Eumpilsches
`Patentaml
`European
`Patent Office
`Office eurapéen
`
`des brevets
`
`(11)
`
`EP1814191 A2
`
`(12)
`
`EUROPEAN PATENT APPLICATION
`
`(43) Date of publication:
`01.08.2007 Bulletin 2007/31
`
`(21) Application number: 07101353.6
`
`(22) Date of filing: 29.01.2007
`
`(51)
`
`Int CL:
`H010 1/22(2006.01}
`606K 19/077(2005.a1)
`
`H010 7/00 (2005-01)
`
`(84) Designated Contracting States:
`AT BE BG CH CY CZ DE DK EE ES FI FR GB GR
`HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI
`SK TR
`
`Designated Extension States:
`AL BA HR MK YU
`
`(30) Priority: 30.01.2006 JP 2006020283
`08.02.2006 JP 2006030810
`02.06.2006 JP 2006154279
`
`(71) Applicant: MATSUSHITA ELECTRIC INDUSTRIAL
`CO., LTD.
`Osaka 571-8501 (JP)
`
`(72) Inventors:
`0 Nakamura, Kouichi
`c/o Matsushita Electric Industrial Co., Ltd.
`Osaka 540-6319 (J P)
`0 Nishino, Tokuii
`c/o Matsushita Electric Industrial Co., Ltd.
`Osaka 540—6319 (J P)
`
`(54)
`
`Antenna apparatus
`
`An antenna apparatus includes a magnetic
`(57)
`sheet and an antenna that is provided in the magnetic
`sheet and has a looped conductorandterminal electrode
`parts arranged at both ends of the conductor, and a
`matching circuit that is provided in the magnetic sheet,
`includes a first capacitor and a second capacitor each of
`which has a pair of electrodes, and sets a resonant fre-
`quency by the antenna and the first and second capac-
`itors. One electrode of the pair of electrodes of the first
`capacitor is connected to one of the terminal electrode
`parts, and the other electrode of the pair of electrodes of
`the first capacitor is connected to the looped conductor.
`One electrode of the pair of electrodes of the second
`capacitor is connected to the other one of the terminal
`electrode parts, and the other electrode of the pair of
`electrodes of the second capacitor is connected to the
`
`Fukada, Kikuo
`c/o Matsushita Electric Industrial Co., Ltd.
`Osaka 540-6319 (JP)
`Kiyosue, Kuniaki
`c/o Matsushita Electric Industrial Co., Ltd.
`Osaka 540-6319 (JP)
`Yano, Hatsuhiro
`c/o Matsushita Electric Industrial Co., Ltd.
`Osaka 540-6319 (JP)
`Fujimura, Munenori
`c/o Matsushita Electric Industrial Co., Ltd.
`Osaka 540-6319 (JP)
`Fukushima Fumio
`
`c/o Matsushita Electric Industrial Co., Ltd.
`Osaka 540-6319 (JP)
`Onaka, Yoshio
`c/o Matsushita Electric Industrial Co., Ltd.
`Osaka 540-6319 (JP)
`
`(74)
`
`Representative: Eisenfiihr, Speiser & Partner
`Patentanwéilte Rechtsanwéilte
`Postfach 10 60 78
`
`28060 Bremen (DE)
`
`
`looped conductor.
`
`
`Printed by Jouve, 75001 PARIS (FR)
`
`EP1814191A2
`
`

`

`‘l
`
`EP 1 814191112
`
`2
`
`Description
`
`BACKGROUND
`
`[0001] The present invention relates to a radio com-
`munication medium processor that performs communi—
`cation with radio communication media, such as RFle,
`i.e., IC cards, and IC tags, or an antenna apparatus used
`for the radio communication media themselves.
`
`In a related art, since a radio communication
`[0002]
`processor that performs communication with radio com-
`munication media by an electromagnetic induction meth-
`od, etc., or an antenna apparatus used forthe radio com-
`munication mediathemselves has aweakened magnetic
`field underthe influence of its surrounding metal, the mu-
`tual
`inductance required for communication is inade-
`quate. Therefore, there are hindrances that a communi—
`cation distance becomes short or communication be—
`
`comes impossible. Thus, in orderto make the processor
`or antenna apparatus hardly affected by a metal, a meth-
`od of making the antenna and the metal spaced apart
`from each other by a resin spacer, etc, or making a mag-
`netic material, such as ferrite, installed in contiguity with
`or in abutment with the antenna, thereby strengthening
`a magneticfield emitted from the antenna, has been con-
`trived. As such, as a technique of strengthening the mag-
`netic field of an antenna and giving durability against
`breakage to the antenna, a patent document (JP-A-
`2002—298095) suggests, for example, that a magnetic
`body having flexibility is installed in a bottom face or side
`face of the antenna.
