WO2015045614A1

WO2015045614A1 - Antenna, antenna structure, and resonator

Info

Publication number: WO2015045614A1
Application number: PCT/JP2014/070160
Authority: WO
Inventors: 淳東條
Original assignee: 株式会社村田製作所
Priority date: 2013-09-25
Filing date: 2014-07-31
Publication date: 2015-04-02

Abstract

An antenna, which can be incorporated in a mobile communication terminal, comprises: an antenna element (20); and resonators (coils 10) each of which is placed at a position remote from the antenna element by a distance of less than a quarter of the resonance wavelength thereof and each of which is isolated from the other parts and each of which resonates in the vicinity of the resonance wavelength of the antenna element. In addition to the antenna element, nothing is required except the resonators each of which is isolated at a position of less than the quarter of the resonance wavelength of the antenna element. Therefore, the layout and structure of the antenna are not restricted. Since each resonator magnetically couples, in the vicinity of the resonance wavelength of the resonator, to the antenna element, it is possible to suppress, to the bare minimum, the SAR, which is on the human body side, of the electromagnetic waves in the vicinity of that wavelength. Since the electromagnetic waves other than that wavelength are not suppressed, the degradation of transmission/reception performances of the antenna can be suppressed.

Description

Antenna, antenna structure, and resonator

The present invention relates to an antenna, an antenna structure, and a resonator, and more particularly to an antenna that can be incorporated into a mobile communication terminal, an antenna structure of the antenna, and a resonator used for the antenna.

Recently, there are concerns about the effects of electromagnetic waves on the human body. One of the indicators of the influence of electromagnetic waves on the human body is SAR (Specific Absorption Rate). According to Article 14-2 of the Radio Equipment Regulations, SAR is obtained by dividing the energy absorbed by any living tissue 10g by exposure to an electromagnetic field in any 6 minutes by 10g, and further dividing by 6 minutes. It refers to the value obtained. The unit of SAR is W / kg. SAR can tell how much energy a human tissue receives from a device that emits electromagnetic waves in a certain period of time.

As the standard of electromagnetic waves allowed for the human body, two standard values of “whole body average SAR” and “local SAR” are defined. Among these, “local SAR” is SAR on the human head of radio waves emitted from radio equipment. As a rule, SAR is set to 2 W / kg or less according to Article 14-2 of the Radio Equipment Regulations.

Recently, a plurality of types of communication methods may be used at the same time in portable communication terminals. For example, while performing voice communication using a method such as CDMA (Code Division Multiple Access), data is transmitted using another type of method such as Wi-Fi (Wireless Fidelity) or LTE (Long Term Evolution). Communication may be performed.

FIG. 28 is a diagram for explaining the synthesis of SAR. When a plurality of types of communication methods are used at the same time, referring to FIG. 28, the SAR distribution of communication in one communication method (SAR distribution 1 in the figure) and the SAR of communication in the other communication method are used. The combined distribution obtained by adding the distribution (SAR distribution 2 in the figure) is the SAR distribution of the mobile communication terminal. Since the SAR of this composite distribution must be equal to or less than the above-mentioned reference value 2 W / kg, it is more difficult to satisfy the reference than before.

Examples of the method for reducing the SAR include the following.
(1) A method of devising the structure and mounting position of an antenna (for example, see Patent Documents 1 to 5).

(2) A method of reducing radiated electromagnetic waves to the head side of the antenna with a magnetic material or the like (for example, see Patent Documents 6 to 9)

(3) A method of reflecting electromagnetic waves from an antenna with a parasitic element or the like (for example, see Patent Document 10).

(4) A method of reducing the strength of the electromagnetic field in the vicinity of the antenna by changing the directivity using a dielectric (see, for example, Patent Document 11).

(5) A method of reducing the antenna transmission / reception performance when proximity of a human body is detected or when the SAR value exceeds a reference value (see, for example, Patent Documents 12 and 13).

Moreover, although it is not a method for reducing SAR, there is one that controls the directivity of the antenna by arranging a left-handed transmission line composed of an inductor and a capacitor in the vicinity of the antenna (see Patent Document 14). .

In addition, there is one that controls the directivity of the antenna by arranging a cavity resonator around the antenna (see Patent Document 15).

JP 2013-74361 A JP 2009-253886 A JP 2009-124635 A JP 2006-31449 A JP 2006-222604 A JP2013-123186A JP 2005-124043 A JP 2005-93908 A JP 2002-198850 A JP 2008-109506 A JP 2010-161441 A JP 2013-162413 A JP 2013-143574 A Japanese Patent Application Laid-Open No. 2010-212980 JP 2010-193397 A

However, according to the methods of Patent Documents 1 to 5, there is a problem that the layout and structure of the antenna are restricted.

According to the methods of Patent Documents 6 to 11, there is a problem that the transmission / reception performance on the human body side is lowered over the entire band. In particular, the method of Patent Document 10 has a problem that the SAR at the resonance frequency of the parasitic element is increased.

According to the methods of Patent Documents 12 and 13, there is a problem that the transmission / reception performance of the antenna in all directions is deteriorated.

According to the method of Patent Document 14, since the left-handed transmission line itself can also be an antenna, the directivity can be controlled at a certain frequency, but there is a problem in that it radiates in the opposite direction at the operating frequency of the left-handed transmission line. . Such a problem can also occur in the conventional Yagi-Uda antenna.

According to the method of Patent Document 15, since a cavity resonator is used, there is a problem that there is a frequency band that radiates in the same manner as in the method of Patent Document 14. In addition, since the size is about half a wavelength, there is a problem that the size becomes large and cannot be used for a mobile communication terminal.

