JP2012115069A - Antenna, power transmission device, power reception device, and non-contact communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna capable of suppressing radiation noise to be emitted without significantly reducing power transmission efficiency, and to provide a power transmission device, a power reception device, and a non-contact communication device using the antenna.SOLUTION: An antenna has a composite antenna 10 consisting of a planar coil 11 and a loop coil 12 arranged inside the planar coil 11. The loop coil 12 has a capacitor 13 in a part of itself. The loop coil 12 is electrically closed from the planar coil 11 and the other electric circuit, and is electromagnetically coupled with the planar coil 11. The electromagnetical coupling degree of the loop coil 12 is set to be a coupling degree by which a magnetic flux generated by the planar coil 11 and a magnetic flux generated by the loop coil 12 cancel each other out to reduce the efficiency at a resonance frequency of a resonance circuit consisting of an inductance of the loop coil 12 and the capacitor 13. The resonance frequency is adjusted to be a frequency twice or more as large as a driving frequency of the planar coil 11.

Description

  The present invention relates to non-contact power transmission performed between a power transmission device and a power reception device, and in particular, a power reception device provided in a portable device such as a mobile phone, a headset, a digital camera, and a digital video, and non-contact to the power reception device. The present invention relates to an antenna suitable for a power transmission device that performs power feeding or charging, and a power transmission device, a power reception device, and a non-contact communication device using the antenna.

  In a non-contact power transmission system using electromagnetic induction, coils are installed in a power transmission device on the power transmission side such as a charger and a power reception device on the power reception side such as a portable device, and power is transmitted by electromagnetic induction between those coils. Has been done. A simple planar coil is used as an antenna for power transmission / reception and data communication between a thin non-contact information recording medium such as a non-contact IC card and a reader / writer, or between a small portable device and a power transmission device. Has been put to practical use. FIG. 6 is a plan view of an antenna using a conventional planar coil, which is used as an antenna in a non-contact power transmission system using electromagnetic induction. The antenna 20 is composed of a planar coil 21.

  When the conventional antenna using a simple planar coil shown in FIG. 6 is used, the power transmission efficiency changes depending on the positional relationship between the power transmission side antenna and the power reception side antenna. For such a problem, for example, means as disclosed in Patent Document 1 is disclosed.

  Patent Document 1 describes an antenna having a tuning circuit composed of a tuning coil and a tuning capacitor that are not connected to other circuits inside a planar coil that serves as a feeding coil. The tuning point of the antenna is set so that a plurality of tuning points appear within the range of the antenna driving frequency. By extending the frequency range that can be driven, the communication efficiency decreases due to the position between the transmitting and receiving antennas. An antenna capable of compensation is disclosed. In this case, in order to generate a plurality of tuning points having the maximum peak of efficiency, it is necessary to increase the distance between them so that the coupling coefficient between the tuning coil and the planar coil becomes sufficiently small. As a result, the magnetic flux generated from the planar coil is sufficiently smaller than the magnetic flux generated from the tuning coil, and there is no reduction in efficiency due to their cancellation.

JP 2003-69336 A

  Generally, radiation noise having a frequency other than the driving frequency is superimposed on the electromagnetic field generated from the antenna, which has a problem of adversely affecting electronic devices around the antenna. In a non-contact power transmission system using electromagnetic induction, when performing a power transmission operation such as charging, there is a problem that this radiation noise becomes significant because large power is emitted from the antenna. In particular, there are many cases in which noise of harmonic components more than twice the antenna drive frequency is generated. When such radiated noise from the power transmission device or external radiation noise is received, problems such as unstable power supply and unstable communication occur, so this radiated noise on the power transmission device side or the power receiving device side. It is necessary to suppress.

  On the other hand, if the electromagnetic field of the drive frequency used for non-contact power transmission is suppressed in order to suppress radiation noise, the power transmission efficiency may be adversely affected. For this reason, it is necessary not to affect the electromagnetic fields of these drive frequencies.

  Since the conventional antenna described in Patent Document 1 is characterized in that power for communication can be transmitted in a wide frequency band, from the viewpoint of radiation noise, there is a risk of noise being radiated in a wide frequency band. .

