The present disclosure relates to an antenna apparatus, as well as an RFID system having the antenna apparatus and an RFID tag that performs wireless communication with the antenna apparatus.
Conventionally, antenna apparatuses exist that uses electromagnetic induction to perform wireless communication with IC cards and RFID tags.
For example, the antenna apparatus described in JP11-282980A is utilized in a reader/writer for writing information to an IC card and reading information from the IC card, and includes a loop antenna for the writing or reading. The loop antenna is twisted so as to form two small loops (coils), that is, to be in an “8” shape. According to such a loop antenna, directions of magnetic fluxes respectively passing through the two coils are different. Therefore, the magnetic fluxes respectively generated by the two coils cancel each other at a position distant from the coil antenna. With this design, it is possible to suppress an influence of a magnetic field generated by the antenna apparatus on other wireless communication devices.
In general, elements within an antenna apparatus are also influenced by a magnetic field generated by an antenna of the antenna apparatus.
For example, a power supply circuit element that is connected to an antenna and supplies power to the antenna is influenced by a magnetic field generated by this antenna.
Thus, an object of the present disclosure is to provide an antenna apparatus that is used, for example, for an RFID system and is capable of reducing an influence of a magnetic field generated by an antenna of the apparatus on a power supply circuit element connected to this antenna.
In order to overcome the technical problems and limitations in conventional antenna apparatuses discussed above, an antenna apparatus is disclosed that includes a substrate; an antenna provided on the substrate; and a power supply circuit element provided on the substrate and connected to the antenna. According to the exemplary aspect, the antenna includes a first coil antenna unit and a second coil antenna unit, each having a coil axis that intersects with the substrate, where the first coil antenna unit and the second coil antenna unit are arranged on the substrate such that a direction in which a current flows through one of the coil antenna units is clockwise and a direction in which a current flows through the other of the coil antenna units is counterclockwise. Moreover, in the exemplary aspect, the power supply circuit element is provided within a region between the first coil antenna unit and the second coil antenna unit.
Another aspect of the present disclosure is to provide an antenna apparatus that includes a substrate; an antenna provided on the substrate; and a power supply circuit element provided on the substrate and connected to the antenna. In this aspect, the antenna includes a first coil antenna unit and a second coil antenna unit, with each being coil-shaped and having a coil axis that intersects with the substrate. Moreover, the first coil antenna unit and the second coil antenna unit are arranged on the substrate such that a direction in which a current flows through one of the coil antenna units is clockwise and a direction in which a current flows through the other of the coil antenna units is counterclockwise. Furthermore, in this aspect, the power supply circuit element is provided on an imaginary straight line on the substrate, with the imaginary straight line being located equidistantly from the coil axis of the first coil antenna unit and the coil axis of the second coil antenna unit.
Yet another exemplary aspect provides an RFID system that includes a product having an RFID tag; and an antenna apparatus that performs wireless communication with the RFID tag of the product. In this aspect, the antenna apparatus includes a substrate; an antenna provided on the substrate; and a power supply circuit element provided on the substrate and connected to the antenna. In this aspect, the antenna includes a first coil antenna unit and a second coil antenna unit, each being coil-shaped and having a coil axis that intersects with the substrate, where the first coil antenna unit and the second coil antenna unit are arranged on the substrate such that a direction in which a current flows through one of the coil antenna units is clockwise and a direction in which a current flows through the other of the coil antenna units is counterclockwise. Moreover, the power supply circuit element is provided within a region between the first coil antenna unit and the second coil antenna unit.
Further another exemplary aspect is to provide an RFID system that includes a product having an RFID tag; and an antenna apparatus that performs wireless communication with the RFID tag of the product. In this aspect, the antenna apparatus includes a substrate; an antenna provided on the substrate; and a power supply circuit element provided on the substrate and connected to the antenna. Moreover, the antenna includes a first coil antenna unit and a second coil antenna unit, each being coil-shaped and having a coil axis that intersects with the substrate, the first coil antenna unit and the second coil antenna unit being arranged on the substrate such that a direction in which a current flows through one of the coil antenna units is clockwise and a direction in which a current flows through the other of the coil antenna units is counterclockwise. Furthermore, the power supply circuit element is provided on an imaginary straight line on the substrate, with the imaginary straight line being located equidistantly from the coil axis of the first coil antenna unit and the coil axis of the second coil antenna unit.