The present invention has been made to solve the above-described problems, and one of the objects of the present invention is to reduce the transmission / reception performance of the antenna and reduce the human body side without being restricted by the layout and structure of the antenna. To provide an antenna, an antenna structure, and a resonator capable of suppressing SAR to the minimum necessary.

In order to achieve the above object, according to one aspect of the present invention, an antenna is an antenna that can be incorporated into a mobile communication terminal, and includes an antenna element and a resonance wavelength of the antenna element to ¼ of the antenna element. And one or a plurality of resonators that are electrically insulated from other portions and resonate at a wavelength near the resonance wavelength of the antenna element.

According to the present invention, in addition to the antenna element, it is only necessary to provide a resonator that is insulated from other parts at a position less than a quarter of the resonance wavelength of the antenna element from the antenna element. For this reason, there is no restriction on the layout and structure of the antenna. Further, since the resonator is magnetically coupled to the antenna element at a wavelength in the vicinity of the resonance wavelength of the resonator, the SAR on the human body side of the electromagnetic wave in the vicinity of this wavelength can be suppressed to the minimum necessary. Moreover, since electromagnetic waves other than this wavelength are not suppressed, the fall of the antenna transmission / reception performance can be suppressed.

As a result, it is possible to provide an antenna that can suppress degradation of antenna transmission / reception performance and SAR on the human body to the minimum necessary without being restricted by the layout and structure of the antenna.

Preferably, the resonator is provided on the side where the frequency of becoming closer to the human body than the antenna element during communication when the antenna is incorporated into the mobile communication terminal. According to the present invention, the SAR on the human body side can be further suppressed to the necessary minimum.

Preferably, the resonator is a coil and is provided so that the magnetic field lines of the magnetic field of the antenna element penetrate the coil. According to the present invention, an inexpensive coil (for example, a wound chip coil) can be used. As a result, the manufacturing cost of the antenna can be reduced.

More preferably, the plurality of resonators are provided such that the coil axes are substantially parallel. According to the present invention, the effect of suppressing the SAR is weakened if the coil axes are substantially orthogonal, but can be prevented from being weakened if they are substantially parallel. As a result, the SAR suppression effect can be prevented from being weakened.

More preferably, the resonance wavelengths of the plurality of resonators are substantially the same, and a part of the plurality of resonators and the remaining resonators are provided so that the coil axes are substantially orthogonal to each other. According to this invention, it can adjust so that the effect of SAR suppression may be weakened.

More preferably, the resonance wavelengths of the plurality of resonators include a first resonance wavelength and a second resonance wavelength, and the resonators having the first resonance wavelength and the resonators having the second resonance wavelength are in respective coils. The axes are provided so as to be substantially orthogonal.

If the coil axes of the first resonance wavelength resonator and the second resonance wavelength resonator are not orthogonal to each other, they are coupled to each other, and the SAR suppression effect is effective only in the vicinity of the resonance wavelength of one of the resonators. I can't get it. According to the present invention, the resonator having the first resonance wavelength and the resonator having the second resonance wavelength are not coupled. As a result, SAR can be suppressed in the frequency band from the vicinity of the first resonance wavelength to the vicinity of the second resonance wavelength.

Preferably, the resonator is an LC resonator. According to the present invention, an inexpensive LC resonator (for example, MLCC) can be used. As a result, the manufacturing cost of the antenna can be reduced.

According to another aspect of the present invention, the antenna structure is an antenna structure of an antenna that can be incorporated into a mobile communication terminal, and is electrically insulated from other parts and resonates at a wavelength near the resonance wavelength of the antenna element. One or a plurality of resonators are provided at a position less than a distance of 1/4 of the resonance wavelength of the antenna element from the antenna element.

As a result, it is possible to provide an antenna structure capable of suppressing deterioration in antenna transmission / reception performance and SAR to the minimum necessary without being restricted by the antenna layout and structure.

According to still another aspect of the present invention, a resonator used for an antenna that can be incorporated into a portable communication terminal is provided at a position less than a quarter of the resonance wavelength of the antenna element from the antenna element, and is electrically It is insulated from other parts and resonates at a wavelength near the resonance wavelength of the antenna element.

As a result, it is possible to provide a resonator used for an antenna capable of suppressing the transmission / reception performance of the antenna and the SAR to the minimum necessary without being restricted by the layout and structure of the antenna.

