated in the second inductance element L2 by the coil elements L1b and L2b are independent, the first inductance element An equivalent magnetic barrier MW is generated between L1 and the second inductance element L2.

  The coil element L1a and the coil element L2a are also coupled by an electric field. Similarly, coil element L1b and coil element L2b are also coupled by an electric field. Therefore, when an AC signal flows through the coil element L1a and the coil element L1b, a current is excited in the coil element L2a and the coil element L2b by electric field coupling. Capacitors Ca and Cb in FIG. 4 are symbols representing the coupling capacitance for the electric field coupling.

  When an alternating current flows through the first inductance element L1, the direction of the current flowing through the second inductance element L2 due to the coupling via the magnetic field and the direction of the current flowing through the second inductance element L2 due to the coupling via the electric field are: The same. Therefore, the first inductance element L1 and the second inductance element L2 are strongly coupled by both the magnetic field and the electric field. That is, loss can be suppressed and high frequency energy can be propagated.

  When an alternating current flows through the first inductance element L1, the impedance conversion circuit 35 has a direction of a current flowing through the second inductance element L2 due to coupling via a magnetic field and a current flowing through the second inductance element L2 due to coupling via an electric field. It can also be said that the circuit is configured to have the same direction.

  FIG. 5 is a circuit diagram of the antenna device 102 corresponding to multiband. This antenna device 102 is an antenna device used in a multiband-compatible mobile radio communication system (800 MHz band, 900 MHz band, 1800 MHz band, 1900 MHz band) that can support the GSM (registered trademark) system and the CDMA system. The antenna element 11 is a branched monopole antenna.

  The impedance conversion circuit 35 'used here is between the first inductance element L1 composed of the coil element L1a and the coil element L1b and the second inductance element L2 composed of the coil element L2a and the coil element L2b. The other configuration is the same as that of the impedance conversion circuit 35 described above.

  This antenna device 102 is used as a main antenna of the communication terminal device. The first radiating part of the branched monopole antenna element 11 mainly functions as an antenna radiating element on the high band side (1800 to 2400 MHz band), and the first radiating part and the second radiating part are mainly on the low band side ( 800 to 900 MHz band). Here, the branched monopole antenna elements 11 do not necessarily have to resonate in their corresponding frequency bands. This is because the impedance conversion circuit 35 ′ matches the characteristic impedance of each radiating section with the impedance of the power feeding circuit 30. For example, the impedance conversion circuit 35 ′ matches the characteristic impedance of the first radiating unit and the second radiating unit with the impedance (usually 50Ω) of the feeder circuit 30 in the 800 to 900 MHz band. Thus, the low-band high-frequency signal supplied from the power supply circuit 30 is radiated from the first radiating unit and the second radiating unit, or the low-band high-frequency signal received by the first radiating unit and the second radiating unit is fed. Can be supplied to. Similarly, the high-band high-frequency signal supplied from the power supply circuit 30 can be radiated from the first radiation unit, or the high-band high-frequency signal received by the first radiation unit can be supplied to the power supply circuit 30.

  In the impedance conversion circuit 35 ', the capacitor C1 passes a signal in a particularly high frequency band among the high band high frequency signals. As a result, the antenna device can be further widened. Further, according to the structure of the present embodiment, the antenna and the power feeding circuit are separated from each other in terms of direct current, and thus are strong against ESD.

<< Third Embodiment >>
FIG. 6A is a perspective view of the impedance conversion circuit 35 of the third embodiment, and FIG. 6B is a perspective view of the impedance conversion circuit 35 as viewed from the lower surface side. FIG. 7 is an exploded perspective view of the laminated body 40 constituting the impedance conversion circuit 35.

  As shown in FIG. 7, the conductor pattern 61 is formed on the uppermost base layer 51a of the laminate 40, and the conductor pattern 62 (62a, 62b) is formed on the second base layer 51b. Conductive patterns 63 and 64 are formed on the base material layer 51c. Two conductor patterns 65 and 66 are formed on the fourth base layer 51d, and conductor patterns 67 (67a and 67b) are formed on the fifth base layer 51e. Further, a ground conductor 68 is formed on the sixth base layer 51f, and a power supply terminal 41, a ground terminal 42, and an antenna terminal 43 are formed on the back surface of the seventh base layer 51g. A plain base material layer (not shown) is laminated on the uppermost base material layer 51a.

  The conductor patterns 62a and 63 constitute a first coil element L1a, and the conductor patterns 62b and 64 constitute a second coil element L1b. The conductor patterns 65 and 67a constitute a third coil element L2a, and the conductor patterns 66 and 67b constitute a fourth coil element L2b.

  The various conductor patterns 61 to 68 can be formed using a conductive material such as silver or copper as a main component. For the base material layers 51a to 51g, a glass ceramic material, an epoxy resin material, or the like can be used as long as it is a dielectric, and a ferrite ceramic material or a resin material containing ferrite can be used as a magnetic material. . As a material for the base layer, it is preferable to use a dielectric material when forming an impedance conversion circuit for the UHF band, and use a magnetic material when forming an impedance conversion circuit for the HF band. Is preferred.

By laminating the base material layers 51a to 51g, the conductor patterns 61 to 68 and the terminals 41, 42, and 43 are connected through interlayer connection conductors (via conductors) to constitute the circuit shown in FIG.
As shown in FIG. 7, the first coil element L1a and the second coil element L1b are adjacently arranged so that the winding axes of the respective coil patterns are parallel to each other. Similarly, the third coil element L2a and the fourth coil element L2b are adjacently arranged so that the winding axes of the respective coil patterns are parallel to each other. Further, the first coil element L1a and the third coil element L2a are arranged close to each other (coaxially) so that the winding axes of the respective coil patterns are substantially the same straight line. Similarly, the second coil element L1b and the fourth coil element L2b are arranged close to each other (coaxially) so that the winding axes of the respective coil patterns are substantially the same straight line. That is, when viewed from the stacking direction of the base material layers, the conductor patterns constituting each coil pattern are arranged so as to overlap each other.

  The coil elements L1a, L1b, L2a, and L2b are each composed of a loop conductor having approximately two turns, but the number of turns is not limited thereto. Further, the winding axes of the coil patterns of the first coil element L1a and the third coil element L2a need not be arranged so as to be exactly the same straight line, and the first coil element L1a and the third coil element in a plan view It is only necessary that the coil openings of L2a are wound so as to overlap each other. Similarly, the coil patterns of the second coil element L1b and the fourth coil element L2b do not have to be arranged so that the winding axes are exactly the same straight line, and the second coil element L1b and the fourth coil in a plan view. It only has to be wound so that the coil openings of the element L2b overlap each other.

  As described above, the coil elements L1a, L1b, L2a, and L2b are built in and integrated in the dielectric or magnetic laminate 40, and in particular, the first inductance element L1 and the coil element L2a formed by the coil elements L1a and L1b. , L2b are provided in the laminated body 40 with a region serving as a coupling portion with the second inductance element L2, and the element values of the elements constituting the impedance conversion circuit 35, and further, the first inductance element L1 and the second inductance element The degree of coupling with L2 is less affected by other electronic elements arranged adjacent to the stacked body 40. As a result, the frequency characteristics can be further stabilized.

