JP3632894B2 - Antenna device and card-like storage medium - Google Patents

Description

【００３８】
従って、データ書込読出装置２１のループアンテナ２２に対してＩＣカード１１を単体（１枚のみ）で配置した場合、キャリア周波数Ｆ_ｃａｒ と共振周波数Ｆ_ｒｅｓ とは一致しない。このため、この状態では共振回路３５は当該電磁波に対して共振せず、ループアンテナ３２はトランスモードで受信電力を得る。図５において、曲線Ｎ１はＩＣカード１１が１枚のみの場合の受信感度曲線を示し、データ書込読出装置２１から放射される電磁波のキャリア周波数Ｆ_ｃａｒ に対してトランスモードによる一定値の感度を示している。
【００３９】
一方、データ書込読出装置２１のループアンテナ２２に対して、ＩＣカード１１を２枚重ねて配置した場合、この２枚重ね状態の共振周波数Ｆ_ｒｅｓ２は次式で与えられる。
【００４０】
【数２】

【００４１】
この状態においても共振回路３５は当該電磁波に対して共振せず、ループアンテナ３２はトランスモードで受信電力を得る。図５において、曲線Ｎ２はＩＣカード１１が２枚重ねられた場合の受信感度曲線を示し、データ書込読出装置２１から放射される電磁波のキャリア周波数Ｆ_ｃａｒ に対してトランスモードによる一定値の感度を示している。
【００４２】
さらに、データ書込読出装置２１のループアンテナ２２に対してＩＣカード１１を３枚重ねて配置した場合、この３枚重ね状態の共振周波数Ｆ_ｒｅｓ３は次式で与えられる。
【００４３】
【数３】

【００４４】
この状態において、３枚重ね状態の共振周波数Ｆ_ｒｅｓ３は電磁波のキャリア周波数Ｆ_ｃａｒ に接近し、これにより共振回路３５は当該電磁波に対して共振し、ループアンテナ３２は共振モードで受信電力を得る。図５において、曲線Ｎ３はＩＣカード１１が３枚重ねられた場合の受信感度曲線を示し、データ書込読出装置２１から放射される電磁波のキャリア周波数Ｆ_ｃａｒ に対して共振モードによる感度を示している。
【００４５】
さらに、データ書込読出装置２１のループアンテナ２２に対してＩＣカード１１を４枚重ねて配置した場合、この４枚重ね状態の共振周波数Ｆ_ｒｅｓ４は次式で与えられる。
【００４６】
【数４】

【００４７】
この状態において、４枚重ね状態の共振周波数Ｆ_ｒｅｓ４は電磁波のキャリア周波数Ｆ_ｃａｒ に一致し、これにより共振回路３５は当該電磁波に対して最良の効率で共振し、ループアンテナ３２は共振モードで受信電力を得る。図５において、曲線Ｎ４はＩＣカード１１が４枚重ねられた場合の受信感度曲線を示し、データ書込読出装置２１から放射される電磁波のキャリア周波数Ｆ_ｃａｒ に対して共振モードによる最良の感度を示している。
【００４８】
かくしてＩＣカード１１は、当該ＩＣカード１１の重ね枚数の増加に応じて、データ書込読出装置２１から放射される電磁波に対する受信感度が向上するようになされている。
【００４９】
ここで、ＩＣカード１１を複数数重ねた場合、あるＩＣカード１１が受信する電磁波の強度は、他のＩＣカード１１が当該電磁波を受信することにより生じる磁界によって相殺され低下する。かかる受信電磁波の強度は、ＩＣカード１１の重ね枚数の増加に応じて低下していく。
【００５０】
本発明によるＩＣカード１１は、当該ＩＣカード１１の重ね枚数の増加に応じた受信感度の向上と、当該ＩＣカード１１の重ね枚数の増加に応じた受信電磁波の強度低下とが相殺されるため、ＩＣカード１１の重ね枚数が変化しても当該ＩＣカード１１の通信距離はほぼ一定となる。
【００５１】
（４）動作及び効果
以上の構成において、データ書込読出装置２１のループアンテナ２２に対してＩＣカード１１を１枚または２枚重ねて配置した場合、共振回路３５の共振周波数と電磁波のキャリア周波数Ｆ_ｃａｒ は一致せず、このため共振回路３５は当該電磁波に対して共振せず、これによりＩＣカード１１はトランスモードで受信電力を得る。
【００５２】
これに対しループアンテナ２２に対してＩＣカード１１を３枚重ねて配置した場合、共振回路３５の共振周波数は電磁波のキャリア周波数Ｆ_ｃａｒ に接近し、これにより共振回路３５は当該電磁波に対して共振し、ＩＣカード１１は共振モードで受信電力を得る。
【００５３】
さらにループアンテナ２２に対してＩＣカード１１を４枚重ねて配置した場合、共振回路３５の共振周波数は電磁波のキャリア周波数Ｆ_ｃａｒ に一致し、これにより共振回路３５は当該電磁波に対して最良の効率で共振し、ＩＣカード１１は共振モードで受信電力を得る。
【００５４】
ここで、ＩＣカード１１の重ね枚数の増加に応じて、各ＩＣカード１１の受信感度が向上するとともに各ＩＣカード１１の受信電磁波の強度が低下するため、結果として受信感度の向上と受信電磁波の強度低下が相殺され、ＩＣカード１１の重ね枚数にかかわらずほぼ一定の通信距離を得ることができる。
【００５５】
以上の構成によれば、ループアンテナ３２の中間に中間タップＴ３を設け、当該中間タップＴ３と端点Ｔ１の間にコンデンサ３１を接続して共振回路３５を形成し、ＩＣカード１１を複数枚重ねた場合の共振周波数低下を考慮して当該共振回路３５の共振周波数Ｆ_ｒｅｓ をデータ書込読出装置２１から放射される電磁波のキャリア周波数Ｆ_ｃａｒ の２倍に設定したことにより、他のＩＣカード１１と重ねられた場合においてもデータ書込読出装置２１から放射された電磁波を最良の受信効率で受信することができ、かくして１枚時の通信距離や通信品質を犠牲にすることなく複数枚重ねられた時においても十分な通信距離や通信品質を得ることができる。
【００５６】
（５）他の実施の形態
なお上述の実施の形態においては、共振回路３５の共振周波数Ｆ_ｒｅｓ をデータ書込読出装置２１から放射される電磁波のキャリア周波数Ｆ_ｃａｒ の２倍に設定したが、本発明はこれに限らず、予想されるＩＣカードの重ね枚数や共振回路の受信感度曲線等に応じて、他の様々な周波数に設定してもよい。
【００５７】
また上述の実施の形態においては、ループアンテナ３２に中間タップＴ３を設け、当該中間タップＴ３と端点Ｔ１とにコンデンサ３１を接続して共振回路３５を設けたが、本発明はこれに限らず、ループアンテナに２つまたはそれ以上の中間タップを設けて当該各中間タップにコンデンサを接続し、ＩＣカードに複数の共振回路を設けるようにしても良い。
