U.S. patent application number 12/496709 was filed with the patent office on 2009-10-22 for wireless ic device.
This patent application is currently assigned to MURATA MANUFACTURING CO., LTD.. Invention is credited to Yuya Dokai, Nobuo Ikemoto, Noboru Kato.
Application Number | 20090262041 12/496709 |
Document ID | / |
Family ID | 40259708 |
Filed Date | 2009-10-22 |
United States Patent
Application |
20090262041 |
Kind Code |
A1 |
Ikemoto; Nobuo ; et
al. |
October 22, 2009 |
WIRELESS IC DEVICE
Abstract
An electromagnetic coupling module includes a wireless IC chip
and a functional substrate. The electromagnetic coupling module is
mounted on a radiation plate, preferably using an adhesive, for
example. On the upper surface of a base material of the radiation
plate, two long radiation electrodes are provided. On the
undersurface of the functional substrate, capacitive coupling
electrodes that individually face inner ends of the radiation
electrodes are provided. A matching circuit arranged to perform the
impedance matching between the wireless IC chip and each of the
radiation electrodes includes the capacitive coupling electrodes.
As a result, it is possible to reduce the size, facilitate the
design, and reduce the cost of a wireless IC device.
Inventors: |
Ikemoto; Nobuo;
(Moriyama-shi, JP) ; Dokai; Yuya; (Nagaokakyo-shi,
JP) ; Kato; Noboru; (Moriyama-shi, JP) |
Correspondence
Address: |
MURATA MANUFACTURING COMPANY, LTD.;C/O KEATING & BENNETT, LLP
1800 Alexander Bell Drive, SUITE 200
Reston
VA
20191
US
|
Assignee: |
MURATA MANUFACTURING CO.,
LTD.
Nagaokakyo-shi
JP
|
Family ID: |
40259708 |
Appl. No.: |
12/496709 |
Filed: |
July 2, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2008/062886 |
Jul 17, 2008 |
|
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12496709 |
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Current U.S.
Class: |
343/860 |
Current CPC
Class: |
H01Q 1/40 20130101; H01L
2224/32225 20130101; G06K 19/073 20130101; H01L 2224/73204
20130101; G06K 19/0723 20130101; H01Q 7/00 20130101; G06K 19/07756
20130101; H01Q 9/16 20130101; H01Q 9/20 20130101; H04B 5/0012
20130101; H01L 2924/19105 20130101; H01Q 1/2225 20130101; H01L
2224/16225 20130101; G06K 19/07749 20130101; H01L 2224/73204
20130101; H01L 2224/16225 20130101; H01L 2224/32225 20130101; H01L
2924/00 20130101 |
Class at
Publication: |
343/860 |
International
Class: |
H01Q 1/50 20060101
H01Q001/50 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 18, 2007 |
JP |
2007-186439 |
Claims
1. A wireless IC device comprising: a wireless IC chip; a radiation
plate including a radiation electrode; and a functional substrate
including a matching circuit arranged to perform impedance matching
between the wireless IC chip and the radiation electrode, the
functional substrate including a coupling electrode coupled to the
radiation electrode, inductance elements, and a capacitance
element; wherein the matching circuit included in the functional
substrate has a configuration such that a relationship between a
reactance component of an impedance obtained by viewing the
wireless IC chip from a connecting portion connecting the wireless
IC chip and the functional substrate to each other and a reactance
component of an impedance obtained by viewing the radiation
electrode from the connecting portion connecting the wireless IC
chip and the functional substrate to each other is a conjugate
relationship.
2. The wireless IC device according to claim 1, wherein the
coupling electrode is electromagnetically coupled to the radiation
electrode.
3. The wireless IC device according to claim 1, wherein the
functional substrate includes a multilayer substrate including
laminated dielectric layers on which electrode patterns are
provided.
4. The wireless IC device according to claim 1, wherein the
radiation electrode has an elongated configuration; the coupling
electrode includes first and second external coupling electrodes
that individually occupy two areas divided from the functional
substrate; and one end of the radiation electrode is coupled to the
first external coupling electrode and another end of the radiation
electrode is coupled to the second external coupling electrode.
