1111111111111111 IIIIII IIIII 11111 1111111111 11111 111111111111111 11111 111111111111111 11111111
`US 20070069961Al
`
`c19) United States
`c12) Patent Application Publication
`Akiho et al.
`
`c10) Pub. No.: US 2007 /0069961 Al
`Mar. 29, 2007
`(43) Pub. Date:
`
`(54) MAGNETIC CORE MEMBER FOR
`ANTENNA MODULE, ANTENNA MODULE
`AND PORTABLE INFORMATION
`TERMINAL EQUIPPED WITH ANTENNA
`MODULE
`
`(75)
`
`Inventors: Hiraku Akiho, Miyagi (JP); Hiroyuki
`Ryoson, Kanagawa (JP); Kazuo Goto,
`Kanagawa (JP)
`
`Correspondence Address:
`SONNENSCHEIN NATH & ROSENTHAL LLP
`P.O. BOX 061080
`WACKER DRIVE STATION, SEARS TOWER
`CHICAGO, IL 60606-1080 (US)
`
`(73) Assignee: SONY CORPORATION, Tokyo (JP)
`
`(21) Appl. No.:
`
`10/595,279
`
`(22) PCT Filed:
`
`Jul. 19, 2005
`
`(86) PCT No.:
`
`PCT/JP05/13231
`
`§ 371(c)(l),
`(2), ( 4) Date: Apr. 4, 2006
`
`(30)
`
`Foreign Application Priority Data
`
`Aug. 4, 2004
`
`(JP) ...................................... 2004-228559
`
`Publication Classification
`
`(51)
`
`Int. Cl.
`HOJQ 1124
`(2006.01)
`(52) U.S. Cl. .............................................................. 343/702
`ABSTRACT
`(57)
`There are provided a magnetic core member for an antenna
`module capable of improving a communication distance
`without thickening the module, an antenna module, and a
`portable information terminal equipped with the antenna
`module. A magnetic core member 18 for an antenna module
`10 of the present invention has a ring groove 18c as a recess
`portion formed on the surface on the side stacking an
`antenna coil 15 in an area facing a loop portion of the
`antenna coil 15. An eddy current generated in the magnetic
`core member 18 in a high frequency magnetic field is
`concentrated on the surface of the magnetic core member 18
`on the side stacking the antenna coil 15 in the area facing the
`loop portion of the antenna coil 15. According to the present
`invention, a ring groove 18c is provided in the area to reduce
`an amount of eddy currents to be generated and improve the
`communication distance characteristics of the antenna mod(cid:173)
`ule.
`
`16a
`
`15
`
`10
`
`I
`
`14
`
`18
`18c
`
`19
`
`18a
`
`Ex.1016
`APPLE INC. / Page 1 of 16
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`

`

`Patent Application Publication Mar. 29, 2007 Sheet 1 of 8
`
`US 2007 /0069961 Al
`
`FIG . 1
`
`16a
`
`15
`
`16
`
`10
`
`/
`
`17
`
`19
`
`Ex.1016
`APPLE INC. / Page 2 of 16
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`

`

`Patent Application Publication Mar. 29, 2007 Sheet 2 of 8
`
`US 2007 /0069961 Al
`
`FIG.2
`
`16
`
`FIG.3
`
`12
`
`2a
`
`2
`
`3
`
`Ex.1016
`APPLE INC. / Page 3 of 16
`
`

`

`Patent Application Publication Mar. 29, 2007 Sheet 3 of 8
`
`US 2007 /0069961 Al
`
`FIG.4
`
`1
`~
`
`2
`
`16b
`
`15
`
`5(4)
`
`2a
`
`16
`
`10 14
`
`Ex.1016
`APPLE INC. / Page 4 of 16
`
`

`

`Patent Application Publication Mar. 29, 2007 Sheet 4 of 8
`
`US 2007 /0069961 Al
`
`FIG.5
`
`µ'
`)
`
`\_
`
`..............
`' r'-... ......
`
`,,,,,. /
`
`-__.,,. ,,.
`
`#
`
`10
`
`FREQUENCY (MHz)
`
`,--
`\
`
`I
`
`I
`
`,,
`
`µ
`
`r--...
`
`'r--
`
`...
`
`100
`
`---
`
`-
`
`60
`
`E 40
`---I
`.........
`::::t , 20
`...
`
`-
`-
`-
`
`- ----
`
`0
`l
`
`Ex.1016
`APPLE INC. / Page 5 of 16
`
`

