United States Patent [191
`Takahira
`
`US 005337063A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,337,063
`Aug. 9, 1994
`
`[54] ANTENNA CIRCUIT FOR NON-CONTACT IC
`CARD AND METHOD 01:‘
`MANUFACTURING THE SAME
`[75] Invenw“ Kellichi Takahira’ Immi’ Japan
`[73] Ass‘gnee gas“??? gfnkl Kabushlkl Kmsha’
`-
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`[21] Appl. No.: 867,538
`_
`Al"- 13, 1992
`[22] Flledi
`[30]
`Foreign Application Priority Data
`Apr. 22, 1991 [JP]
`Japan .................................. .. 390323
`
`[51] Int. Cl.5 ........................................... .. H01Q 11/12
`[52] US. Cl. .................................. .. 343/741; 343/745;
`343/895
`[58] Field Of Search ............. .. 343/741, 742, 743, 744,
`' 343/895, 866, 867, 868, 745; 29/600; H01Q
`9/27, 4/36, 7/00
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`3,956,751 5/1976 Herman ............................. .. 343/744
`4,021,705 5/1977 Lichtblau ..
`.... .. 361/402
`
`4,864,280 9/ 1989 Meij . . . . . . . . . . . . . .
`4,922,261 5/1990 O’Farrell
`
`. . . . .. 343/895
`.... .. 343/742
`
`4,947,180 8/1990 Schotz . . . . . . .
`
`. . . . . . . . . . . . .. 343/743
`
`4,947, 180 8/ 1990 Schotz ............................... .. 343/744
`
`5,108,822 4/1992 Imaichi et a1. .................... .. 343/895
`5,128,686 7/1992 Tan et a1. .......................... .. 343/744
`FOREIGN PATENT DOCUMENTS
`3824870 4/1989 Fed. Rep. of Germany .
`2190819 11/1987 United Kingdom .
`3590698 9/ 1989 Fed. Rep. of Germany .
`2191368 12/1987 United Kingdom .
`_
`_
`,
`Primary Examiner-Donald Hajec
`Assistant Examiner—Tan H0
`Attorney, Agent, or Firm—Leydig, Voit & Mayer
`[57]
`ABSTRACI‘
`
`An antenna circuit for a non-contact IC card exchanges
`signals with an external device utilizing electromagnetic
`waves. The antenna circuit includes a coil and a capaci
`tor connegted to form a resonant circuit. The coil in
`cludes a main coil having a spiral conductive pattern
`disposed on a peripheral portion of a substrate and a
`plurality of adjusting patterns, each electrically con
`necting a portion of the conductive pattern correspond
`ing to a desired number of turns of the main coil to an
`end of the main coil. The plurality of adjusting patterns
`are disconnected from the main coil, except for one
`adjusting pattern, to obtain a coil of desired inductance.
`
`5 Claims, 6 Drawing Sheets
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`US. Patent
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`Aug. 9, 1994
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`Sheet 4 of 6
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`5,337,063
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`US. Patent
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`Aug. 9, 1994
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`Sheet 5 0f 6
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`5,337,063
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`FIG. 6
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`US. Patent
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`Aug. 9, 1994
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`Sheet 6 of 6
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`5,337,063
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`FIG. 7
`
`TO MODEM CIRCUIT 5%
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`1
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`5,337,063
`
`ANTENNA CIRCUIT FOR NON-CONTACT IC
`CARD AND METHOD OF MANUFACTURING THE
`SAL/IE
`
`25
`
`2
`SUMMARY OF THE INVENTION
`Accordingly, an object of the present invention is to
`provide an antenna circuit for a non-contact IC card for
`coping with a change of the carrier frequency and
`matching a resonant frequency after the circuit compo
`nents are fabricated on a substrate.
`Another object of the present invention is to provide
`a method of manufacturing such an antenna circuit for
`a non-contact IC card.
`In order to achieve the above objects, according to
`one aspect of the present invention, there is provided an
`antenna circuit for an IC card comprising a coil and a
`capacitor connected to the coil to form a resonant cir
`cuit. The coil includes a main coil having a spiral con
`ductive pattern disposed on a peripheral portion of a
`substrate, and a plurality of adjusting patterns each of
`which electrically connects a portion of the conductive
`pattern corresponding to a desired number of turns of
`the main coil to one end of the main coil. The plurality
`of adjusting patterns are disconnected from the main
`coil except for one adjusting pattern to obtain desired
`inductance characteristic.