According to the exemplary embodiments disclosed herein, with an antenna apparatus used, for example, for an RFID system, it is possible to reduce an influence of a magnetic field generated by an antenna of the apparatus on a power supply circuit element connected to this antenna.
An antenna apparatus according to an exemplary aspect includes a substrate; an antenna provided on the substrate; and a power supply circuit element provided on the substrate and connected to the antenna. In this aspect, the antenna includes a first coil antenna unit and a second coil antenna unit, each having a coil axis that intersects with the substrate, where the first coil antenna unit and the second coil antenna unit are arranged on the substrate such that a direction in which a current flows through one of the coil antenna units is clockwise and a direction in which a current flows through the other of the coil antenna units is counterclockwise. Moreover, the power supply circuit element is provided within a region between the first coil antenna unit and the second coil antenna unit.
Further, an antenna apparatus according to another exemplary aspect is disclosed that includes a substrate; an antenna provided on the substrate; and a power supply circuit element provided on the substrate and connected to the antenna. In this aspect, the antenna includes a first coil antenna unit and a second coil antenna unit, with each being coil-shaped and having a coil axis that intersects with the substrate, where the first coil antenna unit and the second coil antenna unit are arranged on the substrate such that a direction in which a current flows through one of the coil antenna units is clockwise and a direction in which a current flows through the other of the coil antenna units is counterclockwise. In this aspect, the power supply circuit element is provided on an imaginary straight line on the substrate that is located equidistantly from the coil axis of the first coil antenna unit and the coil axis of the second coil antenna unit.
According to these aspects, with an antenna apparatus used, for example, for an RFID system, it is possible to reduce an influence of a magnetic field generated by an antenna of the apparatus on a power supply circuit element connected to this antenna.
In one exemplary aspect, the power supply circuit element may include an RFIC element that sends and receives signals via the antenna.
In addition, the power supply circuit element may include a matching element that is connected to the antenna and the RFIC element. With this configuration, the RFIC element is able to perform high-quality wireless communication via the antenna.
The power supply circuit element may further include a control IC element that is connected to the RFIC element and controls the RFIC element. With this configuration, an external device connected to the antenna apparatus does not need to have a function for controlling the RFID element. Therefore, it is possible to connect the antenna apparatus to an external device without a function for controlling the RFIC element, that is, a general-purpose external device such as a computer.
If a region between the first coil antenna unit and the second coil antenna unit forms a narrowest region, according to an exemplary aspect, the RFIC element may be disposed on one side with respect to the narrowest region, the control IC element may be disposed on the other side with respect to the narrowest region, and a conductor connecting the RFIC element with the control IC element may pass through the narrowest region. With this configuration, it is possible to reduce a distance between the first coil antenna unit and the second coil antenna unit, and in turn to reduce a size of the substrate. As a result, the antenna apparatus may be made smaller.
The power supply circuit element may include a conductor-for-signal through which a signal current flows, and a conductor-for-return through which a return current for the signal current flows. In this case, it is preferable that the conductor-for-signal and the conductor-for-return are in parallel with each other, and face each other in a direction perpendicular to the substrate. With this configuration, it is possible to suppress interlinkage between magnetic fluxes of a loop-shaped circuit having a conductor-for-signal and a conductor-for-return in which a current flows around and the first coil antenna unit and the second coil antenna unit. As a result, it is possible to suppress mixture of noises into signals that flows through the conductor-for-signal.
The first coil antenna unit and the second coil antenna unit may be helical-shaped according to one exemplary aspect. With this configuration, it is possible to make an area of an opening of a coil larger. As a result, when the RFID tag or the like that wirelessly communicates with the coil antenna is placed within an opening of the coil antenna unit, it is possible to increase an area for placement.
An RFID system according to yet another exemplary aspect includes a product having an RFID tag; and an antenna apparatus that performs wireless communication with the RFID tag of the product. In this aspect, the antenna apparatus includes a substrate; an antenna provided on the substrate; and a power supply circuit element provided on the substrate and connected to the antenna, where the antenna includes a first coil antenna unit and a second coil antenna unit, each being coil-shaped and having a coil axis that intersects with the substrate, the first coil antenna unit and the second coil antenna unit are arranged on the substrate such that a direction in which a current flows through one of the coil antenna units is clockwise and a direction in which a current flows through the other of the coil antenna units is counterclockwise. Moreover, the power supply circuit element is provided within a region between the first coil antenna unit and the second coil antenna unit.