`
`Further, combining a matching circuit with an
`[0003]
`antenna is also considered. Fig. 13 is an exploded per-
`spective view ofan antenna apparatus relatedto a related
`art. Fig. 14 is an enlarged view of a matching circuit re-
`lated to the related art. Fig. 15 is an equivalent circuit
`diagram of the antenna apparatus related to the related
`art. As shown in Figs. 13 and 14, a method of making a
`magnetic sheet 102 made of ferrite, etc. installed in con-
`tiguity with or in abutment with an antenna 103, thereby
`strengthening the magnetic field emitted from the anten—
`na 103 emits has been contrived in a conventional an—
`
`tenna apparatus. Moreover, in order to mount a chip ca-
`pacitor 110 used for the matching circuit 104, a through
`hole 109 is formed in the magnetic sheet 102. However,
`there is a case where the magnetic sheet 102 is largely
`hollowed out depending on the above configuration, and
`consequently the magnetic field cannot be sufficiently
`strengthened. Since the inductance value of an equiva-
`lent circuit shown in Fig. 15 becomes 1.6 pH when a coil
`offourturns is used and the magnetic sheet 1 02 is used,
`the resultant capacitance from C1 to C4 becomes about
`100 pF.
`In this case, in order to adjust a resonant fre—
`quency within a desired range, it is necessary to adjust
`the resultant capacitance of the capacitors with a prede-
`termined degree of accuracy. For example, when the
`range of the resonantfrequency is set to 13.56 : 50 kHz,
`about: 0.5 pF is required as the degree of accuracy of
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`it is
`In order to realize this,
`the resultant capacitance.
`necessary to use capacitors having a small capacitance
`tolerance. This causes a problem in that the operation of
`sorting out capacitors so that the degree of accuracy of
`the resultant capacitance of the capacitors may be set
`within a predetermined range (about : 0.5 pF), which
`may increase the cost of an antenna apparatus, is need-
`ed. This results in a situation where the productivity of
`antenna apparatuses cannot be improved.
`[0004]
`In orderto ensure communicative stability in the
`radio communication processorthat performs communi-
`cation with various radio communication media, and the
`radio communication media themselves, it is necessary
`to adjustthe resonantfrequency of an antenna apparatus
`to a desired frequency (for example, 13.56 MHz). Since
`the resonant frequency of the antenna apparatus may
`be aptto deviate depending on the shape of an antenna,
`the size of a magnetic material, orthe magnetic perme—
`ability ofthe magnetic material, it is necessaryto carefully
`select chip capacitors of a matching circuit to adjust the
`resonant frequency of the antenna apparatus precisely.
`However, forthe purpose of an improvement in the com-
`munication distance in the conventional antenna appa-
`ratus, the inductance value of an antenna is increased,
`orthethickness ofamagneticsheetis made large. There-
`fore, the capacitance of capacitors that adjust the reso-
`nant frequency of the antenna is made low. Therefore,
`high-precision capacitors having a small capacitance tol-
`erance should be mounted on the matching circuit. More—
`over, a process of sorting out the capacitors is needed.
`The process of sorting out the capacitors is very compli—
`cated. Mounting high-precision capacitors on an antenna
`apparatus, and necessitating the process of sorting out
`capacitors in the manufacture of an antenna apparatus
`poses a very big problem about cost reduction of the
`antenna apparatus.
`
`SUMMARY
`
`[0005] The present invention have been made in view
`ofthe aforementioned problems, and aim at providing an
`antenna apparatus that is low in cost, simple in structure,
`high in productivity, and capable of easily performing ad—
`justmentofa resonantfrequency, in an antennathatcom-
`municates using an electromagnetic induction method or
`a microwave method.