`According to another aspect of the present invention,
`there is provided an antenna circuit for a non-contact
`1C card comprising a coil having a conductive pattern
`disposed on a peripheral portion of a substrate, part of
`the conductive pattern being trimmed in a spiral fashion
`to obtain desired inductance characteristics, and a ca
`pacitor connected to the coil to form a resonant circuit.
`According to another aspect of the present invention,
`there is provided an antenna circuit for a non-contact
`IC card comprising a coil having a spiral conductive
`pattern disposed on a peripheral portion of a substrate,
`a plurality of switches each of which is electrically
`connected between a portion of the conductive pattern
`corresponding to a desired number of turns of the coil at
`one end of the coil, and a capacitor connected to the
`other end of the coil to form a resonant circuit.
`According to another aspect of the present invention,
`there is provided a method of manpfacturing an antenna
`circuit for a non-contact IC card comprising forming a
`main coil having a spiral conductive pattern on a pe
`ripheral portion of a substrate, forming on the substrate
`a plurality of adjusting patterns each of which electri
`cally connects a portion of the conductive pattern cor
`responding to a desired number of turns of the main coil
`to one end of the main coil, disconnecting the plurality
`of adjusting patterns from the main coil except for one
`adjusting pattern to obtain desired inductance charac
`teristics, and connecting a capacitor to the other end of
`the main coil to form a resonant circuit.
`According to another aspect of the present invention,
`there is provided a method of manufacturing an antenna
`circuit for a non-contact IC card comprising a conduc
`tive pattern on a peripheral portion of a substrate, form
`ing a coil by trimming part of the conductive pattern in
`a spiral form while measuring the inductance of the
`conductive pattern until a desired inductance is ob
`tained, and connecting one end of the coil to a capacitor
`to form a resonant circuit.
`
`BACKGROUND OF THE INVENTION
`Field of the Invention
`The present invention relates to an antenna circuit for
`a non-contact IC card and a method of manufacturing
`such an antenna circuit.
`Description of the Related Art
`Non-contact IC cards exchanging signals via electro
`magnetic waves or light have been used in recent years.
`FIG. 5 shows the con?guration of such a non-contact
`IC card. A ROM 2 and a RAM 3 are connected through
`a bus 8 to a CPU 1 for controlling the operation of the
`IC card. An input/output control circuit 4 for control
`ling input of data from and output of data to an external
`device (not shown) is connected to the bus 8. An an
`tenna circuit 6 is Connected to the input/output control
`circuit 4 through a modem circuit 5. A battery 7 is
`incorporated for supplying power to the individual
`electric circuits.
`In such an'IC card, a command signal received by the
`antenna circuit 6 from an external device, such as a
`terminal machine, in the form of an electromagnetic
`wave is demodulated by the modem circuit 5 and then
`input to the CPU 1 through the input/output control
`circuit 4. The CPU 1 decodes the command signal and
`creates a predetermined response signal. This response
`signal is input to the modem circuit 5 through the input
`/output control circuit 4 which modulates this signal.
`The modulated signal is transmitted to an external de
`vice from the antenna circuit 6.
`In a practical IC card, as shown in FIG. 6, the CPU
`1, the ROM 2, the RAM 3, the input/output control
`circuit 4, the modem circuit 5 and the bus 8 are fabri
`cated in a single IC 9, and this IC 9 and the battery 7 are
`40
`mounted on a card substrate 10. The antenna circuit 6
`for exchanging signals with an external device has a coil
`62 having an inductance L and consisting of a conduc
`tive pattern 61 formed in a spiral on vthe peripheral
`portion of the card substrate 10, and a capacitor 63
`having a capacitance C and fabricated on the card sub
`strate 10. A combination of the coil 62 and the capacitor
`63 forms an LC parallel resonant circuit as shown in
`FIG. 7, which induces a voltage when it receives an
`electromagnetic wave at a frequency close to the reso
`nant frequency of the resonant circuit. The signal is
`received, by detecting that induced voltage. In that
`case, the frequency of the electromagnetic waves that
`can be received by the antenna circuit 6 is determined
`55
`by the resonant frequency fo= l/{2'rr(L-C)i} of the LC
`parallel resonant circuit.
`As stated above, the coil 62 of the antenna circuit 6 is
`formed on the peripheral portion of the card substrate
`10 in the form of a conductive pattern. Therefore, the
`60
`inductance L of the coil 62 is determined at the time of
`manufacture of the card substrate 10, and a change of
`the inductance L after the manufacture is impossible.