  As described above, in the non-contact power transmission system, when transmitting power, it is desirable that the radiation noise contained in the electromagnetic field radiated from the antenna is small. On the other hand, if the electromagnetic field of the driving frequency for performing non-contact power transmission is suppressed, there is a concern that the power transmission efficiency may be lowered. Therefore, it is necessary that the electromagnetic field of this driving frequency is not affected.

  The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide an antenna that can suppress emitted radiation noise without greatly reducing power transmission efficiency, and an antenna for the antenna. It is in providing the used power transmission apparatus, power receiving apparatus, and non-contact communication apparatus.

  In order to solve the above-described problem, an antenna according to the present invention includes a composite antenna including a planar coil and at least one loop coil disposed inside or outside the planar coil. Has a tuning capacity in part, and the loop coil is not connected to the planar coil and other electric circuits, and is electromagnetically coupled to the planar coil, The degree of electromagnetic coupling between the coil and the loop coil is determined by the resonance frequency of the resonance circuit consisting of the inductance of the loop coil and the tuning capacitance, and the magnetic flux generated from the planar coil and the magnetic flux generated from the loop coil. The degree of coupling is set such that efficiency is reduced by canceling each other, and the resonance frequency of the resonance circuit is the plane. Characterized in that it is adjusted to a frequency at least twice the drive frequency of yl.

  Here, in the composite antenna, the opening area of the loop coil includes an opening area that is ½ or more of the opening area of the planar coil, so that the electromagnetic wave between the planar coil and the loop coil is reduced. It may be set to the degree of coupling of various couplings.

  In the composite antenna, a plurality of the loop coils may be arranged. In this case, at least two of the plurality of loop coils may have different resonance frequencies.

  In addition, a yoke made of a magnetic material may be disposed near one side of the composite antenna, and a shielding plate for shielding electromagnetic waves may be disposed near one side of the composite antenna.

  In the antenna according to the present invention, a plurality of the composite antennas may be arranged.

  A power transmission device according to the present invention is a power transmission device for non-contact power transmission, wherein any one of the antennas described above is used as an antenna for non-contact power transmission.

  A power receiving device according to the present invention is a power receiving device for non-contact power transmission, wherein any one of the antennas described above is used as an antenna for non-contact power transmission.

  A non-contact communication apparatus according to the present invention is a non-contact communication apparatus for RFID, and any one of the above antennas is used as a communication antenna.

  According to the antenna of the present invention, the power transfer efficiency is obtained by canceling out the magnetic flux generated from the planar coil and the magnetic flux generated from the loop coil only at a frequency corresponding to the resonance frequency of the loop coil among the electromagnetic fields radiated from the antenna. Therefore, radiation noise in a specific frequency band is suppressed, and malfunction of surrounding electronic devices can be prevented. By using this antenna, it is possible to obtain a power transmission device, a power reception device, and a non-contact communication device that suppress the generation and reception of radiation noise of a specific frequency.

  That is, according to the present invention, it is possible to obtain an antenna that can suppress emitted radiation noise without significantly reducing power transmission efficiency, and a power transmission device, a power reception device, and a non-contact communication device using the antenna.

The top view which shows the structure of 1st Embodiment of the antenna by this invention. The figure which shows the simulation result of the frequency characteristic of the power transmission efficiency of the antenna of 1st Embodiment by this invention, and the conventional antenna. The figure which shows the frequency characteristic of the power transmission efficiency of the composite antenna which provided the loop coil inside the plane coil, using the opening area ratio with respect to the plane coil of a loop antenna as a parameter. The figure which shows the change with respect to the opening area ratio of a loop coil of the coupling coefficient of the electromagnetic coupling between a plane coil and a loop coil. The top view which shows the structure of 2nd Embodiment of the antenna by this invention. The top view of the antenna by the conventional planar coil. The top view which shows the structure of the conventional antenna 2. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a plan view showing a configuration of a first embodiment of an antenna according to the present invention. As shown in FIG. 1, the antenna according to the present embodiment includes a composite antenna 10 including a planar coil 11 and one loop coil 12 arranged inside the planar coil 11. A part 12 has a capacitor 13 as a tuning capacitor. The loop coil 12 is not electrically connected to the planar coil 11 and other electric circuits, and is electromagnetically coupled to the planar coil 11. The degree of coupling of electromagnetic coupling between the planar coil 11 and the loop coil 12 is such that the magnetic flux generated from the planar coil 11 and the magnetic flux generated from the loop coil 12 at the resonance frequency of the resonance circuit including the inductance of the loop coil 12 and the capacitor 13. Are set so as to cause a reduction in power transmission efficiency by canceling each other, and the resonance frequency of the resonance circuit is adjusted to be twice or more the driving frequency of the planar coil 11.