【００５８】
すなわち図６に示すように、ＩＣカード１２が有するループアンテナ３３の２つの端点Ｔ１及びＴ２が電子回路３６に接続されている。またループアンテナ３３の中間には中間タップＴ３及びＴ４が設けられており、当該ループアンテナ３３は中間タップＴ３及びＴ４によってループアンテナ３３Ａ、３３Ｂ及び３３Ｃに分割されている。そして中間タップＴ３と端点Ｔ１の間には第１のコンデンサ３１Ａが接続され、ループアンテナ３３Ａと第１のコンデンサ３１Ａとによって第１の共振回路３５Ａが形成されている。同様に中間タップＴ４と端点Ｔ２の間には第２のコンデンサ３１Ｂが接続され、ループアンテナ３３Ｃと第２のコンデンサ３１Ｂとによって第２の共振回路３５Ｂが形成されている。第１の共振回路３５Ａの共振周波数Ｆ_ｒｅｓＡと、第２の共振回路３５Ｂの共振周波数Ｆ_ｒｅｓＢとはそれぞれ異なった周波数に設定されている。
【００５９】
実際上ＩＣカード１２は、図７に示すように基板１５上の外周側の縁部分を沿うように実装された全６周のループアンテナ３３の外側から２周目に中間タップＴ３が設けられており、当該ループアンテナ３３の外側２周分がループアンテナ３３Ａとして動作するとともに、ループアンテナ３３の内側から２周目に中間タップＴ４が設けられており、当該ループアンテナ３３の内側２周分がループアンテナ３３Ｃとして動作する。
【００６０】
図６において、ＩＣカード１２に対して第１の共振回路３５Ａの共振周波数Ｆ_ｒｅｓＡと同一の周波数でなる電磁波が外部から加えられた場合、第１の共振回路３５Ａ（ループアンテナ３３Ａ及び第１のコンデンサ３１Ａ）は当該電磁波に対して共振することにより当該電磁波を効率よく受信し（共振モード）、受信した電磁波に応じた受信電力を電子回路３６に供給する。このとき、ループアンテナ３３Ｂ及び３３Ｃは電磁波に対して共振せず、近似的に第１の共振回路３５Ａと電子回路３６とを接続する電線として動作する。
【００６１】
これに対し、ＩＣカード１２に対して第２の共振回路３５Ｂの共振周波数Ｆ_ｒｅｓＢと同一の周波数でなる電磁波が外部から加えられた場合、第２の共振回路３５Ｂ（ループアンテナ３３Ｃ及び第２のコンデンサ３１Ｂ）は当該電磁波に対して共振することにより当該電磁波を効率よく受信し（共振モード）、受信した電磁波に応じた受信電力を電子回路３６に供給する。このとき、ループアンテナ３３Ａ及び３３Ｂは電磁波に対して共振せず、近似的に第２の共振回路３６Ｂと電子回路３６とを接続する電線として動作する。
【００６２】
ＩＣカード１２に対してＦ_ｒｅｓＡ及びＦ_ｒｅｓＢと離れた周波数でなる電磁波が外部から加えられた場合、第１の共振回路３６Ａ及び第２の共振回路３６Ｂは当該電磁波に対して共振しない。この場合ＩＣカード１２はループアンテナ３３全体（ループアンテナ３３Ａ、３３Ｂ及び３３Ｂ）で電磁波を受信し（トランスモード）、当該電磁波に応じた受信電力を電子回路３６に供給する。
【００６３】
図８において曲線Ｐ３は、ＩＣカード１２に加わえられる電磁波の周波数と、ループアンテナ３３から電子回路３６に供給される電圧の関係を示し、第１の共振回路３５Ａの共振周波数Ｆ_ｒｅｓＡ及び第２の共振回路３５Ｂの共振周波数Ｆ_ｒｅｓＢにおいて受信電圧のピークを示している。電磁波の周波数が第１の共振回路３５Ａの共振周波数Ｆ_ｒｅｓＡから低下するに従って電圧は急激に低下するが、８ＭＨｚ付近から受信電圧の低下が止まり、１ＭＨｚ以降までほぼ均一な電圧が得られている。
【００６４】
このように、ＩＣカードに複数の共振回路を設けることによって複数の共振点が得られ、これら複数の共振点（共振周波数）を適宣設定することにより、ＩＣカードを複数枚重ねた場合の受信感度低下を防止することができる。
【００６５】
【発明の効果】
上述のように本発明によれば、所定の電磁波を受信し、当該受信した電磁波に応じた電力を供給するように電子回路に接続されたアンテナ装置において、ループアンテナの一部に対してコンデンサを並列に接続して共振回路を構成し、共振回路の共振により電子回路に受信電力を供給する共振モードと、ループアンテナ全体が電磁波を受信することにより電子回路に受信電力を供給するトランスモードのいずれかで受信するように、共振回路の共振周波数を電磁波のキヤリア周波数よりも高く設定することにより、共振回路の共振周波数が電磁波のキヤリア周波数から離れるアンテナ装置単体の場合は、トランスモードによつて、電磁波をループアンテナを介して受信するとともに、アンテナ装置を複数枚重ねた場合、当該アンテナ装置を複数枚重ねたことによる共振手段の共振周波数の低下により、共振モードによつて、電磁波を共振手段で受信するようにしたことにより、アンテナ装置が単体又は複数枚重ねられた状態でも常に良好な効率で電磁波を受信し得るアンテナ装置を実現することができる。
【００６６】
また本発明によれば、電磁波を介してデータ書込読出装置と通信を行うカード状記憶媒体において、ループアンテナの一部に対してコンデンサを並列に接続して共振回路を構成し、共振回路の共振により電子回路に受信電力を供給する共振モードと、ループアンテナ全体が電磁波を受信することにより電子回路に受信電力を供給するトランスモードのいずれかで受信するように、共振回路の共振周波数を電磁波のキヤリア周波数よりも高く設定することにより、共振回路の共振周波数が電磁波のキヤリア周波数から離れるカード状記憶媒体単体の場合は、トランスモードによつて、電磁波をループアンテナを介して受信するとともに、カード状記憶媒体を複数枚重ねた場合、当該カード状記憶媒体を複数枚重ねたことによる共振手段の共振周波数の低下により、共振モードによつて、電磁波を共振手段で受信するようにしたことにより、カード状記憶媒体が単体又は複数枚重ねられた状態でも常に良好な効率で電磁波を受信し得るカード状記憶媒体を実現することができる。
【図面の簡単な説明】
【図１】非接触ＩＣカードシステムの構成を示すブロック図である。
【図２】本発明によるＩＣカードの構成を示す接続図である。
【図３】ＩＣカードの実装イメージを示す略線図である。
【図４】本発明によるＩＣカードの受信電圧を示す特性曲線図である。
【図５】本発明によるＩＣカードの受信感度を示す特性曲線図である。