`Such an antenna circuit cannot be used when the fre
`quency of a carrier used for exchanging signals is
`changed. Furthermore, matching of the resonant fre
`quency cannot be conducted after the card substrate 10
`is manufactured.
`
`45
`
`65
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a schematic plan view of a coil of a ?rst
`embodiment of an antenna circuit for a non-contact IC
`card according to the present invention;
`FIG. 2 is a schematic plan view of a coil of a second
`embodiment of the antenna circuit;
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`FIG. 3 is a schematic plan view of a conductive pat
`ing of the resonant frequency can be achieved by mak
`tern formed at the initial stage of the manufacturing
`ing a selection among the adjusting patterns 13 to 15.
`process of the antenna circuit shown in FIG. 2;
`Such an antenna circuit will be manufactured in the
`FIG. 4 is a circuit diagram showing the con?guration
`following manner: First, the main coil 12 consisting of
`the spiral conductive pattern is formed on the periph
`of a third embodiment of the antenna circuit according
`eral portion of the substrate, and the adjusting patterns
`to the present invention;
`for respectively connecting the portions D to F of the
`FIG. 5 is a block diagram of a conventional non-con
`main coil 12 to the end portion B are formed. Next, the
`tact IC card;
`adjusting patterns 13 to 15 are cut except for one of
`FIG. 6 is a plan view showing the mechanical struc
`these patterns corresponding to a desired inductance.
`ture of the non-contact IC card of FIG. 5; and
`Cutting of the adjusting patterns is conducted by, for
`FIG. 7 is a circuit diagram of an antenna circuit for
`example, a laser beam, means of sand blasting or chemi
`the non-contact IC card shown in FIG. 5.
`cal etching. Thereafter, the capacitor is connected to
`the end portion A of the main coil 12 to form a resonant
`circuit. Connection of the capacitor to the end portion
`A of the main coil 12 may be made prior to the cutting
`of the adjusting patterns.
`Although the main coil 12 having three turns is
`shown in FIG. 1, the number of turns of the coil is not
`so limited. In a practical circuit, a main coil having a
`several tens of turns is used. The number of adjusting
`patterns is not limited to three but four or more adjust
`ing patterns may be formed.
`FIG. 2 shows a coil 17 according to a second embodi
`ment of an antenna circuit according to the present
`invention. FIG. 2 is a schematic view of the coil 17.
`Practically, the coil 17 is disposed on the peripheral
`portion of a card substrate, while an IC and other com
`ponents, such as a battery, are located within the coil 17,
`as shown in FIG. 6. The coil 17 has a conductive pat
`tern 18 formed on the substrate and partially trimmed in
`a spiral form. The innermost portion G of the conduc
`tive pattern 18 is electrically connected to an end por
`tion pattern 21 disposed on the surface of the substrate
`through via-holes 19 and a connection pattern 20 is
`disposed on the rear surface of the substrate . The con
`ductive pattern 18 is trimmed in a spiral form from
`position e1 to position e2. The number of turns of the
`coil 17 can be changed and the inductance characteris
`tics of the coil 17 can thus be adjusted by changing the
`trimming ending portion e2. In FIG. 2, a dashed line
`indicates a pattern line for further trimming
`A capacitor having a capacitance C is connected to
`an end portion H or J, as shown in FIGS. 6 and 7. This
`capacitor and the coil 17 in combination form an LC
`parallel resonant circuit which acts as an antenna circuit
`. In this embodiment, even after the circuit components
`are fabricated on the substrate, a change in the carrier
`frequency can be coped with and the resonant fre
`quency can be matched by further trimming the con
`ductive pattern 18.
`Such an antenna circuit will be manufactured in the
`manner described below. First, a wide ring-shaped con
`ductive pattern 18 is formed on the peripheral portion
`of the substrate, as shown in FIG. 3, while the connec
`tion pattern 20 and the end portion pattern 21, con
`nected to the portion G of the conductive pattern 18,
`are formed. Next, the conductive pattern 18 is trimmed
`in a spiral form starting from the position el while the
`inductance between the end portion H of the conduc
`tive pattern 18 and the end portion J of the end portion
`pattern 21 is measured using an inductance measuring
`device 'until a desired inductance value is obtained.