An RFID system according to another exemplary aspect includes a product having an RFID tag; and an antenna apparatus that performs wireless communication with the RFID tag of the product. In this aspect, the antenna apparatus includes a substrate; an antenna provided on the substrate; and a power supply circuit element provided on the substrate and connected to the antenna. In addition, the antenna includes a first coil antenna unit and a second coil antenna unit, each being coil-shaped and having a coil axis that intersects with the substrate, where the first coil antenna unit and the second coil antenna unit is arranged on the substrate such that a direction in which a current flows through one of the coil antenna units is clockwise and a direction in which a current flows through the other of the coil antenna units is counterclockwise. Furthermore, the power supply circuit element is provided on an imaginary straight line on the substrate that is located equidistantly from the coil axis of the first coil antenna unit and the coil axis of the second coil antenna unit.
According to these aspects, with the antenna apparatus used, for example, for the RFID system, it is possible to reduce an influence of a magnetic field generated by the antenna of the apparatus on the power supply circuit element connected to this antenna. Further, it is possible to suppress generation of a position of the RFID tag at which the RFID tag is not able to wirelessly communicate with the antenna, i.e., a null point.
If the antenna apparatus includes placement portions on each of which the product is placed, it is preferable that the placement portions are provided respectively within the first coil antenna unit and the second coil antenna unit when viewed in a direction perpendicular to the substrate. With this configuration, the RFID tag of the product and the antenna apparatus may wirelessly communicate in a favorable manner.
Hereinafter, exemplar embodiments of the present disclosure will be described with reference to the drawings.
An RFID system 10 shown in
While not shown, the RFID tag 12 includes an antenna that performs wireless communication with the antenna apparatus 14, a control unit connected to the antenna, and a memory connected to the control unit. Based on a requesting signal from the antenna apparatus 14 received by its antenna, for example, the control unit of the RFID tag 12 obtains information (data) within the memory, and sends the obtained information to the antenna (that is, sends information to the antenna apparatus 14 via the antenna of the RFID tag 12). The control unit of the RFID tag 12 also writes information from the antenna apparatus 14 received by its antenna to the memory.
The antenna apparatus 14 that performs wireless communication with the RFID tag 12 includes a substrate 16, an antenna 18 provided on the substrate 16, and a cover 20 that protects the antenna 18 and on which the product G is placed. Here, the cover 20 is provided with marks 20a indicating positions of placement portions on the cover 20 on each of which the product G is placed.
The substrate 16 of the antenna apparatus 14 includes a main surface 16a and a back surface 16b that faces the main surface 16a. As an example of the substrate 16, a printed circuit board made of an epoxy resin may be used. On the main surface 16a and the back surface 16b of the substrate 16, coil antenna units 30 and 32 that constitute antennas, lands for mounting a capacitor 36 that provides a power supply circuit element 22 and an RFIC element 34, and connecting conductors 38 and 40 for connecting the coil antenna units 30 and 32 with the power supply circuit element 22 are provided as conductor patterns. The conductor patterns are patterned, for example, by etching or like a copper foil over an entire surface of the printed circuit board in a predetermined shape. The main surface 16a of the substrate 16 is provided with the antenna 18, and the power supply circuit element 22 connected to the antenna 18 and supplying power to the antenna 18.
As shown in
In the case of the embodiment 1, as shown in
Here, the placement portions for products G on the cover 20, that is, the marks 20a indicating the placement portions are provided respectively within the first and the second coil antenna units 30, 32 when viewed in a direction perpendicular to the main surface 16a of the substrate 16 (Z axial direction). More specifically, centers of the marks 20a are offset to a side of the imaginary plane VP from centers of the respective coil antenna units. With this configuration, the RFID tags 12 of the products G are respectively arranged within the first and the second coil antenna units 30, 32, that is, respectively within magnetic fluxes passing the first and the second coil antenna units 30, 32. As a result, the RFID tag 12 and the antenna apparatus 14 may wirelessly communicate in a favorable manner.
Specifically, as shown in
One end of the outer conductor 30c of the first coil antenna unit 30 is connected to the power supply circuit element 22. The other end of the outer conductor 30c is connected to one end of the inner conductor 30b. The other end of the inner conductor 30b is connected to one end of the outer conductor 30d via a bridge conductor 30e. As shown in
Similar to the first coil antenna unit 30, the second coil antenna unit 32 includes a substantially circular inner conductor 32b which is partially disconnected (“C” shape), and two semi-circular outer conductors 32c, 32d arranged outside and along the inner conductor 32b. The two semi-circular outer conductors 32c, 32d are arranged along a circumference of the same circle centered at the coil axis 32a.