【図６】他の実施の形態によるＩＣカードの構成を示す接続図である。
【図７】他の実施の形態によるＩＣカードの実装イメージを示す略線図である。
【図８】他の実施の形態によるＩＣカードの受信電圧を示す特性曲線図である。
【図９】従来の非接触ＩＣカードシステムの構成を示すブロック図である。
【図１０】ＩＣカードが１枚のときの同調周波数を示す略線図である。
【図１１】ＩＣカードを複数枚重ねたときの等価回路の構成を示す接続図である。
【図１２】ＩＣカードを複数枚重ねたときの同調周波数の遷移を示す特性曲線図である。
【図１３】複数枚重ねに対応したＩＣカードにおける同調周波数の遷移を示す特性曲線図である。
【図１４】ＩＣカードを４枚重ねた状態における同調周波数の遷移を示す特性曲線図である。
【符号の説明】
１、１０……非接触ＩＣカードシステム、２、２１……データ書込読出装置、６、３２、３３……ループアンテナ、７、３１……コンデンサ、３１Ａ……第１のコンデンサ、３１Ｂ……第２のコンデンサ、８、３５……共振回路、３５Ａ……第１の共振回路、３５Ｂ……第２の共振回路。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an antenna device and a card-shaped storage medium, and is suitable for application to an antenna device and a card-shaped storage medium for writing and reading data without contact with an IC (Integrated Circuit) card, for example.
[0002]
[Prior art]
In recent years, in the fields of station ticket gates, security systems, electronic money systems, etc., an IC card system using a data writing / reading device and an IC card has been experimentally introduced. Reading data from the card is performed without contact.
[0003]
As shown in FIG. 9, the IC card system 1 includes a data writing / reading device 2 and an IC card 5 arranged so as to face each other, and is emitted from the loop antenna 4 of the data writing / reading device 3. The electromagnetic wave is received by the loop antenna 6 of the resonance circuit 8 provided in the IC card 5, and a magnetic field is generated by flowing as a resonance current through the resonance capacitor 7, and the received power corresponding to the energy of the magnetic field is generated in the electronic circuit. 9 to be operated.
[0004]
As shown in FIG. 10, the IC card 5 has a resonance frequency F generated by a resonance circuit 8. _res And the carrier frequency F of the electromagnetic wave radiated from the loop antenna 4 of the data writing / reading unit 3 _car And the reception efficiency of electromagnetic waves is improved.
[0005]
By the way, in the IC card system 1, a predetermined logic protocol is incorporated, and accordingly, when a plurality of IC cards 5 are placed on the loop antenna 4 of the data writer / reader 3 at the same time. However, data processing can be reliably performed without collision between data transmitted and received for each IC card.
[0006]
However, when a plurality (N) of IC cards 5A to 5N are arranged on the loop antenna 4 of the data writing / reading device 3 as shown in FIG. _res Becomes N times and the load resistance R of the electronic circuit 9 _cir Becomes 1 / N times.
[0007]
In such a state where a plurality (N) of IC cards 5A to 5N are stacked, the capacitance C of the resonant capacitor _res With N times the resonance frequency F _res Is reduced to √ (1 / N).