  Here, in the present embodiment, in the composite antenna 10, the opening area of the loop coil 12 is set to be 1/2 or more of the opening area of the planar coil 11. The degree of coupling of electromagnetic coupling is set so as to meet the above conditions.

  The planar coil 11 and the loop coil 12 can be produced by a conductor line pattern such as a thin metal plate or a metal film on a substrate made of a dielectric material such as an FPC substrate or an FR-4 substrate. Or it can also produce with the winding of a metal wire. The planar coil 11 and the loop coil 12 are desirably arranged on the same plane.

  The resonance frequency of the resonance circuit by the loop coil 12 uses a capacitance component generated by the overlap of the copper foil patterns provided on the front surface or the back surface of the substrate, in addition to the capacitance of the capacitor 13 of the loop coil 12. Can also be adjusted.

  In the antenna of the present embodiment, a yoke made of a magnetic material may be disposed in the vicinity of one surface of the composite antenna 10, that is, on the back surface of the substrate on which the composite antenna 10 is installed. Thereby, the efficiency and directivity of the antenna can be improved. The magnetic material in this case is preferably a material that has a low loss even at a high frequency, such as NiZn ferrite. Moreover, the composite material which combined the magnetic material with a several different magnetic permeability may be sufficient.

  Further, a shielding plate for shielding electromagnetic waves may be disposed on the back surface of the substrate on which the composite antenna 10 is installed or on the back surface of the yoke made of the magnetic material. Thereby, the direction of the radiation noise generated from the antenna can be controlled, or the radiation noise received from the antenna can be further reduced.

  In FIG. 1, only one loop coil 12 is installed as the loop coil. However, a plurality of other loop coils may be arranged inside the loop coil 12 or outside the planar coil 11. By setting the plurality of loop coils so as to have different resonance frequencies, radiation noise of a plurality of frequencies can be suppressed.

  FIG. 5 is a plan view showing the configuration of the antenna according to the second embodiment of the present invention. As shown in FIG. 5, in the antenna of the second embodiment, four composite antennas 15, 16, 17, 18 having the same structure as the composite antenna 10 shown in FIG. 1 are arranged in two rows. .

  Here, in the antenna of the second embodiment shown in FIG. 5, the number of arranged composite antennas is four. However, in the present invention, the number is arbitrarily set with the composite antenna as one unit. It is possible to have a structure in which each composite antenna can be removed.

  The maximum transmitted power that can be transmitted from the power transmission device can be adjusted by the number of composite antennas constituting the antenna of the power transmission device. For example, if 1 W of power can be transmitted per composite antenna, a power transmission device having an antenna composed of 4 composite antennas can transmit power up to 4 W.

  In addition, by adding a control system that can select a composite antenna to be excited among a plurality of composite antennas constituting the antenna of the power transmission device, it is also possible to perform power transmission using a part of the antenna of the power transmission device. .

  Moreover, if the total of the transmission power of the power transmission device is equal to or less than the maximum transmission power, power transmission to a plurality of power reception devices is possible at the same time.

  The maximum received power of the power receiving apparatus can be adjusted by the number of composite antennas constituting the antenna. For example, assuming that 1 W of power can be received per composite antenna, a power receiving device having an antenna composed of four composite antennas can receive power up to 4 W.

  Next, specific examples of the antenna according to the first embodiment will be described.