`

`Patent Application Publication Mar. 29, 2007 Sheet 5 of 8
`
`US 2007 /0069961 Al
`
`FIG (cid:127) 6
`18a
`
`18
`
`18b
`
`1 Bd
`
`18b
`
`FIG (cid:127) 7
`
`18a
`
`1 Bd
`
`Ex.1016
`APPLE INC. / Page 6 of 16
`
`

`

`Patent Application Publication Mar. 29, 2007 Sheet 6 of 8
`
`US 2007 /0069961 Al
`
`FIG.SA
`
`(OUTER PERIPHERAL
`SIDE)
`l 5
`
`200µm
`l 20µm
`60 µm
`
`(INNER PERIPHERAL
`SIDE)
`
`18c
`
`l00µm
`
`/ 18
`
`FIG.8B
`
`(OUTER PERIPHERAL
`SIDE)
`
`l 5
`
`(INNER PERIPHERAL
`SIDE)
`
`==
`
`=
`
`300µm
`220µm
`l OOµm
`
`/ 18"
`
`Ex.1016
`APPLE INC. / Page 7 of 16
`
`

`

`Patent Application Publication Mar. 29, 2007 Sheet 7 of 8
`
`US 2007 /0069961 Al
`
`FIG.9
`
`r--
`
`-0
`>< -Ci , -a
`-0:::: ,
`-I
`-...J
`
`::::i.
`
`6
`
`5
`
`4
`
`3
`
`2
`
`0
`
`R
`
`L
`
`0.1
`
`0.2
`
`0.4
`
`0.6
`
`GROOVE DEPTH (mm)
`
`Ex.1016
`APPLE INC. / Page 8 of 16
`
`

`

`Patent Application Publication Mar. 29, 2007 Sheet 8 of 8
`
`US 2007 /0069961 Al
`
`-0 .....
`, -a
`0:::: , -I
`
`><
`' - ' Cf
`
`' - '
`
`::::t
`' - '
`.....J
`
`,-.._
`
`E
`E 125
`LJ.J u
`~ 120
`1-
`V'l
`0
`z
`11 5
`0
`~ u 110
`z
`::::::>
`~
`~ l 05
`0 u
`
`FIG.10
`
`L
`
`6
`
`5
`
`4
`
`3
`
`DIMPLE
`
`2
`RING
`PRODUCT
`GROOVE
`NOT WORKED
`(MAGNETIC
`(MAGNETIC
`(MAGNETIC
`CORE MEMBER CORE MEMBER CORE MEMBER
`18")
`18')
`18)
`
`FIG.11
`
`DIMPLE
`
`RING
`PRODUCT
`GROOVE
`NOT WORKED
`(MAGNETIC
`(MAGNETIC
`(MAGNETIC
`CORE MEMBER CORE MEMBER CORE MEMBER
`18")
`18')
`18)
`
`Ex.1016
`APPLE INC. / Page 9 of 16
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`