It is a figure (plan view) showing the outline of the structure of the antenna according to the first embodiment. It is a figure (side view) which shows the outline of the structure of the antenna which concerns on 1st Embodiment. It is a figure (rear view) which shows the outline of the structure of the antenna which concerns on 1st Embodiment. It is a figure (front view) which shows the outline of the structure of the antenna which concerns on 1st Embodiment. It is a graph which shows the relationship between SAR and the frequency of the antenna which concerns on 1st Embodiment. It is a figure which shows the outline of the structure of the antenna which concerns on 2nd Embodiment. It is a graph which shows the reflective characteristic of the antenna which concerns on 2nd Embodiment. It is a figure which shows the three-dimensional radiation pattern in 2.1 GHz in 2nd Embodiment. It is a figure which shows the three-dimensional radiation pattern in 2.4 GHz in 2nd Embodiment. It is a figure (plan view) which shows the outline of the structure of the antenna which concerns on 3rd Embodiment. It is a figure (side view) which shows the outline of the structure of the antenna which concerns on 3rd Embodiment. It is a figure (rear view) which shows the outline of the structure of the antenna which concerns on 3rd Embodiment. It is a figure (front view) which shows the outline of the structure of the antenna which concerns on 3rd Embodiment. It is a graph which shows the relationship between SAR and the frequency of the antenna which concerns on 3rd Embodiment. It is the 1st figure (plan view of a printed circuit board) showing the outline of the structure of the antenna concerning a 4th embodiment. It is the 1st figure (back view of a printed circuit board) showing the outline of the structure of the antenna concerning a 4th embodiment. It is the 1st figure (front view of a printed circuit board) showing the outline of the structure of the antenna concerning a 4th embodiment. It is the 1st figure (plan view of a case) showing the outline of the structure of the antenna concerning a 4th embodiment. It is a 1st figure (front view of a housing | casing) which shows the outline of the structure of the antenna which concerns on 4th Embodiment. It is a 2nd figure which shows the outline of the structure of the antenna which concerns on 4th Embodiment. It is a 1st figure for demonstrating the coupling between the antennas which concern on 5th Embodiment. It is a 2nd figure for demonstrating the coupling between the antennas which concern on 5th Embodiment. It is a 3rd figure for demonstrating the coupling between the antennas which concern on 5th Embodiment. It is a graph which shows the comparison result of the coupling between the antennas concerning a 5th embodiment. It is a 1st figure which shows the outline of the structure of the antenna for demonstrating the suppression amount adjustment of SAR which concerns on 6th Embodiment. It is a 1st figure which shows the radiation characteristic of the antenna for demonstrating the suppression amount adjustment of SAR which concerns on 6th Embodiment. It is a 1st figure which shows the relationship between the SAR of an antenna, and a frequency for demonstrating the suppression amount adjustment of SAR which concerns on 6th Embodiment. It is a 2nd figure which shows the outline of the structure of the antenna for demonstrating the suppression amount adjustment of SAR which concerns on 6th Embodiment. It is a 2nd figure which shows the radiation characteristic of the antenna for demonstrating the suppression amount adjustment of SAR which concerns on 6th Embodiment. It is a 2nd figure which shows the relationship between the SAR of an antenna, and a frequency for demonstrating the suppression amount adjustment of SAR which concerns on 6th Embodiment. It is a 1st figure which shows the outline of the structure of the antenna for demonstrating the broadband of the suppression of SAR which concerns on 7th Embodiment. It is a 1st figure which shows the radiation characteristic of the antenna for demonstrating the broadbanding of the suppression of SAR which concerns on 7th Embodiment. It is a 1st figure which shows the relationship between the SAR of an antenna, and a frequency for demonstrating the broadbanding of the suppression of SAR which concerns on 7th Embodiment. It is a 2nd figure which shows the outline of the structure of the antenna for demonstrating the broadbanding of the suppression of SAR which concerns on 7th Embodiment. It is a 2nd figure which shows the radiation characteristic of the antenna for demonstrating the broadbanding of the suppression of SAR which concerns on 7th Embodiment. It is a 2nd figure which shows the relationship between the SAR of an antenna, and a frequency for demonstrating the broadbanding of the suppression of SAR which concerns on 7th Embodiment. It is a figure (conventional) for demonstrating the effect of this Embodiment. It is a figure (this example) for demonstrating the effect of this Embodiment. It is a figure for demonstrating the synthesis | combination of SAR. It is a figure which shows the outline of the structure of the antenna which concerns on 8th Embodiment. It is a graph which shows the relationship between SAR and the frequency of the antenna which concerns on 8th Embodiment. It is a figure which shows the outline of the structure of the antenna which concerns on 9th Embodiment. It is a graph which shows the relationship between SAR and the frequency of the antenna which concerns on 9th Embodiment.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, about the same or equivalent part in a figure, the same code | symbol is attached | subjected and the description is not repeated.

1A to 1D are diagrams (plan view, side view, rear view, and front view) showing an outline of the structure of the antenna according to the first embodiment. 1A to 1D, the antenna according to the first embodiment is formed on a printed circuit board 100 and includes an antenna element 20 and a ground 30. Although not shown, the antenna element 20 is provided with a feeding point and is fed from the feeding point.

Normally, it functions as an antenna with the above configuration. In this embodiment, the antenna further includes a coil 10 as a resonator. In this embodiment, a chip coil is used as the coil 10. In the following embodiments, a chip coil is used as the coil. Since the chip coil is a general-purpose product that is easily available and inexpensive, an increase in the manufacturing cost of the antenna for reducing the SAR can be suppressed. Further, the chip coil can be easily mounted on the substrate.

The resonator may be an LC resonator, for example, an MLCC (Multi-Layer Ceramic Capacitor, multilayer ceramic capacitor) instead of the coil. When MLCC is used, it is a general-purpose product that is easy to obtain and inexpensive, so that cost can be reduced, miniaturization can be achieved, and mounting on a substrate is also easy.

The coil 10 is electrically insulated from other parts. In this embodiment, the coil 10 is mounted on the surface of the printed board 100 opposite to the side on which the antenna element 20 is formed. For this reason, it is possible not to affect the structure and arrangement of the antenna. In addition, although the coil 10 is mounted in the figure (five here), it is not limited to this and may be one.

In this embodiment, a magnetic field is generated in the direction in which the screw rotates when the right screw about the longitudinal direction, which is the direction in which the current of the antenna element 20 flows, is screwed in the current direction. The coil 10 is mounted so that the axis of the coil 10 is parallel to the printed circuit board 100 and perpendicular to the longitudinal direction of the antenna element 20 so that the magnetic field lines generated by the antenna element 20 penetrate the coil 10. Thereby, the antenna element 20 and the coil 10 are magnetically coupled.