One end of the outer conductor 32c of the second coil antenna unit 32 is connected to the other end of the outer conductor 30d of the first coil antenna unit 32. The other end of the outer conductor 32c is connected to one end of the inner conductor 32b. The other end of the inner conductor 32b is connected to one end of the outer conductor 32d via a bridge conductor 32e. As also shown in
In the case of the embodiment 1, the power supply circuit element 22 includes the RF (Radio Frequency) IC element 34 and the capacitor 36.
The RFIC element 34 is connected to the antenna 18. More specifically, the RFIC element 34 includes two input/output terminals, and the input/output terminals are respectively connected to one end and the other end of the antenna 18. The RFIC element 34 is also configured to send and receive signals via the antenna 18. For example, the RFIC element 34 receives information within the memory of the RFID tag 12 as a signal via the antenna 18 that communicates with the RFIC tag 12. Alternatively, the RFIC element 34 sends information recorded in the RFID tag 12 as a signal to the RFID tag 12 via the antenna 18.
Here, the RFIC element 34 is configured to be able to output information received from the RFID tag 12 to an external device (not shown) external to the antenna apparatus 14, and to receive an input of information from the external device. With this configuration, the antenna apparatus 14 is able to function as a reader/writer device in the RFID system 10 that reads and writes information from and to the RFID tag 12. The RFIC element includes an RFIC chip.
The capacitor 36 is connected in parallel to the coil-shaped antenna 18. This constitutes a resonant circuit configured by the coil-shaped antenna 18 and the capacitor 36. Capacitance of the capacitor 36 is determined such that a resonant frequency of the resonant circuit is a predetermined frequency (here, an HF band frequency).
According to such a configuration, as shown in
Thus, directions of a magnetic flux generated by the first coil antenna unit 30 and a magnetic flux generated by the second coil antenna unit 32 are different. A magnetic field distribution as shown in
As the directions of a magnetic flux generated by the first coil antenna unit 30 and a magnetic flux generated by the second coil antenna unit 32 are different in this manner, there is a portion on the substrate 16 at which a magnetic flux density is relatively lower than a different portion.
Specifically, as shown in
By contrast, for example, in a region facing the second coil antenna unit 32 across the first coil antenna unit 30 (a region on a left side of the first coil antenna unit 30 in
Here, the magnetic flux density is the lowest (substantially zero) at a position on the imaginary plane VP at which the distances from the first and the second coil antenna units 30, 32 are equal.
Further, as shown in
As shown in
It should be noted that, in the case of the embodiment 1, as shown in
Therefore, the RFIC element 34 of the power supply circuit element 22 and the connecting conductors 38, 40 are insusceptible to the magnetic fluxes as compared to a case in which these components are provided outside the low magnetic flux density region A. With this configuration, noises attributed to the antenna 18 may not be easily mixed with signals output from the RFIC element 34. Further, noises attributed to the antenna 18 may not be easily mixed with signals input to the RFIC element 34. As a result, a communication quality of the RFID system 10 including the antenna apparatus 14 is highly reliable according to the configuration of the exemplary embodiment.
According to the embodiment 1 described above, with the antenna apparatus 14 used for the RFID system 10, it is possible to reduce an influence of a magnetic field generated by the antenna 18 of the apparatus on the power supply circuit element 22 connected to the antenna 18.
Further, In the case of the embodiment 1, the antenna 18 includes the two coil antenna units 30, 32. With this configuration, it is possible to suppress generation of a position of the RFID tag 12 at which the RFID tag 12 is not able to wirelessly communicate with the antenna 18, i.e., a null point.
When lengths of the conductors are the same, an area of an opening of one coil antenna unit (an area within the conductor of the coil) is larger than an area of an opening of each of the two coil antenna units. If the area of the opening is larger, a magnetic flux density at a center of the coil antenna unit that is distant form from the conductor is low, and a null point where antenna sensitivity is low occurs at this position.