  In the composite antenna 10, the planar coil 11 is formed so as to enter a rectangular substrate having an outer diameter of 40 mm × 20 mm, the line pattern width constituting the planar coil is 0.7 mm, the line pattern gap is 0.3 mm, and the number of turns. Is made as 4T. The loop coil 12 has an opening area that is 2/3 times the opening area of the planar coil 11 and is manufactured with a line pattern width of 0.4 mm. The planar coil 11 and the loop coil 12 are produced on the same substrate surface. The loop coil 12 is connected to the capacitor 13 to form a resonance circuit including the inductance of the loop coil 12 and the capacitance of the capacitor 13, and the resonance frequency is adjusted to be around 200 MHz. The planar coil 11 is suitable as an antenna for a non-contact power transmission system with a driving frequency of 13.56 MHz.

  Here, a NiZn ferrite, which is a magnetic material, is used to form a yoke, its outer shape is a rectangle of 40 mm × 20 mm, its thickness is 0.3 mm, and it is disposed on the back surface of the substrate on which the composite antenna 10 is installed.

  The operation of the antenna of this embodiment configured as described above will be described. When a current is passed through the planar coil 11, the loop coil 12 is excited by electromagnetic induction only when the frequency of the current matches the resonant frequency of the resonant circuit comprising the loop coil 12, and the magnetic flux generated from the planar coil 11. The magnetic flux in the opposite direction is generated. For this reason, the magnetic flux generated from the planar coil 11 can be canceled by the loop coil 12, and the radiation of the electromagnetic field can be suppressed. In addition, when the frequency of the current flowing through the planar coil 11 does not match the resonance frequency of the loop coil 12, the loop coil 12 is not excited, and the electromagnetic field generated from the planar coil 11 is not affected.

  FIG. 2 is a diagram showing a simulation result of frequency characteristics of power transmission efficiency of the antenna according to the first embodiment of the present invention and the conventional antenna. Here, frequency characteristics of the antenna having the shape of the above-described example (referred to as the antenna 1 of the present embodiment) are shown as the antenna of the present embodiment. In addition, as a conventional antenna for comparison, an antenna having only a planar coil having the same shape as the planar coil of the above embodiment (referred to as the conventional antenna 1 in FIG. 6), and the planar coil of the above embodiment. The frequency characteristics of an antenna (referred to as the conventional antenna 2 in FIG. 7) provided with a planar coil having the same shape as and a loop coil having an opening area of 1/12 of the opening area of the planar coil inside the planar coil are shown. FIG. 7 is a plan view showing the configuration of the conventional antenna 2. The opening area of the loop coil 32 is 1/12 of the opening area of the planar coil 31. Accordingly, the degree of electromagnetic coupling between the planar coil 33 and the loop coil 32, that is, the coupling coefficient is smaller than that of the antenna 1 of the present embodiment. The resonance frequency of the loop coil 32 is adjusted to 200 MHz by the capacitor 33.

  As shown in FIG. 2, when the antenna of the present embodiment and the conventional antenna 1 are compared, the power transmission efficiency of the antenna of the present embodiment is significantly reduced in the vicinity of the resonance frequency of 200 MHz that the loop coil 12 has. Yes. From this, it can be seen that in the antenna of the present embodiment, the electromagnetic field generated from the planar coil 11 is canceled out by the loop coil 12 at the resonance frequency of the loop coil and is not easily radiated. That is, it can be seen that when noise around 200 MHz is input to the antenna of the present embodiment, this noise is canceled out by the loop coil 12 and radiation is suppressed.

  Further, when comparing the antenna of the present embodiment with the conventional antenna 2, the conventional antenna 2 has a smaller amount of decrease in power transmission efficiency near 200 MHz than the antenna of the present embodiment. It turns out that the effect is small. Further, in the conventional antenna 2, the power transmission efficiency is increased in the frequency band of 700 MHz or higher as compared with the antenna of the present embodiment and the conventional antenna 1, so that the radiation noise in this frequency band is rather large. End up.

  FIG. 3 is a diagram showing the frequency characteristics of the power transmission efficiency of the composite antenna having a loop coil inside the planar coil, with the aperture area ratio of the loop antenna to the planar coil as a parameter. That is, the ratio of the opening area of the loop coil to the opening area of the planar coil is 2/3, 1/2, 1/4, and 1/12, respectively, and the power transmission is performed when the resonance frequency of each loop coil is adjusted to 200 MHz. It shows the frequency characteristics of efficiency. As described above, the opening area ratio of the loop coil of the antenna 1 of the present embodiment in FIG. 2 corresponds to 2/3, and the opening area ratio of the loop coil of the conventional antenna 2 corresponds to 1/12.