[0008]
Therefore, in the state where the IC cards 5A to 5N are simultaneously stacked as shown in FIG. _res Is the carrier frequency F of the electromagnetic wave radiated from the loop antenna 4 of the data writing / reading device 3 _car Greatly deviating from the above, causing a significant decrease in reception efficiency and making communication difficult.
[0009]
Therefore, as shown in FIG. 13 as a conventional method, the resonance frequency F of the IC card 5 _res Carrier frequency F _car Carrier frequency F _car It is generally performed to set a little higher in advance. When two or three such IC cards 5 are stacked, the lowered resonance frequency and carrier frequency F _car The amount of deviation is minimal, thereby preventing a significant drop in reception efficiency and enabling data transmission / reception over a certain communication distance.
[0010]
[Problems to be solved by the invention]
By the way, in the IC card 5 having such a configuration, the resonance frequency F _res Carrier frequency F _car When a single IC card 5 is arranged so as to face the loop antenna 4 of the data write / read device 3, the resonance frequency F is set. _res And carrier frequency F _car Could not be fully tuned.
[0011]
For this reason, the IC card 5 not only sacrifices the communication distance of one card, but also cannot improve the reception efficiency even when a plurality of cards are stacked. There was a problem that it was desired to improve the reception efficiency even when
[0012]
Furthermore, in the IC card 5 having such a configuration, when four IC cards 5 are stacked, for example, as shown in FIG. _res Is the carrier frequency F _car There is a problem that data cannot be transmitted / received.
[0013]
The present invention has been made in consideration of the above points, and an object of the present invention is to propose an antenna device and a card-shaped storage medium that can always efficiently receive electromagnetic waves.
[0014]
[Means for Solving the Problems]
In order to solve this problem, in the present invention, in an antenna device connected to an electronic circuit so as to receive a predetermined electromagnetic wave and supply power corresponding to the received electromagnetic wave, a capacitor is provided to a part of the loop antenna. Are connected in parallel to form a resonant circuit, and a resonance mode that supplies received power to the electronic circuit by resonance of the resonant circuit and a transformer mode that supplies the received power to the electronic circuit when the entire loop antenna receives electromagnetic waves. In the case of a single antenna device in which the resonance frequency of the resonance circuit is separated from the carrier frequency of the electromagnetic wave by setting the resonance frequency of the resonance circuit higher than the carrier frequency of the electromagnetic wave so as to be received by either When electromagnetic waves are received via a loop antenna and a plurality of antenna devices are stacked, Due to the decrease in the resonance frequency of the resonance means due to the overlapping of a plurality of tenor devices, the electromagnetic wave is received by the resonance means according to the resonance mode, so that the antenna device is always in a single or a plurality of overlapping states. Electromagnetic waves can be received with good efficiency.
[0015]
According to the present invention, in a card-like storage medium that communicates with a data writing / reading device via electromagnetic waves, a resonance circuit is configured by connecting a capacitor in parallel to a part of the loop antenna. The resonance frequency of the resonance circuit is set so that the resonance frequency of the resonance circuit is received in either the resonance mode that supplies the reception power to the electronic circuit or the transformer mode that supplies the reception power to the electronic circuit when the entire loop antenna receives the electromagnetic wave. In the case of a single card-like storage medium in which the resonance frequency of the resonance circuit is separated from the carrier frequency of the electromagnetic wave by setting it higher than the carrier frequency, the electromagnetic wave is received via the loop antenna by the transformer mode, When multiple storage media are stacked, the resonance of the resonance means due to the stack of multiple card-shaped storage media Due to the decrease in the wave number, the electromagnetic wave is received by the resonance means according to the resonance mode, so that the electromagnetic wave can always be received with good efficiency even in a state where the card-like storage medium is stacked alone or in a plurality of layers. .
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0017]
(1) Overall configuration of IC card system
In FIG. 1, reference numeral 10 denotes a non-contact IC (Integrated Circuit) card system as a whole, which is composed of an IC card 11 as a card-like storage medium and a data writing / reading device 21 arranged so as to face each other. ing.
[0018]
The IC card 11 is a battery-less IC card that does not have a battery for power supply. For example, the IC card 11 is mounted on a flat card-like substrate 15 like a credit card and is radiated from a data writing / reading device 21 (broken line). A coil-like loop antenna 32 that receives and converts into an electrical signal, a modulation / demodulation circuit 13 that modulates transmission data or demodulates reception data, and a signal processing circuit 14 that analyzes reception data and generates transmission data It is comprised with the electronic circuit 36 which consists of.
[0019]
In practice, in the IC card 11, the electromagnetic wave radiated from the data writing / reading device 21 is received by the loop antenna 32, and this is transmitted to the modem circuit 13 as a modulated wave. The modem circuit 13 demodulates the modulated wave and sends it to the signal processing circuit 14 as the reproduction data D1 sent from the data writing / reading device 21.
[0020]
The signal processing circuit 14 is composed of a CPU (Central Processing Unit), and has a ROM (Read Only Memory) and a RAM (Random Access Memory) (not shown), and reads out a program stored in the ROM to reproduce data. D1 is analyzed on the RAM, response data D2 stored in an internal non-volatile memory (not shown) is read based on the reproduction data D1, and this is sent to the modem circuit 13. The modulation / demodulation circuit 13 modulates the response data D2 and radiates it from the loop antenna 32 to the data write / read device 21 as an electromagnetic wave.
[0021]
Here, the modulation / demodulation circuit 13 has a power supply circuit (not shown) that converts the magnetic field energy of the electromagnetic wave into a stable DC power supply, and is radiated from the data writing / reading device 21 and received by the loop antenna 32. Based on the electromagnetic wave, the power supply circuit converts it to a DC power source DC1 and supplies it to the signal processing circuit 14. The clock signal CLK1 generated based on the received electromagnetic wave is sent to the signal processing circuit 14, and control signals for various controls. CTL1 is received from the signal processing circuit 14.
