US007334736B2
`
`a2) United States Patent
`US 7,334,736 B2
`(10) Patent No.:
`
` Uesaka (45) Date of Patent: Feb. 26, 2008
`
`
`(54) ANTENNA-COIL DESIGN APPARATUS AND
`DESIGN METHOD
`
`(75)
`
`Inventor: Kouichi Uesaka, Yokohama(JP)
`
`(73) Assignee: Hitachi, Ltd., Tokyo (JP)
`
`(*) Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 393 days.
`
`(21) Appl. No.: 10/890,320
`
`(22)
`
`Filed:
`
`Jul. 14, 2004
`
`......... 235/492
`5/2002 Kobayashiet al.
`2002/0053598 A1*
`7/2002 Arisawa oo... cece 235/492
`2002/0096568 Al*
`1/2003 Fujii eee 361/737
`2003/0016506 AL*
`2005/0272371 A1* 12/2005 Komatsuzaki et al.
`..... 455/41.2
`2006/0097874 Al*
`5/2006 Salesky et al.
`.......... 340/572.1
`2006/0164249 Al*
`7/2006 Lutz et al.
`......
`.. 340/572.7
`
`. 340/572.1
`2006/0220863 Al* 10/2006 Koyama.....
`2006/0283948 Al* 12/2006 Naito... eee 235/451
`
`FOREIGN PATENT DOCUMENTS
`
`JP
`JP
`JP
`JP
`WO
`
`07-022976
`7-22976
`10-079613
`11-272826
`02/095870
`
`1/1995
`1/1995
`3/1998
`10/1999
`11/2002
`
`(65)
`
`(30)
`
`Prior Publication Data
`
`* cited by examiner
`
`US 2005/0011961 Al
`
`Jan. 20, 2005
`
`Foreign Application Priority Data
`
`Primary Examiner—Steven S. Paik
`(74) Attorney, Agent, or Firm—Antonelli, Terry, Stout &
`Kraus, LLP.
`
`Jul. 14, 2003
`
`(JP)
`
`eeeeeeeeeeeseseseteeeeeees 2003-196179
`
`(51)
`
`Int. Cl.
`(2006.01)
`G06K 19/06
`(52) U.S. Ch wees 235/492; 235/451; 235/487;
`235/380
`
`(58) Field of Classification Search ................ 235/492,
`235/451, 487, 380; 343/855, 867
`See application file for complete search history.
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`4,430,729 A *
`6,593,841 B1*
`2002/0014859 Al*
`
`2/1984 Toyooka et al. oe 365/6
`
`7/2003 Mizoguchi et al.
`.
`2/2002 Boulesteix .............0.. 315/219
`
`(57)
`
`ABSTRACT
`
`A method of designing on a short-time basis an antenna
`whichsatisfies desired electrical characteristic values. There
`
`is provided the methodof designing the antenna coil used in
`a non-contact IC card or a RFID. Here, the antenna-coil
`design method includes the following steps: Inputting infor-
`mation about plural configurations of the antenna coil and
`materials thereof, analyzing resistance, inductance, and stray
`capacitance of the antenna coil relative to the number of
`turns of the antennacoil in the inputted plural configurations
`of the antenna coil, and, based on the analysis result,
`selecting one ofthe plural configurations of the antennacoil.
`
`10 Claims, 7 Drawing Sheets
`
`wy
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`Py
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`ly
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`rx
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`Wx
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`px
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`
`SQUARE-FIGURED TYPE
`
`Infineon Exhibit 1025
`Infineon Exhibit 1025
`Infineon v. AmaTech
`
`Infineon v. AmaTech
`
`

`

`U.S. Patent
`
`Feb. 26, 2008
`
`Sheet 1 of 7
`
`US 7,334,736 B2
`
`FIG. 1
`
`FIG. 2
`
`Wy
`
`Wx
`
`
`Lx
`
`SQUARE-FIGURED TYPE
`
`
`

`

`U.S. Patent
`
`Feb. 26, 2008
`
`Sheet 2 of 7
`
`US 7,334,736 B2
`
`NUMBER OF TURNS- RESISTANCE: R
`
`
`_
`—@— SQUARE CONFIGURATION. 1H <>] AO : ACTUALLY-MEASUREDVALUES
`
`q | —a SQUARECONFIGURATION. 2a|
`3 —~the— ELLIPTIC CONFIGURATION. 3|4
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`—@— ELLIPTIC CONFIGURATION. 4
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`UMBER OF TURNS [N]
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`
`

