Patent Application
20120176288
The present invention relates to a magnetic dielectric antenna.
Antennas for wireless communication are known which are provided in electronic apparatuses. Examples of the electronic apparatuses include mobile apparatuses such as mobile phones, and antennas therefore have been required to be downsized.
Dielectric antennas are known as antennas capable of being downsized (for example, see Patent Literature 1). A dielectric antenna includes an electrode having, for example, a meandering shape and a dielectric base provided with the electrode. The effect of shortening the wavelength of a radio wave due to the relative permittivity of this base allows the antenna length to be shortened to downsize the dielectric antenna.
When a conventional dielectric antenna has a base of high permittivity material for downsizing, the antenna exhibits decreased radiation efficiency and a narrow band thereof.
It is an object of the present invention to downsize an antenna and to prevent a decrease in radiation efficiency and narrowing of a band.
In order to solve the above problem, a magnetic dielectric antenna in accordance with the present invention includes an L-shaped meandering electrode and a magnetic dielectric base portion covering at least part of the electrode, and the electrode includes a first electrode portion disposed so as to extend in parallel to a ground portion with a predetermined interval and a second electrode portion connected to the first electrode portion.
Preferably, in the magnetic dielectric antenna, the base portion includes a first base portion having a thickness in the direction from the first electrode portion toward the ground portion, and the first base portion is disposed so as to have a predetermined interval between a bottom surface thereof and the ground portion.
Preferably, in the magnetic dielectric antenna, the first electrode portion is provided with a second base portion having a thickness in the direction opposite to the ground portion from the first electrode portion.
Preferably, in the magnetic dielectric antenna, the first base portion has a thickness equal to the thickness of the second base portion.
Preferably, in the magnetic dielectric antenna, the second base portion has a larger thickness than the thickness of the first base portion.
Preferably, in the magnetic dielectric antenna, the second base portion has a smaller thickness than the thickness of the first base portion.
Preferably, in the magnetic dielectric antenna, the ground portion is provided on a substrate, and the electrode is disposed so as to have a meandering surface orthogonal to a surface of the substrate.
Preferably, in the magnetic dielectric antenna, the ground portion is provided on a substrate, and the electrode is disposed such that the second electrode portion is orthogonal to a surface of the substrate.
The present invention can downsize an antenna and prevent a decrease in radiation efficiency and narrowing of a band.
An embodiment, a first variation, and a second variation in accordance with the present invention will now be described in detail sequentially with reference to the accompanying drawings. However, the scope of the present invention is not limited to examples shown in the drawings.
The embodiment in accordance with the present invention will be described with reference to
The magnetic dielectric antenna 10 of the embodiment will be described as a wireless antenna having a resonant frequency of 700 [MHz] in accordance with a communication standard of LTE (Long Term Evolution). The present invention, however, should not be limited to this. The magnetic dielectric antenna 10 may be a wireless antenna in accordance with any other communication standard or having any other resonant frequency.
The magnetic dielectric antenna 10 is mounted on the substrate 20 as shown in
The magnetic dielectric antenna 10 includes the base portion 11 and an electrode 12 as an antenna element as shown in
The electrode 12 is a metallic L-shaped bent electrode embedded inside the base portion 11 as shown in
The electrode 12 also includes an electrode portion 12a and an electrode portion 12b. The electrode portion 12a is disposed so as to extend in parallel to the ground portion 21 with a predetermined interval therebetween. The electrode portion 12b is connected to the electrode portion 12a and is disposed so as to extend orthogonal to the ground portion 21.
The length of the electrode portion 12a in its extending direction is defined as a length L1. The length of the electrode portion 12b in its extending direction is defined as a length L2. The length of the base portion 11 in the direction orthogonal to the extending directions of the electrode portion 12a and the electrode portion 12b on a plane of
The base portion 11 also includes a base portion 11a as a first base portion and a base portion 11b as a second base portion. The base portion 11a has a thickness in the direction from the electrode portion 12a toward the ground portion 21. The base portion 11a is disposed so as to have a predetermined interval between its bottom surface and the ground portion 21. The base portion 11b has a thickness in the direction opposite to the ground portion 21 from the electrode portion 12a. The thickness of the base portion 11a is defined as a thickness d1, and the thickness of the base portion 11b as a thickness d2. The base portion 11a and the base portion 11b have a relationship of d1=d2.