`
`[0006] According tothe present invention, an antenna
`apparatus includes: an antenna (3) that has a looped
`conductor, and a matching circuit (4) that includes a first
`capacitor (1 0) and a second capacitor (1 0) each of which
`has a pair of electrodes, and that sets a resonant fre-
`quency by the antenna (3) and the first and second ca—
`pacitors (10), wherein one electrode of the pair of elec—
`trodes of the first capacitor (1 O) is connected to one end
`of the looped conductor, and the other electrode of the
`pair of electrodes of the first capacitor (10) is connected
`to the looped conductor, and wherein one electrode of
`the pair of electrodes ofthe second capacitor (1 0) is con-
`
`

`

`3
`
`EP1 814191112
`
`4
`
`nected to the other end (5) one ofthe looped conductor,
`and the other electrode of the pair of electrodes of the
`second capacitor (10) is connected to the looped con-
`ductor.
`
`Sincethe above configuration makes it possible
`[0007]
`to form a resonantcircuitwith each of thefirst and second
`
`capacitors, the capacitance per capacitor can be set
`greatly compared with a case where terminal electrodes
`are connected to each other by a capacitor to form a
`resonant circuit. For example, even in a case where high
`precision is required for setting of a resonant frequency,
`the productivity of an antenna apparatus can be improved
`because the allowable range of the capacitance per ca-
`pacitor can be extended.
`[0008]
`Further, an embodiment related to a magnetic
`sheet of the antenna apparatus to be described below
`has a configuration in which a magnetic sheet includes
`a magnetic layer in which a magnetic material is contin—
`uously arranged and formed, and a sheet base (53) with
`flexibility, and the sheet base (53) holds the magnetic
`layer
`[0009] According to the above configuration, since the
`magnetic sheet has a magnetic layer in which a magnetic
`material is continuously arranged and formed, the mag-
`netic function ofthe magnetic sheet can be improved and
`therefore variations in magnetic properties can be sup-
`pressed. Further, since the sheet base holds the mag-
`netic layer, it is possible to provide a magnetic sheet that
`satisfies physical performances, such as flexibility.
`[0010]
`Further, an embodiment related to an antenna
`apparatus to be described below has a configuration in
`which an antenna apparatus includes a magnetic sheet
`(2) and an antenna (3) consisting of looped antenna el-
`ements arranged in proximity to the magnetic sheet (2),
`and the outside dimension of the magnetic sheet (2) is
`larger than the outside dimension of the antenna (3).
`[0011]
`Since the above configuration is a simple con-
`figuration in which the outside dimension ofthe magnetic
`sheet is made larger than the outside dimension of the
`antenna, fluctuation of a resonantfrequency can be sup—
`pressed. Accordingly, generation of defective art icles
`caused by deviation of a resonant frequency in a manu—
`facturing process can be reduced, and the productivity
`can be improved. Accordingly, the cost-reducing effect
`of an antenna apparatus can be expected. Also, since
`high precision is not required for alignment of the mag-
`netic sheet with the antenna, and an inexpensive meas-
`ure that only one side of the base may be used can be
`taken, the cost of an antenna apparatus can also be re-
`duced from this point of view.
`In addition, since the sta-
`bility of communication improves, the communication
`range of an antenna apparatus can be ensured, and a
`communication distance can be extended.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[cm 2}
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`F'g. 1 is a perspective view of an antenna apparatus
`according to Embodiment 1.
`Pg. 2 is a sectional view showing the structure of
`the antenna apparatus according to Embodiment 1.
`Pg. 3 is an enlarged view of a matching circuit ac—
`ording to Embodiment 1.
`'g. 4 is an equivalent circuit diagram according to
`mbodiment 1.
`
`‘rtrn-no
`
`‘nm'1'!!!)
`
`g. 5 is an enlarged view of the matching circuit
`ccording to Embodiment 1.
`g. 6 is an enlarged view of the matching circuit
`ccording to Embodiment 1.
`'g. 7 is an enlarged view of the matching circuit
`ccording to Embodiment 1.
`'g. 8 is an enlarged view of the matching circuit
`ccording to Embodiment 1.
`g. 9 is a sectional view of a magnetic sheet accord—
`ng to Embodiment 1.
`g. 10 is a sectional view of a matching circuit ac-
`ording to Embodiment 1.
`g. 11 is a sectional view of a matching circuit ac-
`ording to Embodiment 1.