5. The wireless IC device according to claim 4, wherein the
radiation electrode is a loop-shaped radiation electrode arranged
such that both ends of the radiation electrode face each other; a
first one of the both ends of the radiation electrode is coupled to
the first external coupling electrode; and a second one of the both
ends of the radiation electrode is coupled to the second external
coupling electrode.
6. The wireless IC device according to claim 4, further comprising
an auxiliary matching circuit portion including a matching
electrode arranged to connect a location near the first one of the
both ends of the radiation electrode to a location near the second
one of the both ends of the radiation electrode, a portion of the
radiation electrode extending from the first one of the both ends
of the radiation electrode to a location near the one of the both
ends of the radiation electrode, and a portion of the radiation
electrode extending from the second of the both ends of the
radiation electrode to a location near the second of the both ends
of the radiation electrode.
7. The wireless IC device according to claim 1, wherein the
inductance elements are loop-shaped inductance elements; and
winding axes of the loop-shaped inductance elements are arranged so
that they cross an area in which the radiation electrode is
located.
8. The wireless IC device according to claim 1, wherein the
coupling electrode is a capacitive coupling electrode that faces
the radiation electrode and is capacitively coupled to the
radiation electrode.
9. The wireless IC device according to claim 8, wherein the
capacitive coupling electrode is provided on a surface of the
functional substrate facing the radiation plate; the radiation
electrode is provided on a surface of the radiation plate facing
the functional substrate; and the functional substrate is attached
to the radiation plate so that the capacitive coupling electrode
and the radiation electrode face each other.
10. The wireless IC device according to claim 8, wherein the
external coupling electrode included in the functional substrate
extends to a surface other than the surface of the functional
substrate facing the radiation plate.
11. The wireless IC device according to claim 1, wherein the
coupling electrode is a loop-shaped external coupling electrode;
and the loop-shaped external coupling electrode is magnetically
coupled to the radiation electrode.
12. The wireless IC device according to claim 11, wherein at least
one of the inductance elements has a double helix shape in which
two different linear electrodes are adjacent to each other; and one
end of one of the two different linear electrodes is electrically
connected to one end of the other one of the two different linear
electrodes.
13. The wireless IC device according to claim 11, wherein the
radiation electrode is a loop-shaped radiation electrode; and the
loop-shaped radiation electrode is electromagnetically coupled to
the inductance elements included in the functional substrate.
14. The wireless IC device according to claim 1, wherein the
matching circuit includes an element included in the functional
substrate and an element mounted on the functional substrate.
15. The wireless IC device according to claim 1, further comprising
a protection film covering at least one of the wireless IC chip,
the functional substrate, and the radiation plate.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a wireless IC device used
for an RFID (Radio Frequency Identification) system for performing
wireless data communication using electromagnetic waves.
[0003] 2. Description of the Related Art
[0004] Recently, as a product management system, an RFID system has
been used in which a reader/writer arranged to generate an
induction field communicates with a wireless IC device attached to
a product in a wireless manner so as to obtain predetermined
information stored in the wireless IC device.
[0005] FIG. 1 is a diagram illustrating an example of a wireless IC
tag (RFID tag) disclosed in Japanese Unexamined Patent Application
Publication No. 2005-244778 in which an IC tag label is attached to
an IC tag antenna.
[0006] In a wireless IC tag TO, a pair of main antenna elements 81,
an auxiliary antenna element 82, and a pair of matching portions 83
are provided on the surface of a dielectric substrate 84.
[0007] The main antenna elements 81 are meandering antennas in
which meandering conducting lines are provided, and are
symmetrically arranged on the dielectric substrate 84. Between the
main antenna elements 81 occupying areas at both ends of the
dielectric substrate 84, the auxiliary antenna element 82 is
disposed.
[0008] The matching portions 83 are meandering conducting lines
(inductors). One end of each of the matching portions 83 is
individually connected to an inner end of the main antenna elements
81, and the other end of each of the matching portions 83 is
connected to a wireless IC chip 86.
[0009] However, the wireless IC tag disclosed in Japanese
Unexamined Patent Application Publication No. 2005-244778 has the
following problems. Since the matching portions are individually
arranged adjacent to the main antennas on the same substrate, the
size of the wireless tag is increased.