`Preferably, trimming is conducted such that the width
`of the conductive pattern which is not trimmed is con
`stant. As trimming proceeds, the number of turns of the
`coil 17 as viewed from the end portions H and J gradu
`ally increases, thus increasing the inductance L of the
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`Embodiments of the present invention will be de
`scribed below with reference to the accompanying
`drawings. '
`FIG. 1 shows a coil 11 of a ?rst embodiment of an
`antenna circuit for a non-contact IC card according to
`the present invention. FIG. 1 is a schematic view of the
`coil 11. Practically, the coil 11 is disposed on the periph
`eral portion of a card substrate, while an IC and other
`components, such as a battery, are located within the
`coil 11, as shown in FIG. 6. The coil 11 has a main coil
`12 including of a conductive spiral pattern formed in
`three turns on the substrate. A ?rst adjusting pattern 13
`for connecting a portion D at which the ?rst turn inter
`sects the second turn, as viewed from an end portion A
`of the main coil 12, to the other end portion B of the
`main coil 12 is disposed on the substrate. A second
`adjusting pattern 14 for connecting a portion E at which
`the third turn terminates, as viewed from the end por
`tion A of the main coil 12, to the other end portion B of
`35
`the main coil 12 is disposed on the rear surface of the
`substrate. The second adjusting pattern 14 is electrically
`connected to the main coil 12 through via-holes 16. A
`third adjusting pattern 15 for connecting a portion F at
`which the third turn terminates, as viewed from the end
`portion A of the main coil 12, to the other end portion
`B of the main coil 12 is disposed on the rear surface of
`the substrate. This adjusting pattern 15 is electrically
`connected to the main coil 12 through via-holes 16.
`The number of turns needed to form the coil 11 can
`be selected from among one to three by electrically
`disconnecting these three adjusting patterns 13 to 15 by
`cutting them at cutting lines L1, L2 or L3 except for
`one adjusting pattern. For example, if the adjusting
`pattern 13 is left connected while the other adjusting
`patterns 14 and 15 are disconnected, a coil 11 having a
`single turn is provided. Similarly, if the adjusting pat
`tern 14 is left connected, a coil 11 having two turns is
`provided. Leaving the adjusting pattern 15 connected
`provides a coil 11 having three turns.
`Generally, a relationship, expressed by L=a-N2, es
`tablishes the inductance L of the coil for the number of
`turns N of the coil, where a is a constant determined by
`the shape of a coil. Therefore, the inductance L of the
`coil 11 can be adjusted by changing the number of turns
`of the coil 11 .
`A capacitor having a capacitance C is connected to
`the end portion A of the coil 11, as shown in FIGS. 6
`and 7. This capacitor and the coil 11 in combination
`form an LC parallel resonant circuit which acts as an
`antenna circuit. In this antenna circuit, even after the
`circuit components are built on the substrate, a change
`of the carrier frequency can be coped with and match
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`coil 17. Trimming is ended when the desired inductance
`measuring the inductance of the conductive pat
`value has been obtained. Thereafter, the capacitor is
`tern;
`connected to the end portion H of the conductive pat
`stopping removal of part of the conductive pattern
`tern 18 or to the end portion J to form a resonant circuit.
`when a desired inductance is obtained; and
`Connection of the capacitor may be conducted prior
`connecting the end of the coil to a capacitor to form
`to trimming of the conductive pattern 18.
`a resonant circuit.
`.In this method of manufacturing the antenna circuit,
`3. An inductor for forming an antenna circuit of a
`non-contact IC card comprising:
`since trimming of the conductive pattern 18 is con
`ducted while measuring the inductance'of the coil 17,
`a substrate of a non-contact IC card, the substrate
`including opposed ?rst and second surfaces;
`the inductance can be adjusted with a very high degree
`an electrically conducting coil layer disposed on the
`of accuracy.
`?rst surface of the substrate having at least one turn
`FIG. 4 shows a third embodiment of the antenna
`with ?rst and second ends disposed on the ?rst
`circuit according to the present invention. One end of a
`surface of the substrate, the second end being lo
`coil 22 having an inductance L is connected to one end
`cated inside the at least one turn;
`of a capacitor 23 having a capacitance C to form an LC
`an electrically conducting adjusting pattern disposed
`15
`resonant circuit. The coil 22 is in the form of a solenoid
`on the ?rst surface of the substrate outside the turn
`coil. Coil taps P, Q and R corresponding to predeter
`electrically connected to the electrically conduct
`mined numbers of turns are respectively connected to
`ing coil layer; and
`one end of switches S1, S2 and S3. The other ends of
`an electrically conducting pattern disposed on the
`these switches S1, S2 and S3 are connected with each
`second surface of the substrate and penetrating
`20
`other and to ground, thereby forming the other end of
`through the substrate at the adjusting pattern and
`the coil 22.