  By the way, a printed wiring board (not shown) on which the laminate 40 is mounted is provided with various wirings, and these wirings and the impedance conversion circuit 35 may interfere with each other. As in this embodiment, the ground conductor 68 is provided at the bottom of the multilayer body 40 so as to cover the opening of the coil pattern formed by the conductor patterns 61 to 67, so that the magnetic field generated in the coil pattern is generated on the printed wiring board. Less susceptible to magnetic fields from various wirings. In other words, the inductance values of the coil elements L1a, L1b, L2a, and L2b are less likely to vary.

  FIG. 8 is a diagram showing the operating principle of the impedance conversion circuit 35. In FIG. As shown in FIG. 8, when the high-frequency signal current input from the power supply terminal 41 flows as indicated by arrows a and b, the first coil element L1a (conductor patterns 62a and 63) is indicated by arrows c and d. And then guided to the second coil element L1b (conductor patterns 62b and 64) as indicated by arrows e and f. Since the first coil element L1a (conductor patterns 62a, 63) and the third coil element L2a (conductor patterns 65, 67a) run in parallel with each other, the third coil element L2a ( High-frequency signal currents indicated by arrows g and h are induced in the conductor patterns 65 and 67a).

  Similarly, since the second coil element L1b (conductor patterns 62b and 64) and the fourth coil element L2b (conductor patterns 66 and 67b) are parallel to each other, the fourth coil is generated by mutual inductive coupling and electric field coupling. High-frequency signal currents indicated by arrows i and j are induced in the element L2b (conductor patterns 66 and 67b).

  As a result, a high-frequency signal current indicated by an arrow k flows through the antenna terminal 43, and a high-frequency signal current indicated by an arrow l flows through the ground terminal 42. Note that if the current flowing through the power supply terminal 41 (arrow a) is in the opposite direction, the direction of other currents is also reversed.

  Here, since the conductor pattern 63 of the first coil element L1a and the conductor pattern 65 of the third coil element L2a are opposed to each other, electric field coupling occurs between them, and the current flowing through this electric field coupling is the induced current. Flows in the same direction. That is, the coupling degree is strengthened by magnetic field coupling and electric field coupling. Similarly, magnetic field coupling and electric field coupling also occur in the conductor pattern 64 of the second coil element L1b and the conductor pattern 66 of the fourth coil element L2b.

  The first coil element L1a and the second coil element L1b are coupled in phase with each other, and the third coil element L2a and the fourth coil element L2b are coupled in phase with each other to form a closed magnetic circuit. Therefore, the two magnetic fluxes C and D are confined to reduce energy loss between the first coil element L1a and the second coil element L1b and between the third coil element L2a and the fourth coil element L2b. can do. If the inductance values of the first coil element L1a and the second coil element L1b and the inductance values of the third coil element L2a and the fourth coil element L2b are set to substantially the same element value, the leakage magnetic field of the closed magnetic circuit is reduced. Energy loss can be further reduced. Of course, the impedance conversion ratio can be controlled by appropriately designing the element value of each coil element.

  In addition, since the third coil element L2a and the fourth coil element L2b are electrically coupled by the capacitors Cag and Cbg via the ground conductor 68, the current flowing by this field coupling further enhances the degree of coupling between L2a and L2b. . If there is a ground on the upper side, the coupling between L1a and L1b can be further increased by generating electric field coupling between the first coil element L1a and the second coil element L1b by the capacitors Cag and Cbg.

Further, the magnetic flux C excited by the primary current flowing in the first inductance element L1 and the magnetic flux D excited by the secondary current flowing in the second inductance element L2 are repelled by the induced current (repulsion). To occur). As a result, since the magnetic field generated in the first coil element L1a and the second coil element L1b and the magnetic field generated in the third coil element L2a and the fourth coil element L2b are confined in a narrow space, respectively, the first coil element L1a and the first coil element L1a The three-coil element L2a, the second coil element L1b, and the fourth coil element L2b are coupled with a higher degree of coupling. That is, the first inductance element L1 and the second inductance element L2 are coupled with a high degree of coupling.
<< Fourth Embodiment >>
FIG. 9 is a circuit diagram of the antenna device of the fourth embodiment. The impedance conversion circuit 34 used here includes a first inductance element L1 and two second inductance elements L21 and L22. The fifth coil element L2c and the sixth coil element L2d constituting the second inductance element L22 are coupled in phase with each other. The fifth coil element L2c is coupled with the first coil element L1a in reverse phase, and the sixth coil element L2d is coupled with the second coil element L1b in reverse phase. One end of the fifth coil element L2c is connected to the radiating element 11, and one end of the sixth coil element L2d is connected to the ground.

  FIG. 10 is an exploded perspective view of the laminated body 40 constituting the impedance conversion circuit 34. In this example, the base material layer 51i in which the conductors 71, 72, and 73 constituting the fifth coil element L2c and the sixth coil element L2d are further formed on the stacked body 40 shown in FIG. 7 in the third embodiment. , 51j are stacked. That is, similarly to the first to fourth coil elements described above, the fifth and sixth coil elements are respectively configured, the fifth and sixth coil elements L2c and L2d are configured by the conductors of the coil pattern, and the first The fifth and sixth coil elements L2c and L2d are wound so that the magnetic flux generated in the fifth and sixth coil elements L2c and L2d forms a closed magnetic path.

  The operation principle of the impedance conversion circuit 34 of the fourth embodiment is basically the same as that of the first to third embodiments. In the fourth embodiment, the stray capacitance generated between the first inductance element L1 and the ground is suppressed by arranging the first inductance element L1 so as to be sandwiched between the two second inductance elements L21 and L22. The By suppressing such a capacitive component that does not contribute to radiation, the radiation efficiency of the antenna can be increased.

  Further, the first inductance element L1 and the second inductance elements L21, L22 are more tightly coupled, that is, the leakage magnetic field is reduced, and the high-frequency signal between the first inductance element L1 and the second inductance elements L21, L22 is reduced. Energy transmission loss is reduced.

<< Fifth Embodiment >>
FIG. 11A is a perspective view of the impedance conversion circuit 135 of the fifth embodiment, and FIG. 11B is a perspective view of the impedance conversion circuit 135 viewed from the lower surface side. FIG. 12 is an exploded perspective view of the laminate 40 constituting the impedance conversion circuit 135.

  The laminated body 140 is formed by laminating a plurality of base material layers made of a dielectric material or a magnetic material, and has a power supply terminal 141 connected to the power supply circuit 30, a ground terminal 142 connected to the ground, and the antenna element 11 on the back surface thereof. An antenna terminal 143 connected to is provided. In addition, an NC terminal 144 used for mounting is also provided on the back surface. Note that an inductor or a capacitor for impedance matching may be mounted on the surface of the multilayer body 140 as necessary. Further, an inductor or a capacitor may be formed in the multilayer body 140 with an electrode pattern.