[0010] If the tag is attached to a product having a high dielectric
constant, the frequency characteristics of the matching circuit
portions are changed due to the influence of the dielectric
constant of the product. Accordingly, the frequency characteristic
of the tag is significantly changed. If a protection film arranged
to cover the surface of a product to which the tag is attached or
the surface of the tag, the impedances of the matching portions are
changed. Accordingly, it is necessary to design the wireless tag in
consideration of the use condition of the wireless tag.
[0011] Since the auxiliary antenna is used to increase the design
flexibility of the main antenna elements, the size of the tag is
increased. Since matching design is performed at portions other
than the matching portions, the number of design parameters is
increased and the design complexity of the tag is increased.
[0012] Since the IC chip must be mounted on a small mounting
electrode on a large substrate on which the main antennas and the
matching portions are disposed, a high-precision mounting apparatus
is required. Since the mounting position adjustment requires a long
period of time and the manufacturing time for the tag therefore is
increased, the cost of the tag is increased.
[0013] Since each of the main antennas is connected to the IC chip
so that the DC continuity between them is achieved, static
electricity may flow from the main antenna into the wireless IC
chip and break the wireless IC chip.
SUMMARY OF THE INVENTION
[0014] To overcome the problems described above, preferred
embodiments of the present invention reduce the size and cost of a
wireless IC device and facilitate the design of the wireless IC
device.
[0015] A wireless IC device according to a preferred embodiment of
the present includes a wireless IC chip, a radiation plate
including a radiation electrode, and a functional substrate
including an external coupling electrode coupled to the radiation
electrode and a matching circuit arranged to perform impedance
matching between the wireless IC chip and the radiation electrode.
The matching circuit included in the functional substrate is
determined such that a relationship between a reactance component
of an impedance obtained by viewing the wireless IC chip from a
connecting portion connecting the wireless IC chip and the
functional substrate to each other and a reactance component of an
impedance obtained by viewing the radiation electrode from the
connecting portion connecting the wireless IC chip and the
functional substrate to each other is a conjugate relationship.
[0016] The external coupling electrode is preferably
electromagnetically coupled to the radiation electrode. The
functional substrate preferably includes a multilayer substrate
including laminated dielectric layers on which electrode patterns
are provided.
[0017] The radiation electrode is preferably relatively long. The
external coupling electrode preferably includes first and second
external coupling electrodes that individually occupy two areas
divided from the functional substrate. One of two ends of the
radiation electrode is preferably coupled to the first external
coupling electrode and the other one of the two ends of the
radiation electrode is preferably coupled to the second external
coupling electrode.
[0018] The radiation electrode is preferably a loop-shaped
radiation electrode having two ends that face each other. One of
the ends is preferably coupled to the first external coupling
electrode. The other one of the ends is preferably coupled to the
second external coupling electrode.
[0019] An auxiliary matching circuit portion preferably includes a
matching electrode arranged to connect a location near one of the
two ends of the radiation electrode to a location near the other
one of the two ends of the radiation electrode, a portion of the
radiation electrode from one of the two ends to the location near
one of the two ends, and to connect a portion of the radiation
electrode from the other one of the two ends to the position near
the other one of the two ends.
[0020] The inductance elements are preferably loop-shaped
inductance elements. Winding axes of the loop-shaped inductance
elements are arranged so that they cross an area in which the
radiation electrode is provided.
[0021] The external coupling electrode is preferably a capacitive
coupling electrode that faces the radiation electrode and is
capacitively coupled to the radiation electrode.
[0022] The capacitive coupling electrode is preferably disposed on
a surface of the functional substrate facing the radiation plate.
The radiation electrode is preferably disposed on a surface of the
radiation plate facing the functional substrate. The functional
substrate is preferably attached to the radiation plate so that the
capacitive coupling electrode and the radiation electrode face each
other.
[0023] The external coupling electrode included in the functional
substrate preferably extends to a surface other than the surface of
the functional substrate facing the radiation plate.
[0024] The external coupling electrode is preferably a loop-shaped
external coupling electrode. The loop-shaped external coupling
electrode is magnetically coupled to the radiation electrode.
[0025] At least one of the inductance elements preferably has a
double helix shape in which two different linear electrodes are
adjacent to each other. One end of one of the two different linear
electrodes is preferably electrically connected to one end of the
other one of the two different linear electrodes.