It should be noted that the coil 10 may be mounted in another direction in a different direction as long as the magnetic field lines generated by the antenna element 20 are provided so as to penetrate the coil 10.

FIG. 2 is a graph showing the relationship between the SAR and the frequency of the antenna according to the first embodiment. Referring to FIG. 2, a broken line indicates a case where the coil 10 is not included in the antenna of FIGS. 1A to 1D, and a solid line indicates a case where the coil 10 is included in the antenna of FIGS. 1A to 1D. The antenna element 20 of the present embodiment has a shape that matches the frequency of 1.9 GHz. Further, the coil 10 of the present embodiment has a resonance frequency of about 2.0 GHz.

As shown in the graph of FIG. 2, there is almost no difference in the SAR value between the case of including the coil 10 and the case of not including the coil 10 for radio waves other than the vicinity of 2.0 GHz. When compared with the case of not including SAR, the value of SAR is reduced by about 0.4 W / kg. Moreover, since the coil 10 is a coil, it hardly re-radiates the absorbed energy.

Thus, at a frequency at which the coil 10 has a negative magnetic permeability, a part of the electromagnetic wave from the antenna element 20 is reflected to the antenna element 20 side. Furthermore, there is a reflection on the power feeding side due to a loss in the coil 10 and an antenna matching change. For this reason, transmission of the electromagnetic wave of the said frequency vicinity to the coil 10 side of the antenna element 20 can be suppressed, and SAR can be suppressed.

Further, since the coil 10 is arranged so as to be closer to the human body than the antenna element 20, the electromagnetic wave from the antenna element 20 is attenuated when it exceeds the coil 10, so that SAR can be more effectively suppressed. .

[Second Embodiment]
FIG. 3 is a diagram schematically illustrating the structure of the antenna according to the second embodiment. With reference to FIG. 3, the antenna of the second embodiment includes an antenna element 20 D and a coil 10 D similar to the coil 10 of the first embodiment. The antenna element 20D of this embodiment has a dipole antenna shape. In this embodiment, a magnetic field is generated in the direction in which the screw rotates when the right screw about the longitudinal direction (X-axis direction in the figure), which is the direction in which the current of the antenna element 20D flows, is screwed in the current direction.

The coil 10D is directed so that the magnetic field lines generated by the antenna element 20D penetrate the coil 10D. Thereby, antenna element 20D and coil 10D are magnetically coupled.

FIG. 4 is a graph showing the reflection characteristics of the antenna according to the second embodiment. Referring to FIG. 4, the resonance of the antenna at 2.4 GHz is suppressed. Further, resonance is not suppressed at frequencies other than the vicinity of 2.4 GHz. For this reason, the SAR is reduced in the vicinity of 2.4 GHz while maintaining the transmission / reception characteristics except in the vicinity of 2.4 GHz.

5 and 6 are diagrams showing three-dimensional radiation patterns at 2.1 GHz and 2.4 GHz, respectively, in the second embodiment. With reference to FIG. 5 and FIG. 6, these radiation patterns are radiation patterns viewed from the X-axis direction. Compared to 2.1 GHz, in the 2.4 GHz radiation pattern, the negative direction of the Y axis, which is the direction in which the coil 10D is disposed with respect to the antenna element 20D, is whitish. In this radiation pattern, the stronger the radiation, the darker the color. For this reason, it turns out that the radiation | emission from the antenna to the negative direction of this Y-axis is weak.

Such an effect that the radiation of the antenna element 20D in the direction in which the coil 10D is arranged is weakened is not limited to the antenna of the second embodiment, and is also achieved by the antenna of the first embodiment described above. It can also be achieved by the antenna of the embodiment described later.

[Third Embodiment]
7A to 7D are views (plan view, side view, rear view, and front view) schematically showing the structure of the antenna according to the third embodiment. Referring to FIGS. 7A to 7D, the structure of the antenna according to the third embodiment is the same as the structure of the antenna according to the first embodiment except for the arrangement of coil 10A. In the first embodiment, the antenna element 20 resonates around 1.9 GHz. However, in the third embodiment, the ground 30A resonates around 850 MHz instead of the antenna element 20A.

Unlike the first embodiment, in the third embodiment, radio waves are radiated from the ground 30A. For this reason, a magnetic field is generated in the direction in which the screw rotates when the right screw about the longitudinal direction, which is the direction in which the current of the ground 30A flows, is screwed in the current direction. The coil 10A is mounted so that the axis of the coil 10A is parallel to the printed circuit board 100A and perpendicular to the longitudinal direction of the ground 30A so that the magnetic field lines of the magnetic field generated by the ground 30A pass through the coil 10A. Thereby, the ground 30A and the coil 10A are magnetically coupled.

It should be noted that the coil 10A may be mounted in another direction in a different direction as long as the magnetic field lines generated by the ground 30A pass through the coil 10A.

FIG. 8 is a graph showing the relationship between the SAR and the frequency of the antenna according to the third embodiment. Referring to FIG. 8, the broken line indicates a case where the antenna of FIGS. 7A to 7D does not include the coil 10A, and the solid line indicates a case where the antenna of FIGS. 7A to 7D includes the coil 10A. The ground 30A of the present embodiment has a shape that matches the frequency of 850 MHz. The coil 10 of the present embodiment has a resonance frequency of about 840 MHz.

As shown in the graph of FIG. 8, there is almost no difference in the SAR value between the case of including the coil 10A and the case of not including the coil 10A for radio waves other than those near 840 MHz, but the case of not including the coil 10A for radio waves of 840 MHz. SAR value is reduced by about 0.5 W / kg. Further, since the coil 10A is a coil, it hardly reradiates the absorbed energy.