  As shown in FIG. 12, the impedance conversion circuit 135 built in the laminate 140 has the various terminals 141, 142, 143, and 144 formed on the first base layer 151a. Conductive patterns 161 and 163 to be the first and third coil elements L1a and L2a are formed on the base layer 151b, and the conductive pattern 162 to be the second and fourth coil elements L1b and L2b are formed on the third base layer 151c. , 164 are formed.

  The conductor patterns 161 to 164 can be formed by screen printing of a paste mainly composed of a conductive material such as silver or copper, or etching of a metal foil. As the base material layers 151a to 151c, a glass ceramic material, an epoxy resin material, or the like can be used as long as it is a dielectric, and a ferrite ceramic material or a resin material containing ferrite can be used as a magnetic material. .

  By laminating the base material layers 151a to 151c, the conductor patterns 161 to 164 and the terminals 141, 142, and 143 are connected via the interlayer connection conductors (via hole conductors), as shown in FIG. Configure an equivalent circuit. That is, the power supply terminal 141 is connected to one end of the conductor pattern 161 (first coil element L1a) via the via-hole conductor pattern 165a, and the other end of the conductor pattern 161 is connected to the conductor pattern 162 (second coil element) via the via-hole conductor 165b. L1b) is connected to one end. The other end of the conductor pattern 162 is connected to the ground terminal 142 via the via-hole conductor 165c, and the other end of the branched conductor pattern 164 (fourth coil element L2b) is connected to the conductor pattern 163 (third coil element) via the via-hole conductor 165d. L2a) is connected to one end. The other end of the conductor pattern 163 is connected to the antenna terminal 143 through a via-hole conductor 165e.

  As described above, the coil elements L1a, L1b, L2a, and L2b are built in the multilayer body 140 made of a dielectric material or a magnetic material, and in particular, a region serving as a coupling portion between the first inductance element L1 and the second inductance element L2. By providing the laminated body 140 inside, the impedance conversion circuit 135 is hardly affected by other circuits and elements arranged adjacent to the laminated body 140. As a result, the frequency characteristics can be further stabilized.

  In addition, the first coil element L1a and the third coil element L2a are provided in the same layer (base material layer 151b) of the laminate 140, and the second coil element L1b and the fourth coil element L2b are provided in the same layer of the laminate 140 ( By providing in the base material layer 151c), the thickness of the laminated body 140 (impedance conversion circuit 135) becomes thin. Furthermore, since the first coil element L1a and the third coil element L2a and the second coil element L1b and the fourth coil element L2b that are coupled to each other can be formed in the same process (for example, application of conductive paste), stacking deviation, etc. The variation in the coupling degree due to the is suppressed, and the reliability is improved.

<< Sixth Embodiment >>
FIG. 13 is a circuit diagram of the antenna device 106 according to the sixth embodiment, and FIG. 13B is an equivalent circuit diagram thereof.
As shown in FIG. 13A, the antenna device 106 includes an antenna element 11 and an impedance conversion circuit 25 connected to the antenna element 11. The antenna element 11 is a monopole antenna, and an impedance conversion circuit 25 is connected to the feeding end of the antenna element 11. The impedance conversion circuit 25 (strictly speaking, the first inductance element L1 of the impedance conversion circuit 25) is inserted between the antenna element 11 and the power feeding circuit 30. The power feeding circuit 30 is a power feeding circuit for feeding a high frequency signal to the antenna element 11 and generates and processes a high frequency signal, but may include a circuit that combines and demultiplexes the high frequency signal.

  The impedance conversion circuit 25 includes a first inductance element L1 connected to the power feeding circuit 30 and a second inductance element L2 coupled to the first inductance element L1. More specifically, the first end of the first inductance element L1 is connected to the power feeding circuit 30, the second end is connected to the antenna, the first end of the second inductance element L2 is connected to the antenna element 11, and the second end. Each end is connected to ground.

  The first inductance element L1 and the second inductance element L2 are tightly coupled. As a result, a pseudo negative inductance component is generated. The inductance component of the antenna element 11 is apparently reduced by canceling out the inductance component of the antenna element 11 itself by the negative inductance component. That is, since the effective inductive reactance component of the antenna element 11 is reduced, the antenna element 11 is less dependent on the frequency of the high frequency signal.

  The impedance conversion circuit 25 includes a transformer type circuit in which the first inductance element L1 and the second inductance element L2 are tightly coupled via the mutual inductance M. As shown in FIG. 13B, this transformer type circuit can be equivalently converted into a T type circuit including three inductance elements Z1, Z2, and Z3. That is, the T-type circuit includes a first port P1 connected to the power feeding circuit, a second port P2 connected to the antenna element 11, a third port P3 connected to the ground, the first port P1 and the branch point A. The first inductance element Z1 connected between the second port P2 and the second inductance element Z2 connected between the branch point A, and the second inductance element Z2 connected between the third port P3 and the branch point A. It is comprised by 3 inductance element Z3.

  When the inductance of the first inductance element L1 shown in FIG. 13A is L1, the inductance of the second inductance element L2 is L2, and the mutual inductance is M, the inductance of the first inductance element Z1 of FIG. , L1 + M, the inductance of the second inductance element Z2 is −M, and the inductance of the third inductance element Z3 is L2 + M. That is, the inductance of the second inductance element Z2 is a negative value regardless of the values of L1 and L2. That is, a pseudo negative inductance component is formed here.

  On the other hand, the antenna element 11 is equivalently composed of an inductance component LANT, a radiation resistance component Rr, and a capacitance component CANT as shown in FIG. The inductance component LANT of the antenna element 11 alone acts so as to be canceled by the negative inductance component (−M) in the impedance conversion circuit 25. That is, the inductance component (of the antenna element 11 including the second inductance element Z2) viewed from the point A of the impedance conversion circuit is small (ideally zero), and as a result, The impedance frequency characteristic of the antenna device 106 is reduced.

  In order to generate such a negative inductance component, it is important to couple the first inductance element and the second inductance element with a high degree of coupling. Specifically, although it depends on the element value of the inductance element, the degree of coupling is preferably 0.5 or more, and more preferably 0.7 or more. That is, with such a configuration, an extremely high degree of coupling such as the degree of coupling in the first embodiment is not necessarily required.

<< Seventh Embodiment >>
FIG. 14A is a circuit diagram of the antenna device 107 of the seventh embodiment, and FIG. 14B is a diagram showing a specific arrangement of each coil element.
The basic configuration of the seventh embodiment is the same as that of the sixth embodiment, but a more specific configuration for coupling (tight coupling) the first inductance element and the second inductance element with a very high degree of coupling. Is shown.