[0022]
The data writing / reading device 21 sends an instruction signal S1 from the input unit 26 such as a keyboard or an operation panel to the signal processing unit 24. The signal processing unit 24 is composed of a CPU, and has a ROM and a RAM (not shown), reads a program built in the ROM, and performs signal processing in accordance with the instruction signal S1 on the IC card. 11 is generated and transmitted to the modem circuit 23.
[0023]
The modem circuit 23 performs a modulation process based on the transmission data D3 using a carrier wave in a predetermined frequency band that can be radiated efficiently, and radiates it from the loop antenna 22 as an electromagnetic wave.
[0024]
The data writing / reading device 21 receives the electromagnetic wave radiated from the IC card 11 by the loop antenna 22 and sends it to the modulation / demodulation circuit 23 as a modulated wave. The modem circuit 23 demodulates the modulated wave and sends it to the signal processing unit 24 as reproduction data D4 sent from the IC card 11.
[0025]
Here, the signal processing unit 24 supplies the DC power supply DC2 supplied from a power supply circuit (not shown) to the modulation / demodulation circuit 23, and sends the clock signal CLK2 and various control signals CTL2 to the modulation / demodulation circuit 23. Has been made.
[0026]
The signal processing unit 24 performs signal processing based on the received reproduction data D4 and displays the result on the display 25. The signal processing unit 24 is also configured to send a signal processing result based on the reproduction data D4 to the external device 27.
[0027]
(2) Configuration of IC card
Next, a specific configuration of the IC card 11 that is configured to receive the electromagnetic wave radiated from the data writing / reading device 21 by the loop antenna 12 with the best reception efficiency even in a state where a plurality of sheets are stacked. explain.
[0028]
As shown in FIG. 2, in the IC card 11, two end points T <b> 1 and T <b> 2 of the loop antenna 32 are connected to the electronic circuit 36. Further, an intermediate tap T3 is provided at a substantially intermediate position of the loop antenna 32, and the loop antenna 32 is divided into loop antennas 32A and 32B by the intermediate tap T3. A capacitor 31 is connected between the intermediate tap T3 and the end point T1, and a resonance circuit 35 is formed by the loop antenna 32A and the capacitor 31.
[0029]
In practice, the IC card 11 is provided with end points T1 on the outermost periphery of the loop antenna 32 of all six turns mounted along the outer peripheral edge portion on the substrate 15 as shown in FIG. An end point T2 is provided on the innermost circumference of the antenna 32, and an intermediate tap T3 is provided on the second round from the outside of the loop antenna 32, and the outer two rounds of the loop antenna 32 operate as the loop antenna 32A. It is made to do.
[0030]
In FIG. 2, the resonance frequency F of the resonance circuit 35 with respect to the IC card 11. _res When an electromagnetic wave having the same frequency is applied from the outside, the resonance circuit 35 (the loop antenna 32A and the capacitor 31) efficiently receives the electromagnetic wave by resonating with the electromagnetic wave, and responds to the received electromagnetic wave. Received power is supplied to the electronic circuit 36. Such a state is called a resonance mode. In the resonance mode, the loop antenna 32B does not resonate with the electromagnetic wave and operates as an electric wire that connects the resonance circuit 35 and the electronic circuit 36 approximately. The reception sensitivity of the entire loop antenna 32 in the resonance mode is defined as the frequency of the electromagnetic wave and the resonance frequency F. _res Decreases depending on the difference.
[0031]
On the other hand, with respect to the IC card 11, the resonance frequency F of the resonance circuit 35. _res When an electromagnetic wave having a frequency away from is applied from the outside, the resonance circuit 35 does not resonate with the electromagnetic wave. In this case, the IC card 11 receives the electromagnetic waves by the entire loop antenna 32 (loop antennas 32A and 32B), and supplies received power corresponding to the electromagnetic waves to the electronic circuit 36. Such a state is called a transformer mode. In the transformer mode, the loop antenna 32 and the loop antenna 22 (FIG. 1) of the data writing / reading device 21 operate as a transformer having no iron core. Although the reception sensitivity of the entire loop antenna 32 in the transformer mode is lower than that in the resonance mode, it maintains a substantially constant value regardless of the frequency of the electromagnetic wave.
[0032]
In FIG. 4, a curve P1 shows the relationship between the frequency of the electromagnetic wave applied to the IC card 11 and the voltage supplied from the loop antenna 32 to the electronic circuit 36, and the resonance frequency F of the resonance circuit 35. _res The maximum voltage (about 200 mV) is obtained at (in this case 13.56 MHz). This is the received power in the resonance mode.
[0033]
The frequency of the electromagnetic wave is the resonance frequency F _res As the voltage drops, the voltage drops sharply. However, the received voltage stops dropping from around 10 MHz, and a substantially uniform voltage is obtained from 1 MHz onwards. This is the received power in the transformer mode.
[0034]
Thus, the IC card 11 has the resonance frequency F of the resonance circuit 35. _res And the resonance frequency F _res A predetermined level of received power can be obtained even by electromagnetic waves having a frequency far from.
[0035]
Incidentally, the curve P2 in FIG. 4 shows the reception voltage by the conventional resonance type loop antenna, and the resonance frequency F _res At a lower frequency, the voltage is about 1/3 of the curve P1.