[Fourth Embodiment]
9A to 9E and FIG. 10 are respectively a first diagram (a plan view of a printed circuit board, a rear view and a front view, and a plan view of a housing) showing an outline of the structure of an antenna according to a fourth embodiment. It is a figure and a front view), and a 2nd figure. Referring to FIGS. 9A to 9E and FIG. 10, FIG. 10 is an assembly view in which the printed circuit board 100B shown in FIGS. 9A to 9C and the casing 200B shown in FIGS. 9D and 9E are assembled.

The antenna according to the fourth embodiment is formed on the printed circuit board 100B and the housing 200B, and includes an antenna element 20B and a coil 10B. The antenna element 20B is formed by plating or the like on the inner surface of a housing 200B formed of a resin that does not conduct electricity. Although not shown, the antenna element 20B is provided with a feeding point, and the feeding point is fed from the antenna connection connector 30B of the printed circuit board 100B.

The coil 10B is electrically insulated from other parts. In this embodiment, the coil 10B is mounted on a printed circuit board 100B different from the housing 200B in which the antenna element 20B is formed. For this reason, it is possible not to affect the structure and arrangement of the antenna. In addition, although the coil 10B is mounted in the figure by a plurality (five here), it is not limited to this and may be one.

In this embodiment, a magnetic field is generated in the direction in which the screw rotates when the right screw about the longitudinal direction, which is the direction in which the current of the antenna element 20B flows, is screwed in the current direction. The coil 10B is mounted so that the axis of the coil 10B is parallel to the printed circuit board 100B and perpendicular to the longitudinal direction of the antenna element 20B so that the magnetic field lines generated by the antenna element 20B penetrate the coil 10B. Thereby, the antenna element 20B and the coil 10B are magnetically coupled.

It should be noted that the coil 10B may be mounted in another direction in a different direction as long as the magnetic field lines generated by the antenna element 20B penetrate the coil 10B.

As with the antenna of the first embodiment, the antenna of the fourth embodiment also has the effect of suppressing SAR near the resonance frequency of the coil 10B.

[Fifth Embodiment]
FIGS. 11 to 13 are first to third diagrams for explaining coupling between antennas according to the fifth embodiment, respectively. FIG. 11 shows a case where no coil is provided. FIG. 12 shows a case where the

coils

10X and 10Y are provided outside the

antennas

20X and 20Y, respectively. FIG. 13 shows a case where the

coils

10X and 10Y are provided inside the

antennas

20X and 20Y, respectively.

FIG. 14 is a graph showing a comparison result of coupling between antennas according to the fifth embodiment. Referring to FIG. 14, the wavy line shows the case of FIG. 11, the alternate long and short dash line shows the case of FIG. 12, and the solid line shows the case of FIG.

As shown by S11, the radiation for the

respective antennas

20X and 20Y shows the effect of suppressing the radiation from the antenna, that is, the SAR, regardless of whether the

coils

10X and 10Y are provided outside or inside.

As shown by S21, when the coil is not provided and when the

coils

10X and 10Y are provided outside, the effect of preventing the coupling of the

antennas

20X and 20Y is not shown. On the other hand, compared with the case where the

coils

10X and 10Y are provided outside, the effect of suppressing the coupling of the

antennas

20X and 20Y by 6 dB is shown when the

coils

10X and 10Y are provided inside.

Thus, by providing the

coils

10X and 10Y between the

antennas

20X and 20Y, coupling between the antennas can be suppressed.

[Sixth Embodiment]
FIGS. 15 and 18 are first and second diagrams, respectively, showing an outline of the antenna structure for explaining the SAR suppression amount adjustment according to the sixth embodiment. FIGS. 16 and 19 are first and second diagrams showing the radiation characteristics of the antenna, respectively, for explaining the SAR suppression amount adjustment according to the sixth embodiment. FIGS. 17 and 20 are first and second diagrams showing the relationship between the SAR of the antenna and the frequency, respectively, for explaining the SAR suppression amount adjustment according to the sixth embodiment.

Referring to FIG. 15 and FIG. 18, in the case of the present embodiment, the right screw about the longitudinal direction, which is the direction in which the current of

antenna elements

20E and 20F flows, is screwed in the direction of current. A magnetic field is generated in the direction of rotation.

In the case of FIG. 15, all the coils 10 E are mounted so that the axes thereof are parallel to the plane of the antenna element 20 E and perpendicular to the longitudinal direction of the antenna element 20 E. On the other hand, in the case of FIG. 18, the coil 10F is mounted so that the axis of the coil 10F is parallel to the plane of the antenna element 20F and inclined at 45 degrees or −45 degrees in the direction perpendicular to the longitudinal direction of the antenna element 20F. In FIG. 18, the coils 10F are alternately inclined at 45 degrees or −45 degrees, but the present invention is not limited to this, and the coils 10F may not be alternated.

FIG. 16 shows the reflection characteristics of the antenna when it is not tilted at 45 degrees or −45 degrees. FIG. 19 shows the reflection characteristics of the antenna when tilted by 45 degrees or −45 degrees. In FIG. 16 and FIG. 19, the broken line indicates a case where no coil is provided, and the solid line indicates a case where a coil is provided. Thus, the degree of weakening the resonance of the coil is less when tilted than when not tilted.