By contrast, when the same currents flow, magnetic flux densities at centers of two coil antenna units are higher than the magnetic flux density at the center of the one coil antenna unit. Therefore, it is possible to suppress generation of a null point more effectively by two coil antenna units than by one coil antenna unit if the lengths of the conductors and the currents flowing therethrough are the same.
Differences between an RFID system of according to an embodiment 2 and the RFID system 10 according to the embodiment 1 lie in the antenna apparatus. In particular, configurations of an antenna and a power supply circuit element are different from those in the embodiment 1. Therefore, the embodiment 2 will be described focusing on the configurations of the antenna and the power supply circuit element different from the embodiment 1.
As shown in
The first and the second coil antenna unit 130, 132 of the embodiment 2 are helical-shaped, unlike the double loop first coil antenna units 30, 32 of the embodiment 1.
Specifically, the first coil antenna unit 130 includes a “C”-shaped main-side conductor 130b which is provided on the main surface 116a of the substrate 116, and a substantially circular back-side conductor 130c which is provided on a back surface 116b of the substrate 116 and partially disconnected (“C” shape).
One end of the main-side conductor 130b of the first coil antenna unit 130 is connected to an RFIC element 134 of a power supply circuit element 122 that will be later described in detail. The other end of the main-side conductor 130b is connected to one end of the back-side conductor 130c via a hole conductor (not shown). The other end of the back-side conductor 130c is connected to the second coil antenna unit 132.
On the other hand, the second coil antenna unit 132 includes a “C”-shaped main-side conductor 132b which is provided on the main surface 116a of the substrate 116, and a substantially circular back-side conductor 132c which is provided on a back surface 116b of the substrate 116 and partially disconnected (“C” shape).
One end of the back-side conductor 132c of the second coil antenna unit 132 is connected to the other end of the back-side conductor 130c of the first coil antenna unit 130 via a connecting conductor 136. The other end of the back-side conductor 132c is connected to one end of the main-side conductor 132b via a via hole conductor (not shown). Then, the other end of the main-side conductor 132b is connected to the RFIC element 134.
According to such a configuration, for example, a current from the RFIC element 134 flows through the main-side conductor 130b, and the back-side conductor 130c of the first coil antenna unit 130, and the back-side conductor 132c, and the main-side conductor 132b of the second coil antenna unit 132, in that order according to the exemplary embodiment. Further, when viewed from top of the antenna apparatus 114, in
Thus, a magnetic flux passing the first coil antenna unit 130 in which the current I flows in the clockwise direction is directed from top to bottom (toward a negative direction along a Z axis). On the other hand, the magnetic flux passing the second coil antenna unit 132 in which the current I flows in the counterclockwise direction is directed from bottom to top (toward a positive direction along the Z axis). As a result, as compared to the different portion, the magnetic flux density is low in a region between the first coil antenna unit 130 and the second coil antenna unit 132, for example, a low magnetic flux density region A′ within an imaginary circle VC′ centered at a midpoint of a connecting straight line JL′ connecting the coil axes 130a, 132a and outside the first and the second coil antenna unit 130, 132.
Here, the magnetic flux density is the lowest (substantially zero) at a position on the imaginary plane VP′ at which the distances from the first and the second coil antenna units 130, 132 are equal.
As shown in
As shown in
The RF front-end circuit 144 includes a matching unit 146 (as shown in
The MCU 142 sends and receives signals (information) with the RFIC element 134 to control the RFIC element 134. Therefore, a plurality of conductors 170 connecting the MCU 142 and the RFIC element 134 is arranged on the substrate 116.
In the case of the embodiment 2, as shown in
According to such an arrangement, the plurality of conductors 170 connecting the RFIC element 134 and the MCU 142 are arranged at positions where the magnetic flux density is low, and thus insusceptible to the magnetic field. Therefore, noises are not easily mixed in signals carried by the conductors 170. Further, as almost all of the grand patterns are arranged in the low magnetic flux density region A′, no significant influence is given to communication characteristics of the antenna.
Further, as compared to a case in which the RFIC element 134 and the MCU 142 are located on the same side with respect to the narrowest region within the region between the first coil antenna unit 130 and the second coil antenna unit 132, it is possible to make a distance between the first coil antenna unit 130 and the second coil antenna unit 132 smaller. With this configuration, a size of the substrate 116 may be reduced, and as a result, it is possible to make the antenna apparatus 114 small.