  As shown in FIG. 14A, the first inductance element L1 is composed of a first coil element L1a and a second coil element L1b, and these coil elements are connected in series to each other, and a closed magnetic circuit Is wound to constitute. The second inductance element L2 includes a third coil element L2a and a fourth coil element L2b, and these coil elements are connected in series with each other and wound so as to form a closed magnetic circuit. . In other words, the first coil element L1a and the second coil element L1b are coupled in opposite phases (polarity coupling), and the third coil element L2a and the fourth coil element L2b are coupled in opposite phases (polarity coupling). .

  Further, the first coil element L1a and the third coil element L2a can be coupled in phase (depolarized coupling), and the second coil element L1b and the fourth coil element L2b can be coupled in phase (depolarized coupling). preferable.

  FIG. 15A is a diagram showing the transformer ratio of the impedance conversion circuit based on the equivalent circuit shown in FIG. FIG. 15B is a diagram in which various arrows indicating states of magnetic field coupling and electric field coupling are entered in the circuit illustrated in FIG. 14B.

  As shown in FIG. 15B, when a current is supplied from the power feeding circuit in the direction of the arrow a in the figure, a current flows in the first coil element L1a in the direction of the arrow b in the figure, and in the coil element L1b, Current flows in the direction of arrow c. These electric currents form a magnetic flux (magnetic flux passing through a closed magnetic path) indicated by an arrow A in the figure.

  Since the coil element L1a and the coil element L2a are parallel to each other, the magnetic field generated by the current b flowing through the coil element L1a is coupled to the coil element L2a, and the induced current d flows through the coil element L2a in the reverse direction. Similarly, since the coil element L1b and the coil element L2b are parallel to each other, the magnetic field generated by the current c flowing through the coil element L1b is coupled to the coil element L2b, and the induced current e is applied to the coil element L2b in the reverse direction. Flowing. Then, as indicated by an arrow B in the figure, a magnetic flux passing through the closed magnetic path is formed by these currents.

  Since the closed magnetic circuit of the magnetic flux A generated in the first inductance element L1 by the coil elements L1a and L1b and the closed magnetic circuit of the magnetic flux B generated in the second inductance element L2 by the coil elements L1b and L2b are independent, the first inductance element An equivalent magnetic barrier MW is generated between L1 and the second inductance element L2.

  The coil element L1a and the coil element L2a are also coupled by an electric field. Similarly, coil element L1b and coil element L2b are also coupled by an electric field. Therefore, when an AC signal flows through the coil element L1a and the coil element L1b, a current is excited in the coil element L2a and the coil element L2b by electric field coupling. Capacitors Ca and Cb in FIG. 4 are symbols representing the coupling capacitance for the electric field coupling.

  When an alternating current flows through the first inductance element L1, the direction of the current flowing through the second inductance element L2 due to the coupling via the magnetic field and the direction of the current flowing through the second inductance element L2 due to the coupling via the electric field are: The same. Therefore, the first inductance element L1 and the second inductance element L2 are strongly coupled by both the magnetic field and the electric field.

  When an alternating current flows through the first inductance element L1, the impedance conversion circuit 25 directs the direction of the current flowing through the second inductance element L2 through coupling via a magnetic field and the current flowing through the second inductance element L2 through coupling through an electric field. It can also be said that the circuit is configured to have the same direction.

  When this impedance conversion circuit 25 is equivalently converted, it can be expressed as a circuit of FIG. That is, the combined inductance component between the power feeding circuit and the ground is L1 + M + L2 + M = L1 + L2 + 2M, as shown by the one-dot chain line in the figure, and the combined inductance component between the antenna element and the ground is shown by the two-dot chain line in the figure. And L2 + M−M = L2. That is, the transformer ratio in this impedance conversion circuit is L1 + L2 + 2M: L2, and an impedance conversion circuit with a large transformer ratio can be configured.

  FIG. 16 is a circuit diagram of the antenna device 107 corresponding to the multiband. The antenna device 107 is an antenna device used in a multiband-compatible mobile radio communication system (800 MHz band, 900 MHz band, 1800 MHz band, 1900 MHz band) that can support the GSM (registered trademark) system and the CDMA system. The antenna element 11 is a branched monopole antenna.

  This antenna device 102 is used as a main antenna of the communication terminal device. The first radiating part of the branched monopole antenna element 11 mainly functions as an antenna radiating element on the high band side (1800 to 2400 MHz band), and the first radiating part and the second radiating part are mainly on the low band side ( 800 to 900 MHz band). Here, the branched monopole antenna elements 11 do not need to resonate in their corresponding frequency bands. This is because the impedance conversion circuit 25 matches the characteristic impedance of each radiation unit with the impedance of the power feeding circuit 30. For example, in the 800 to 900 MHz band, the impedance conversion circuit 25 matches the characteristic impedance of the second radiating unit with the impedance (usually 50Ω) of the power feeding circuit 30. Accordingly, the low-band high-frequency signal supplied from the power feeding circuit 30 can be radiated from the second radiating unit, or the low-band high-frequency signal received by the second radiating unit can be supplied to the power feeding circuit 30. Similarly, the high-band high-frequency signal supplied from the power supply circuit 30 can be radiated from the first radiation unit, or the high-band high-frequency signal received by the first radiation unit can be supplied to the power supply circuit 30.

<< Eighth Embodiment >>
FIG. 17 is a diagram illustrating an example of a conductor pattern of each layer when the impedance conversion circuit 25 according to the eighth embodiment is configured on a multilayer substrate. Each layer is composed of a magnetic sheet, and the conductor pattern of each layer is formed on the back surface of the magnetic sheet in the direction shown in FIG. 17, but each conductor pattern is represented by a solid line. Moreover, although the linear conductor pattern has a predetermined line width, it is represented by a simple solid line here.

  In the range shown in FIG. 17, the conductor pattern 73 is formed on the back surface of the base material layer 51a, the conductor patterns 72 and 74 are formed on the back surface of the base material layer 51b, and the conductor patterns 71 and 75 are formed on the back surface of the base material layer 51c. Is formed. Conductive pattern 63 is formed on the back surface of base material layer 51d, conductive patterns 62 and 64 are formed on the back surface of base material layer 51e, and conductive patterns 61 and 65 are formed on the back surface of base material layer 51f. A conductor pattern 66 is formed on the back surface of the base material layer 51g, and a power feeding terminal 41, a ground terminal 42, and an antenna terminal 43 are formed on the back surface of the base material layer 51h. A broken line extending in the vertical direction in FIG. 17 is a via electrode, and the conductor patterns are connected between the layers. These via electrodes are actually cylindrical electrodes having a predetermined diameter, but are represented here by simple broken lines.