FIG. 17 shows the relationship between the SAR and the frequency of the antenna when it is not tilted by 45 degrees or −45 degrees. FIG. 20 shows the relationship between the antenna SAR and the frequency when tilted by 45 degrees or −45 degrees. In FIG. 17 and FIG. 20, the broken line indicates a case where no coil is provided, and the solid line indicates a case where a coil is provided. Thus, the effect of suppressing SAR is weakened when tilted compared to when tilted.

Thereby, the suppression amount of SAR can be adjusted by mixing the inclined coil and the non-inclined coil.

[Seventh Embodiment]
FIG. 21 and FIG. 24 are first and second diagrams, respectively, showing an outline of the antenna structure for explaining the broadbanding of SAR suppression according to the seventh embodiment. FIG. 22 and FIG. 25 are first and second diagrams showing the radiation characteristics of the antenna for explaining the increase in the bandwidth of SAR suppression according to the seventh embodiment, respectively. FIG. 23 and FIG. 26 are first and second diagrams showing the relationship between the SAR of the antenna and the frequency, respectively, for explaining the increase in the bandwidth of SAR suppression according to the seventh embodiment.

Referring to FIGS. 21 and 24, in the case of the present embodiment, the right screw about the longitudinal direction, which is the direction in which the current of

antenna elements

20G and 20H flows, is screwed in the current direction. A magnetic field is generated in the direction of rotation.

In the case of FIG. 21, the axes of all the first resonance frequency coils 10GA and all the second resonance frequency coils 10GB are parallel to the plane of the antenna element 20G and perpendicular to the longitudinal direction of the antenna element 20G. To be mounted.

On the other hand, in the case of FIG. 24, the coils 10GA of all the first resonance frequencies are mounted so that the axes thereof are parallel to the plane of the antenna element 20G and inclined by 45 degrees in the direction perpendicular to the longitudinal direction of the antenna element 20G. Then, the coils 10GB of all the second resonance frequencies are mounted so that the axes thereof are parallel to the plane of the antenna element 20G and inclined by -45 degrees in the direction perpendicular to the longitudinal direction of the antenna element 20Gno.

FIG. 22 shows the reflection characteristics of the antenna when it is not tilted. FIG. 25 shows the reflection characteristics of the antenna when tilted. 22 and 25, a broken line indicates a case where no coil is provided, and a solid line indicates a case where a coil is provided. As described above, when not tilted, an effect of weakening the resonance of the coil is obtained in the resonance frequency band of one coil, but the resonance of the coil is conversely strengthened in the resonance frequency band of the other coil. On the other hand, when tilted, the effect of weakening the resonance is produced in the resonance frequency band of both coils.

FIG. 23 shows the relationship between the SAR and the frequency of the antenna when tilted. FIG. 26 shows the relationship between the SAR and frequency of the antenna when it is not tilted. 22 and 25, a broken line indicates a case where no coil is provided, and a solid line indicates a case where a coil is provided. As described above, in the case of not tilting, there is an SAR suppression effect in the resonance frequency band of one coil, but no SAR suppression effect is obtained in the resonance frequency band of the other coil. On the other hand, when tilted, the effect of suppressing SAR is obtained in the resonance frequency band of both coils.

As a result, when the axes of the coils having a plurality of resonance frequencies are arranged in parallel, the coils having different resonance frequencies are coupled to each other. SAR suppression effect can be broadened by arranging the frequency coils in a tilted manner. Note that it is desirable that the angle formed by the axes of the coils having different resonance frequencies is a right angle since the coupling between the coils can be completely prevented.

[Eighth Embodiment]
FIG. 29 is a diagram schematically illustrating the structure of the antenna according to the eighth embodiment. The antenna according to the eighth embodiment is obtained by replacing the coil 10 as the resonator of the antenna according to the first embodiment with an MLCC that is an example of an LC resonator.

Referring to FIG. 29, the antenna of the eighth embodiment is formed on printed circuit board 100J and includes antenna elements 20JA and 20JB and a ground 30J. The antenna element 20JB is provided with a feeding point 50J and is fed from the feeding point 50J. The antenna of the eighth embodiment further includes an LC resonator 40J as a resonator. By providing the resonator in this way, the SAR due to the antenna can be reduced. In this embodiment, MLCC is used as the LC resonator 40J. Since MLCC is a general-purpose product that is easily available and inexpensive, it is possible to suppress an increase in the manufacturing cost of an antenna for reducing SAR.

LC resonator 40J is electrically insulated from other parts of the antenna. The LC resonator 40J is magnetically coupled to one of the antenna elements 20JA and JB in the vicinity of one of the antenna elements 20JA and 20JB on the surface where the antenna elements 20JA and 20JB and the ground 30J of the printed board 100J are formed. The position and direction are determined and mounted. Here, the distance between the antenna elements 20JA and 20JB and the LC resonator 40J is 0.1 mm. For this reason, it is possible not to affect the structure and arrangement of the antenna. Although four LC resonators 40J are mounted in FIG. 29, the present invention is not limited to this, and other plural or one LC resonator 40J may be used.

FIG. 30 is a graph showing the relationship between the SAR and the frequency of the antenna according to the eighth embodiment. Referring to FIG. 30, the broken line indicates a case where the antenna of FIG. 29 does not include the LC resonator 40J, and the solid line indicates a case where the antenna of FIG. 29 includes the LC resonator 40J. The antenna elements 20JA and 20JB of the present embodiment have shapes that match the frequencies of 0.8 GHz and 1.9 GHz.