The electrode 12 has a meandering shape as shown in
The electrode 12 is disposed inside the base portion 11 to cause an effect of shortening the wavelength of a radio wave as described by the following numerical expression (1).
Here, λr is the wavelength of a radio wave in a magnetic dielectric antenna, λ is the wavelength of a radio wave in a free space, ∈r is relative permittivity of a base portion of magnetic dielectric material, and pr is relative magnetic permeability of a base body of magnetic dielectric material.
Expression (1) demonstrates that the base portion 11 can decrease the wavelength of a radio wave in the magnetic dielectric antenna 10 and thus can shorten the antenna length of the electrode 12.
The electrode 12 is also disposed such that the lateral direction of a meandering surface (direction orthogonal to the extending direction of the electrode 12) is orthogonal to a surface of the substrate 20. The base portion 11 is not provided over the entire surface between the electrode 12 and the ground portion 21. This configuration is implemented to suppress the electrostatic capacitance between the electrode 12 and the ground portion 21.
The electrode 12 is disposed at the center in the thickness direction of the base portion 11. In other words, the electrode 12 is disposed at a length of d/2 in the thickness direction from a surface surrounding the base portion 11. The electrode 12 is disposed at the center in the thickness direction of the base portion 11 in order to utilize a magnetic field generated around the electrode 12.
Connector pins (not shown in the drawing) for supplying an antenna current are provided at the substrate portion 22. The connector pins are connected to a feeder portion for feeding the antenna current through a transmission-line pattern (not shown in the drawing) formed on the substrate 20 (the ground portion 21) or a coaxial cable (not shown in the drawing). The connector pins are connected to an end of the electrode 12 (the electrode portion 12b), and the antenna current is fed through the connector pins to the electrode 12.
The magnetic dielectric antenna 10 is manufactured by, for example, an integral molding process of casting magnetic dielectric material for the base portion 11 into a fixed mold containing the electrode 12. This integral molding process is preferable since the base portion 11 is formed also in the spaces of a meandering shape. The magnetic dielectric antenna 10 may be manufactured in other ways of, for example, sandwiching the electrode 12 between two base portions.
Next, operational characteristics of the magnetic dielectric antenna 10 will be described with reference to
The dielectric antenna 30 to be compared with the magnetic dielectric antenna 10 will now be described with reference to
The dielectric antenna 30 includes a base portion 31 and an electrode 12. This electrode 12 is the same electrode portion as that of the magnetic dielectric antenna 10. The base portion 31 is composed of dielectric material and is a rectangular-parallelepiped base portion provided inside the electrode 12 (near the ground portion 21). The base portion 31 is provided inside the electrode 12 since the electric field of the electrode 12 acts toward the ground portion 21. In contrast to that, the magnetic field of the electrode 12 acts around the electrode 12.
For example, the base portion 31 of the dielectric antenna 30 has relative permittivity ∈r of 40, and the base portion 11 of the magnetic dielectric antenna 10 has relative magnetic permeability μr of 5. Frequency characteristics of VSWR of the dielectric antenna 30 and the magnetic dielectric antenna 10 are calculated by simulation and the characteristics illustrated in
Similarly, frequency characteristics of radiation efficiency of the dielectric antenna 30 and the magnetic dielectric antenna 10 are calculated by simulation and the characteristics illustrated in
As described above, the magnetic dielectric antenna 10 in accordance with this embodiment includes the meandering electrode 12 and the magnetic dielectric base portion 11 disposed around the electrode 12. The meandering shape of the electrode 12 allows the antenna length to be shortened, use of the relative permittivity and the relative magnetic permeability of the base portion 11 allows the effect of shortening the wavelength to be enhanced to downsize the magnetic dielectric antenna 10A and to prevent a decrease in the radiation efficiency and narrowing of the band caused by high permittivity.