  In FIG. 17, the first coil element L1a is constituted by the right half of the conductor pattern 63 and the conductor patterns 61 and 62. Further, the second coil element L1b is constituted by the left half of the conductor pattern 63 and the conductor patterns 64 and 65. Further, the right half of the conductor pattern 73 and the conductor patterns 71 and 72 constitute the third coil element L2a. The left half of the conductor pattern 73 and the conductor patterns 74 and 75 constitute a fourth coil element L2b. The winding axis of each coil element L1a, L1b, L2a, L2b is oriented in the stacking direction of the multilayer substrate. The winding axes of the first coil element L1a and the second coil element L1b are juxtaposed in a different relationship. Similarly, the third coil element L2a and the fourth coil element L2b are juxtaposed with each other with different winding axes. And each winding range of the 1st coil element L1a and the 3rd coil element L2a overlaps at least partially by planar view, and each winding range of the 2nd coil element L1b and 4th coil element L2b is planar view At least partly overlaps. In this example, they overlap almost completely. In this way, four coil elements are constituted by a conductor pattern having an 8-shaped structure.

  Each layer may be composed of a dielectric sheet. However, if a magnetic sheet having a high relative permeability is used, the coupling coefficient between the coil elements can be further increased.

  FIG. 18 shows the main magnetic flux passing through the coil element by the conductor pattern formed in each layer of the multilayer substrate shown in FIG. The magnetic flux FP12 passes through the first coil element L1a constituted by the conductor patterns 61 to 63 and the second coil element L1b constituted by the conductor patterns 63 to 65. Further, the magnetic flux FP34 passes through the third coil element L2a by the conductor patterns 71 to 73 and the fourth coil element L2b by the conductor patterns 73 to 75.

  FIG. 19 is a diagram showing the magnetic coupling relationship of the four coil elements L1a, L1b, L2a, and L2b of the impedance conversion circuit 25 according to the eighth embodiment. Thus, the first coil element L1a and the second coil element L1b are wound such that the first coil element L1a and the second coil element L1b constitute a first closed magnetic path (a loop indicated by the magnetic flux FP12). The third coil element L2a and the fourth coil element L2b are wound so that the third coil element L2a and the fourth coil element L2b form a second closed magnetic circuit (a loop indicated by the magnetic flux FP34). It has been turned. Thus, the four coil elements L1a, L1b, L2a, and L2b are wound so that the magnetic flux FP12 passing through the first closed magnetic path and the magnetic flux FP34 passing through the second closed magnetic path are in opposite directions. A straight line indicated by a two-dot chain line in FIG. 19 represents a magnetic barrier in which the two magnetic fluxes FP12 and FP34 are not coupled. Thus, magnetic barriers are generated between the coil elements L1a and L2a and between L1b and L2b.

<< Ninth embodiment >>
FIG. 20 is a diagram illustrating a configuration of an impedance conversion circuit according to the ninth embodiment, and is a diagram illustrating an example of a conductor pattern of each layer when the impedance conversion circuit is configured on a multilayer substrate. The conductor pattern of each layer is formed on the back surface in the direction shown in FIG. 20, but each conductor pattern is represented by a solid line. Moreover, although the linear conductor pattern has a predetermined line width, it is represented by a simple solid line here.

  In the range shown in FIG. 20, the conductor pattern 73 is formed on the back surface of the base material layer 51a, the conductor patterns 72 and 74 are formed on the back surface of the base material layer 51b, and the conductor patterns 71 and 75 are formed on the back surface of the base material layer 51c. Is formed. Conductive pattern 63 is formed on the back surface of base material layer 51d, conductive patterns 62 and 64 are formed on the back surface of base material layer 51e, and conductive patterns 61 and 65 are formed on the back surface of base material layer 51f. A conductor pattern 66 is formed on the back surface of the base material layer 51g, and a power feeding terminal 41, a ground terminal 42, and an antenna terminal 43 are formed on the back surface of the base material layer 51h. A broken line extending in the vertical direction in FIG. 20 is a via electrode, and the conductor patterns are connected between the layers. These via electrodes are actually cylindrical electrodes having a predetermined diameter, but are represented here by simple broken lines.

  In FIG. 20, the first coil element L1a is constituted by the right half of the conductor pattern 63 and the conductor patterns 61 and 62. Further, the second coil element L1b is constituted by the left half of the conductor pattern 63 and the conductor patterns 64 and 65. Further, the right half of the conductor pattern 73 and the conductor patterns 71 and 72 constitute the third coil element L2a. The left half of the conductor pattern 73 and the conductor patterns 74 and 75 constitute a fourth coil element L2b.

  FIG. 21 is a diagram showing main magnetic fluxes passing through the coil element by the conductor pattern formed in each layer of the multilayer substrate shown in FIG. FIG. 22 is a diagram showing the magnetic coupling relationship of the four coil elements L1a, L1b, L2a, and L2b of the impedance conversion circuit according to the ninth embodiment. As shown by the magnetic flux FP12, a closed magnetic circuit is constituted by the first coil element L1a and the second coil element L1b, and as shown by the magnetic flux FP34, a closed magnetic circuit is constituted by the third coil element L2a and the fourth coil element L2b. Is done. Further, a closed magnetic circuit is formed by the first coil element L1a and the third coil element L2a as shown by the magnetic flux FP13, and a closed magnetic circuit by the second coil element L1b and the fourth coil element L2b is shown by the magnetic flux FP24. Is configured. Further, a closed magnetic circuit FPall is formed by four coil elements L1a, L1b, L2a, and L2b.

  Even with the configuration of the ninth embodiment, since the inductance values of the coil elements L1a and L1b and L2a and L2b become smaller due to the respective coupling, the impedance conversion circuit shown in the ninth embodiment is the same as that of the seventh embodiment. The same effect as the impedance conversion circuit 25 is obtained.

<< Tenth Embodiment >>
FIG. 23 is a diagram illustrating an example of a conductor pattern of each layer of the impedance conversion circuit according to the tenth embodiment configured on a multilayer substrate. Each layer is composed of a magnetic sheet, and the conductor pattern of each layer is formed on the back surface of the magnetic sheet in the direction shown in FIG. 23, but each conductor pattern is represented by a solid line. Moreover, although the linear conductor pattern has a predetermined line width, it is represented by a simple solid line here.

  In the range shown in FIG. 23, the conductor pattern 73 is formed on the back surface of the base material layer 51a, the conductor patterns 72 and 74 are formed on the back surface of the base material layer 51b, and the conductor patterns 71 and 75 are formed on the back surface of the base material layer 51c. Is formed. Conductive patterns 61 and 65 are formed on the back surface of the base material layer 51d, conductive patterns 62 and 64 are formed on the back surface of the base material layer 51e, and conductive patterns 63 are formed on the back surface of the base material layer 51f. A power supply terminal 41, a ground terminal 42, and an antenna terminal 43 are formed on the back surface of the base material layer 51g. A broken line extending in the vertical direction in FIG. 23 is a via electrode, and the conductor patterns are connected between the layers. These via electrodes are actually cylindrical electrodes having a predetermined diameter, but are represented here by simple broken lines.

