WO2013168690A1

WO2013168690A1 - Antenna device

Info

Publication number: WO2013168690A1
Application number: PCT/JP2013/062809
Authority: WO
Inventors: 駒木邦宏
Original assignee: 株式会社村田製作所
Priority date: 2012-05-11
Filing date: 2013-05-07
Publication date: 2013-11-14

Abstract

An antenna device (201) comprises a chip antenna (101) and a print substrate (40). The chip antenna (101) is mounted upon the print substrate (40). The chip antenna (101) is configured from a rectangular dielectric substrate (30), and a conductor pattern which is formed on the surface of this dielectric substrate. The dielectric substrate (30) has first radiating electrodes (31a, 31b, 31c) formed thereon which extend from a near side face thereof toward an upper face thereof. Similarly, second radiating electrodes (32a, 32b, 32c) are formed extending from the near side face of the dielectric substrate (30) to the upper face thereof. In the upper face of the dielectric substrate (30), the first radiating electrodes (31a, 31b, 31c) and the second radiating electrodes (32a, 32b, 32c) are primarily coupled with a coupling part (CP), and an Odd mode from an electrical field coupling and an Even mode from a magnetic field coupling arise. Directionality is determined thereby.

Description

Antenna device

The present invention relates to an antenna including a radiation electrode connected to a feeding point and a radiation electrode connected to a ground conductor, and in particular, mobile communication devices such as mobile phone terminals and GPS receivers, Bluetooth (registered trademark) The present invention relates to a small antenna device used in an electronic device having such a short-range wireless communication function.

In mobile communication devices and electronic devices having a short-range wireless communication function, an antenna device having a chip antenna is often used. The basic structure of a chip antenna is that in which a radiation electrode is formed on a dielectric substrate, but radiation electrodes of various shapes are provided according to required antenna characteristics. For example, a chip antenna having a plurality of radiation electrodes is often used for the purpose of widening the bandwidth. Patent Document 1 discloses an antenna including a feeding element connected to a feeding terminal and a parasitic element connected to the ground.

FIG. 6 is a perspective view of a chip antenna provided in the antenna device disclosed in Patent Document 1. FIG. In FIG. 6, the chip antenna 10 is formed on a base body 11, first and

second radiation electrodes

12 and 13 constituting comb-shaped electrodes on the upper surface of the base body 11, and side surfaces of the base body 11. A power supply electrode 14 connected to one end of the electrode 12, a first ground electrode 15 formed on the side surface and connected to the second radiation electrode 13, and terminal electrodes 17 to 19 formed on the bottom surface of the substrate 11. It has. The first terminal electrode 17 is connected to a power supply line formed on the printed circuit board, and is connected to a ground pattern on the printed circuit board through an inductance pattern formed on the printed circuit board. The second terminal electrode 18 is connected to a ground pattern on the printed board.

JP 2011-61638 A

Small antennas are often used in portable electronic devices, and their posture during use is not stable. Therefore, the optimal antenna directivity during use is determined by the positional relationship of the communication partner (base station, etc.) with the antenna and the attitude of the portable electronic device (own device) in use. It cannot be determined.

On the other hand, an antenna using a ground pattern has a direction (Null point) where radio wave emission is weak due to the mechanism of its operation, and the direction cannot be changed. Therefore, depending on the posture at the time of use, the null point is directed in the direction of the antenna of the communication partner, and a state in which communication is not possible occurs. In particular, in GPS, since the communication target exists in the zenith direction, if the null point is directed in this direction, there is a problem that positioning cannot be performed or positioning accuracy is deteriorated.

In a chip antenna having a feeding element and a parasitic element as shown in FIG. 6, so-called multiple resonance characteristics are generated by the feeding element and the parasitic element, so as to widen the band. Yes. The two obtained antenna characteristics both obtain radiation characteristics by passing a current through the ground pattern. The parasitic element operates by electromagnetic coupling with the feeding element, and the two elements operate in the same mode for the convenience of coupling. Therefore, the distribution of the ground current by each element is very similar, and as a result, the radiation patterns are almost the same. Therefore, with regard to directivity, only a single directivity pattern can be obtained as with a single resonance antenna.

As described above, in the conventional chip antenna, the bandwidth and the radiation efficiency can be appropriately designed depending on the shape of the radiating element, but it is difficult to determine the directivity depending on the shape of the radiating element.

An object of the present invention is to provide an antenna device in which directivity is defined or directivity can be controlled.