`'g. 12 is a sectional view when a roller according
`to Embodiment 1 is used.
`
`
`
`‘I‘IO'Tlo11-'-r1m'nm
`
`F'g. 13 is an exploded perspective view of an anten-
`na apparatus in a related art.
`Pg. 14 is an enlarged view of a matching circuit in
`the related art.
`
`F'g. 15is an equivalentcircuitdiagram ofthe antenna
`apparatus in the related art.
`Pg. 16 shows comparison between the communica—
`tion performance of the antenna apparatus accord-
`ing to Embodiment 1 and the communication per-
`formance of a conventional antenna apparatus.
`Fig. 17 is an exploded perspective view illustrating
`an antenna apparatus according to Embodiment 2.
`Fig. 18 is a sectional view, taken along an A-A line,
`of a matching circuit portion shown in Fig. 17.
`Fig. 19 is an enlarged view showing an exemplary
`configuration of a matching circuit in a case where
`a looped antenna element that constitutes the an—
`tenna shown in Fig. 17 makes fourturns.
`Fig. 20 is an equivalentcircuit diagram of an antenna
`in a case where a looped antenna element that con-
`stitutes the antenna shown in Fig. 17 makes four
`turns.
`
`Fig. 21 shows the change characteristics of a reso-
`nant frequency when the outside dimension of the
`magnetic sheet shown in Fig. 17 is changed to a
`dimension around the outside dimension of the an-
`tenna.
`
`Fig. 22 is a sectional view showing the configuration
`of an antenna apparatus according to Embodiment
`3.
`
`Fig.23 showscomparisonbetweenthechangechar-
`acteristics of a resonant frequency when the outside
`dimension of the magnetic sheet is changed to a
`dimension around the outside dimension of an an-
`
`

`

`5
`
`EP1 814191112
`
`6
`
`tenna, in a case where the low magnetic-permeabil-
`ity layer is provided between the antenna and the
`magneticsheetshown in Fig. 22, and in acasewhere
`the antenna and the magnetic sheet are brought into
`close contact with each other.
`
`Fig. 24 is a sectional view showing the configuration
`of an antenna apparatus according to Embodiment
`4.
`
`Fig. 25 shows comparison between the change char-
`acteristics of a resonantfrequency when the outside
`dimension of the magnetic sheet is changed to a
`dimension around the outside dimension of an an-
`
`tenna, in a case where the low magnetic-permeabil-
`ity layeris provided between the magnetic sheet and
`the metal member shown in Fig. 24, and in a case
`where the magnetic sheet and the metal member
`are brought into close contact with each other.
`Fig. 26 is a sectional view showing the configuration
`of an antenna apparatus according to Embodiment
`5.
`
`Fig. 27 shows comparison between the change char-
`acteristics of a resonantfrequency when the outside
`dimension of the magnetic sheet is changed to a
`dimension around the outside dimension of an an-
`
`tenna, in a case where the low magnetic-permeabil-
`ity layers are provided between the antenna and the
`magneticsheetand betweenthe magnetic sheetand
`the metal member, respectively, shown in Fig. 24,
`and in a case where the antenna and the magnetic
`sheet are brought into close contact with each other
`and the magnetic sheet and the metal member are
`brought into close contact with each other, without
`providing the low magnetic-permeability layers ther-
`ebetween.
`
`Fig. 28 is an exploded perspective view of a magnetic
`sheet according to Embodiment 6.
`Fig. 29 is a sectional view of the magnetic sheet ac-
`cording to Embodiment 6.
`Fig. 30 is a sectional view of the magnetic sheet ac-
`cording to Embodiment 6.
`Fig. 31 is a sectional view of the magnetic sheet ac—
`cording to Embodiment 6.
`Fig. 32 is a sectional view of the magnetic sheet ac-
`cording to Embodiment 6.
`Fig. 33 is a sectional view of the magnetic sheet ac-
`cording to Embodiment 6.
`Fig. 34 is a view showing a manufacturing process
`of the magnetic sheet according to Embodiment 6.
`Fig. 35 is a sectional view of a magnetic sheet ac-
`cording to Embodiment 7.
`Fig. 36 is a view showing a manufacturing process
`of the magnetic sheet according to Embodiment 7.
`Fig. 37 is a sectional view of a magnetic sheet ac—
`cording to Embodiment 8.