`

`U.S. Patent
`
`Feb. 26, 2008
`
`Sheet 3 of 7
`
`US 7,334,736 B2
`
`NUMBER OF TURNS — SELF-RESONANCE FREQUENCY: fe
`—+— SQUARE CONFIGURATION. 11] <>] A\ © :ACTUALLY-HEASURED VALUES
`
`—e— SQUARE CONFIGURATION.2
`—e— ELLIPTIC CONFIGURATION. 3
`
`
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`RESONANCEFREQUENCYfc[MHzI
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`DISTANCE d [mm]
`
`FIG. 4A
`
`FIG. 4B
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`

`

`U.S. Patent
`
`Feb. 26, 2008
`
`Sheet 4 of 7
`
`US 7,334,736 B2
`
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`Sheet 5 of 7
`
`US 7,334,736 B2
`
`U.S. Patent
`
`Feb. 26, 2008
`
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`

`U.S. Patent
`
`Feb. 26, 2008
`
`Sheet 6 of 7
`
`US 7,334,736 B2
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`

`U.S. Patent
`
`Feb. 26, 2008
`
`Sheet 7 of 7
`
`US 7,334,736 B2
`
`FIG. 8
`
`ANTENNA ELEMENTS MAKING
`NOTATION|SIGNIFICANT CONTRIBUTIONS TO
`CHARACTERISTICS
`ELECTRICAL CHARACTERISTICS
`
`
`
`RESISTANCE R
`
`INDUCTANGEL
`
`WIRING CROSS-SECTION
`CONFIGURATION, MATERIAL
`
`WIRING CONFIGURATION
`
`STRAY
`CAPACITANCE C
`
`Crw.
`
`rw,
`
`Ced
`Cc
`
`WIRING CONFIGURATION,
`MATERIAL
`
` ELECTRICAL
`
`
`
`
`
`
`
`COMMUN pe|WIRING CONFIGURATION
`
`
`
`
`
`COMMUNICATIONS
`
`COUPLING
`
`RESONANCE
`
`COMMUNICATIONS
`BANDWIDTH
`
`
`
`RLC
`iL,
`
`
`
`FIG. 9
`
`
`
`ELLIPTIC
`ELLIPTIC
`SQUARE
`SQUARE
`CONFIGURATION|CONFIGURATION 4|CONFIGURATION 2| CONFIGURATION 3| CONFIGURATION4
`
`
`OUTER:
`
`L(mm)
`LINEWIDTH
`
`CONFIGURATION|80.0%50.0 57.0 46.0
`
`
`
`
`
`
`
`LINE THICKNESS
`
`36.0
`
`