  In FIG. 23, the first coil element L1a is constituted by the right half of the conductor pattern 63 and the conductor patterns 61 and 62. Further, the second coil element L1b is constituted by the left half of the conductor pattern 63 and the conductor patterns 64 and 65. Further, the right half of the conductor pattern 73 and the conductor patterns 71 and 72 constitute the third coil element L2a. The left half of the conductor pattern 73 and the conductor patterns 74 and 75 constitute a fourth coil element L2b.

  FIG. 24 is a diagram showing the relationship of magnetic coupling between the four coil elements L1a, L1b, L2a, and L2b of the impedance conversion circuit according to the tenth embodiment. As described above, the first coil element L1a and the second coil element L1b constitute a first closed magnetic circuit (a loop indicated by the magnetic flux FP12). Further, the third coil element L2a and the fourth coil element L2b constitute a second closed magnetic circuit (a loop indicated by a magnetic flux FP34). The directions of the magnetic flux FP12 passing through the first closed magnetic path and the magnetic flux FP34 passing through the second closed magnetic path are opposite to each other.

  Here, when the first coil element L1a and the second coil element L1b are expressed as “primary side” and the third coil element L2a and the fourth coil element L2b are expressed as “secondary side”, as shown in FIG. Since the power feeding circuit is connected to the secondary side closer to the secondary side, the potential in the vicinity of the secondary side of the primary side can be increased, and the electric field between the coil element L1a and the coil element L2a can be increased. Coupling increases and the electric current due to this electric field coupling increases.

  Even with the configuration of the tenth embodiment, the inductance values of the coil elements L1a and L1b and L2a and L2b become smaller due to their respective couplings. Therefore, the impedance conversion circuit shown in the tenth embodiment is also the seventh embodiment. The same effect as that of the impedance conversion circuit 25 is obtained.

<< Eleventh Embodiment >>
FIG. 25 is a circuit diagram of an impedance conversion circuit according to the eleventh embodiment. The impedance conversion circuit includes a first series circuit 26 connected between the power feeding circuit 30 and the antenna element 11, a third series circuit 28 connected between the power feeding circuit 30 and the antenna element 11, and an antenna. The second serial circuit 27 is connected between the element 11 and the ground.

  The first series circuit 26 is a circuit in which a first coil element L1a and a second coil element L1b are connected in series. The second series circuit 27 is a circuit in which a third coil element L2a and a fourth coil element L2b are connected in series. The third series circuit 28 is a circuit in which a fifth coil element L1c and a sixth coil element L1d are connected in series.

  In FIG. 25, an enclosure M12 represents a coupling between the coil elements L1a and L1b, an enclosure M34 represents a coupling between the coil elements L2a and L2b, and an enclosure M56 represents a coupling between the coil elements L1c and L1d. An enclosure M135 represents the coupling of the coil elements L1a, L2a, and L1c. Similarly, box M246 represents the coupling of coil elements L1b, L2b, and L1d.

  In the eleventh embodiment, the coil elements L2a and L2b constituting the second inductance element are arranged so as to be sandwiched between the coil elements L1a, L1b, L1c and L1d constituting the first inductance element. The stray capacitance generated between the two-inductance element and the ground is suppressed. By suppressing such a capacitive component that does not contribute to radiation, the radiation efficiency of the antenna can be increased.

  FIG. 26 is a diagram illustrating an example of a conductor pattern of each layer when the impedance conversion circuit according to the eleventh embodiment is configured on a multilayer substrate. Each layer is composed of a magnetic sheet, and the conductor pattern of each layer is formed on the back surface of the magnetic sheet in the direction shown in FIG. 26, but each conductor pattern is represented by a solid line. Moreover, although the linear conductor pattern has a predetermined line width, it is represented by a simple solid line here.

  In the range shown in FIG. 26, a conductor pattern 82 is formed on the back surface of the base material layer 51a, conductor patterns 81 and 83 are formed on the back surface of the base material layer 51b, and a conductor pattern 72 is formed on the back surface of the base material layer 51c. ing. Conductive patterns 71 and 73 are formed on the back surface of the base material layer 51d, conductive patterns 61 and 63 are formed on the back surface of the base material layer 51e, and conductive patterns 62 are formed on the back surface of the base material layer 51f. A power feeding terminal 41, a ground terminal 42, and an antenna terminal 43 are formed on the back surface of the base material layer 51g. The broken line extending in the vertical direction in FIG. 26 is a via electrode, and the conductor patterns are connected between the layers. These via electrodes are actually cylindrical electrodes having a predetermined diameter, but are represented here by simple broken lines.

  In FIG. 26, the right half of the conductor pattern 62 and the conductor pattern 61 constitute a first coil element L1a. Further, the left half of the conductor pattern 62 and the conductor pattern 63 constitute a second coil element L1b. Further, the third coil element L2a is constituted by the conductor pattern 71 and the right half of the conductor pattern 72. The left half of the conductor pattern 72 and the conductor pattern 73 constitute the fourth coil element L2b. Further, the fifth coil element L1c is constituted by the conductor pattern 81 and the right half of the conductor pattern 82. Further, the left half of the conductor pattern 82 and the conductor pattern 83 constitute a sixth coil element L1d.

  In FIG. 26, a broken line ellipse represents a closed magnetic circuit. The closed magnetic circuit CM12 is linked to the coil elements L1a and L1b. Further, the closed magnetic circuit CM34 is linked to the coil elements L2a and L2b. Further, the closed magnetic circuit CM56 is linked to the coil elements L1c and L1d. As described above, the first coil element L1a and the second coil element L1b constitute a first closed magnetic circuit CM12, and the third coil element L2a and the fourth coil element L2b constitute a second closed magnetic circuit CM34. The fifth coil element L1c and the sixth coil element L1d constitute a third closed magnetic circuit CM56. In FIG. 26, the alternate long and two short dashes line plane is such that the coil elements L1a and L2a, L2a and L1c, L1b and L2b, and L2b and L1d are coupled in the opposite direction between the three closed magnetic paths. Thus, two magnetic barriers MW that are equivalently generated. In other words, the two magnetic barriers MW confine the magnetic flux in the closed magnetic circuit by the coil elements L1a and L1b, the magnetic flux in the closed magnetic circuit by the coil elements L2a and L2b, and the magnetic flux in the closed magnetic circuit by the coil elements L1c and L1d.

  In this way, the second closed magnetic circuit CM34 is sandwiched in the layer direction between the first closed magnetic circuit CM12 and the third closed magnetic circuit CM56. With this structure, the second closed magnetic circuit CM34 is sandwiched between two magnetic barriers and sufficiently confined (the confinement effect is enhanced). That is, it can act as a transformer having a very large coupling coefficient.

  Therefore, the gap between the closed magnetic paths CM12 and CM34 and between the CM34 and CM56 can be widened to some extent. Here, a circuit in which a series circuit composed of coil elements L1a and L1b and a series circuit composed of coil elements L1c and L1d are connected in parallel is referred to as a primary circuit, and a series circuit composed of coil elements L2a and L2b is referred to as a secondary circuit. Then, between the first series circuit 26 and the second series circuit 27 and between the second series circuit 27 and the second series circuit 27 by widening between the closed magnetic circuits CM12 and CM34 and between CM34 and CM56. The capacitance generated between each of the three series circuits 28 can be reduced. That is, the capacitance component of the LC resonance circuit that determines the frequency of the self-resonance point is reduced.