`

`US 2007/0069961 Al
`
`Mar. 29, 2007
`
`1
`
`MAGNETIC CORE MEMBER FOR ANTENNA
`MODULE, ANTENNA MODULE AND PORTABLE
`INFORMATION TERMINAL EQUIPPED WITH
`ANTENNA MODULE
`
`TECHNICAL FIELD
`
`[0001] The present invention relates to a magnetic core
`member for an antenna module suitable for use with a
`non-contact IC tag utilizing radio frequency identification
`(RFID) techniques, an antenna module and a portable infor(cid:173)
`mation terminal equipped with the antenna module.
`
`BACKGROUND ART
`[0002] Conventionally, a device having an IC chip with
`recorded information and a resonance capacitor electrically
`connected to an antenna coil is known as a non-contact IC
`card and an identification tag utilizing RFID techniques
`(hereinafter, these are collectively called a "non-contact IC
`tag").
`
`[0003] Anon-contact IC tag is activated upon transmission
`of radio waves having a predetermined frequency (e.g.,
`13.56 MHz) from a transmission/reception antenna of a
`reader/writer, with an antenna coil of the non-contact IC tag.
`And, individual identification or authentication management
`becomes possible upon reading information recorded in an
`IC chip in response to a read command through data
`communications via radio waves, or upon resonance to radio
`waves of the specific frequency. In addition to this, most of
`non-contact IC tags are structured so that read information
`can be renewed or history information and the like can be
`written.
`
`[0004] A main conventional antenna module used for a
`non-contact IC tag has the structure that a magnetic core
`member is inserted into an antenna coil wound in a spiral
`shape along a flat plane, generally in parallel to the flat plane
`of the antenna coil (refer to Japanese Patent Application
`Publication No. 2000-48152). The magnetic core member of
`the antenna module is made of a high permeability material
`such as an amorphous sheet and an electromagnetic steel
`plate and the magnetic core member is inserted generally in
`parallel to the flat plane of the antenna! coil to increase an
`inductance of the antenna coil and improve a communica(cid:173)
`tion distance.
`
`[0005]
`Japanese Patent Application Publication No. 2000-
`113142 discloses an antenna module having a structure that
`planar magnetic core members are stacked in parallel to a
`flat plane of an antenna coil wound in a spiral shape along
`the flat plane.
`
`[0006] Portable information terminals widely prevailed
`recently such as personal digital assistants (PDA) and por(cid:173)
`table phones are carried about during an outing or the like
`and always held by users. Therefore, if a portable informa(cid:173)
`tion terminal is provided with the functions of a non-contact
`IC tag, it is not necessary for a user to have, for example, a
`non-contact IC card in addition to the portable information
`terminal always held by the user, and it becomes very
`convenient for the user. Techniques of building the functions
`of a non-contact IC tag into a portable information terminal
`in this manner are disclosed in, for example, Japanese Patent
`Application Publication No. 2003-37861 and have already
`proposed by the present applicant (Japanese Patent Appli(cid:173)
`cation Serial Number 2004-042149).
`
`[0007] A portable information terminal is compact on one
`hand and is an apparatus having multi-functions on the other
`hand, so that metal components are mounted in a compact
`housing at a high density. For example, some printed wiring
`boards now in use have a multi-layer conductive layer, and
`electronic components are mounted on a multi-layer printed
`wiring board at a high density. A battery pack as a power
`source is accommodated in a portable information terminal,
`and metal components are used for a package and the like in
`this battery pack.
`
`[0008] Therefore, an antenna module for a non-contact IC
`tag disposed in the housing of a portable information ter(cid:173)
`minal has a degraded communication performance and, for
`example, a tendency that its communication distance
`becomes short, more than a separated antenna module before
`it is assembled in the housing, because of the influence of
`metal components mounted in the housing.
`
`[0009] As the communication distance of an antenna mod(cid:173)
`ule becomes short, it becomes necessary for the antenna
`module to be set as near the reader/write as possible in real
`use, possibly resulting in damaging the convenience of a
`non-contact IC card system capable of transferring informa(cid:173)
`tion easily and quickly. Even if an antenna module is used
`by being accommodated in the housing of a portable infor(cid:173)
`mation terminal, a communication distance of at least 100
`mm is considered necessary. This conforms to the specifi(cid:173)
`cation of a non-contact IC card system for railroad automatic
`ticket examination presently in use.
`
`DISCLOSURE OF THE INVENTION
`
`[Problem to Be Solved By the Invention]
`
`[0010] High permeability magnetic powders have been
`used conventionally as a magnetic core member in order to
`improve a communication distance of an antenna module. If
`magnetic powders are mixed with binder and shaped in a
`sheet member or plate member to use the member as a
`magnetic core member, a permeability of the whole mag(cid:173)
`netic core member can be increased by making large the
`particle size of magnetic powders.
`
`[0011] However, as the particle size of magnetic powders
`is made large, a power loss caused by an eddy current loss
`of the magnetic core member becomes conspicuous, with an
`IC read voltage lowered and a communication distance
`shortened. More specifically, as a magnetic substance is
`magnetized in a high frequency magnetic field, a change in
`magnetic fluxes corresponding to the frequency occurs.
`According to electromagnetic induction law, an electromo(cid:173)
`tive force is generated in the direction cancelling the change
`in magnetic fluxes. Induction current by the generated
`electromotive force is converted into Joule heat. This is the
`eddy current loss.
`
`[0012]
`In order to reduce the eddy current loss while a
`permeability of a magnetic core member is maintained high,
`most of conventional approaches are to limit a large particle
`size of magnetic powders and reduce an absolute quantity of
`magnetic powders to be mixed.
`
`[0013] However, to reduce the absolute quantity of mag(cid:173)
`netic powders results in a thick and large magnetic core
`member, and in a thick antenna module. For example, a
`sheet thickness of a conventional magnetic core member
`having the structure described above is at least over 1 mm
`
`Ex.1016
`APPLE INC. / Page 10 of 16
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`