As shown in the graph of FIG. 30, for radio waves other than those in the vicinity of 0.8 GHz and 1.9 GHz, there is almost no difference in the SAR value between the case where the LC resonator 40J is included and the case where the LC resonator 40J is not included. For high 0.80 GHz to 0.85 GHz and 1.9 GHz to 2.0 GHz radio waves, when the LC resonator 40J is included, the SAR value is about 0. 0 compared to the case where the LC resonator 40J is not included. It decreases from 1 to 0.7 W / kg.

The SAR from 0.80 GHz to 0.85 GHz is suppressed by the LC resonator 40J mounted near the ground 30J of the antenna element 20JA, and 1 by the LC resonator 40J mounted near the antenna element 20JB. .9 GHz to 2.0 GHz SAR is suppressed.

When an LC resonator is used instead of a coil as a resonator, the Q value of the resonator is lower than that in the case of using a coil and the resonance bandwidth is narrowed, but the size can be reduced. Further, since the MLCC alone has a higher-order resonance mode that becomes an LC resonator, a commercially available MLCC can be used without creating a dedicated resonator.

In addition, since the LC resonator 40J is disposed close to the antenna elements 20JA and 20JB, the magnetic coupling between the antenna elements 20JA and 20JB and the LC resonator 40J becomes strong. For this reason, even if the number of LC resonators 40J is as small as 1 to several, the effect of suppressing SAR can be obtained.

Further, since the LC resonator 40J is arranged so as to be closer to the human body than the antenna elements 20JA and 20JB, the electromagnetic wave from the antenna elements 20JA and 20JB is attenuated when exceeding the LC resonator 40J. SAR can be suppressed.

[Ninth Embodiment]
FIG. 31 is a diagram schematically illustrating the structure of the antenna according to the ninth embodiment. Referring to FIG. 31, in the antenna according to the ninth embodiment, as in the antenna according to the eighth embodiment, a plurality of (48 in this case) LC resonators 40KA and 40KB are formed of the antenna element 20KB. It is mounted in the vicinity (surface opposite to the side on which the antenna element of the printed board 100K is formed). The LC resonator 40KA and the LC resonator 40KB are mounted alternately at an angle of 90 degrees. The distance between the antenna element 20KB and the LC resonators 40KA and 40KB is 3 mm.

FIG. 32 is a graph showing the relationship between the SAR and the frequency of the antenna according to the ninth embodiment. Referring to FIG. 32, a broken line indicates a case where the antenna of FIG. 31 does not include the LC resonators 40KA and 40KB, and a solid line indicates a case where the antenna of FIG. 31 includes the LC resonators 40KA and 40KB. The antenna elements 20KA and 20KB of the present embodiment have a shape that matches the frequency of the 1.9 GHz band.

As shown in the graph of FIG. 32, for radio waves other than those in the vicinity of 1.9 GHz, there is almost no difference in the SAR value between the case where the LC resonators 40KA and 40KB are included and the case where the LC resonators 40KA and 40KB are not included, but the SAR value is high. For radio waves from .9 GHz to 2.0 GHz, when the LC resonators 40KA and 40KB are included, the SAR value is about 0.2 to 1.1 W / in comparison with the case where the LC resonators 40KA and 40KB are not included. It has decreased by about kg.

Thus, in the ninth embodiment, the LC resonator is arranged on the surface of the printed board 100K opposite to the side on which the antenna element is formed. For this reason, the degree of freedom in the arrangement and mounting direction of the LC resonator is increased. However, the distance between the antenna element and the LC resonator is larger in the ninth embodiment than in the eighth embodiment. To compensate for this disadvantage, the ninth embodiment uses more LC resonators than the eighth embodiment. Thereby, in the ninth embodiment, the same SAR suppression effect as that in the eighth embodiment can be obtained.

In addition, since the resonator has anisotropy, the LC resonators 40KA and 40KB are periodically arranged at an angle of 90 degrees as in this embodiment, so that the SAR suppression effect is enhanced. It is effective for.

Further, since the LC resonators 40KA and 40KB are arranged so as to be closer to the human body than the antenna elements 20KA and 20KB, electromagnetic waves from the antenna elements 20KA and 20KB are attenuated when they exceed the LC resonators 40KA and 40KB. SAR can be more effectively suppressed.

[Summary]
FIG. 27A and FIG. 27B are diagrams (conventional and the present example) for explaining the effects of the present embodiment, respectively. Referring to FIG. 27A, in a part of the conventional method, the SAR is configured to be suppressed with respect to all frequencies so that the SAR becomes 2 W / kg or less which is the reference value of the radio equipment rule. . With this method, since the SAR in the band where the SAR is originally 2 W / kg or less also decreases, the transmission / reception performance of the antenna in such a band has been lowered.

In contrast, FIG. 2 of the first embodiment, FIG. 8 of the third embodiment, FIGS. 17 and 20 of the sixth embodiment, FIGS. 26 and 8 of the seventh embodiment. Referring to FIG. 30 of the present embodiment and FIG. 27B schematically showing FIG. 32 of the ninth embodiment, SAR at some frequencies is suppressed in this embodiment. So that the SAR is 2 W / kg. For this reason, the SAR is suppressed only for the band that needs to be suppressed, and the SAR need not be suppressed for the band that does not need to be suppressed. Therefore, the SAR is suppressed to the minimum necessary without lowering the antenna transmission / reception performance more than necessary. be able to.

[Modification]
(1) In the above-described embodiment, in order to suppress the SAR to the minimum necessary, the portion where the SAR exceeds 2 W / kg is 2 W / kg or less in the transmission state where the SAR exceeds 2 W / kg. As such, the parameters (for example, inductance, resonance frequency, etc.), number, and arrangement of the resonator (the coil in the present embodiment) are adjusted.