The electrode 12 is L-shaped. Thereby, the magnetic dielectric antenna 10 can be further downsized for installation in a limited space.
The electrode portion 12a of the electrode 12 is disposed so as to extend in parallel to the ground portion 21 with a predetermined interval therebetween. Thereby, the electrostatic capacitance between the electrode 12 and the ground portion 21 can be suppressed to further prevent the radiation efficiency of the magnetic dielectric antenna 10 from decreasing.
Unlike the dielectric antenna 30 including the base portion 31 occupying the entire area between the electrode 12 and the ground portion 21, the magnetic dielectric antenna 10 includes the base portion 11 covering the electrode 12. Thereby, the electrostatic capacitance between the electrode 12 and the ground portion 21 can be suppressed to further prevent the radiation efficiency of the magnetic dielectric antenna 10 from decreasing.
The electrode 12 is disposed so as to have a meandering surface orthogonal to a surface of the substrate 20. Thereby, the electrostatic capacitance between the electrode 12 and the ground portion 21 can be suppressed to further prevent the radiation efficiency of the magnetic dielectric antenna 10 from decreasing.
The magnetic dielectric antenna 10 includes the base portion 11a having a thickness d1 equal to the thickness d2 of the base portion 11b. Thereby, the effect of the permittivity can be enhanced to downsize the magnetic dielectric antenna 10, and the electrostatic capacitance between the electrode 12 and the ground portion 21 can be suppressed to further prevent the radiation efficiency of the magnetic dielectric antenna 10 from decreasing.
A first variation of the preceding embodiment will be described with reference to
The device configuration of this variation will now be described with reference to
The magnetic dielectric antenna 10A includes the base portion 11A and an electrode 12A as shown in
The electrode 12A is a metallic L-shaped bent electrode embedded inside the base portion 11A. The electrode 12A includes an electrode portion 12Aa similar to the electrode portion 12a and an electrode portion 12Ab similar to the electrode portion 12b. The electrode portion 12Aa is shifted outward (opposite to the ground portion 21) from the center in the thickness direction of the base portion 11A. The electrode 12Ab is shifted outward (rightward in
The base portion 11A also includes a base portion 11Aa as a first base portion and a base portion 11Ab as a second base portion similarly to the base portion 11. The base portion 11Aa has a thickness in the direction from the electrode portion 12Aa toward the ground portion 21. The base portion 11b has a thickness in the direction opposite to the ground portion 21 from the electrode portion 12Aa. The thickness of the base portion 11Aa is defined as a thickness d1, and the thickness of the base portion 11Ab as a thickness d2. The base portion 11Aa and the base portion 11Ab have a relationship of d1>d2.
The magnetic dielectric antenna 10B includes the base portion 11B and an electrode 12B as shown in
The electrode 12B is a metallic L-shaped bent electrode embedded inside the base portion 11B. The electrode 12B includes an electrode portion 12Ba similar to the electrode portion 12a and an electrode portion 12Bb similar to the electrode portion 12b. The electrode portion 12Ba is shifted inward (toward the ground portion 21) from the center in the thickness direction of the base portion 11B. The electrode portion 12Bb is shifted inward (leftward in
The base portion 11B includes a base portion 11Ba as a first base portion and a base portion 11Bb as a second base portion like the base portion 11. The base portion 11Ba has a thickness in the direction from the electrode portion 12Ba toward the ground portion 21. The base portion 11Bb has a thickness in the direction opposite to the ground portion 21 from the electrode portion 12Ba. The thickness of the base portion 11Ba is defined as a thickness d1, and the thickness of the base portion 11Bb as a thickness d2. The base portion 11Ba and the base portion 11Bb have a relationship of d1<d2.