`Fig. 38 is a view showing a manufacturing process
`of the magnetic sheet according to Embodiment 8.
`Fig. 39 is a sectional view of a magnetic sheet ac-
`cording to Embodiments 9 and 10.
`
`F'g. 40 is a view showing a manufacturing process
`of the magnetic sheet according to Embodiment 9.
`F'g. 41 is a view showing a manufacturing process
`of the magnetic sheet according to Embodiment 10.
`F'g. 42 is a sectional view of a magnetic sheet ac—
`cording to Embodiment 11.
`F'g. 43 is a view showing a manufacturing process
`of the magnetic sheet according to Embodiment 1 1.
`F'g. 44 is a view showing a manufacturing process
`of the magnetic sheet according to Embodiment 1 1.
`F'g. 45 is a sectional view of a magnetic sheet ac-
`cording to Embodiment 12.
`F'g. 46 is a view showing a manufacturing process
`of the magnetic sheet according to Embodiment 12.
`F'g. 47 is a view showing a manufacturing process
`of the magnetic sheet according to Embodiment 12.
`
`
`
`DETAILED DESCRIPTION
`
`[0013] Hereinafter, embodiments of the present inven-
`tion will be described with reference to the accompanying
`drawings.
`
`(Embodiment 1)
`
`First, the shape and structure of an antenna ap-
`[0014]
`paratus of the present invention and structure will be de-
`scribed.
`
`is
`[0015] As shown in Fig. 1, an antenna apparatus 1
`comprised of a magnetic sheet 2 mainly composed of a
`ferrite—based magnetic substance, protective members
`7 and 8 arranged so as to sandwich the magnetic sheet
`2 therebetween, an antenna 3, a matching circuit 4, ter-
`minal connecting parts 5, a base 6, and chip capacitors
`10a and 10b for matching. The antenna apparatus 1 may
`be contained in a radio communication medium, such as
`an IC card or an IC tag, and may be contained in a radio
`communication medium processor, such as a reader or
`a writer.
`
`First, each of the parts that constitute the an-
`[0016]
`tenna apparatus 1 will be described in detail.
`[0017] The magnetic sheet 2 has a form that consti-
`tutes an element ofthe antenna apparatus 1, and is made
`of a metallic material, such as ferrite, permalloy, sendust,
`orsilicon alloy sheet. It is preferableto use asoft magnetic
`ferrite as a material that constitutes the magnetic sheet
`2, and it is possible to dry-press and bake ferrite powder,
`thereby obtaining a high-density ferrite baked body. It is
`preferable that the density of the soft magnetic ferrite be
`3.5 g/cm3 or more. Moreover, it is preferable thatthe size
`of a magnetic substance composed of the soft magnetic
`ferrite be more than a crystal grain boundary. Further,
`the magnetic sheet 2 is formed in the shape of a sheet
`(or a plate, a film, or a layer) having a thickness of about
`0.05 mm to 3 mm.
`
`[0018] The soft magnetic ferrite may be composed of
`Ni-Zn03, ZnO, NiO, CuO, Fe203, ZnO, MnO, or CuO.
`Moreover, the soft magnetic ferrite may be a monolayer
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`EP1 814191112
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`8
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`made of any one of magnetic substances including an
`amorphous alloy, a permalloy, electromagnetic copper,
`ferrosilicon, an Fe-Al alloy, and a sendust alloy. Further,
`the soft magnetic ferrite may be a laminated body of fer-
`rite, an amorphous foil, a permalloy, electromagnetic
`copper, and a sendust. Further, the soft magnetic ferrite
`may be a laminated body obtained by combining various
`magnetic substances. Further, the soft magnetic ferrite
`may be obtained by coating a simple body of ferrite, an
`amorphous alloy, a permalloy, electromagnetic copper,
`ferrosilicon, an Fe-A1 alloy, or a sendust alloy, as shown
`in Fig. 9, or a laminated body as shown in Fig. 10, with
`at least one means of resin, an ultraviolet curable resin,
`avisible lightcurable resin, athermoplastic resin, ather-
`mosetting resin, a heat-resistant resin, a synthetic rub-
`ber, a double-sided tape, an adhesion layer, or a film.
