Patent Application
20090160717
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2007-326968, filed on Dec. 19, 2007; the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an antenna device and a wireless device.
2. Related Art
When a lossy material such as a human body comes close to an antenna, the antenna characteristics will deteriorate. To solve this problem, Patent Document JP-A 2006-217129 (Kokai) proposes a technique of branching a conductor wire of at least one of the feeding portion and the short-circuit portion of the antenna into a plurality of lines; running the lines in parallel at a predetermined spacing; and then joining together the lines again at another point. Since at least one of the feeding portion and the short-circuit portion of the antenna which will be most affected when a lossy material and the like come close to the lines is divided into a plurality of lines, this technique can suppress the antenna characteristics from deteriorating even if any one of the plurality of lines is affected by the lossy material or the like.
Unfortunately, according to the conventional antenna device described above, when any one of the plurality of lines is affected by a lossy material or the like, a flowing electric current is changed in the remaining lines connected to the affected line and the antenna input impedance is fluctuated. In the first place, it is a rare case that any one of the plurality of lines is affected by a lossy material or the like, and in fact, the overall effect is considered to deteriorate the radiation efficiency.
According to an aspect of the present invention, there is provided with an antenna device comprising:
a dipole element that includes a first linear element and a second linear element with each one end thereof being provided closely, the dipole element having a length of approximately one-half of a wavelength of an operating frequency;
a loop-shaped element that includes a third linear element and a fourth linear element provided approximately in parallel to the first linear element and the second linear element with each one end thereof being provided closely, and a fifth linear element with one end thereof being connected to the other end of the third linear element and the other end thereof being connected to the other end of the fourth linear element, the loop-shaped element having a length of approximately one wavelength of an operating frequency; and
a feeding point feeding power to each one ends of the first linear element and the second linear element and to each one ends of the third linear element and the fourth linear element.
According to an aspect of the present invention, there is provided with a wireless device comprising:
an antenna device as claimed in claim 1; and
a wireless chip configured to perform wireless communication through the antenna device.
Hereinafter, present embodiments will be described in detail with reference to drawings.
This antenna device is provided with a first metal portion 2 and a second metal portion 3 forming a dipole element; a third metal portion 4 forming a loop-shaped element; and a feeding point 1 feeding power to the dipole element and the loop-shaped element. The first metal portion 2, the second metal portion 3 and the third metal portion 4 are configured with a wire or a strip line, which is formed, for example, by copper, aluminum, gold, or the like.
The first metal portion 2 and the second metal portion 3 are approximately linearly arranged with a respective one end thereof close to each other. The first metal portion 2 and the second metal portion 3 correspond to, for example, a first linear element and a second linear element. Each of the first metal portion 2 and the second metal portion 3 has an electrical length of approximately one-fourth of a wavelength of an operating frequency. In other words, the dipole element consisting of the first metal portion 2 and the second metal portion 3 has an electrical length of approximately one-half of a wavelength of the operating frequency.
The third metal portion (loop-shaped element) 4 has an electrical length of approximately one wavelength of a of the operating frequency with a conductor element arranged around in a loop shape starting at one end thereof. More specifically, the third metal portion 4 includes a third linear element 41a and a fourth linear element 41b with a respective one end thereof close to each other; and a fifth linear element 41c with one end thereof connected to the other end of the third linear element 41a and the other end thereof connected to the other end of the fourth linear element 41b; and the third linear element 41a and the fourth linear element 41b are approximately in parallel to the first metal portion (first linear element) 2 and the second metal portion (second linear element) 3. The third linear element 41a and the fourth linear element 41b are close to the first metal portion 2 and the second metal portion 3 respectively with the spacing being approximately one-tenth or less of a wavelength.
The both ends (i.e., one end portion of the third linear element and the fourth linear element) of the third metal portion (loop-shaped element) 4 are folded outward of the loop, and each one end of the first metal portion 2 and the second metal portion 3 is connected to each folded end thereof.
The feeding point 1 feeds power to the one and the other end of the third metal portion (loop-shaped element) 4; and feeds power to each one of the first metal portion (first loop-shaped element) 2 and the second metal portion (second loop-shaped element) 3. In other words, the feeding point 1 serves as a feeding point common to the loop-shaped element and the dipole element.