`

`US 7,334,736 B2
`
`1
`ANTENNA-COIL DESIGN APPARATUS AND
`DESIGN METHOD
`
`CROSS-REFERENCE TO RELATED
`APPLICATION
`
`The disclosure of Japanese Patent Application No.
`JP2003-196179 filed on Jul. 14, 2003 including the speci-
`fication, drawings and abstract is incorporated herein by
`reference in its entirety.
`
`10
`
`BACKGROUND OF THE INVENTION
`
`The present invention relates to a design method and
`design apparatus for designing an antenna coil used in a
`non-contact IC card or a RFID.
`
`15
`
`In the non-contact IC card, the RFID,or the like (which,
`hereinafter, will be referred to as “IC card or the like’), an
`electromagnetic field (magnetic field) radiated by a reader/
`writer unit (hereinafter, referred to as “R/W”)is received by
`an antenna formed on the IC card or the like. Then, the
`electromagnetic field (magnetic field) received is converted
`into electric power so as to drive the IC. Also, communica-
`tions from the R/W to the IC cardor the like are performed
`using signal components contained in modulation orthe like
`of the electromagnetic field (more essentially magnetic field
`in this case) radiated by the R/W. Moreover, in communi-
`cations from the IC card or the like to the R/W, the signal
`transmissions to the R/W are performed by load modulation
`or the like.
`Atthis time, the electric power which is receivable by the
`IC card or the like is determined based on the self induc-
`tances, mutual inductance, and coupling coefficient of the
`antenna formed on the IC card or the like and an antenna
`formed on the R/W. Furthermore,
`it is required that the
`electric power which is supplyable to the R/W antenna be
`suppressed within a range in whichthe electric field radiated
`from the R/W antennasatisfies the regulations by the Radio
`Law orthe like.
`
`This requirement determines an upper-limit ofthe electric
`power supplyable to the R/W antenna.
`In addition,
`the
`electric power to be received is determined from a trans-
`mission efficiency ofthe electric power to the IC card or the
`like. As a result, the communications area is determined.
`Accordingly, it is required that electrical elements of the
`coil antenna to be formed on the IC cardorthelike, e.g., the
`antenna’s
`inductance,
`resistance,
`and capacitance, be
`designed while satisfying various conditions by considering
`the coil antennaitself and its relationship with the R/W.
`Meanwhile, as antenna design technologies and analysis
`technologies for the antenna design, there exist such meth-
`ods as the moment methodandfinite-element method. These
`techniques, however, are the following methods: Configu-
`ration data on an antenna is inputted first, and then respec-
`tive types of set conditions(i.e., boundary conditions and so
`on) are set for this configuration, and after that, the analysis
`is performed. A conventional antenna design method has
`been disclosed in, e.g., JP-A-7-22976. This conventional
`method is as follows: With respect to a frequency range
`necessary for the antenna design, frequency characteristics
`of respective elements of an impedance matrix in the
`moment method are stored into a memory in advance. This
`in-advance storage allows a significant reduction in the
`computation time necessary for the antenna design.
`
`SUMMARY OF THE INVENTION
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`In the conventional techniques, the antenna configuration
`is determinedat first, and after that, the antenna’s electrical
`characteristic values for the time or frequency are computed.
`
`2
`if, after the determination of the antenna
`Consequently,
`configuration, the computed antenna’s electrical character-
`istic values for the time or frequency have failed to satisfy
`predefined values, it becomes required to determine a new
`antenna configuration once again. Namely, there has existed
`a problem ofbeing incapableofeffectively reducing the time
`for the antenna design.
`The present invention has been devised in order to solve
`the above-described problem. Namely, an object of the
`present invention is to design, on a short-time basis, an
`antenna which satisfies preset electrical characteristic values
`without the necessity for redesigning configuration of the
`antenna manytimes in accordancewith the analysis result of
`the electrical characteristics or the like.
`
`In the present invention, a frequency to be used for the IC
`card or the like is determinedatfirst. After that, the anten-
`na’s electrical characteristic values for configuration of the
`antenna on the IC card or the like are computed. Also, when
`computing and displaying the electrical characteristic values
`for a predetermined frequency, e.g., relationship between the
`antenna’s numberof turns andresistance value, the display
`is performed in such a manner that a comparison is made
`among the results computed for each antenna configuration
`prepared in advance.
`Other objects, features and advantages of the invention
`will become apparent from the following description of the
`embodiments of the invention taken in conjunction with the
`accompanying drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG.1 illustrates an equivalentcircuit of a non-contact IC
`card and a R/W;
`FIG. 2 illustrates an example of input parameters of
`square-figured and ellipse-figured spiral antennas;
`FIGS. 3A to 3C illustrate an example of analysis result of
`the antenna according to the present application;
`FIGS. 4A to 4C illustrate an example of analysis result of
`the antenna according to the present application;
`FIG. 5 illustrates an example of analysis result of the
`antenna according to the present application;
`FIG. 6 illustrates an example of analysis result of the
`antenna according to the present application;
`FIG. 7 illustrates an example of input parameters for
`square-figured and ellipse-figured spiral antennas;
`FIG. 8 is a table for illustrating electrical characteristics of
`the IC-card antenna and those of the R/W antenna; and
`FIG.9 is a table for summarizing antenna configurations
`in the respective embodiments of the IC card.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`Referring to the drawings, the explanation will be given
`below concerning embodiments of the present invention.
`Incidentally, it is needless to say that, although the expla-
`nation will be given below regarding a non-contact IC card,
`the explanation is also applicable to the design and analysis
`of such antennas as a RFID.
`
`First, electrical elements will be investigated which
`become important between the non-contact IC card or the
`like and a reader/writer unit (:R/W)in the case of designing
`the non-contact IC card or the like.
`
`FIG. 1 illustrates an equivalent circuit of the R/W and the
`IC card. In this equivalent circuit, the R/W includes circuit
`impedance R,, resonance capacitance Co, inductanceL,,,, of
`a R/Wantenna, resistance R,.,,, and capacitance C,,,. Here,
`
`