Next, characteristics of the magnetic dielectric antennas 10A and 10B will be described with reference to
The magnetic dielectric antenna 10 is used for comparison. In this example, the base portions 11, 11A, and 11B each have a thickness of 2 [mm]. The electrode 12 is disposed at a position (at the center) 1[mm] distant from an end surface of the base portion 11 in the thickness direction. The electrode 12A is disposed at a position 0.5[mm] outward from the center in the thickness direction of the base portion 11A. The electrode 12B is disposed at a position 0.5[mm] inward from the center in the thickness direction of the base portion 11B. The resonant frequency of the magnetic dielectric antenna 10 is set to 1 [GHz], and the magnetic dielectric antennas 10A and 10B each have the same external shape as that of the magnetic dielectric antenna 10. The relative permittivity of the base portions 11, 11A, and 11B is set to the same value. The relative magnetic permeability of the base portions 11, 11A, and 11B is set to the same value.
The magnetic dielectric antenna 10A has a lower resonant frequency than that of the magnetic dielectric antenna 10 as shown in
The magnetic dielectric antenna 10B has higher radiation efficiency than that of the magnetic dielectric antenna 10 as shown in
As described above, the magnetic dielectric antenna 10A in accordance with this variation provides similar advantageous effects to the magnetic dielectric antenna 10. Additionally, the magnetic dielectric antenna 10A includes the base portion 11Aa having a larger thickness d1 than the thickness d2 of the base portion 11Ab. Thereby, the effect of the permittivity can be enhanced to further downsize the magnetic dielectric antenna 10A compared to the magnetic dielectric antenna 10.
The magnetic dielectric antenna 10B in accordance with this variation also provides similar advantageous effects to the magnetic dielectric antenna 10. Additionally, the magnetic dielectric antenna 10B includes the base portion 11Ba having a smaller thickness d1 than the thickness d2 of the base portion 11Bb. Thereby, the electrostatic capacitance between the electrode 12B and the ground portion 21 can be suppressed to further prevent the radiation efficiency of the magnetic dielectric antenna 10B from decreasing compared to that of the magnetic dielectric antenna 10.
A second variation of the preceding embodiment will be described with reference to
The device configuration of this variation will be described with reference to
The magnetic dielectric antenna 10C in this variation is mounted on the substrate 20C as shown in
The electrode portion 12Ca is disposed so as to extend in parallel to the ground portion 21C with a predetermined interval therebetween. The electrode portion 12Ca is also disposed so as to have a meandering surface in parallel to a surface of the ground portion 21C. The electrode portion 12Cb is disposed so as to extend orthogonal to the ground portion 21C.
As described above, the magnetic dielectric antenna 10C in accordance with this variation provides similar advantageous effects to the magnetic dielectric antenna 10. In particular, the electrode portion 12Ca of the electrode 12C extends in parallel to the ground portion 21C with a predetermined interval therebetween. Thereby, the electrostatic capacitance between the electrode 12C and the ground portion 21C can be suppressed to further prevent the radiation efficiency of the magnetic dielectric antenna 10C from decreasing.
Additionally, the electrode portion 12Cb of the electrode 12C extends orthogonal to the ground portion 21C. This can decrease the area for mounting the magnetic dielectric antenna 10C.
The preceding embodiment and the variations have been described as examples of the magnetic dielectric antennas in accordance with the present invention, which is not limited to these examples.
For example, at least two of the preceding embodiment and the variations may be properly combined. For example, the substrate 20C in the second variation may include a ground portion and a substrate portion. In this configuration, the magnetic dielectric antenna 10C (the electrode portion 12Cb) is mounted on the substrate portion of the substrate 20C.
Alternatively, at least part of the electrodes 12, 12A, 12B, and 12C may be covered with a base portion.
Other details of the configurations and operations of the magnetic dielectric antennas 10, 10A, 10B, and 10C in the preceding embodiment and the variations can also be properly modified without departing from the scope of the present invention.
As described above, the magnetic dielectric antennas in accordance with the present invention are suitable for wireless communication such as LTE.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-227342 | Sep 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/066374 | 9/22/2010 | WO | 00 | 3/29/2012 |