  According to the eleventh embodiment, the first series circuit 26 including the coil elements L1a and L1b and the third series circuit 28 including the coil elements L1c and L1d are connected in parallel. The inductance component of the LC resonance circuit that determines the frequency of the point is reduced.

  In this way, the capacitance component and the inductance component of the LC resonance circuit that determines the frequency of the self-resonance point are reduced, and the frequency of the self-resonance point can be set to a high frequency sufficiently away from the use frequency band.

<< Twelfth Embodiment >>
In the twelfth embodiment, a configuration example for increasing the frequency of the self-resonance point of the transformer unit from that shown in the eighth to tenth embodiments is different from that of the eleventh embodiment.

  FIG. 27 is a circuit diagram of an impedance conversion circuit according to the twelfth embodiment. The impedance conversion circuit includes a first series circuit 26 connected between the power feeding circuit 30 and the antenna element 11, a third series circuit 28 connected between the power feeding circuit 30 and the antenna element 11, and an antenna. The second serial circuit 27 is connected between the element 11 and the ground.

  The first series circuit 26 is a circuit in which a first coil element L1a and a second coil element L1b are connected in series. The second series circuit 27 is a circuit in which a third coil element L2a and a fourth coil element L2b are connected in series. The third series circuit 28 is a circuit in which a fifth coil element L1c and a sixth coil element L1d are connected in series.

  In FIG. 27, an enclosure M12 represents a coupling between the coil elements L1a and L1b, an enclosure M34 represents a coupling between the coil elements L2a and L2b, and an enclosure M56 represents a coupling between the coil elements L1c and L1d. An enclosure M135 represents the coupling of the coil elements L1a, L2a, and L1c. Similarly, box M246 represents the coupling of coil elements L1b, L2b, and L1d.

  FIG. 28 is a diagram illustrating an example of a conductor pattern of each layer when the impedance conversion circuit according to the twelfth embodiment is configured on a multilayer substrate. Each layer is composed of a magnetic sheet, and the conductor pattern of each layer is formed on the back surface of the magnetic sheet in the direction shown in FIG. 28, but each conductor pattern is represented by a solid line. Moreover, although the linear conductor pattern has a predetermined line width, it is represented by a simple solid line here.

  What is different from the impedance conversion circuit shown in FIG. 26 is the polarity of the coil elements L1c and L1d by the conductor patterns 81, 82, and 83. In the example of FIG. 28, the closed magnetic circuit CM36 is linked to the coil elements L2a, L1c, L1d, and L2b. Therefore, an equivalent magnetic barrier does not occur between the coil elements L2a and L2b and L1c and L1d. Other configurations are as shown in the eleventh embodiment.

  According to the twelfth embodiment, the closed magnetic circuits CM12, CM34, and CM56 shown in FIG. 28 and the closed magnetic circuit CM36 are generated, so that the magnetic flux generated by the coil elements L2a and L2b is absorbed by the magnetic flux generated by the coil elements L1c and L1d. . For this reason, the magnetic flux hardly leaks even in the structure of the twelfth embodiment, and as a result, it can act as a transformer having a very large coupling coefficient.

  Also in the twelfth embodiment, the capacitance component and the inductance component of the LC resonance circuit that determines the frequency of the self-resonance point are reduced, and the frequency of the self-resonance point can be set to a high frequency sufficiently away from the use frequency band.

<< Thirteenth embodiment >>
In the thirteenth embodiment, a configuration different from those in the eleventh embodiment and the twelfth embodiment is used to increase the frequency of the self-resonance point of the transformer unit from that shown in the eighth to tenth embodiments. The example of a structure is shown.

  FIG. 29 is a circuit diagram of an impedance conversion circuit according to the thirteenth embodiment. The impedance conversion circuit includes a first series circuit 26 connected between the power feeding circuit 30 and the antenna element 11, a third series circuit 28 connected between the power feeding circuit 30 and the antenna element 11, and an antenna. The second serial circuit 27 is connected between the element 11 and the ground.

  FIG. 30 is a diagram illustrating an example of a conductor pattern of each layer when the impedance conversion circuit according to the thirteenth embodiment is configured on a multilayer substrate. Each layer is composed of a magnetic sheet, and the conductor pattern of each layer is formed on the back surface of the magnetic sheet in the direction shown in FIG. 30, but each conductor pattern is represented by a solid line. Moreover, although the linear conductor pattern has a predetermined line width, it is represented by a simple solid line here.

  26 differs from the impedance conversion circuit shown in FIG. 26 in the polarities of the coil elements L1a and L1b by the conductor patterns 61, 62, and 63 and the polarities of the coil elements L1c and L1d by the conductor patterns 81, 82, and 83. In the example of FIG. 30, the closed magnetic circuit CM16 is linked to all the coil elements L1a to L1d, L2a, and L2b. Therefore, in this case, an equivalent magnetic barrier does not occur. Other configurations are as shown in the eleventh embodiment and the twelfth embodiment.

  According to the thirteenth embodiment, the closed magnetic circuits CM12, CM34, and CM56 shown in FIG. 30 and the closed magnetic circuit CM16 are generated, so that the magnetic flux from the coil elements L1a to L1d is difficult to leak, and as a result, the coupling coefficient is large. Can act as a transformer.

  Also in the thirteenth embodiment, both the capacitance component and the inductance component of the LC resonance circuit that determines the frequency of the self-resonance point are reduced, and the frequency of the self-resonance point can be set to a high frequency sufficiently away from the use frequency band.

<< Fourteenth embodiment >>
The fourteenth embodiment shows an example of a communication terminal device.
FIG. 31A is a configuration diagram of a communication terminal apparatus as a first example of the fourteenth embodiment, and FIG. 31B is a configuration diagram of a communication terminal apparatus as a second example. These are terminals (470 to 770 MHz) for receiving high-frequency signals of, for example, a one-segment partial reception service (common name: one-segment) for mobile phones and mobile terminals.

  A communication terminal device 1 shown in FIG. 31A includes a first housing 10 that is a lid portion and a second housing 20 that is a main body portion, and the first housing 10 is foldable with respect to the second housing 20. It is connected by sliding. The first casing 10 is provided with a first radiating element 11 that also functions as a ground plate, and the second casing 20 is provided with a second radiating element 21 that also functions as a ground plate. The first and second radiating elements 11 and 21 are formed of a conductive film made of a thin film such as a metal foil or a thick film such as a conductive paste. The first and second radiating elements 11 and 21 obtain substantially the same performance as a dipole antenna by being differentially fed from the feeding circuit 30. The power feeding circuit 30 has a signal processing circuit such as an RF circuit or a baseband circuit.