`

`US 2007/0069961 Al
`
`Mar. 29, 2007
`
`2
`
`in order to obtain a connnunication distance of 100 nnn of
`the magnetic core itself. The module thickness increases
`further by laminating a board for supporting the antenna!
`coil and a shield plate for eliminating the influence of a
`metal portion inside the housing.
`
`[0014] Recently, a portable information terminal is much
`more reqired compact and thin, and there is no room left in
`the housing of the portable information terminal for accom(cid:173)
`modating an antenna module of a large or thick size. As
`described above, an antenna module built in a compact
`electronic apparatus such as a portable information terminal
`is required to satisfy two contradictory requests for further
`improving a connnunication distance and further thinning a
`module thickness.
`
`[0015] The present invention has been made in consider(cid:173)
`ation of the above-described problems and has an issue of
`providing a magnetic core member for an antenna module
`capable of improving a connnunication distance without
`thickening the module, an antenna module and a portable
`information terminal equipped with the antenna module.
`
`[Means for Solving the Problem]
`
`[0016]
`In order to solve the above issue, the present
`inventors have vigorously studied and found that an eddy
`current in a magnetic core member is generated on the
`surface facing an antenna coil stacked, and concentrated on
`an area facing a loop portion of the antenna coil. It has been
`found that by forming a recess portion in this area, a
`generation amount of eddy currents can be reduced.
`
`[0017] Namely, the magnetic core member for an antenna
`module of the present invention is characterized in that the
`recess portion is formed on the surface facing the stacked
`antenna coil, at least in an area facing the loop portion of the
`antenna coil.
`
`[0018] By forming the recess portion, a gap corresponding
`to a depth of the recess portion is formed between the
`surface of the magnetic core member and the loop portion of
`the antenna coil, and intervention of this gap reduces the
`amount of eddy currents to be generated on the surface of the
`magnetic core member. The deeper the recess portion is, the
`generation of eddy current can therefore be expected to be
`suppressed. However, since the magnetic core member is
`positioned away from the loop portion of the antenna coil,
`the inductance of the antenna coil reduces and the connnu(cid:173)
`nication distance is degraded. To avoid this, according to the
`present invention, an area where the recess portion is formed
`is set to at least the area facing the loop portion of the
`antenna coil to balance between reduction of the amount of
`the eddy current generation and prevention of the inductance
`from being lowered.
`
`[0019] A depth of the recess portion can be properly set in
`accordance with the magnetic characteristics of the magnetic
`core member. Namely, since an eddy current is generated
`more as the magnetic core member has a higher conductiv(cid:173)
`ity, a depth of the recess portion may be shallow if the
`magnetic core member having a low conductivity is used.
`For example, if a communication frequency of the antenna
`coil is 13.56 MHz and the magnetic core member (0.58 nnn
`thick) is formed by mixing Fe-Si-Cr system magnetic
`powders in binder, then a depth of the recess portion is set
`to 0.1 nnn or shallower in order to acquire a connnunication
`
`distance of 100 mm or longer in the state that the antenna
`coil is acconnnodated in the housing of a portable informa(cid:173)
`tion terminal.
`
`[0020] The shape of the recess portion is not limited
`specifically, but the recess portion may be a ring groove
`formed in correspondence with the loop portion of the
`antenna coil or dimples formed on the surface of the
`magnetic core member at a plurality of positions.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0021] FIG. 1 is a broken perspective view of an antenna
`module 10 according to an embodiment of the present
`invention.
`
`[0022] FIG. 2 is a cross sectional side view showing a
`main part of the antenna module 10.
`
`[0023] FIG. 3 is a schematic diagram showing an inner
`structure of a portable information terminal 1 with the
`built-in antenna module 10, as viewed sideways.
`
`[0024] FIG. 4 is a partially broken back view of the
`portable information terminal 1.
`
`[0025] FIG. 5 is a diagram showing an example of a
`relation between a real part µ' and an imaginary part µ" of a
`permeability of a magnetic core material 18.
`
`[0026] FIG. 6 is a plan view of the magnetic core member
`18.
`
`[0027] FIG. 7 is a plan view showing another example of
`the structure of a magnetic core member 18'.
`
`[0028] FIGS. SA and SB are distribution diagrams of eddy
`currents generated on the surface of a magnetic core mem(cid:173)
`ber. FIG. SA shows a magnetic core member 18 having a
`ring groove 18c formed on the surface thereof, and FIG. SB
`shows a magnetic core member 18" whose surface is not
`worked.
`
`[0029] FIG. 9 is a diagram illustrating a relation between
`a depth of the ring groove 18c and an inductance L, a
`resistance R and a Q value respectively of the antenna coil.
`
`[0030] FIG. 10 is a diagram comparing L, Rand Q of an
`antenna coil using a magnetic core member with a recess
`portion (ring groove 18c, dimples 18d) with L, R and Q of
`an antenna coil using a magnetic core member having a
`conventional shape whose surface is not worked.
`
`[0031] FIG. 11 is a diagram comparing a connnunication
`distance of the antenna coil using the magnetic core member
`with the recess portion (ring groove 18c, dimples 18d) with
`a connnunication distance of an antenna coil using the
`magnetic core member having the conventional shape whose
`surface is not worked.
`
`BEST MODE FOR CARRYING OUT THE
`INVENTION
`
`[0032] An embodiment of the present invention will be
`described in the following by referring to the drawings.
`
`[0033] FIG. 1 and FIG. 2 are a broken perspective view
`and a cross sectional side view showing the structure of an
`antenna module 10 for non-contact data connnunications
`according to an embodiment of the present invention.
`
`Ex.1016
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`