`

`US 7,334,736 B2
`
`3
`resonance frequency of the R/W is determined as being
`equalto carrier-wave frequency, or frequency which exceeds
`the carrier-wave frequency. Next,
`the IC card includes
`inductance L,, of a card antenna,resistance R,,, capacitance
`Coa capacitance C,, which an IC to be mounted thereon
`exhibits, and resistance R,. which is equivalentto the electric
`power consumed.
`Here, resonance frequency of the IC card is also deter-
`mined as being equal to the carrier-wave frequency, or the
`frequency which exceeds the carrier-wave frequency. More-
`over, coupling coefficient k, which means coupling between
`the R/W and the IC card,
`is set simultaneously, thereby
`formingthe entire equivalent circuit. In the above-described
`equivalent circuit, power supply V,
`is determined from
`R/W-antennaelectric power which satisfies the regulations
`by the Radio Law orthelike.
`From this situation, it becomes required to determineL,,,,,
`Crs Cos Lea Cog and C,. which maximize electric-power
`transmissionefficiency, and the coupling coefficient k which
`is to be determined by position relationship between the
`R/Wandthe IC card. Also, from the objective of performing
`communications, it becomes required to determine commu-
`nications bandwidth so that sub carrier wave can be trans-
`
`mitted enough. This communications bandwidth is deter-
`ico
`mined by R,,,, Liss Cows Cos Rear Leas Coas Cres
`and R;., and
`the coupling coefficient k.
`Here, it is true that the electrical characteristic values of
`the antennas depend on the used frequency to a certain
`extent. Basically, however,
`the characteristic values are
`determined by configuration or material of the antennas.
`Concretely, the details are just what are explained in FIG.8.
`Subsequently, the explanation will be given below con-
`cerning the electrical characteristics explained above, and an
`antenna design method using antenna elements(i.e., wiring
`configuration, material, and the like) which make significant
`contributions to the electrical characteristics. As described
`earlier, the conventional antenna design methodis as fol-
`lows: The antenna configuration is determined and inputted
`at
`first, and then the antenna elements, which become
`foundation of the respective types of electrical characteristic
`parameters, are determined and inputted. Next, the electro-
`magnetic-field analysis is performed, and then the analysis
`result is displayed. Furthermore, if the analysis result has
`failed to satisfy the predetermined conditions, the antenna
`configuration is considered and inputted once again.
`On the other hand, in the application according to the
`present invention, parameters of plural different antenna-coil
`configurations prepared in advance are inputted. Here, the
`plural antenna configurations are selected, and the param-
`eters having a predetermined range are inputted. FIG. 2
`illustrates an example of the analysis method andthe input
`parameters of square-figured and ellipse-figured spiral
`antennas. In the case of the square-figured spiral antenna, the
`configuration is set for antenna parameters, 1.e., outer-
`configuration size L,, L,, line width w,, w,, pitch p,, p,, line
`thickness t, and cornerradiusr,, r,. Similarly, in the case of
`the ellipse-figured spiral antenna, the configuration is set for
`antenna parameters,i.e., outer-configuration size L,, L,, line
`width w,, w,, pitch p,, p,,
`line thickness t, and radius
`r,(=(L,-w,)/2), ,(=(L,-w,)/2). In the present embodiment,
`the following parameters have been inputted as an example:
`In this case, by selecting the number N of turns of an
`antenna as a parameter,
`it
`is possible to determine the
`respective types of electrical characteristic values (e.g.,
`resistance R,
`inductance L, and capacitance C) of the
`antenna.