[0026] The radiation electrode preferably is a loop-shaped
radiation electrode. The loop-shaped radiation electrode is
preferably electromagnetically coupled to the inductance elements
included in the functional substrate.
[0027] The matching circuit is preferably defined by an element
included in the functional substrate and an element mounted on the
functional substrate.
[0028] At least one of the wireless IC chip, the functional
substrate, and the radiation plate is preferably covered with a
protection film.
[0029] According to various preferred embodiments of the present
invention, the following advantages are obtained. Since the
wireless IC chip is mounted on the small functional substrate, it
is possible to use an IC mounting apparatus in the related art and
reduce the cost of mounting the wireless IC chip. Even if a
wireless IC chip having a different output impedance is used and an
RFID frequency characteristic is changed, it is only necessary to
change the design of the matching circuit included in the
functional substrate. This significantly reduces design costs.
[0030] Since the wireless IC chip and the functional substrate are
DC-insulated from the radiation electrode, it is possible to
prevent the wireless IC chip and the functional substrate from
being broken by static electricity and improve the resistance of
the wireless IC device to static electricity.
[0031] Since the inductance elements and/or the capacitance element
are included in the multilayer substrate, it is possible to
stabilize an inductance value and a capacitance value and reduce
the change in impedance caused by an external factor, such as a
protection film or an attachment product. Accordingly, it is not
necessary to change the design of the wireless IC device in
consideration of the dielectric constant of a product attached to
the wireless IC device.
[0032] The first and second external coupling electrodes that
individually occupy two areas divided from the functional substrate
are provided, one of two ends of the long radiation electrode faces
the first external coupling electrode, and the other one of the two
ends of the long radiation electrode faces the second external
coupling electrode. As a result, it is possible to easily supply
electric power to the radiation electrode.
[0033] The radiation electrode is a loop-shaped radiation electrode
in which both ends face each other, one of the ends is coupled to
the first external coupling electrode, and the other one of the
ends is coupled to the second external coupling electrode. As a
result, a wireless IC device can perform communication using a
magnetic field, is not significantly affected by the dielectric
constant of an attachment product, and can obtain a more stable
characteristic.
[0034] An auxiliary matching circuit portion is defined by a
matching electrode arranged to connect a location near one of the
two ends of the radiation electrode to a location near the other
one of the two ends of the radiation electrode, a portion of the
radiation electrode from one of the two ends to the location near
one of the two ends, and a portion of the radiation electrode from
the other one of the two ends to the location near the other one of
the two ends. As a result, the impedance matching between the
functional substrate and the radiation plate is performed twice.
Therefore, it is possible to maintain a state in which the
impedance matching between the functional substrate and the
radiation plate is achieved in a wide frequency band, that is, to
obtain a high gain in a wide frequency band.
[0035] The inductance elements are preferably loop-shaped
inductance elements, and winding axes of the loop-shaped inductance
elements are preferably arranged so that they cross an area in
which the radiation electrode is disposed. As a result, magnetic
fields are generated at the loop-shaped inductance elements in a
direction that is parallel or substantially parallel to the winding
axes of the loop-shaped inductance elements and is vertical or
substantially vertical to the radiation electrode. Furthermore, a
magnetic field is generated around the radiation electrode, since
the radiation electrode is a planar electrode provided on a base
material. Accordingly, the magnetic field loop generated at the
functional substrate and the magnetic field loop generated at the
radiation electrode are interlinked with each other. This
strengthens the degree of coupling between the inductance elements
and the radiation electrode.
[0036] Preferably, the external coupling electrode is a capacitive
coupling electrode that is capacitively coupled to the radiation
electrode. As a result, it is possible to strengthen the degree of
coupling between the external coupling electrode and the radiation
electrode. Furthermore, it is possible to simplify the shapes of
the external coupling electrode and the radiation electrode and
reduce the cost of the wireless IC device.
[0037] Preferably, the capacitive coupling electrode is provided on
a surface of the functional substrate facing the radiation plate,
the radiation electrode is arranged on a surface of the radiation
plate facing the functional substrate, and the functional substrate
is attached to the radiation plate so that the capacitive coupling
electrode and the radiation electrode face each other. As a result,
the gap between the capacitive coupling electrode and the radiation
electrode is reduced, and the capacitance generated at the gap is
increased. This strengthens the degree of coupling between the
capacitive coupling electrode and the radiation electrode.