`US 2007/0069961 Al
`
`Mar. 29, 2007
`
`3
`
`[0034] The antenna module 10 has a lamination structure
`of a baseboard 14 as a support body, a magnetic core
`member 18 and a metal shield plate 19. The baseboard 14
`and magnetic core member 18 are stacked via an adhesive
`double coated sheet 13A, and the magnetic core member 18
`and metal shield plate 19 are stacked via an adhesive double
`coated sheet 13B. In FIG. 2, the double-sided adhesive
`sheets 13A and 13B are not shown in the drawing.
`
`[0035] Although the baseboard 14 is configured as an
`insulating flexible board made of a plastic film such as
`polyimide, polyethylene terephthalate (PET) and polyethyl(cid:173)
`ene naphthalate (PEN), it may be structured as a rigid board
`such as glass epoxy resin.
`
`[0036] An antenna coil 15 wound in a loop shape in a flat
`plane is mounted on the baseboard 14. The antenna coil 15
`is used for a non-contact IC tag function and makes com(cid:173)
`munications through inductive coupling with an antenna
`portion of an external reader/writer (not shown in the
`drawing). The antenna coil 15 is made of a metal of copper,
`aluminum or the like patterned on the baseboard 14.
`
`In this embodiment, the antenna coil 15 is com(cid:173)
`[0037]
`posed of a loop part wound in the flat plane and a wiring part
`for electric connection to a signal processing circuit unit 16
`to be described later, only the loop part shown in the
`drawing.
`
`[0038] A second antenna coil for a reader/write function
`may be mounted on the antenna module 10. In this case, the
`second antenna coil may be mounted on the baseboard 14 on
`an inner side of the antenna! coil 15.
`
`[0039] The signal processing circuit unit 16 is mounted on
`the surface of the baseboard 14 on the side of the magnetic
`core member 18. The signal processing circuit unit 16 is
`disposed on the inner side of the antenna coil 15 and
`electrically connected to the antenna coil 15.
`
`[0040] The signal processing circuit unit 16 is composed
`of an IC chip 16a including a signal processing circuit
`necessary for non-contact data communications and storing
`information, and electric/electronic components such as a
`tuning capacitor. The signal processing circuit unit 16 may
`be composed of a group of a plurality of components such
`as shown in FIG. 1 and FIG. 2, or may be composed of a
`single component 16b such as shown in FIG. 4. The signal
`processing circuit unit 16 is connected to a printed wiring
`board 12 (FIG. 3) of a portable information terminal 1 to be
`described later, via an external connection unit 17 mounted
`on the baseboard 14.
`
`[0041] The magnetic core member 18 is an injection
`molding body formed in a sheet member or plate member,
`for example, by mixing or filling soft magnetic powders with
`or in insulating binder such as synthetic resin and rubber. As
`soft magnetic powders, Sendust (Fe-Al-Si system), Per(cid:173)
`malloy (Fe-Ni system), amorphous (Fe-Si-B system),
`ferrite (Ni-Zn ferrite, Mn-Zn ferrite, etc.), sintered ferrite
`and the like may be adopted, which are selectively used in
`accordance with a desired communication performance and
`usage.
`
`[0042] The magnetic core member 18 functions as a
`magnetic core of the antenna coil 15, and avoids electro(cid:173)
`magnetic interference between the antenna coil 15 and the
`metal shield plate 19. An opening 18a is formed through a
`