`Further, a simple body and a laminated body of ferrite,
`an amorphous foil, a permalloy, electromagnetic copper,
`or a sendust may be an aggregate of magnetic blocks
`18, as shown in fig. 11. By arranging the blocks, a mag-
`netic substance can be efficiently formed with respect to
`the total thickness of the magnetic sheet 2. Moreover, by
`arranging all the magnetic blocks 18 so that their upper
`and lower sides may become almostthe same plane, the
`maximum volume of a magnetic substance can be uti-
`lized in a range of the thickness dimension, mechanical
`strength, other physical performances that are required
`for the magnetic sheet 2, and consequently a high mag-
`netic performance can be obtained.
`[0019] The magnetic sheet 2 is made up of a single
`magnetic layer, multiple magnetic layers, or magnetic
`blocks as shown in Figs. 9 to11. As shown in Fig. 9 to
`11,the magnetic sheet 2 is coated bythe protective mem-
`bers 7 and 8 (for example, resin, an ultraviolet curable
`resin, a visible light curable resin, a thermoplastic resin,
`a thermosetting resin, a heat-resistant resin, a synthetic
`rubber, a double-sidedtape, an adhesion layer, orafilm,
`etc.), so that the flexibility, durability, and surface resist-
`ance thereof can be improved. Further, it is possible to
`form a circuit by performing pattern printing, plating, etc.
`on the surfaces of the protective members 7 and 8.
`[0020]
`Further, since the magnetic sheet 2 coated by
`the protective members 7 and 8 has excellent flexibility,
`it can be easily blanked and formed by punching, etc.
`Accordingly, the magnetic sheet also has features that
`working of a complicated shape can also be performed
`at low cost, and in large amounts. By punching the mag-
`netic sheet 2, as shown in Figs. 2 and 3, the matching
`circuit 4 and the terminal connecting parts 5 can be pro-
`vided in an opening 7a of the magnetic sheet 2.
`[0021] The matching circuit 4 is configured by mount-
`ing a conductor of the looped antenna 3 and the chip
`capacitors 10a and 10b, which are formed in the base 6,
`as shown in Fig. 3. This allows the matching circuit 4 to
`beformed onthe antenna3.Althoughthe matching circuit
`4 is conventionally formed in a space separate from the
`antenna 3, the antenna apparatus 1 can be miniaturized
`byformingthe matching circuit4 on the antenna3.There-
`
`fore, since the opening 7a of the magnetic sheet 2 can
`be made small, the antenna apparatus 1 having excellent
`magnetic properties can be realized.
`[0022]
`Further, since a baked body of the magnetic
`sheet2 is ordinarily very brittle, the antenna 3, the match—
`ing circuit 4, and the terminal connecting parts 5 cannot
`be formed on the baked body. However, by coating the
`magnetic sheet 2 in advance with resin, an ultraviolet
`curable resin, avisible lightcurable resin, athermoplastic
`resin, athermosetting resin, a heat-resistant resin, a syn-
`thetic rubber, a double-sided tape, an adhesion layer, or
`a film, the antenna 3, the matching circuit 4, and the ter-
`minal connecting parts 5 can be formed on the magnetic
`sheet 2, so that the antenna apparatus 1 can be made
`small and thin. In addition, the magnetic sheet 2 may be
`formed in the shape of a substantially triangular prism, a
`substantially quadrangular prism, a substantial cylinder,
`a substantial sphere, etc.
`[0023] The magnetic sheet 2 of the present invention,
`as shown in Fig. 12, is fixed to a double-sided tape or a
`fine adhesive tape, and crushed by the roller 19, so that
`flexibility can be given to the magnetic sheet 2. Further,
`since crushing of the sheet by the roller 19 improves the
`workability of the magnetic sheet 2 and reduces a load
`at the time of working, cost reduction of products can
`also be realized. Moreover, as the magnetic sheet 2 is
`crushed by the roller 1 9, voids are formed in the magnetic
`sheet 2. Then, when resin is printed on the magnetic
`sheet 2, the resin permeates into the magnetic sheet 2,
`serving as a binder. As a result, flexibility can be further
`given to the magnetic sheet 2. Further, the magnetic
`sheet 2 is provided with slits, so that the magnetic sheet
`2 can be easily divided. Accordingly, the magnetic sheet
`2 having excellent flexibility and workability can be real-
`ized. The chip capacitors 10a correspond to first and sec-
`ond capacitors, and connect the terminal connecting
`parts 5 with the conductor of the antenna 3. The chip
`capacitor 10b corresponds to a third capacitor, and con-
`nects adjoining conductors of the antenna 3 with each
`other. In the following description, if the chip capacitors
`10a and 10b are not distinguishedfrom each other, these
`are simply called "chip capacitor 10."