[0038] Preferably, the external coupling electrode included in the
functional substrate extends to a surface other than the surface of
the functional substrate facing the radiation plate. As a result,
if the external coupling electrode is connected to the radiation
electrode via a conductive joining material, such as solder, it is
possible to strengthen the connection between the external coupling
electrode and the radiation electrode and increase the impact
residence of the wireless IC device.
[0039] Preferably, the external coupling electrode is a loop-shaped
external coupling electrode, and a magnetic field of the
loop-shaped external coupling electrode is coupled to a magnetic
field of the radiation electrode. As a result, it is possible to
mount the functional substrate on the radiation plate in any
suitable orientation. Furthermore, it is possible to reduce the
influence of the dielectric constant of a joining material used to
connect the functional substrate and the radiation plate.
[0040] Preferably, at least one of the inductance elements has a
double helix shape in which two different linear electrodes are
arranged adjacent to each other. As a result, the two different
linear electrodes can have different resonance frequencies, since
they have different lengths. This increases a frequency band used
by the wireless IC device.
[0041] Preferably, the radiation electrode is a loop-shaped
radiation electrode, and an electromagnetic field of the
loop-shaped radiation electrode is coupled to electromagnetic
fields of the inductance elements included in the functional
substrate. As a result, it is possible to strengthen the degree of
coupling between the electromagnetic field of the loop-shaped
radiation electrode and each of the electromagnetic fields of the
inductance elements included in the functional substrate.
Furthermore, since a necessary inductance component can be obtained
in a relatively small area, it is possible to reduce the size of
the wireless IC device. In addition, since the magnetic field of
the loop-shaped portion of the radiation electrode is coupled to
the magnetic field of the loop-shaped external coupling electrode,
it is possible to obtain a predetermined characteristic regardless
of the mounting orientation of the functional substrate with
respect to the radiation plate.
[0042] Preferably, the matching circuit is defined by an element
included in the functional substrate and an element mounted on the
functional substrate. As a result, it is possible to reduce the
size of the functional substrate by mounting a chip inductor having
a large inductance value and a chip capacitor having a large
capacitance value on the functional substrate so as to reduce the
value of the element included in the functional substrate.
[0043] Preferably, the wireless IC device further includes a
protection film covering at least one of the wireless IC chip, the
functional substrate, and the radiation plate. As a result, it is
possible to increase the environmental resistance of the wireless
IC device and reduce the change in the characteristic of the
wireless IC device due to an environmental change.
[0044] Other features, elements, steps, characteristics and
advantages of the present invention will become more apparent from
the following detailed description of preferred embodiments of the
present invention with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] FIG. 1 is a diagram illustrating a wireless IC device
disclosed in Japanese Unexamined Patent Application Publication No.
2005-244778.
[0046] FIGS. 2A and 2B are cross-sectional views of a wireless IC
device according to a first preferred embodiment of the present
invention and a plan view of a main portion of the wireless IC
device.
[0047] FIG. 3 is an exploded perspective view of a multilayer
substrate included in a functional substrate included in the
wireless IC device shown in FIGS. 2A and 2B.
[0048] FIG. 4 is an oblique perspective view of a functional
substrate on which a wireless IC chip is mounted.
[0049] FIG. 5 is an equivalent circuit diagram of the wireless IC
device shown in FIGS. 2A and 2B.
[0050] FIG. 6 is a plan view illustrating the shape of a radiation
electrode provided on a radiation plate used in a wireless IC
device according to a second preferred embodiment of the present
invention.
[0051] FIG. 7 is a plan view illustrating the shape of a radiation
electrode formed on a radiation plate used in a wireless IC device
according to a third preferred embodiment of the present
invention.
[0052] FIGS. 8A to 8D are cross-sectional views of main portions of
some wireless IC devices according to a fourth preferred embodiment
of the present invention.
[0053] FIGS. 9A to 9D are cross-sectional views of main portions of
some other wireless IC devices according to the fourth preferred
embodiment of the present invention.
[0054] FIG. 10 is a cross-sectional view of a main portion of a
wireless IC device according to a fifth preferred embodiment of the
present invention.