`center region of the magnetic core member 18 in order to
`accommodate the signal processing circuit unit 16 mounted
`on the baseboard 14. A recess 18b is provided at one side of
`the magnetic core member 18, the recess being used for the
`external connection unit 17 during stacking on the baseboard
`14.
`
`[0043] The details of the magnetic core member 18 will be
`later described.
`
`[0044] The metal shield plate 19 is made of a stainless
`plate, a copper plate, an aluminum plate or the like. As will
`be later described, the antenna module 10 of this embodi(cid:173)
`ment is accommodated at a predetermined inner position of
`a terminal main body 2 of the portable information terminal
`1. Therefore, the metal shield plate 19 is provided to protect
`the antenna coil 15 from electromagnetic interference with
`a metal portion (components, wirings) on a printed wiring
`plate 12 in the terminal main body 2.
`
`[0045] The metal shield plate 19 is used for coarse adjust(cid:173)
`ment of a resonance frequency (in this example, 13.56 MHz)
`of the antenna module 10, and is used for suppression of
`large variations in resonance frequency of the antenna
`module 10 between the states where the antenna module 10
`resides alone, and the antenna module is assembled in the
`terminal main body 2.
`
`[0046] FIG. 3 and FIG. 4 are schematic diagrams showing
`a state that the antenna module 10 having the above(cid:173)
`described structure is assembled in the portable information
`terminal 1. FIG. 3 is a schematic diagram showing the inside
`of the terminal main body 2 as viewed sideways, and FIG.
`4 is a partially broken diagram showing the inside of the
`terminal main body 2 as viewed from a back side.
`
`[0047] The portable information terminal 1 shown in the
`drawings is structured as a portable phone having the
`terminal main body 1 and a panel unit 3 rotatably mounted
`on the terminal main body 1. In FIG. 3, the terminal main
`body 2 constitutes a housing made of synthetic resin, and on
`the surface of the panel unit 3 provided is an operation panel
`disposed with ten-key input buttons and the like although
`not shown.
`
`[0048] The terminal main body 2 has therein a battery
`pack 4 for supplying power, and the printed wiring plate 12
`as a control panel for controlling the functions or operations
`of the portable information terminal 1. The battery pack 4 is,
`for example, a lithium ion battery. Its overall shape is a
`rectangular solid, and its outer housing is made of metal
`material such as aluminum. The battery pack 4 is disposed
`inside a partition member 5 made of plastic disposed in the
`terminal main body 2.
`
`[0049] The antenna module 10 is accommodated in the
`terminal main body 2. In this embodiment in particular, the
`antenna module 10 is accommodated just above the partition
`member 5 for housing the battery pack 4, facing a back
`surface 2a of the terminal main body 2. The accommodation
`position of the antenna module 10 is not limited to the
`position described above.
`
`[0050] Therefore, for data communications with an exter(cid:173)
`nal reader/writer (not shown in the drawing) by using the
`antenna module 10, the back surface 2a of the terminal main
`body 2 of the portable information terminal 1 is moved near
`to the antenna portion of the reader/writer. As an electro-
`
`Ex.1016
`APPLE INC. / Page 12 of 16
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`