As the adjustment of the arrangement of the resonators, not only the planar arrangement as shown in FIGS. 15, 18 and 24 described above, but also the distance between the resonator and the antenna element may be adjusted. The distance between the resonator and the antenna element may be at least less than ¼ of the resonance wavelength of the antenna element, but the shorter the distance, the better.

If it is 1/4 or more of the resonant wavelength of the antenna element, the distance between the director and the radiator of the Yagi-Uda antenna and the distance between the radiator and the reflector will be wider, and even the Yagi-Uda antenna can be used as a portable communication terminal. Since it is too large to apply, it is difficult to use it for a portable communication terminal. In the case of directivity control with the Yagi-Uda antenna, the frequency may change, and the reflector may function as a director. In this case, many electromagnetic waves are radiated from the radiator to the reflector side, and the SAR on the side where SAR is desired to be increased increases.

(2) It is preferable that the resonator (coil) of the above-described embodiment has a size of 1/4 or less of the resonance wavelength of the antenna element. Thereby, the distance of a resonator and an antenna element can be shortened. Also, by using a resonator smaller than the antenna element, re-radiation from the resonator itself can be almost eliminated, and SAR can be suppressed only in the target frequency band. In addition, since the resonator mounting space can be reduced, the influence on the size reduction of the portable communication terminal due to the mounting of the resonator can be reduced.

(3) In the embodiment described above, a resonator is provided for one antenna. However, the present invention is not limited to this, and when a plurality of antennas are provided, a resonator may be provided for each antenna.

(4) “A resonator is provided on the side that is closer to the human body than the antenna element during communication when the antenna is incorporated in a mobile communication terminal” means that a transmitter used for voice communication in a mobile communication terminal And a resonator is provided on the side closer to the human body than the antenna element when the receiver is brought close to the user's mouth and ear during voice communication, and the display used for data communication in the portable communication terminal is data A resonator is provided on the side closer to the human body than the antenna element when directed toward the user's eye during communication. Thereby, since a resonator (for example, coil) is provided on the human body side of the antenna element, SAR on the human body side can be suppressed.

(5) The frequency f (MHz) and wavelength λ (m) of radio waves (electromagnetic waves) have a relationship of λ = 300 / f. For this reason, the term “frequency” used in the description of the above-described embodiment can be replaced with the term “wavelength” based on this relationship.

(6) In the above-described embodiment, coils are arranged at regular intervals as shown in FIGS. 1A to 1D, FIG. 3, FIG. 7A to FIG. 7D, FIG. 10, FIG. 15, FIG. I did it. However, it is not necessary to arrange them at regular intervals. The SAR suppression effect is evenly closer when arranged at equal intervals. However, the SAR values that are sparsely suppressed need only be equal to or less than the reference value 2 W / kg without being arranged at equal intervals.

(7) When the resonator (coil) is half the wavelength of the electromagnetic wave radiated from the antenna element, the resonator functions as a metamaterial. Thereby, the magnetic permeability and dielectric constant of the resonator become negative, and electromagnetic field radiation can be further suppressed.

(8) The above-described mobile communication terminal may be any terminal provided with an antenna and capable of being carried by a person, and may be, for example, a smartphone or a conventional mobile phone. However, it may be a tablet terminal that has a data communication function but no call function.

The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

10, 10A, 10B, 10D, 10E, 10F, 10GA, 10GB, 10HA, 10HB, 10X, 10Y coil, 20, 20A, 20B, 20D, 20E, 20F, 20G, 20H, 20JA, 20JB, 20KA, 20KB, 20X , 20Y antenna element, 30, 30A, 30J, 30K ground, 30B antenna connector, 40J, 40KA, 40KB LC resonator, 50J, 50K feed point, 100, 100A, 100B, 100J, 100K printed circuit board, 200B housing.

Claims

An antenna that can be incorporated into a mobile communication terminal,
An antenna element;
One or more resonances provided at a position less than a quarter of the resonance wavelength of the antenna element from the antenna element, electrically insulated from other portions and resonating at a wavelength near the resonance wavelength of the antenna element And an antenna.
The antenna according to claim 1, wherein the resonator is provided on a side that is closer to a human body than the antenna element during communication when the antenna is incorporated in the mobile communication terminal.
The antenna according to claim 1 or 2, wherein the resonator is a coil and is provided so that a magnetic field line of the magnetic field of the antenna element penetrates the coil.
The antenna according to claim 3, wherein the plurality of resonators are provided so that coil axes are substantially parallel to each other.
Resonance wavelengths of the plurality of resonators are substantially the same,
The antenna according to claim 3, wherein a part of the plurality of resonators and the remaining resonators are provided so that their coil axes are substantially orthogonal to each other.
The resonance wavelengths of the plurality of resonators include a first resonance wavelength and a second resonance wavelength,
The antenna according to claim 3, wherein the first resonance wavelength resonator and the second resonance wavelength resonator are provided so that their coil axes are substantially orthogonal to each other.
The antenna according to claim 1 or 2, wherein the resonator is an LC resonator.
An antenna structure of an antenna that can be incorporated into a mobile communication terminal,
One or a plurality of resonators that are electrically insulated from other portions and resonate at a wavelength in the vicinity of the resonance wavelength of the antenna element are provided at a position less than a quarter of the resonance wavelength of the antenna element from the antenna element. Antenna structure.
A resonator used for an antenna that can be incorporated into a mobile communication terminal,
A resonator provided at a position less than a quarter of the resonance wavelength of the antenna element from the antenna element, electrically insulated from other portions, and resonating at a wavelength near the resonance wavelength of the antenna element.