[0055] FIG. 11 is a cross-sectional view of a main portion of a
wireless IC device according to a sixth preferred embodiment of the
present invention.
[0056] FIG. 12 is a cross-sectional view of a main portion of
another wireless IC device according to the sixth preferred
embodiment of the present invention.
[0057] FIG. 13 is a cross-sectional view of a main portion of a
wireless IC device according to a seventh preferred embodiment of
the present invention.
[0058] FIG. 14 is a cross-sectional view of a main portion of a
wireless IC device according to an eighth preferred embodiment of
the present invention.
[0059] FIG. 15 is diagram illustrating the configuration of a
radiation electrode provided on a radiation plate and the shape of
a loop-shaped external coupling electrode included in a functional
substrate in the wireless IC device.
[0060] FIGS. 16A and 16B are impedance circuit diagrams of the
wireless IC device shown in FIG. 14.
[0061] FIG. 17 is a cross-sectional view of a main portion of a
wireless IC device according to a ninth preferred embodiment of the
present invention.
[0062] FIG. 18 is an impedance circuit diagram of the wireless IC
device shown in FIG. 17.
[0063] FIG. 19 is a plan view of an electromagnetic coupling module
used in a wireless IC device according to a tenth preferred
embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
First Preferred Embodiment
[0064] A wireless IC device according to the first preferred
embodiment of the present invention will be described with
reference to FIGS. 2A to 5. FIG. 2A is a cross-sectional view of a
main portion of a wireless IC device according to the first
preferred embodiment. FIG. 2B is a plan view of the main portion of
the wireless IC device.
[0065] As illustrated in FIG. 2A, a wireless IC device 300 includes
a wireless IC chip 1, a functional substrate 20, and a radiation
plate 30. The wireless IC chip 1 is preferably a semiconductor chip
including a signal processing circuit functioning as an RFID tag,
for example.
[0066] The radiation plate 30 includes radiation electrodes 32a and
32b provided on the upper surface of a base material 31, such as a
PET film, for example.
[0067] The functional substrate 20 includes a multilayer substrate
21. On the upper surface of the multilayer substrate 21, mounting
electrodes 22a and 22b arranged to mount the wireless IC chip 1 are
disposed. In the multilayer substrate 21, capacitive coupling
electrodes 24a and 24b that are capacitively coupled to the
radiation electrodes 32a and 32b, respectively are provided. The
capacitive coupling electrodes 24a and 24b are external coupling
electrodes of the functional substrate 20. A matching circuit 23
including the capacitive coupling electrodes 24a and 24b performs
impedance matching between the wireless IC chip 1 and each of the
radiation electrodes 32a and 32b provided on the radiation plate
30.
[0068] The functional substrate 20 is mounted on the radiation
plate 30 via an adhesive 40 so that the capacitive coupling
electrodes 24a and 24b face the internal ends of the radiation
electrodes 32a and 32b, respectively.
[0069] On a surface on which the wireless IC chip 1 is mounted, a
soldering bump or an Au bump, for example, is provided so that an
underfill is applied in an area between the wireless IC chip 1 and
the functional substrate 20 on which the mounting electrodes 22a
and 22b are provided.
[0070] FIG. 2B is a plan view of an area on the upper surface of
the radiation plate 30 in which the radiation electrodes 32a and
32b are provided. In this drawing, the illustration of the wireless
IC chip 1 and the mounting electrodes 22a and 22b is omitted. As
illustrated in FIG. 2B, the capacitive coupling electrodes 24a and
24b included in the functional substrate 20 are arranged so that
they occupy two areas that are divided from the functional
substrate 20. The radiation electrodes 32a and 32b are relatively
long. The functional substrate 20 is disposed on the radiation
plate 30 so that the capacitive coupling electrodes 24a and 24b
face the internal ends of the radiation electrodes 32a and 32b,
respectively.
[0071] Thus, the wireless IC chip 1 supplies electric power to the
radiation electrodes 32a and 32b via the functional substrate 20,
so that the radiation electrodes 32a and 32b operate as a dipole
antenna.