`

`US 2007/0069961 Al
`
`Mar. 29, 2007
`
`4
`
`magnetic wave or a high frequency magnetic field irradiated
`from the antenna portion of the reader/writer passes through
`the antenna coil 15 of the antenna module 10, induction
`current flows through the antenna coil 15 corresponding in
`amount to the intensity of the electromagnetic wave or high
`frequency magnetic field. This induction current is rectified
`by the signal processing circuit unit 16 and converted into a
`read voltage for reading information recorded in the IC chip
`16a. The read information is modulated by the signal
`processing circuit unit 16 and transmitted to the antenna
`portion of the reader/writer via the antenna coil 15.
`
`[0051] Generally, when a soft magnetic substance (here(cid:173)
`inafter simply called a magnetic substance) which has a high
`permeability, is applied with a high frequency magnetic
`filed, the magnetic substance is magnetized by a magneti(cid:173)
`zation mechanism such as magnetic domain wall displace(cid:173)
`ment and rotation magnetization. A permeability indicating
`a degree of magnetization feasibility is represented by a
`complex permeability and expressed by the following equa(cid:173)
`tion (1):
`
`µ-µ'-i·µ"
`(1)
`[0052] where µ' is a real part of a permeability represent(cid:173)
`ing the components capable of following an external mag(cid:173)
`netic field, whereas µ" represents an imaginary part of the
`permeability representing the components unable to follow
`an external magnetic field and the components whose phase
`is delayed by 90°, which is called a loss term of the
`permeability. i represents an imaginary unit.
`
`[0053] There is a close relation between the real part and
`imaginary part of a permeability, and the material having a
`larger real part of a permeability has a larger imaginary part.
`It is known that the permeability becomes lower as the
`frequency of an applied magnetic field becomes higher when
`a magnetic substance is magnetized by applying a high
`frequency magnetic field. FIG. 5 shows an example of the
`magnetic characteristics of a magnetic core member using
`Fe-Si-Cr system as magnetic powders. It is understood
`that as the frequency becomes higher, µ' becomes lower and
`µ" becomes higher. A loss coefficient of a magnetic sub(cid:173)
`stance at an applied frequency is expressed by the following
`equation (2) by using the real part µ' and imaginary part µ"
`of a complex permeability µ expressed by the equation (1 ):
`
`tan ii-µ"/µ'
`(2)
`[0054] A high frequency loss by dynamic magnetization of
`a magnetic substance is equivalent to the loss coefficient,
`and can be expressed as a sum of three types of energy losses
`as shown in the following equation (3):
`
`tan ii-tan oh+tan i\e+tan Or
`
`(3)
`
`[0055] where tan oh is a hysteresis loss and a work volume
`of a magnetization change indicated by a hysteresis curve,
`which increases in proportion to a frequency. tan oe is an
`eddy current loss which is an energy loss consumed as Joule
`heat converted from an eddy current induced in a conductive
`magnetic substance and corresponding in amount to a
`change in magnetic fluxes when an a.c. magnetic field is
`applied to the magnetic substance. tan or is a residual loss
`which is a remaining loss other than the above-described
`losses.
`
`and becomes large in proportion to the frequency used as
`shown in the following equation ( 4):
`
`tan oe-e2·µfo
`
`(4)
`
`where e2 is a coefficient, µ is a permeability, f is a frequency,
`and a is a conductivity.
`
`[0057] As described above, the magnetic core member 18
`constituting the antenna module 10 has an increased eddy
`current loss at a higher conductivity. An eddy current
`generated in the magnetic core member 18 acts in a direction
`of cancelling an external magnetic field so that an induction
`current flowing through the antenna coil 15 is reduced.
`Namely, the eddy current generated in the magnetic core
`member 18 becomes resistance components relative to the
`current flowing through the antenna coil 15. The resistance
`components cause adverse effects such as lowering an IC
`read voltage and shortening a communication distance of
`radio waves transmitted from the antenna coil 15. It is
`therefore necessary to suppress the eddy current generated in
`the magnetic core member 18 as much as possible.
`
`[0058] An eddy current generated in the magnetic core
`member 18 appears conspicuously on the surface facing the
`antenna coil 15. It is determined that an eddy current is
`generated and concentrated particularly in the region of the
`surface facing a loop portion of the antenna coil 15. In this
`embodiment, a recess portion 18c is formed on the surface
`of the magnetic core member 18 in an area facing a loop
`portion of the antenna coil 15, covering the whole circum(cid:173)
`ference of the loop portion to thereby reduce a generation
`quantity of an eddy current.
`
`[0059] As shown in FIG. 1 and FIG. 6, the magnetic core
`member 18 of this embodiment is provided with a ring
`groove 18c as the recess portion in the region facing the loop
`portion of the antenna coil 15. A width of the ring groove 18c
`is wider than the whole width of the loop portion of the
`antenna coil 15.
`
`Instead of the ring groove 18c, a plurality of
`[0060]
`dimples 18d may be provided as the recess portion on the
`stacked surface of the antenna coil 15, like a magnetic core
`member 18' shown in FIG. 7. In the example shown in the
`drawing, although the dimples 18d are provided over the
`whole surface of the magnetic core member 18', it is
`sufficient if the dimples are formed at least in the region
`facing the loop portion of the antenna coil.
`
`[0061] FIGS. SA and 8B are diagrams showing the distri(cid:173)
`butions of eddy currents generated in the region facing the
`loop portion of the antenna coil 15 along a depth direction
`from the surface of the magnetic core member. FIG. SA
`shows the magnetic core member 18 formed with the ring
`groove 18c, and FIG. 8B shows a magnetic core member 18"
`having a conventional configuration not worked with the
`ring groove 18c ( dimples 18d). The distribution on gray
`scale gradation in the drawing is indicated by borderlines
`indicating the distribution of eddy currents generation in the
`thickness direction of the magnetic core member. The dens(cid:173)
`est region Sl on the surface facing the antenna coil 15 has
`the largest amount of eddy current generation, and the
`amount of eddy current generation reduces from the region
`S2 to the region S3 in order.
`
`[0056] An eddy current loss (tan oe) in a high frequency
`magnetic field at 13.56 MHz is influenced by conductivity
`
`In the magnetic core member 18" shown in FIG.
`[0062]
`8B, the depths of the regions Sl to S3 from the surface were
`
`Ex.1016
`APPLE INC. / Page 13 of 16
`
`