  FIG. 4 is a diagram showing a change in the coupling coefficient of electromagnetic coupling between the planar coil and the loop coil with respect to the opening area ratio of the loop coil. Here, the coupling coefficient at the resonance frequency of the loop coil is shown. The coupling coefficient between the planar coil and the loop coil is 0.32 for the antenna 1 of the present embodiment and 0.05 for the conventional antenna 2.

  As can be seen from FIG. 3, the effect of suppressing the 200 MHz radiated noise of the loop coil is large when the opening area ratio of the loop coil is 1/2 or 2/3, and is small at 1/12. In addition, when the ratio of the opening area of the loop coil is 1/4 or 1/12, the power transmission efficiency in the 900 MHz band is increased as compared with other antennas, and radiation noise in this frequency band is easily generated. ing. From the relationship between the opening area ratio of the loop coil and the coupling coefficient shown in FIG. 4, the larger the coupling coefficient between the planar coil of the composite antenna and the loop antenna, the higher the radiation noise suppression effect. Not only is the suppression effect small, but radiation noise in other high frequency bands increases.

  The increase in radiation noise in the high frequency band as described above is remarkable when the opening area ratio of the loop coil is 1/4 or 1/12. On the other hand, when the opening area ratio of the loop coil is 2/3, 1/2, no increase in radiation noise is observed. For this reason, in order to suppress radiation noise, the opening area ratio of the loop coil needs to be 1/2 or more.

  By applying the antenna of this embodiment as described above to a power transmission device or a power receiving device for non-contact power transmission, power transmission efficiency can be reduced without greatly reducing power transmission efficiency. A device or a power receiving device is obtained. In addition, in the non-contact communication device for RFID, the non-contact communication device in which the influence of radiation noise is reduced can be obtained by using the antenna of the present embodiment as a communication antenna.

  Although the embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples, and changes in members and configurations are within the scope of the present invention. Is possible. For example, the configuration of the composite antenna is not limited to that shown in FIG. 1, and various modifications such as omitting some of the components, adding other components, and changing the connection relationship are performed. Can be implemented. The resonance frequency of the loop coil can be set to an arbitrary frequency.

10, 15, 16, 17, 18, 30 Composite antenna 11, 21, 31 Planar coil 12, 33 Loop coil 13, 33 Capacitor 20 Antenna

Claims (10)

  A composite antenna comprising a planar coil and at least one loop coil disposed inside or outside the planar coil, wherein the loop coil has a tuning capacity in part thereof; The loop coil is not connected to the planar coil and other electric circuits, and is electromagnetically coupled to the planar coil, and is electromagnetically coupled between the planar coil and the loop coil. The coupling is such that the magnetic flux generated from the planar coil and the magnetic flux generated from the loop coil cancel each other and the efficiency is lowered at the resonance frequency of the resonance circuit including the inductance of the loop coil and the tuning capacitor. The resonance frequency of the resonance circuit is adjusted to a frequency more than twice the driving frequency of the planar coil. Antenna characterized by Rukoto.   In the composite antenna, the opening area of the loop coil includes an opening area of 1/2 or more of the opening area of the planar coil, so that the electromagnetic coupling between the planar coil and the loop coil can be reduced. The antenna according to claim 1, wherein the antenna is set to a degree of coupling.   3. The antenna according to claim 1, wherein a plurality of the loop coils are arranged in the composite antenna.   The antenna according to claim 3, wherein at least two of the plurality of loop coils have different resonance frequencies.   The antenna according to any one of claims 1 to 4, wherein a yoke made of a magnetic material is disposed adjacent to one side of the composite antenna.   The antenna according to any one of claims 1 to 5, wherein a shielding plate that shields electromagnetic waves is disposed in proximity to one side of the composite antenna.   The antenna according to claim 1, wherein a plurality of the composite antennas are arranged.   A power transmission device using the antenna according to any one of claims 1 to 7 as an antenna for non-contact power transmission.   A power receiving device using the antenna according to any one of claims 1 to 7 as an antenna for non-contact power transmission.   A non-contact communication apparatus using the antenna according to any one of claims 1 to 7 as an antenna for communication.

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