[0072] There are several procedures for assembling the wireless IC
chip 1, the functional substrate 20, and the radiation plate 30
into the wireless IC device 300. Preferably, a method of creating
an electromagnetic coupling module by mounting the wireless IC chip
1 on the functional substrate 20 and mounting the created
electromagnetic coupling module on the radiation plate 30 is used.
A general method used to mount a semiconductor chip on a substrate
can preferably be used for the mounting of the wireless IC chip 1
on the functional substrate 20 having a relatively small size. The
electromagnetic coupling module can be easily mounted on the
radiation plate 30 having a relatively large size via the adhesive
40.
[0073] FIG. 3 is an exploded perspective view of the multilayer
substrate 21 included in the functional substrate 20. In this
example, the wireless IC chip 1 is also illustrated. The multilayer
substrate 21 preferably includes dielectric layers 21a, 21b, 21c,
21d, 21e, 21f, and 21g. On the dielectric layer 21a, the mounting
electrodes 22a and 22b and mounting electrodes 22c and 22d, which
are used to mount the wireless IC chip 1, are provided. On the
dielectric layers 21b, 21c, 21d, 21e, and 21f, inductor electrodes
23a, 23b, 23c, 23d, and 23e are provided, respectively. On the
dielectric layers 21b, 21c, and 21d, inductor electrodes 23f, 23g,
and 23h are provided, respectively. On the dielectric layer 21g,
capacitive coupling electrodes 24a and 24b are provided. As
illustrated in FIG. 3, these dielectric layers are preferably
connected to one another by a via hole.
[0074] FIG. 4 is an oblique perspective view of the functional
substrate 20 on which the wireless IC chip 1 is mounted. The
multilayer substrate included in the functional substrate 20
includes an inductor defined by the inductor electrodes 23a to 23e
and an inductor defined by the inductor electrodes 23f to 23h.
[0075] FIG. 5 is an equivalent circuit diagram of the wireless IC
chip, the functional substrate, and the radiation plate. As
illustrated in FIG. 5, the matching circuit 23 included in the
functional substrate is preferably defined by the radiation plate,
capacitors C1 and C2, and inductors L1 and L2. The inductor L1
represents the inductor defined by the inductor electrodes 23a to
23e illustrated in FIGS. 3 and 4. The inductor L2 represents the
inductor defined by the inductor electrodes 23f to 23h illustrated
in FIGS. 3 and 4. The capacitor C1 represents a capacitor defined
between the capacitive coupling electrode 24a and the radiation
electrode 32a. The capacitor C2 represents a capacitor defined
between the capacitive coupling electrode 24b and the radiation
electrode 32b.
[0076] An impedance obtained by viewing the wireless IC chip from a
connecting portion connecting the wireless IC chip and the
functional substrate to each other is represented by
R.sub.IC+jX.sub.IC, and an impedance obtained by viewing the
radiation electrodes provided on the radiation plate from a
connecting portion connecting the functional substrate and the
radiation plate to each other is represented by Rant+jXant. For
example, assuming that an impedance obtained by viewing the
radiation plate (radiation electrodes) from the connecting portion
connecting the wireless IC chip and the functional substrate to
each other in or near a frequency range such as UHF is R1+jX1, the
circuit constant of the matching circuit 23 included in the
functional substrate is determined so that the relationship between
X.sub.IC and X1 is a conjugate relationship, that is,
X1=-X.sub.IC.
[0077] The matching circuit 23 included in the functional substrate
performs impedance matching between the wireless IC chip and the
radiation plate (radiation electrodes). If R.sub.IC=R1 is
satisfied, that is, the relationship between R.sub.IC+jX.sub.IC and
R1+jX1 is a complex conjugate relationship, the perfect impedance
matching between the wireless IC chip and the radiation plate
(radiation electrodes) can be achieved. However, in reality, it is
difficult for the real parts to be equal or substantially equal to
each other (R.sub.IC=R1). Accordingly, it is necessary to achieve
the conjugate relationship at least between reactive components. In
the above-described impedance matching, the consistency between
imaginary parts is more important than the consistency between real
parts.
[0078] Thus, according to the first preferred embodiment, since the
capacitive coupling electrodes 24a and 24b included in the
electromagnetic coupling module obtained by mounting the wireless
IC chip 1 on the functional substrate 20 are disposed apart from
the radiation plate 30 on which the radiation electrodes 32a and
32b are provided, the electromagnetic coupling module is
DC-insulated from the radiation electrodes 32a and 32b. As a
result, an excellent electrostatic discharge (ESD) characteristic
can be obtained.