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`FIGS. 3A to 3C, with respect to the above-described input
`parameter, illustrate relationship between the turn-number
`of the antenna and the resistance R thereof (FIG. 3A),
`relationship between the turn-numberof the antenna and the
`inductance L thereof (FIG. 3B), and relationship between the
`turn-number of the antenna and the stray capacitance C
`thereof (FIG. 3C). FIGS. 3A to 3C indicate the following
`results: Concerning the resistance R, since the turn-number
`of the spiral configuration is defined from the outer circum-
`ference, an increase in the line-path length becomes smaller
`as the turn-numberincreases. This results in saturation of an
`
`increase in the resistance R in accompaniment with the
`increase in the turn-number. Also, regarding the inductance
`L,
`as
`the turn-number
`increases,
`the self inductance
`increases in responseto the line-path length, and also mutual
`inductance betweentheline paths increases. This allows the
`inductance L to exhibit an S-character-like characteristic.
`
`Also, the stray capacitance C (i.e., parasite capacitance)
`increases in accompaniment with the increase in the turm-
`number.
`
`Incidentally, the antenna outer-configuration (i.e., length
`of the outermost circumference) and the antenna’s pitch
`have been inputted. This makes it possible to determine
`upper-limit of the turn-numberof the antenna.
`Here, the electrical characteristics of the antenna will be
`investigated. The increase in the resistance R meansthat a
`loss in the antenna increases, which is not an advisable
`policy from the standpoint of the electric-power transmis-
`sion. The increase in the inductance L, however, is desirable,
`because the increase in the inductanceincreasesthe electric-
`
`power transmission efficiency. Also, as regards the stray
`capacitance(i.e., parasite capacitance), considering that the
`antennas are made resonant with each other at a used
`frequency(i.e., carrier-wave frequency), the increase in the
`stray capacitance (1.e., parasite capacitance) is desirable. The
`reason for this is as follows: For the purpose of earning
`capacitance needed at the frequency with respect to the
`inductance, as this capacitance gets larger, the capacitance
`C,, to be mounted within the IC gets smaller. This meansthat
`the resultant chip area becomes smaller, which is desirable.
`If, however, the resonance frequency grows lower than the
`carrier-wave frequency, it becomes impossible to optimize
`the electric-powertransmission efficiency. This brings about
`a disadvantage, although the capacitance within the IC is
`unnecessary. This whole situation indicates that, depending
`ona usedprotocolor the like, there exist optimum values for
`the resistance R, inductance L, and capacitance C of the
`antenna.
`
`In order to determine these optimum values, the further
`investigation needs to be performed concerning self-reso-
`nance frequency f, and quality Q of the inductance L from
`the resistance R, inductance L, and capacitance C of the
`antenna. Here, Q denotes “Quality Factor’, which means
`quality of the configuration components L, C, and thelike,
`i.e., essential attribute of L which is specific to L, essential
`attribute of C which is specific to C, and the like.
`FIGS. 4A to 4C illustrate the results which, using the
`resistance R, inductance L, and capacitance C of the antenna
`computed above, are acquired by computing relationship
`between the turn-number of the antenna andthe self-reso-
`nance frequency f, thereof (FIG. 4A), and relationship
`between the turn-number of the antenna and the quality as
`the inductance thereof or Q containing the IC (FIG. 4B).
`Incidentally, in the simulation of the present embodiment,
`the bandwidth BWof the sub carrier wave is equal to (847.5
`
`