The antenna device of the present invention includes a first radiation electrode connected to a feeding point and a second radiation electrode connected to a ground conductor, and the first radiation electrode and the second radiation electrode are electromagnetically coupled, The first radiation electrode and the second radiation electrode resonate in a degenerate relationship at a use frequency.

The first radiating electrode and the second radiating electrode are composed of a conductor pattern formed on a dielectric substrate which is a dielectric composite resin material molded body in which a dielectric ceramic filler is dispersed in a resin material. Is preferred.

It is preferable that the dielectric substrate has a groove formed between the first radiation electrode and the second radiation electrode.

It is preferable that the first radiation electrode and the second radiation electrode have a mirror-symmetric or rotationally symmetric relationship.

According to the present invention, the first radiation electrode and the second radiation electrode are set to substantially the same resonance frequency, and are electromagnetically coupled to resonate in a degenerate relationship. Thereby, two types of directivity can be obtained at the same time without switching with one antenna.

FIG. 1 is a perspective view of an antenna device 201 according to an embodiment of the present invention. 2A and 2B are diagrams showing electric field distributions in the vicinity of the first radiation electrode and the second radiation electrode. FIG. 3A and FIG. 3B are diagrams showing current distribution in the vicinity of the first radiation electrode and the second radiation electrode. 4A and 4B are diagrams showing the directivity of the antenna device in the two coupling modes. FIG. 4A shows the radiation intensity of the electromagnetic field in the odd mode, and FIG. 4B shows the radiation intensity of the electromagnetic field in the even mode. Expressed in concentration. FIG. 5 is a perspective view of the antenna device 202 according to the second embodiment. FIG. 6 is a perspective view of a chip antenna provided in the antenna device disclosed in Patent Document 1. FIG.

<< First Embodiment >>
FIG. 1 is a perspective view of an antenna device 201 according to an embodiment of the present invention. The antenna device 201 includes a chip antenna 101 and a printed board 40. The chip antenna 101 is mounted on the printed board 40. The chip antenna 101 includes a rectangular parallelepiped dielectric base 30 and a conductor pattern formed on the surface of the dielectric base 30. The dielectric substrate 30 is formed with

first radiation electrodes

31a, 31b, 31c extending from the front surface to the upper surface. Similarly,

second radiation electrodes

32a, 32b, and 32c extending from the front surface of the dielectric substrate 30 to the upper surface are formed. The dielectric substrate 30 is, for example, a dielectric ceramic sintered body.

The first radiation electrodes (31a, 31b, 31c) are fed at a feeding point FP. That is, the first radiation electrode is a feeding radiation electrode. Of the first radiation electrodes (31a, 31b, 31c), the electrode 31c is close to the open end OE, and a predetermined capacitance is formed between the electrode 31c and the open end OE. The resonance frequency of the first radiation electrode (31a, 31b, 31c) is determined mainly by its inductance and the capacitance generated between the electrode 31c and the open end OE.

The second radiation electrodes (32a, 32b, 32c) are grounded at the ground point GP. That is, the second radiation electrode is a parasitic radiation electrode. Of the second radiation electrodes (32a, 32b, 32c), the electrode 32c is close to the open end OE, and a predetermined capacitance is formed between the electrode 32c and the open end OE. The resonance frequency of the second radiation electrode (32a, 32b, 32c) is determined mainly by its inductance and the capacitance generated between the electrode 32c and the open end OE.

Among the first radiation electrodes (31a, 31b, 31c), an impedance matching pattern 33 is formed between the middle of the electrode 31a and the ground conductor of the printed board 40. Similarly, an impedance matching pattern 34 is formed between the second radiation electrode (32a, 32b, 32c) and the ground conductor of the printed board 40 in the middle of the electrode 32a.

As shown in FIG. 1, the first radiation electrode (31a, 31b, 31c) and the second radiation electrode (32a, 32b, 32c) are mirror-symmetric. That is, the plane is symmetrical with respect to a plane that passes through the center of the dielectric substrate 30 and is perpendicular to the mounting surface and perpendicular to the longitudinal direction.

A ground conductor is formed on almost the entire surface of the upper surface of the printed circuit board 40. A ground conductor is also formed on the mounting surface of the chip antenna 101. However, no ground conductor is formed in the vicinity where the wiring pattern 41 connected to the feeding point FP is formed. That is, the wiring pattern 41 is insulated from the ground conductor. No electrode is formed on the lower surface of the dielectric substrate 30. When the chip antenna 101 is mounted on the printed circuit board 40, the wiring pattern 41 formed on the end surface of the printed circuit board 40 is electrically connected to the feeding point FP of the first radiation electrode. The ground point GP of the second radiation electrode is electrically connected to the ground conductor formed on the end surface of the printed board 40. On the lower surface of the printed circuit board 40, a power supply line that connects the high-frequency circuit and the power supply point FP is formed.