According to the exemplary aspect of embodiment 2, the RFIC element 134 and the MCU 142 are connected to the grand pattern 138 provided on the back surface 116b of the substrate 116. Further, as shown in
Specifically, a loop L including the RFIC element 134, the conductors 170, the MCU 142, and the grand pattern 138 (return path) through which a current flows around is occurred. The loop L is perpendicular to the main surface 116a of the substrate 116. With this configuration, interlinkages of the magnetic fluxes of the first and the second coil antenna units 130, 132 into the loop L may be suppressed. As a result, it is possible to suppress mixture of noises due to the magnetic fluxes of the first and the second coil antenna units 130, 132 into signals carried by the conductors 170.
As shown in
According to the embodiment 2 described above, similar to the embodiment 1, with the antenna apparatus 114 used for the RFID system, it is possible to reduce an influence of a magnetic field generated by the antenna 118 of the apparatus on the power supply circuit element 122 connected to the antenna 118. Further, similar to the embodiment 1, it is possible to suppress generation of a position of the RFID tag 12 at which the RFID tag 12 is not able to wirelessly communicate with the antenna 118, i.e., a null point.
Moreover, according to the exemplary aspect of embodiment 2, the MCU 142 as a control IC element, which controls the RFIC element 134, is incorporated into the antenna apparatus 114. Therefore, an external device connected to the antenna apparatus 114 does not need to have a function for controlling the RFID element 134. Therefore, it is possible to connect the antenna apparatus 114 to an external device without a function for controlling the RFIC element 134, that is, a general-purpose external device such as a computer. Specifically, the antenna apparatus 114 of the embodiment 2 is more versatile than that of the embodiment 1.
As described above, the present invention has been described with reference to the embodiments. However, embodiments of the present invention are not limited to the above examples.
For example, in the case of the embodiment 1, as shown in
However, when the coil antenna units are helical-shaped as in the embodiment 2, it is possible to make the area of an opening of the coil (an area within the conductor of the coil) larger as compared to the multi-loop shape as in the embodiment 1 (when sizes of the substrates for which the coil antenna units are provided are the same). Therefore, as shown in
Furthermore, in the case of the embodiments 1 and 2, two coil antenna units for the antenna are provided, but 2 or more coil antenna units may be provided. For example, 2 or more coil antenna units may be arranged in series or in parallel.
Further, in the case of the embodiments 1 and 2 described above, the first coil antenna unit and the second coil antenna unit of the antenna are connected in series. Specifically, a current supplied from the power supply circuit element and passing one of the coil antenna units also passes the other of the coil antenna unit. Unlike the above example, the antenna apparatus may be configured such that a current is supplied from the power supply circuit element to each of the first coil antenna unit and the second coil antenna unit separately.
Moreover, in the case of the embodiments 1 and 2 described above, the antenna apparatus is able to wirelessly communicate with RFID tags respectively of two products, as shown in
In addition, in the case of the embodiments 1 and 2 described above, the antenna apparatus is able to function as a reader/writer device in the RFID system that reads and writes information from and to the RFID tag. However, embodiments of the present invention are not limited to such an example. The antenna apparatus according to the embodiments of the present invention may be used, for example, in a communication system in which antenna apparatuses wireless communicates with each other. Further, the antenna apparatus is not limited to the use in the HF band RFID system, and may be used as an antenna apparatus for UHF band RFID system or the like.
Finally, as used herein, an “element” is not limited to a chip-like component, and may be interpreted as an individual component that constitutes an electrical circuit. Therefore, examples of the “element” are not limited to a chip-like component, and include circuits of patterns provided on the substrate. If the element is chip-like, the element may be mounted on the main surface or the back surface of the substrate, or built within the substrate.
Further, it is possible to achieve a new embodiment by partially combining the embodiments 1 and 2. For example, the MCU 142 of the embodiment 2 may be mounted on the antenna apparatus 14 of the embodiment 1.
The present invention may be applied to antenna apparatuses for sending and receiving information, as well as systems that employ such an antenna apparatus, for example, RFID systems and communication systems.
Number | Date | Country | Kind |
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2015-033807 | Feb 2015 | JP | national |
The present application is a continuation of PCT/JP2016/051153 filed Jan. 15, 2016, which claims priority to Japanese Patent Application No. 2015-033807, filed Feb. 24, 2015, the entire contents of each of which are incorporated herein by reference.
Number | Date | Country | |
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Parent | PCT/JP2016/051153 | Jan 2016 | US |
Child | 15681669 | US |