`at the second end, electrically connecting the sec
`By turning on one of the switches S1, S2 and S3 while
`ond end to the adjusting pattern.
`turning off the other switches, the number of turns of
`4. An inductor for forming an antenna circuit of a
`the coil 22 can be selected from among three values.
`non-contact IC card comprising:
`That is, by changing the switch that is turned on, the
`a substrate of a non-contact IC card, the substrate
`number of turns of the coil 22 can be changed. Conse
`including opposed ?rst and second surfaces;
`quently, the inductance of the resonant circuit can be
`an electrically conducting coil layer disposed on the
`adjusted.
`?rst surface of the substrate in the form of a spiral
`The third embodiment may be implemented by form
`coil including at least two turns with ?rst and sec
`ing a coil including a spiral conductive pattern and a
`ond ends disposed on the ?rst surface of the sub
`plurality of adjusting patterns on the peripheral portion
`strate, the second end being located inside the at
`of the substrate in a similar manner to that of the ?rst
`least two turns;
`embodiment shown in FIG. 1 and then by providing a
`an electrically conducting adjusting pattern disposed
`switch for connecting and disconnecting the adjusting
`on the ?rst surface of the substrate outside the turns
`pattern on each adjusting pattern.
`extending from and electrically connected to the
`electrically conducting coil layer; and
`The switches S1, S2 and S3 may be semiconductor
`analog switches. Also, the number of switches is not
`an electrically conducting pattern disposed on the
`limited to three.
`second surface of the substrate and penetrating
`through the substrate at the adjusting pattern and
`In the third embodiment, the positions of the switches
`at the second end, electrically connecting the sec
`S1, S2 and S3 can be controlled by a control signal from
`40
`ond end to the adjusting pattern.
`a CPU (not shown) incorporated in the non-contact IC
`5. An inductor for forming an antenna circuit of a
`card. That is, the essential inductance of the coil 22 can
`non-contact IC card comprising:
`be changed by a program which controls the CPU.
`What is claimed is:
`a substrate of a non-contact IC card, the substrate
`including opposed ?rst and second surfaces;
`1. A method of manufacturing an antenna circuit of a
`an electrically conducting coil layer disposed on the
`non-contact IC card comprising:
`?rst surface of the substrate in the form of a spiral
`forming a main coil having ?rst and second ends and
`coil including at least ?rst, second, and third turns
`a multiple turn spiral conductive pattern on a ?rst
`with ?rst and second ends disposed on the ?rst
`surface of a substrate having opposed ?rst and
`surface of the substrate and an intermediate con
`second surfaces;
`nection point disposed on the ?rst surface between
`forming on the second surface of the substrate a plu
`the ?rst and second ends, the second end being
`rality of adjusting patterns, each adjusting pattern
`located inside the at least ?rst, second, and third
`electrically connecting a portion of the conductive
`turns;
`pattern on the ?rst surface corresponding to a re
`an electrically conducting adjusting pattern disposed
`spective number of turns of the main coil to the
`on the ?rst surface of the substrate outside the turns
`?rst end of the main coil;
`extending from and electrically connected to the
`cutting and thereby electrically disconnecting said
`electrically conducting coil layer; and
`plurality of adjusting patterns from the main coil
`?rst and second electrically conducting patterns dis
`except for one adjusting pattern to obtain a desired
`posed on the second surface of the substrate, the
`main coil inductance; and
`?rst electrically conducting pattern penetrating
`connecting a capacitor to the second end of the main
`through the substrate at the adjusting pattern and
`coil to form a resonant circuit.
`at the second end, electrically connecting the sec
`2. A method of manufacturing an antenna circuit of a
`ond end to the adjusting pattern, and the second
`non-contact 10 card comprising:
`electrically
`conducting pattern
`penetrating
`forming a conductive pattern on a peripheral portion
`through the substrate at the intermediate connec
`of a surface of a substrate;
`tion point and at the second end, electrically con
`forming an at least partially spiral coil having an end
`necting the intermediate connection point to the
`from the conductive pattern and removing part of
`adjusting pattern.
`the conductive pattern along a spiral path while
`
`* * * * *
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