`

`US 7,334,736 B2
`
`5
`kHzx2) in the case where the carrier-wave frequency and
`transmission rate are set as 13.56 MHz and 211.875 k
`
`respectively.
`On accountof this, the self-resonance frequency f, needs
`to be higher than 13.56 MHz. On account of this,
`the
`turn-numberneedsto be smaller than 11 to 15. Also, the chip
`area makes it possible to determine upper-limit of the
`capacitance C,, which is mountable within the IC. If the
`upper-limit falls within, e.g., 50 pF, judging from C,.=1/
`(Qxf.)2xL.)-C,2, the turn-numberneeds to be larger than
`5 here. Also, since the necessary communications band
`satisfies Q<13.56 MHz/(847.5 kHzx2)=8, the turn-number
`needs to be smaller than 7 to 10.
`Summarizing the above-described conditions indicates
`that the optimum turn-numberrange tums out to be 5 to 7.
`Moreover, FIG. 4C illustrates the result acquired by
`computing relationship between the distance and the cou-
`pling coefficient between the non-contact IC card or the like
`and the reader/writer unit (:R/W). This coupling coeflicient
`exerts tremendous influences on the electric-power trans-
`mission efficiency. Namely, the larger this value gets, the
`better the efficiency becomes.
`In the present embodiment, from the above-described
`relationship between the antenna turn-numberandtheself-
`resonance frequency f,, (FIG. 4A), and relationship between
`the antenna turn-number and the Q value (FIG. 4B), it has
`been recognized that the antenna turn-number smaller than
`7 is desirable. Consequently, the turn-number 6 has been
`selected as target turn-number by taking the margin into
`consideration.
`
`The distance characteristic of the coupling coefficient k is
`determined regarding a case of two square-figured spiral
`antennas having different pitches, and a case of a square-
`figured spiral antenna andan ellipse-figured spiral antenna.
`Here, in the case of the two square-figured spiral anten-
`nas, it is true that the value of the coupling coeflicient is
`large. Causing the IC to operate at the maximum value,
`however, makes the operation impossible at a location where
`the coupling coefficient is small. On the other hand, the
`operation is made possible at the location where the cou-
`pling coefficient is small. This operation causes an induced
`voltage to exceed the withstand voltage of the IC at a
`location where the coupling coefficientis large, thus becom-
`ing the cause of a failure. On account ofthis, in the case of
`wishing to enlarge the communications area, the combina-
`tion of the square-figured spiral antenna and the ellipse-
`figured spiral antennais desirable where a variation Ak in the
`coupling coefficient is small.
`Finally, FIG. 5 illustrates the result acquired by analyzing
`the electromagnetic field (electric field or magnetic field)
`radiated from the antenna. Here,
`the value is illustrated
`which can be considered to be converted into the electric-
`
`field strength from a voltage value in the case where the
`electric-field strength or magnetic-field strength with respect
`to the distance from the spiral antenna is received by a loop
`antenna stipulated by the regulations.
`The upper-limit of the electric power which is supplyable
`
`to the R/W antenna becomes a value which satisfies the
`
`
`
`Radio-Law regulation value(i.e., 54 dBOV/m@3 m). In the
`present application, further, the electric power acquired by
`taking into consideration the margin 6 dB to the Radio-Law
`regulation value is supplied to the R/W.
`FIG. 5 simultaneously illustrates computation result of the
`voltage (i.e., voltage to be received) induced at an IC-end
`portion on the IC-card side when this electric power is
`supplied to the R/W antenna. As a result of this,
`in the
`system of this antenna andthe IC,the voltage attainsto, e.g.,
`
`55
`
`60
`
`65
`
`6
`the maximum voltage 5.35 V when the distance between the
`R/W andthe IC card is equal to 2 mm. This showsthat the
`IC withstand voltage is satisfied. Also,
`the IC-operating
`voltage 3V is satisfied up to the inter-R/W-card distance
`whichis close to 20 mm.Accordingly, this distance turns out
`to be the limit of the communications distance.
`Ashaving been explained so far, by employing the design
`method and design apparatus of the present invention for
`designing the antenna coil used in the non-contact IC card or
`the like, it becomes possible to input such input parameters
`as the antenna configurations which have a predetermined
`range. This characteristic, accordingly, allows the resistance
`R, inductance L, and capacitance C of the antenna to be
`computed without specifying the antenna configurations as
`a single antenna configuration from the beginning. This
`computation, further, allows the determination ofthe self-
`resonance frequency f, and the Q value of the antenna,
`which, namely, are computed by using the computedresis-
`tance R, inductance L, and capacitance C.
`Moreover, the resonance frequency of each antenna can
`be determined from the R/W and the capacitance C,,
`mounted within the IC, and the Q value can be determined
`from the load resistance. Namely, making a comparison
`among these computation results makesit possible to design
`(i.e., specify) the optimum antenna configuration in a final
`manner.
`
`Incidentally, when designing the optimum antenna con-
`figuration, it is possible to take into consideration proximate/
`remote electric-field/magnetic-field analysis results, and
`also to set the antenna-supplied electric power. Furthermore,
`the analysis based on the equivalent circuit also allows the
`analysis of the electric-power transmission and communi-
`cations.
`
`In the above-described description, the explanation has
`been given concerning the optimum antenna-configuration
`design. As illustrated in FIG. 6, however, the present analy-
`sis method and apparatus allow presentation of a result
`which is computed as to how the magnetic-field distribution
`will change when the non-contact
`IC card having the
`antenna configuration determined above has passed over the
`reader/writer unit.
`
`Incidentally, in the above-described description, the outer-
`configuration, line width, pitch, and line thickness have been
`presented as the antenna-configuration information to be
`inputted. As illustrated in FIG. 7, however, it is possible to
`input a variety of antenna configurations in such a manner
`that the antenna configurations are made to have predeter-
`mined widths.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`It becomespossible to design, on a short-time basis, the
`antenna whichsatisfies desired electrical characteristic val-
`
`ues without the necessity for redesigning the antenna con-
`figuration many times in accordance with the analysis result
`of the electrical characteristics or the like.
`
`It should be further understood by those skilled in the art
`that although the foregoing description has been made on
`embodiments of the invention, the invention is not limited
`thereto and various changes and modifications may be made
`without departing from the spirit of the invention and the
`scope of the appended claims.
`The invention claimedis:
`
`1. A method of designing a coil, comprising:
`inputting information aboutplural configurations of a coil
`and materials thereof;
`calculating resistance, inductance, and stray capacitance
`of said coil relative to numberof turns of said coil on
`
`said plural configurations of said coil inputted by using
`
`