[0036]
(3) IC card resonance frequency
The IC card 11 according to the present invention has a resonance frequency F of the resonance circuit 35 in consideration of a decrease in resonance frequency when a plurality of the IC cards 11 are stacked. _res , The carrier frequency F of the electromagnetic wave radiated from the data writing / reading device 21 _car It is set to twice. That is, the resonance frequency F _res Is given by:
[0037]
[Expression 1]

[0038]
Accordingly, when the IC card 11 is disposed alone (only one) with respect to the loop antenna 22 of the data write / read device 21, the carrier frequency F _car And resonance frequency F _res Does not match. For this reason, in this state, the resonance circuit 35 does not resonate with the electromagnetic wave, and the loop antenna 32 obtains received power in the transformer mode. In FIG. 5, a curve N1 indicates a reception sensitivity curve when only one IC card 11 is provided, and the carrier frequency F of the electromagnetic wave radiated from the data writing / reading device 21. _car Shows a constant sensitivity in the transformer mode.
[0039]
On the other hand, when two IC cards 11 are arranged on the loop antenna 22 of the data writing / reading device 21, the resonance frequency F in the two-stacked state is obtained. _res2 Is given by:
[0040]
[Expression 2]

[0041]
Even in this state, the resonance circuit 35 does not resonate with the electromagnetic wave, and the loop antenna 32 obtains received power in the transformer mode. In FIG. 5, a curve N2 indicates a reception sensitivity curve when two IC cards 11 are stacked, and a carrier frequency F of an electromagnetic wave radiated from the data writing / reading device 21. _car Shows a constant sensitivity in the transformer mode.
[0042]
Further, when the three IC cards 11 are stacked on the loop antenna 22 of the data writing / reading device 21, the resonance frequency F in the three-stacked state is set. _res3 Is given by:
[0043]
[Equation 3]

[0044]
In this state, the resonance frequency F in the three-ply state _res3 Is the carrier frequency F of the electromagnetic wave _car Thus, the resonance circuit 35 resonates with respect to the electromagnetic wave, and the loop antenna 32 obtains received power in the resonance mode. In FIG. 5, a curve N3 indicates a reception sensitivity curve when three IC cards 11 are stacked, and the carrier frequency F of the electromagnetic wave radiated from the data writing / reading device 21. _car Shows the sensitivity in the resonance mode.
[0045]
Further, when four IC cards 11 are arranged on the loop antenna 22 of the data writing / reading device 21, the resonance frequency F in the four-stacked state is obtained. _res4 Is given by:
[0046]
[Expression 4]

[0047]
In this state, the resonance frequency F in the four-ply state _res4 Is the carrier frequency F of the electromagnetic wave _car Thus, the resonance circuit 35 resonates with the best efficiency with respect to the electromagnetic wave, and the loop antenna 32 obtains received power in the resonance mode. In FIG. 5, a curve N4 indicates a reception sensitivity curve when four IC cards 11 are stacked, and the carrier frequency F of the electromagnetic wave radiated from the data writing / reading device 21. _car Shows the best sensitivity due to the resonance mode.
[0048]
Thus, the IC card 11 is configured such that the reception sensitivity to the electromagnetic wave radiated from the data writing / reading device 21 is improved in accordance with the increase in the number of the IC cards 11 to be stacked.
[0049]
Here, when a plurality of IC cards 11 are stacked, the intensity of the electromagnetic wave received by a certain IC card 11 is canceled and reduced by the magnetic field generated by the reception of the electromagnetic wave by another IC card 11. The intensity of the received electromagnetic wave decreases as the number of stacked IC cards 11 increases.
[0050]
In the IC card 11 according to the present invention, the improvement in reception sensitivity according to the increase in the number of overlapped IC cards 11 and the decrease in received electromagnetic wave intensity according to the increase in the number of overlapped IC cards 11 are offset. Even if the number of stacked IC cards 11 changes, the communication distance of the IC card 11 becomes substantially constant.
[0051]
(4) Operation and effect
In the above configuration, when one or two IC cards 11 are placed on the loop antenna 22 of the data writing / reading device 21, the resonance frequency of the resonance circuit 35 and the carrier frequency F of the electromagnetic wave _car Therefore, the resonance circuit 35 does not resonate with the electromagnetic wave, and the IC card 11 obtains received power in the transformer mode.
[0052]
On the other hand, when three IC cards 11 are placed on the loop antenna 22, the resonance frequency of the resonance circuit 35 is the carrier frequency F of the electromagnetic wave. _car Thus, the resonance circuit 35 resonates with respect to the electromagnetic wave, and the IC card 11 obtains received power in the resonance mode.
[0053]
Further, when four IC cards 11 are arranged on the loop antenna 22, the resonance frequency of the resonance circuit 35 is the carrier frequency F of the electromagnetic wave. _car Thus, the resonance circuit 35 resonates with the best efficiency with respect to the electromagnetic wave, and the IC card 11 obtains received power in the resonance mode.
[0054]
Here, as the number of stacked IC cards 11 increases, the reception sensitivity of each IC card 11 improves and the intensity of the reception electromagnetic wave of each IC card 11 decreases. As a result, the reception sensitivity is improved and the reception electromagnetic wave is reduced. The strength reduction is offset and a substantially constant communication distance can be obtained regardless of the number of IC cards 11 stacked.
[0055]
According to the above configuration, the intermediate tap T3 is provided in the middle of the loop antenna 32, the capacitor 31 is connected between the intermediate tap T3 and the end point T1, the resonant circuit 35 is formed, and a plurality of IC cards 11 are stacked. The resonance frequency F of the resonance circuit 35 in consideration of the resonance frequency drop in the case _res The carrier frequency F of the electromagnetic wave radiated from the data writing / reading device 21 _car Therefore, even when it is superimposed on another IC card 11, the electromagnetic wave radiated from the data writing / reading device 21 can be received with the best receiving efficiency. Even when a plurality of sheets are stacked without sacrificing the distance and communication quality, a sufficient communication distance and communication quality can be obtained.