`[0024] Next, the antenna 3 will be described.
`[0025] The antenna 3 is an antenna pattern and is
`formed from a looped conductor. As the structure of the
`looped conductor, the conductor has only to be formed
`in a surrounding shape, and their shape is not limited to
`a spiral shape. Further, the shape ofthe loop may be any
`of a circular shape, a substantially rectangular shape, or
`a polygonal shape. The loop structure of the antenna
`causes a sufficient magneticfield to be generated, there-
`by allowing communication between a radio communi—
`cation medium and a radio communication medium proc—
`essor by generation of induced powder and mutual in—
`ductance.
`
`Further, since the surface resistance of the
`[0026]
`magnetic sheet 2 is large, a circuit can be directly formed
`on the surface of or inside the magnetic sheet 2. Thus,
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`EP1 814191 A2
`
`10
`
`it is possible to directly form the antenna 3, the matching
`circuit 4, and the terminal connecting parts 5 in the mag-
`netic sheet 2.
`
`[0027] Moreover, a material for the antenna can be
`appropriately selected from a conductive metal wire, a
`metallic plate material, a metallic foil material, and a me—
`tallic cylinder material, such as gold, silver, copper, alu-
`minum, and nickel, and the antenna can be formed by a
`metal wire, a metallic foil, conductive paste, plating trans-
`fer, sputtering, vapor deposition, or screen printing.
`Thereby, it is conventionally necessary to form the an-
`tenna 3 and the magnetic sheet 2 separately, whereas
`the antenna 3, the matching circuit 4, orthe terminal con-
`necting parts 5 can beformed integrally with the magnetic
`sheet 2. Thus, a very thin antenna apparatus 1 can also
`be formed.
`
`Further, the base 6 provided with the antenna
`[0028]
`3 can be formed from polyimide, PET, a glass epoxy sub—
`strate, etc. By forming the base from polyimide, PET,
`etc., it is possible to form athin flexible antenna 3. Further,
`since the cost of films of polyimide, PET, etc. is low, a
`low-cost antenna apparatus 1 can be manufactured.
`[0029] Next, the matching circuit 4 will be described.
`[0030] The matching circuit 4 is connected to the an-
`tenna 3, whereby the resonant frequency of an antenna
`is adjusted to a desired frequency, generation of a sta-
`tionary wave caused by mismatching is suppressed.
`Thereby, it is possible to obtain an antenna apparatus 1
`with stable operation and little loss. As shown in Fig. 3,
`the chip capacitors 10a and 10b used as matching ele—
`ments are mounted so that they may serve as an inter—
`mediary between the conductors of the looped antenna
`3. Examples ofthe mounting position of the chip capacitor
`10 are shown in Figs. 3A and SB. The chip capacitors
`10a and 10b are arranged linearly in one straight line or
`in a zigzag pattern between the two terminal connecting
`parts 5. This can reduce the opening of the magnetic
`sheet 2, and can improve the magnetic properties of the
`antenna apparatus 1. As forthe arrangement of the chip
`capacitors 10a and 10b, they may be mounted in arbitrary
`places ofthe antenna 3. in that case, a terminal connect—
`ing part of the antenna 3 becomes a connecting part be—
`tween one terminal part of a chip capacitor and the an-
`tenna 3. Ifformation ofthe opening ofthe magnetic sheet
`2 is considered, it is preferable that the chip capacitors
`10a and 10b are arranged as shown in Figs. 3A and SB.
`A case where a loop makes four turns will be described
`as an example. An equivalent circuit of Fig. 3A takes a
`form as shown in Fig. 4A, and can adjust its capacitance
`to about 4 times the capacitance of a conventional ca-
`pacitor. The values of L1 to L4 are inductance values in
`every round of a loop, and become about 0.4 pH as val-
`ues calculated experimentally. When chip capacitors
`having the same capacitance value are mounted, the ca—
`pacitors C1 to C4 have a capacitance of about 400 pF,
`whereby adjustmentto a desired frequency can be made.