`

`US 7,334,736 B2
`
`7
`parameters including at least ones of outside dimen-
`sions, line width, pitch, line thickness and corner radius
`of said coil;
`selecting one of said plural configurations of said coil on
`a basis of a result of said calculating;
`wherein the inputting, calculating and selecting opera-
`tions are conducted prior to a manufacture ofthe coil.
`2. The coil design method according to claim 1, compris-
`ing:
`inductance, and stray
`using said calculated resistance,
`capacitance of said coil
`to calculate self-resonance
`frequency of said coil relative to said numberof turns
`of said coil.
`3. The coil design method according to claim 1, wherein
`said coil is an antenna coil for use in a non-contact IC card
`or an RFID.
`
`4. The coil design method according to claim 3, compris-
`ing:
`inductance, and stray
`using said calculated resistance,
`capacitance of said antenna coil to analyze a coupling
`coefficient relative to distance,
`said coupling coefficient being established between said
`antenna coil used in said non-contact IC card or said
`RFID andan antennacoil of a reader/writer,
`said distance being measured between said antenna coil
`used in said non-contact IC card or said RFID and said
`antenna coil of said reader/writer.
`5. The coil design method according to claim 4, compris-
`ing:
`inductance, and stray
`using said calculated resistance,
`capacitance of said antenna coil to analyze a commu-
`nication band of said antenna coil.
`6. A method of pre-manufacture designing of a coil,
`comprising:
`inputting information aboutplural configurationsof a coil
`and materials thereof;
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`8
`calculating resistance, inductance, and stray capacitance
`of said coil relative to numberof turns of said coil on
`
`said plural configurations of said coil inputted by using
`parameters including at least ones of outside dimen-
`sions, line width, pitch, line thickness and corner radius
`of said coil;
`selecting one of said plural configurations of said coil;
`wherein the inputting and calculating operations are con-
`ducted prior to a manufacture of the coil.
`7. The coil design method according to claim 6, compris-
`ing:
`inductance, and stray
`using said calculated resistance,
`capacitance of said coil
`to, calculate self-resonance
`frequency of said coil relative to said numberof turns
`of said coil.
`8. The coil design method according to claim 6, wherein
`said coil is an antenna coil for use in a non-contact IC card
`or an RFID.
`
`9. The coil design method according to claim 8, compris-
`ing:
`inductance, and stray
`using said calculated resistance,
`capacitance of said antenna coil to analyze a coupling
`coefficient relative to distance,
`said coupling coefficient being established between said
`antenna coil used in said non-contact IC card or said
`RFID andan antenna coil of a reader/writer,
`said distance being measured between said antenna coil
`used in said non-contact IC card or said RFID andsaid
`antenna coil of said reader/writer.
`10. The coil design method according to claim 9, com-
`prising:
`inductance, and stray
`using said calculated resistance,
`capacitance of said antenna coil to analyze a commu-
`nication band of said antenna coil.
`
`