[0056]
(5) Other embodiments
In the above-described embodiment, the resonance frequency F of the resonance circuit 35 _res The carrier frequency F of the electromagnetic wave radiated from the data writing / reading device 21 _car However, the present invention is not limited to this, and various other frequencies may be set according to the expected number of IC cards to be stacked, the reception sensitivity curve of the resonance circuit, and the like.
[0057]
In the above-described embodiment, the loop antenna 32 is provided with the intermediate tap T3, the capacitor 31 is connected to the intermediate tap T3 and the end point T1, and the resonance circuit 35 is provided. However, the present invention is not limited to this. Two or more intermediate taps may be provided on the loop antenna, a capacitor may be connected to each intermediate tap, and a plurality of resonance circuits may be provided on the IC card.
[0058]
That is, as shown in FIG. 6, two end points T 1 and T 2 of the loop antenna 33 included in the IC card 12 are connected to the electronic circuit 36. Intermediate taps T3 and T4 are provided in the middle of the loop antenna 33. The loop antenna 33 is divided into loop antennas 33A, 33B, and 33C by the intermediate taps T3 and T4. The first capacitor 31A is connected between the intermediate tap T3 and the end point T1, and the loop antenna 33A and the first capacitor 31A form a first resonance circuit 35A. Similarly, a second capacitor 31B is connected between the intermediate tap T4 and the end point T2, and a second resonance circuit 35B is formed by the loop antenna 33C and the second capacitor 31B. Resonance frequency F of the first resonance circuit 35A _resA And the resonance frequency F of the second resonance circuit 35B _resB Are set to different frequencies.
[0059]
In practice, the IC card 12 is provided with an intermediate tap T3 on the second turn from the outside of the loop antenna 33 of all six turns mounted along the outer peripheral edge portion on the substrate 15 as shown in FIG. In addition, the outer two rounds of the loop antenna 33 operate as the loop antenna 33A, and an intermediate tap T4 is provided in the second round from the inner side of the loop antenna 33, and the inner two rounds of the loop antenna 33 are looped. It operates as an antenna 33C.
[0060]
In FIG. 6, the resonance frequency F of the first resonance circuit 35 </ b> A with respect to the IC card 12. _resA When the electromagnetic wave having the same frequency is applied from the outside, the first resonance circuit 35A (the loop antenna 33A and the first capacitor 31A) efficiently receives the electromagnetic wave by resonating with the electromagnetic wave ( Resonance mode), the received power corresponding to the received electromagnetic wave is supplied to the electronic circuit 36. At this time, the loop antennas 33 </ b> B and 33 </ b> C do not resonate with the electromagnetic wave, and operate as electric wires that approximately connect the first resonance circuit 35 </ b> A and the electronic circuit 36.
[0061]
On the other hand, the resonant frequency F of the second resonant circuit 35B with respect to the IC card 12 _resB When the electromagnetic wave having the same frequency is applied from the outside, the second resonance circuit 35B (the loop antenna 33C and the second capacitor 31B) efficiently receives the electromagnetic wave by resonating with the electromagnetic wave ( Resonance mode), the received power corresponding to the received electromagnetic wave is supplied to the electronic circuit 36. At this time, the loop antennas 33 </ b> A and 33 </ b> B do not resonate with respect to the electromagnetic waves, and operate as electric wires that approximately connect the second resonance circuit 36 </ b> B and the electronic circuit 36.
[0062]
F for IC card 12 _resA And F _resB When an electromagnetic wave having a frequency away from the outside is applied from the outside, the first resonance circuit 36A and the second resonance circuit 36B do not resonate with the electromagnetic wave. In this case, the IC card 12 receives the electromagnetic waves by the entire loop antenna 33 (loop antennas 33A, 33B and 33B) (transformer mode) and supplies the received power corresponding to the electromagnetic waves to the electronic circuit 36.
[0063]
In FIG. 8, a curve P3 shows the relationship between the frequency of the electromagnetic wave applied to the IC card 12 and the voltage supplied from the loop antenna 33 to the electronic circuit 36, and the resonance frequency F of the first resonance circuit 35A. _resA And the resonance frequency F of the second resonance circuit 35B. _resB The peak of the received voltage is shown in FIG. The frequency of the electromagnetic wave is the resonance frequency F of the first resonance circuit 35A. _resA As the voltage drops, the voltage drops sharply, but the drop in the received voltage stops from around 8 MHz, and a substantially uniform voltage is obtained from 1 MHz onwards.
[0064]
As described above, by providing a plurality of resonance circuits in the IC card, a plurality of resonance points are obtained, and by appropriately setting the plurality of resonance points (resonance frequencies), reception when a plurality of IC cards are stacked is received. Sensitivity deterioration can be prevented.
[0065]
【The invention's effect】
As described above, according to the present invention, in an antenna device connected to an electronic circuit so as to receive a predetermined electromagnetic wave and supply electric power according to the received electromagnetic wave, a capacitor is connected to a part of the loop antenna. A resonance circuit is configured by connecting them in parallel, and either a resonance mode in which received power is supplied to the electronic circuit by resonance of the resonant circuit, or a transformer mode in which the entire loop antenna receives electromagnetic waves to supply received power to the electronic circuit. In the case of an antenna device alone in which the resonance frequency of the resonance circuit is separated from the carrier frequency of the electromagnetic wave by setting the resonance frequency of the resonance circuit higher than the carrier frequency of the electromagnetic wave, When electromagnetic waves are received via a loop antenna and a plurality of antenna devices are stacked, the antenna devices are By reducing the resonance frequency of the resonance means due to the stacking, the electromagnetic wave is received by the resonance means according to the resonance mode, so that the efficiency is always good even in the state where the antenna device is single or plural. An antenna device that can receive electromagnetic waves can be realized.