`An equivalent circuit of Fig. SB takes a form as shown in
`Fig. 4B, and can adjust its capacitance to about twice the
`
`capacitance of a conventional capacitor. The values of
`L5 and L6 are inductance valuesfortwo rounds of a loop,
`and become about 0.8 pH that is twice the values of L1
`to L4. When chip capacitors having the same capaci-
`tance value are mounted, the capacitors CS to C6 have
`a capacitance of about 200 pF, whereby adjustment to
`a desired frequency can be made. When both ends of a
`looped conductor are connected with each other by a
`capacitor as in the related art, the capacitance of the
`capacitor required to make adjustment to a desired fre-
`quency becomes about 100 pF, and almost coincides
`with the resultant capacitance of C1 to C4 or 05 to C6.
`In this case, if the resultant capacitance of a capacitor is
`adjusted with a predetermined degree of precision, for
`example, if the range of a resonant frequency is set to
`13.56 t 50 kHz, the degree of precision of the resultant
`capacitance is about : 2 pF (4 x :0.5 pF), which is
`enough.
`For this reason, by mounting capacitors having
`[0031]
`different capacitances as well as capacitors having the
`same capacitance, the four chip capacitors can adjust a
`resultantcapacitance and can adjust a resonantfrequen-
`cy. Therefore, by changing the combination of the capac-
`itances of C1 to C4 or CS to C6, fine adjustment of a
`frequency can be made, thereby improving productivity.
`Figs. 5 to 8 are enlarged views of the matching circuit in
`Embodiment 1. Referring to these figures, fine adjust-
`ment afterthe chip capacitors 10a and 10b are mounted
`can be made by adjusting a distributed constant circuit.
`Fig. 5 shows an example where a capacitor 12 is ar—
`ranged between a terminal connecting part 5 and an an—
`tenna adjacentthereto. An equivalent circuittakes a form
`where capacitors are connected in parallel with C1 and
`C4. As a result, adjustment of C1 and C4 can be made.
`Although Fig. 5 shows that the capacitors 12 are formed
`in both the terminal connecting parts 5, respectively, a
`configuration where a capacitor 12 is formed only in one
`terminal connecting part 5 may be adopted. Fig. 6 shows
`an example where patterns 13thatcan adjust inductance
`are arranged in the terminal connecting parts 5, and por-
`tions of the patterns 13 as distributed constant circuits
`can be trimmed so as to finely adjust an inductance value.
`An equivalent circuit takes such a form that L1 and L4
`can be adjusted. Although Fig. 6 shows thatthe patterns
`13 that can adjust inductance are formed in both the ter-
`minal connecting parts 5, a configuration where a pattern
`is formed only in one terminal connecting part may be
`adopted. Fig. 7 shows an example where one of the pat-
`terns 13 shown in Fig. 6 is replaced with a chip capacitor
`for frequency adjustment. An equivalent circuit has ca-
`pacitance L that can adjust L1, and has a configuration
`in which capacitors 15 forfine adjustment are connected
`in parallel with C4. Although three capacitors 15 forfine
`adjustment are mounted in the example shown in Fig. 7,
`one or plural capacitors may be mounted. The capacitors
`15 forfine adjustment can be finely adjusted by perform-
`ing trimming 14. Fig. 8 shows a configuration in which a
`stub 16 is connected to a terminal connecting part 5. An
`
`10
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`15
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`25
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`35
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`EP‘! 814191112
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`1‘?
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`equivalent circuit takes such a form that a capacitor is
`added to grounding from a terminal part. Bytrimming this
`stub 16, grounding capacitance can be adjusted, and res-
`onant frequency can be finely adjusted. Fine adjustment
`may be performed by combinations ofthe adjusting meth-
`ods shown in Figs. 5 to 8.
`[0032] Next, the terminal connecting parts 5 will be de-
`scribed.
`
`Since the surface resistance of the magnetic
`[0033]
`sheet 2 is large, the terminal connecting parts 5 can be
`directly formed in the surface of the magnetic sheet 2.
`The terminal connecting parts 5 may be formed on both
`sides of a loop, and may be formed so thatthey may face
`each other at the ends of a loop.
`[0034]
`Further, a material for the terminal connecting
`parts 5 can be appropriatel