`

`US 2007/0069961 Al
`
`Mar. 29, 2007
`
`5
`
`100 µm in the region Sl, 200 µm in the region S2, and 300
`µmin the region S3. In contrast, as shown in FIG. SA, in the
`magnetic core member 18 formed with the ring groove
`(recess portion) 18c, the depths of the regions Sl to S3 from
`the surface (bottom of the ring groove 18c) were 60 µm in
`the region Sl, 120 µmin the region S2, and 200 µmin the
`region S3. A depth of the ring groove 18c is 100 µm.
`[0063] The distribution of eddy current generation is
`obtained by a computerized electromagnetic field simulation
`by a finite element method. Both the magnetic core members
`18 and 18" are made of the same composite magnetic
`material formed by dispersing magnetic powders of
`Fe-Si-Cr system in binder and shaped in the sheet
`member. A thickness of each of the magnetic core members
`is 0.58 mm and an external high frequency magnetic field
`has a frequency of 13.56 MHz.
`[0064] As described above, the depth of each of the
`regions Sl to S3 of the magnetic core member 18 formed
`with the ring groove 18c, along the magnetic core member
`depth direction, is made thinner than that of the magnetic
`core member 18" shown in FIG. 8B whose surface is not
`worked. The eddy current generation amount particularly in
`the region Sl on the uppermost surface side is reduced
`greatly. It is understood that a gap having a size correspond(cid:173)
`ing to the depth of the ring groove 18c is provided between
`the loop portion of the antenna coil 15 and the surface of the
`magnetic core member 18, and intervention of this gap
`reduces the eddy current generation amount on the surface
`of the magnetic core member 18.
`[0065]
`If the depth of the ring groove 18c to be formed is
`made deeper, the eddy current generation amount on the
`surface of the magnetic core member 18 can be reduced.
`FIG. 9 shows a relation between a depth of the ring groove
`18c, an inductance L, a resista