[0066]
According to the present invention, in a card-like storage medium that communicates with a data writing / reading device via electromagnetic waves, a resonance circuit is configured by connecting a capacitor in parallel to a part of the loop antenna. The resonance frequency of the resonance circuit is set to the electromagnetic wave so that it is received in either the resonance mode that supplies the reception power to the electronic circuit by resonance or the transformer mode that supplies the reception power to the electronic circuit when the entire loop antenna receives the electromagnetic wave. In the case of a single card-like storage medium in which the resonance frequency of the resonance circuit is separated from the carrier frequency of the electromagnetic wave by setting it higher than the carrier frequency, the electromagnetic wave is received via the loop antenna by the transformer mode, When a plurality of card-shaped storage media are stacked, the resonance circumference of the resonance means is obtained by stacking a plurality of the card-shaped storage media. Due to the decrease in the number, the resonance mode allows the electromagnetic wave to be received by the resonance means, so that the card-like storage medium can always receive the electromagnetic wave with good efficiency even in the state where the card-like storage media are stacked alone or in plural. A storage medium can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a non-contact IC card system.
FIG. 2 is a connection diagram showing a configuration of an IC card according to the present invention.
FIG. 3 is a schematic diagram showing a mounting image of an IC card.
FIG. 4 is a characteristic curve diagram showing the reception voltage of the IC card according to the present invention.
FIG. 5 is a characteristic curve diagram showing the reception sensitivity of the IC card according to the present invention.
FIG. 6 is a connection diagram showing a configuration of an IC card according to another embodiment.
FIG. 7 is a schematic diagram showing a mounting image of an IC card according to another embodiment.
FIG. 8 is a characteristic curve diagram showing a reception voltage of an IC card according to another embodiment.
FIG. 9 is a block diagram showing a configuration of a conventional non-contact IC card system.
FIG. 10 is a schematic diagram showing a tuning frequency when there is one IC card.
FIG. 11 is a connection diagram showing a configuration of an equivalent circuit when a plurality of IC cards are stacked.
FIG. 12 is a characteristic curve diagram showing transition of tuning frequency when a plurality of IC cards are stacked.
FIG. 13 is a characteristic curve diagram showing a transition of tuning frequency in an IC card corresponding to a plurality of stacked sheets.
FIG. 14 is a characteristic curve diagram showing transition of tuning frequency in a state where four IC cards are stacked.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 10 ... Non-contact IC card system, 2, 21 ... Data writing / reading apparatus, 6, 32, 33 ... Loop antenna, 7, 31 ... Capacitor, 31A ... First capacitor, 31B ... Second capacitor, 8, 35... Resonance circuit, 35A... First resonance circuit, 35B... Second resonance circuit.

Claims (4)

In an antenna device connected to an electronic circuit so as to receive electromagnetic waves and supply electric power according to the received electromagnetic waves ,
A loop antenna,
A resonance circuit having a resonance frequency higher than the carrier frequency of the electromagnetic wave, formed by connecting a capacitor in parallel to a part of the loop antenna ;
With
Receiving in either a resonance mode in which received power is supplied to the electronic circuit by resonance of the resonant circuit, or a transformer mode in which the entire loop antenna receives the electromagnetic wave to supply received power to the electronic circuit. An antenna device characterized by setting a value of the resonance frequency . The resonant circuit is formed by connecting a first capacitor in parallel to a first intermediate tap provided on the loop antenna and a first end of the loop antenna, which is higher than the carrier frequency of the electromagnetic wave. formed by connecting a first resonant circuit having a first resonance frequency values, the second capacitor to the second end of the second intermediate tap and the loop antenna provided in the loop antenna in parallel It has been higher than the carrier frequency of the electromagnetic wave, and a second resonant circuit having a second resonance frequency different values from the first resonant frequency,
And the first of the first resonant mode supplies the received power to the electronic circuit by the resonance of the resonant circuit, and a second resonance mode supplies the received power to the electronic circuit by the resonance of the second resonant circuit, The values of the first and second resonance frequencies are set so that the entire loop antenna receives the electromagnetic wave and receives it in one of the transformer modes that supplies received power to the electronic circuit. The antenna device according to claim 1, wherein: In a card-like storage medium that communicates with a data writing / reading device via electromagnetic waves ,
A loop antenna,
The electromagnetic wave formed by connecting a capacitor in parallel to a part of the loop antenna.
A resonant circuit having a higher resonant frequency than the carrier frequency of the wave;
An electronic circuit connected to the loop antenna ,
Receiving in either a resonance mode in which received power is supplied to the electronic circuit by resonance of the resonant circuit, or a transformer mode in which the entire loop antenna receives the electromagnetic wave to supply received power to the electronic circuit. A card-shaped storage medium, wherein the resonance frequency value is set . The resonant circuit is formed by connecting a first capacitor in parallel to a first intermediate tap provided on the loop antenna and a first end of the loop antenna, which is higher than the carrier frequency of the electromagnetic wave. formed by connecting a first resonant circuit having a first resonance frequency values, the second capacitor to the second end of the second intermediate tap and the loop antenna provided in the loop antenna in parallel It has been higher than the carrier frequency of the electromagnetic wave, and a second resonant circuit having a second resonance frequency different values from the first resonant frequency,
And the first of the first resonant mode supplies the received power to the electronic circuit by the resonance of the resonant circuit, and a second resonance mode supplies the received power to the electronic circuit by the resonance of the second resonant circuit, The values of the first and second resonance frequencies are set so that the entire loop antenna receives the electromagnetic wave and receives it in one of the transformer modes that supplies received power to the electronic circuit. The card-shaped storage medium according to claim 3, wherein:

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