On the upper surface of the dielectric substrate 30, the first radiation electrodes (31 a, 31 b, 31 c) and the second radiation electrodes (32 a, 32 b, 32 c) are mainly coupled at the coupling portion CP.

FIGS. 2 and 3 are views showing a state of coupling between the first radiation electrode and the second radiation electrode. 2A and 2B are diagrams showing electric field distributions in the vicinity of the first radiation electrode and the second radiation electrode, and FIGS. 3A and 3B show the first radiation electrode and the second radiation electrode. It is a figure which shows the electric current distribution of a radiation electrode vicinity.

Two coupling modes (Odd mode and Even mode) are generated by the resonance by the first radiation electrode (31a, 31b, 31c) and the resonance by the second radiation electrode (32a, 32b, 32c) shown in FIG. FIG. 2A shows the electric field distribution near the first and second radiation electrodes in the odd mode. FIG. 2B shows the electric field distribution near the first and second radiation electrodes in the Even mode. In these figures, the direction of the electric field is indicated by the direction of the arrow, and the electric field strength is indicated by the size of the arrow. In the Odd mode, the electric field strength between the feeding element and the parasitic element (coupling portion CP) is high. This indicates that the first radiation electrode and the second radiation electrode are electric field coupled. On the other hand, in the Even mode, the electric field strength between the first radiation electrode and the second radiation electrode (coupling portion CP) is low. That is, the magnetic field strength is high, indicating that the first radiation electrode and the second radiation electrode are magnetically coupled.

FIG. 3A shows the current distribution in the vicinity of the first radiation electrode and the second radiation electrode in the odd mode. FIG. 3B shows current distribution in the vicinity of the first radiation electrode and the second radiation electrode in the Even mode. In these drawings, the direction of the current represents the direction of current, and the magnitude of the arrow represents the current intensity. Arrows Af and An indicate rough directions of current on the ground conductor of the printed circuit board. 3A and 3B also show the currents flowing through the first and second radiation electrodes, so the current flowing through the ground conductor near the chip antenna mounting position is hidden in the figure. Yes. In the Odd mode, the currents flowing in the ground conductors near the first radiation electrode and the second radiation electrode are in the same direction. On the other hand, in the Even mode, the current flowing through the ground conductor near the first and second radiation electrodes is in the reverse direction. As described above, the state of the resonance current of the coupling portion (CP in FIG. 1) is greatly different, so that the current distribution of the entire ground conductor of the printed circuit board is different. In the Even mode, the mounting position of the chip antenna 101 becomes a node of current flowing in the ground conductor. The antinode of the current flowing through the ground conductor in the Even mode occurs on a side different from (adjacent to) the side of the printed circuit board along the chip antenna 101.

FIG. 4 is a diagram showing the directivity of the antenna device in the two coupling modes. FIG. 4A shows the radiation intensity of the electromagnetic field in the Odd mode as a concentration. FIG. 4B shows the radiation intensity of the electromagnetic field in the Even mode as a concentration. The directivity can be seen from the density in the circle in the figure. This indicates that radiation is strongly radiated in a higher concentration direction, and the antenna directivity is in that direction. Conversely, the recessed portion is a so-called Null point, indicating a direction of lower gain.

◎ Arrows at both ends in the figure indicate the general directivity of the antenna as a whole. As is clear from FIG. 4, the directivity in the Odd mode is in the y-axis direction (vertical direction in the figure), and the directivity in the Even mode is in the x-axis direction (horizontal direction in the figure).

As described above, a small antenna mounted on a mounting board as in the present invention obtains radiation characteristics by using a mounting board as a radiating element by passing a current through the mounting board. In the Odd mode, the mounting position of the chip antenna 101 becomes an anti-node of the current flowing through the ground conductor. Therefore, radio waves are radiated by operating the mounted side as a dipole antenna. Therefore, since the axis of the dipole antenna is the X axis, directivity is directed in the Y axis direction orthogonal to the axis.

Similarly, since the antinode of the current flowing through the ground conductor in the Even mode is generated on a side different from (adjacent to) the side of the printed circuit board along the chip antenna 101, radio waves are radiated by operating this side as a dipole antenna. To do. In this case, since the axis of the dipole antenna is the Y axis, the directivity is directed in the X axis direction orthogonal to the axis.