The inductance value of the impedance conversion circuit 35 is preferably smaller than the inductance value of the connection line 33 that connects the two radiating elements 11 and 21. This is because the influence of the inductance value of the connection line 33 relating to the frequency characteristics can be reduced.
A communication terminal device 2 shown in FIG. 31B is provided with the first radiating element 11 as a single antenna. As the first radiating element 11, various antenna elements such as a chip antenna, a sheet metal antenna, and a coil antenna can be used. Moreover, as this antenna element, you may utilize the linear conductor provided along the internal peripheral surface or outer peripheral surface of the housing 10, for example. The second radiating element 21 also functions as a ground plate of the second casing 20, and various antennas may be used similarly to the first radiating element 11. Incidentally, the communication terminal device 2 is a terminal having a straight structure that is not a folding type or a sliding type. The second radiating element 21 does not necessarily function sufficiently as a radiator, and the first radiating element 11 may behave like a so-called monopole antenna.

  One end of the power feeding circuit 30 is connected to the second radiating element 21, and the other end is connected to the first radiating element 11 via the impedance conversion circuit 35. The first and second radiating elements 11 and 21 are connected to each other by a connection line 33. This connection line 33 functions as a connection line for electronic components (not shown) mounted on each of the first and second housings 10 and 20, and acts as an inductance element for high-frequency signals, but the performance of the antenna. It does not act directly.

  The impedance conversion circuit 35 is provided between the power feeding circuit 30 and the first radiating element 11, and is a high-frequency signal transmitted from the first and second radiating elements 11 or 21, or the first and second radiating elements 11, 21 stabilizes the frequency characteristics of the high-frequency signal received. Therefore, the frequency characteristics of the high-frequency signal are stabilized without being affected by the shape of the first radiating element 11 or the second radiating element 21, the shape of the first casing 10 or the second casing 20, the arrangement state of adjacent components, and the like. To do. In particular, in the case of a foldable or slide type communication terminal device, the first and second radiating elements 11, 1 and 2 according to the open / close state of the second housing 20 that is the main body of the first housing 10 that is the lid. The impedance of the high-frequency signal can be stabilized by providing the impedance conversion circuit 35. That is, it is possible for the impedance conversion circuit 35 to carry out frequency characteristic adjustment functions such as setting of the center frequency, setting of the pass bandwidth, setting of impedance matching, which are important matters regarding the antenna design, and the antenna element itself. Since it is only necessary to consider directivity and gain, antenna design becomes easy.

C1 ... Capacitor Ca, Cb ... Capacitor CANT ... Capacitance components CM12, CM34, CM56 ... Closed magnetic circuit CM36, CM16 ... Closed magnetic circuit FP12, FP13, FP24, FP34 ... Magnetic flux L1 ... First inductance elements L2, L21, L22 ... Second inductance Element L1a ... 1st coil element L1b ... 2nd coil element L2a ... 3rd coil element L2b ... 4th coil element L1c, L2c ... 5th coil element L1d, L2d ... 6th coil element LANT ... Inductance component M ... Mutual inductance MW ... Magnetic barrier Rr ... Radiation resistance component Z1 ... First inductance element Z2 ... Second inductance element Z3 ... Third inductance element 1, 2 ... Communication terminal device 10, 20 ... Housing 11 ... Antenna element (first radiation element)
21 ... 2nd radiation element 25 ... impedance conversion circuit 26 ... 1st series circuit 27 ... 2nd series circuit 28 ... 3rd series circuit 30 ... power feeding circuit 33 ... connection line 34, 35 ... impedance conversion circuit 36 ... primary Side series circuit 37 ... Secondary side series circuit 40 ... Laminate 41 ... Feed terminal 42 ... Ground terminal 43 ... Antenna terminal 45 ... Impedance conversion circuits 51a-51j ... Base material layers 61-66 ... Conductor pattern 68 ... Ground conductors 71- 75 ... Conductor patterns 81, 82, 83 ... Conductor patterns 101, 102, 106, 107 ... Antenna device 135 ... Impedance conversion circuit 140 ... Laminate 141 ... Feed terminal 142 ... Ground terminal 143 ... Antenna terminal 144 ... NC terminals 151a, 151b , 151c ... base material layers 161-164 ... conductor patterns 165a-165e ... beer ho Conductor

Claims (9)

An antenna device including an antenna element and an impedance conversion circuit connected to the antenna element,
The impedance conversion circuit includes a transformer type circuit in which a first inductance element and a second inductance element are coupled via a mutual inductance M;
A first end of the first inductance element is connected to a power feeding circuit, a second end of the first inductance element is connected to a ground, a first end of the second inductance element is connected to the antenna element, and the second The second end of the inductance element is connected to ground,
The antenna device according to claim 1, wherein the mutual inductance M is larger than an inductance of the second inductance element.   The first inductance element includes a first coil element and a second coil element, the first coil element and the second coil element are connected in series with each other, and a conductor winding is formed so as to form a closed magnetic circuit. The antenna device according to claim 1, wherein a pattern is formed.   The second inductance element includes a third coil element and a fourth coil element, the third coil element and the fourth coil element are connected in series with each other, and a conductor is wound so as to form a closed magnetic circuit. The antenna device according to claim 1, wherein a pattern is formed. The first inductance element and the second inductance element are coupled via a magnetic field and an electric field,
When an alternating current flows through the first inductance element, a direction of a current flowing through the second inductance element due to coupling via the magnetic field and a direction of a current flowing through the second inductance element due to coupling via the electric field are determined. The antenna device according to claim 1, which is the same.   The direction of the current flowing through the second inductance element when an alternating current flows through the first inductance element is a direction in which a magnetic barrier is generated between the first inductance element and the second inductance element. The antenna apparatus in any one of -4.   The first inductance element and the second inductance element are configured by conductor patterns arranged in a multilayer body in which a plurality of dielectric layers or magnetic layers are stacked, and the first inductance element, the second inductance element, The antenna device according to claim 1, wherein the antenna devices are coupled inside the laminated body.   The said 1st inductance element is comprised by the at least 2 inductance element electrically connected in parallel, These two inductance elements are arrange | positioned in the positional relationship on both sides of the said 2nd inductance element. An antenna device according to claim 1.   The said 2nd inductance element is comprised by the at least 2 inductance element electrically connected in parallel, These two inductance elements are arrange | positioned in the positional relationship which pinches | interposes the said 1st inductance element. An antenna device according to claim 1. A communication terminal device including an antenna device including an antenna element, a power feeding circuit, and an impedance conversion circuit connected between the antenna element and the power feeding circuit,
The impedance conversion circuit includes a transformer type circuit in which a first inductance element and a second inductance element are coupled via a mutual inductance M;
The first end of the first inductance element is connected to the power supply circuit, the second end of the first inductance element is connected to the ground, the first end of the second inductance element is connected to the antenna element, and The second end of the two-inductance element is connected to ground,
The communication terminal apparatus, wherein the mutual inductance M is larger than an inductance of the second inductance element.

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