Hereinafter, the operation of the antenna device of
The antenna device of
With reference to
As described above, since the A-A′ portion and the B-B′ portion are approximately in parallel and close to each other, strong binding occurs therebetween, strengthening the current intensity with each other. As a result, the current intensity distribution of the B-B′ portion is larger than that of the C-C′ portion; and the intensity distributions of the current of the A-A′ portion and the current of the loop-shaped element (synthetic current of the B-B′ portion and the remaining portion including C-C′ portion) are approximately the same. In other words, the flowing current of the dipole-shaped element is larger than that of the loop-shaped element, for the reasons that from the point of view of the feeding point 1, the dipole-shaped element seems to be lower in impedance than the loop-shaped element, and the like. A large current of the dipole-shaped element strengthens the current intensity of the B-B′ portion; on the contrary, the current (lower than that of the dipole-shaped element) of the loop-shaped element strengthens the current intensity of the dipole-shaped element. As a result, the intensity distributions of the current of the A-A′ portion and the current of the loop-shaped element (synthetic current of the B-B′ portion and the remaining portion including C-C′ portion) are approximately the same.
In the Y direction (see
Here, the reason that the radiation in the Y direction can be greatly suppressed by electromagnetic wave cancellation, and the radiation in the X direction cannot be suppressed will be described in detail.
The current of the dipole-shaped element 22 (first metal portion 2 and second metal portion 3) advances in phase by about R° than the current of the third metal portion (loop-shaped element) 21. Assuming that the phase of an electromagnetic wave radiated from the third metal portion (loop-shaped element) 21 at a certain time is 0°, the phase of an electromagnetic wave radiated from the dipole-shaped element 22 is R°. Seeing from the loop-shaped element 21 toward the dipole-shaped element 22 on the basis of the position of the dipole-shaped element 22, the phase corresponding to the distance between the loop-shaped element 21 and the dipole-shaped element 22 (approximately one-tenth wavelength or less as described above) is K°. Therefore, the phase of the electromagnetic wave which is radiated from the loop-shaped element 21 and reaches the dipole-shaped element 22 is 0°−K°=−K°. Consequently, in the direction seen from the loop-shaped element 21 to the dipole-shaped element 22, the phase difference between the phase (−K°) of the electromagnetic wave radiated from the loop-shaped element 21 and the phase (R°) of the electromagnetic wave radiated from the dipole-shaped element 22 is R°−(−K°)=(R+K)°. This phase is about near anti-phase. Accordingly, in the direction from the loop-shaped element 21 to the dipole-shaped element 22, the electromagnetic waves are cancelled and practically no radiation occurs.
On the contrary, when seen from the dipole-shaped element 22 to the loop-shaped element 21, the phase difference between the phase (R°+(−K°) of the electromagnetic wave which is radiated from the dipole-shaped element 22 and reaches the loop-shaped element 21 and the phase (0°) of the electromagnetic wave radiated from the loop-shaped element 21 is (R−K)°−0°=(R−K)° by considering in the same way. Since the value is greatly out of phase from the 180 degrees, the radiation in the direction seen from the dipole-shaped element 22 to the loop-shaped element 21 is not suppressed.
Here, in order to enhance the effect of electromagnetic wave cancellation, the current of the loop-shaped element (synthetic current of the B-B′ portion and the remaining portion including the C-C′ portion) is required to be approximately equal to the current of the A-A′ portion. For this purpose, according to the present embodiment, as described above, the A-A′ portion is placed close to the B-B′ portion to generate strong binding, thereby strengthening the current of the B-B′ portion. With that in mind, the present inventors performed an electromagnetic field simulation to find how far the distance should be between the B-B′ portion and the A-A′ portion required to generate strong binding between the B-B′ portion and the A-A′ portion. The results will be described as follows.
As described above, the present antenna device is little affected by a metal or lossy material provided in the Y direction and can suppress the radiation efficiency from deteriorating. Further, the present antenna device also has an advantage of reducing the variation of input impedance at the feeding point 1 even if the metal or lossy material comes close to the antenna device. Further detailed description is given below.
As described above, the antenna device of
The phase of the current at feeding point 1 of the loop antenna of
According to the first embodiment, each one end of the first metal portion 2 and the second metal portion 3 is connected directly to the feeding point 1; while according to the second embodiment, each one end thereof is connected to a middle of the folded portion of the third metal portion 4. Consequently, according to the first embodiment, the dipole element is composed of the first metal portion 2 and the second metal portion 3; while according to the second embodiment, the dipole element is composed of the portions 4a and 4b each extending from the connection point with the first and the second metal portion 2, 3 to one end and the other end of the third metal portion 4; and the first metal portion 2 and the second metal portion 3. The power feeding is performed to the dipole element by the power feeding from one end and the other end of the third metal portion 4. The dipole element has an electrical length of approximately one-half of a wavelength of the operating frequency in the same way as in the first embodiment.
In this configuration, the distance between the first metal portion 2 and the second metal portion 3 and the feeding point 1 increases and the distance between the loop portion serving as the main radiation portion of the third metal portion 3 and the feeding point 1 increases. Consequently, the present antenna is difficult to be affected by a circuit element or the like (not shown) to be connected to the feeding point 1 and can further suppress the radiation efficiency from deteriorating.