Since the antenna device 201 has a characteristic in which the Odd mode and the Even mode overlap, the directivity of the antenna device 201 is obtained by superimposing the two patterns shown in FIGS. 4A and 4B. . This superposition eliminates the NULL point, and a nearly omnidirectional antenna characteristic can be obtained.

As described above, the current distribution on the ground conductor of the substrate near the antenna differs between the Even mode and the Odd mode because there is a difference in the coupling mechanism between magnetic field coupling and electric field coupling. As a result, the distribution of current flowing through the ground conductor is different between the Even mode and the Odd mode, although they have substantially the same frequency. Therefore, two types of directivity can be used at the same frequency. Even mode frequency is slightly lower than Odd mode frequency, and by setting the frequency of Even mode and Odd mode so that the frequency used is intermediate between the frequency of Even mode and Odd mode, An almost omnidirectional antenna can be configured at the operating frequency. In some cases, the antenna can be used as an antenna having directivity different between the frequency of the Even mode and the frequency of the Odd mode.

The first radiation electrode (31a, 31b, 31c) and the second radiation electrode (32a, 32b, 32c) are substantially mirror-symmetrical and are arranged so that parts of the electrodes are substantially parallel to each other. When the area ratio of the formation range of the first radiation electrodes (31a, 31b, 31c) and the formation range of the second radiation electrodes (32a, 32b, 32c) is set within a range of approximately 1: 3 to 3: 1, It is easy to obtain two coupled modes that are degenerate.

<< Second Embodiment >>
FIG. 5 is a perspective view of the antenna device 202 according to the second embodiment. The antenna device 202 includes a chip antenna 102 and a printed board 40. The chip antenna 102 is mounted on the printed board 40. In the first embodiment, the dielectric substrate 30 made of dielectric ceramics is used. However, in the second embodiment, the dielectric composite resin material molding in which the dielectric ceramic filler is dispersed in the resin material is used as the dielectric substrate. Using the body. A groove SL is formed at the center of the upper surface of the dielectric substrate 30. Other configurations are the same as those shown in FIG. 1 in the first embodiment.

The groove SL is formed to adjust the capacitance between the first radiation electrode (31a, 31b, 31c) and the second radiation electrode (32a, 32b, 32c). The capacity between the first radiation electrode (31a, 31b, 31c) and the second radiation electrode (32a, 32b, 32c) decreases as the width and depth of the groove SL increase. And, by this capacitance, the resonance frequency of the Odd mode due to electric field coupling can be adjusted independently of the resonance frequency of the Even mode due to magnetic field coupling.

As described above, since the dielectric substrate 30 is formed of a dielectric composite resin material molded body, it can be manufactured by molding, so that the degree of freedom of the shape is high and the resonance frequency of each mode can be easily controlled.

The dielectric substrate 30 may simply be a resin molded body.

<< Other embodiments >>
In the first and second embodiments, the first radiating electrode and the second radiating electrode have a mirror-symmetrical relationship with each other. However, the first radiating electrode and the second radiating electrode resonate with each other at a use frequency. do it. For example, the first radiation electrode and the second radiation electrode may be rotationally symmetric.

CP: coupling portion FP ... feeding point GP ... grounding point OE ... open end SL ... groove 30 ...

dielectric substrate

31a, 31b, 31c ...

first radiation electrode

32a, 32b, 32c ...

second radiation electrode

33, 34 ... for alignment Pattern 40 ... Printed circuit board 41 ...

Wiring patterns

101, 102 ...

Chip antennas

201, 202 ... Antenna device

Claims

A chip antenna having a dielectric substrate and a radiation electrode formed on the dielectric substrate; and a substrate having a substrate and a ground conductor formed on the substrate; and the chip antenna is mounted on a mounting surface of the substrate. In the antenna device configured and implemented,
The chip antenna includes a first radiating electrode connected to a feeding point and a second radiating electrode connected to the ground conductor, and the first radiating electrode and the second radiating electrode are electromagnetically coupled to each other and used frequency In the antenna device, the first radiation electrode and the second radiation electrode resonate in a degenerate relationship.
The first radiating electrode and the second radiating electrode are composed of a conductor pattern formed on a dielectric substrate which is a dielectric composite resin material molded body in which a dielectric ceramic filler is dispersed in a resin material. The antenna device according to claim 1.
The antenna device according to claim 1 or 2, wherein the dielectric substrate has a groove formed between the first radiation electrode and the second radiation electrode.
The antenna device according to any one of claims 1 to 3, wherein the first radiation electrode and the second radiation electrode are in a mirror-symmetrical relationship.
The antenna device according to any one of claims 1 to 3, wherein the first radiation electrode and the second radiation electrode are in a rotationally symmetric relationship.