The direction X and the direction Y in
The simulation was performed by changing “h” in three ways: 20.5 mm, 10.0 mm, 6.0 mm, assuming the distance between a plane where the antenna device exists and the infinite ground plate is “h”. As a result, the reflection coefficient remains reduced in about 1,700 MHz of operating frequency when the infinite ground plate comes close to the antenna device of
The antenna device is characterized in that the first metal portion 2 and the second metal portion 3 are formed on a plane different from a plane where the third metal portion 4 and the feeding point 1 exist.
As described above, the direction of suppressing radiation is inclined from the horizontal direction by forming the first metal portion 2 and the second metal portion 3 on a plane different from a plane where the third metal portion 4, and it is possible to further strengthen the effect of suppressing radiation efficiency when a metal or lossy material is placed in the inclined direction.
Here, the example shows that the first metal portion 2 and the second metal portion 3 of the antenna device of
This antenna device is provided with a dielectric substrate 6 and the antenna device of
Consequently, design flexibility can be increased and the antenna can be easily provided far away from a metal or lossy material by forming the antenna device of
Here, the example shows that the antenna device of
This antenna device is configured such that the antenna device of
Here, the example shows that the antenna device of
The wireless device is provided with a dielectric substrate 6; a semiconductor chip (wireless chip) 7 provided on the dielectric substrate 6; and the antenna device of
Even if the antenna device is connected to the semiconductor chip 7, it is possible to suppress the deterioration of the radiation efficiency and the variation of input impedance by the lossy semiconductor chip 7.
Here, the example shows that the antenna device of
This wireless device is a modification of the wireless device of
The antenna device can be provided as high as the semiconductor chip 7 or higher than the semiconductor chip 7 by providing the antenna device on the second dielectric substrate 8 in this manner. Therefore, it is possible to enhance the flexibility of where the antenna device is placed.
Here, the example shows that the antenna device of
The wireless device is configured such that the antenna device of
A solder ball 9 is provided on the bottom face of the semiconductor chip 7 and is sandwiched between the semiconductor chip 7 and the dielectric substrate 6. The solder ball 9 may be replaced with wire bonding. Further, the solder ball 9 for installation on a circuit board or the like is provided on the bottom face of the dielectric substrate 6. The antenna device is connected to the semiconductor chip 7 through the feeding point 1. The antenna device and the semiconductor chip 7 are sealed by the sealing medium 10. Alternatively, a dielectric such as a glass substrate and a silicon substrate may be separately provided in the sealing medium 10 above the antenna device of
In this way, a built-in antenna semiconductor package module which is difficult to be affected by a lossy material, metal or the like inside the package can be implemented. Since an antenna device has already been built in the package, the antenna device is not required to be disposed on any other location when the package is positioned, thereby contributing to saving space.
Here, the example shows that the antenna device of
The wireless communication device is configured such that the wireless device of
The wireless device of
Here, the description is made by the example showing that the wireless device of
Subsequently, an example of installing the wireless device of
The mobile terminal 14 shown in
For example, the mobile terminal 14 performs data communication (e.g., music downloading) to and from the main unit 11 shown in
As described above, according to the present embodiment, data and images can be preferably sent and received by installing the modularized wireless device of
In addition, since the wireless device of
The wireless device is an IC tag for use in an RFID system and is provided with the wireless communication device of
Here, the example shows that the antenna device of
As described above, the antenna device in accordance with the present invention provided in an IC tag for use in an RFID system can provide a preferable communication with little degradation of radiation efficiency and with little variation of impedance in any communication whether the IC tag is attached to a metal or lossy material or the IC tag is provided in a free space.
The wireless device is configured such that the antenna device of
As described above, the antenna device in accordance with the present invention provided in the reader/writer device can provide a preferable communication with little degradation of radiation efficiency and with little variation of impedance even if the reader/writer device must be close to a metal or lossy material at the time of reading or writing.
The wireless communication device is configured such that the antenna device of
As described above, the antenna device in accordance with the present invention provided in the cell phone can provide a preferable communication with little degradation of radiation efficiency and with little variation of impedance even if a metal or lossy material such as a human body is close to the cell phone.
The present invention is not limited to the exact embodiments described above and can be embodied with its components modified in an implementation phase without departing from the scope of the invention. Also, arbitrary combinations of the components disclosed in the above-described embodiments can form various inventions. For example, some of the all components shown in the embodiments may be omitted. Furthermore, components from different embodiments may be combined as appropriate.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-326968 | Dec 2007 | JP | national |