[0079] Furthermore, since the matching circuit 23 is included in
the functional substrate 20 including the multilayer substrate
disposed between the wireless IC chip 1 and the radiation plate 30,
that is, since it is not necessary to provide an impedance matching
circuit on the side of the radiation plate 30, an area required for
the radiation electrodes 32a and 32b on the radiation plate 30 can
be significantly reduced. As a result, the size of the wireless IC
device can be reduced.
[0080] Still furthermore, since the matching circuit 23 is included
in the multilayer substrate 21, a change in the characteristic of
the matching circuit 23 is relatively small, that is, the change in
the frequency characteristic of the wireless IC device 300 is
relatively small even if the wireless IC device 300 is attached to
a product having a high dielectric constant. Accordingly, it is not
necessary to design a wireless IC device in consideration of a
product to which the wireless IC device is attached. Since the
matching circuit 23 is included in the multilayer substrate, it is
possible to use a complex matching circuit that cannot easily be
provided on a single surface as the matching circuit 23.
Accordingly, it is possible to improve the impedance matching and
obtain a high-gain wireless IC device.
Second Preferred Embodiment
[0081] FIG. 6 is a plan view illustrating an electrode pattern of a
main portion on the upper surface of a radiation plate in a
wireless IC device according to the second preferred embodiment of
the present invention. On the upper surface of the radiation plate,
the long radiation electrodes 32a and 32b and a matching electrode
34 are provided. The matching electrode 34 connects a portion of
the radiation electrode 32a apart from the internal end of the
radiation electrode 32a by a predetermined distance to a portion of
the radiation electrode 32b apart from the internal end of the
radiation electrode 32b by the predetermined distance.
[0082] As in the case illustrated in FIG. 2B, near the internal
ends of the radiation electrodes 32a and 32, the functional
substrate 20 is arranged so that the capacitive coupling electrodes
24a and 24b included in the functional substrate 20 face the
internal ends of the radiation electrodes 32a and 32b,
respectively. The illustration of the wireless IC chip mounted on
the upper surface of the functional substrate is omitted in FIG.
6.
[0083] An auxiliary matching circuit portion 35 is defined by the
matching electrode 34, and a portion of the radiation electrode 32a
from the internal end of the radiation electrode 32a to a location
connected to the matching electrode 34, and a portion of the
radiation electrode 32b from the internal end of the radiation
electrode 32b to a location connected to the matching electrode 34.
Thus, if predetermined portions of the radiation electrodes 32a and
32b are connected to each other using the matching electrode 34,
the wireless IC chip performs tap feeding so as to supply electric
power to a dipole antenna via the functional substrate 20. In an
area in which the tap feeding is performed, the auxiliary matching
circuit portion 35 performs impedance matching twice, that is, the
impedance matching between the functional substrate 20 and the
radiation electrode 32a and the impedance matching between the
functional substrate 20 and the radiation electrode 32b.
Accordingly, it is possible to maintain a state in which impedance
matching is achieved in a wide frequency band, that is, obtain a
high gain in a wide frequency band. While the auxiliary matching
circuit portion 35 is provided in the area in which the tap feeding
is performed, it is impossible to provide a large inductor on the
radiation plate due to limitations of space. Furthermore, it is
difficult to provide a capacitor and a circuit in which lines cross
each other on the radiation plate. However, if a functional
substrate is used, it is possible to provide an inductor, a
capacitor, and a circuit in which lines cross each other on the
radiation plate. As a result, as described previously, it is
possible to maintain a state in which impedance matching is
achieved in a wide frequency band, that is, obtain a high gain in a
wide frequency band.
Third Preferred Embodiment
[0084] FIG. 7 is a plan view illustrating an electrode pattern of a
main portion on an upper surface of a radiation plate in a wireless
IC device according to the third preferred embodiment of the
preferred embodiment. On the upper surface of the radiation plate,
a loop-shaped radiation electrode 36 is provided. The loop-shaped
radiation electrode 36 is preferably arranged so that both ends
thereof face each other and it surrounds a predetermined area. The
functional substrate 20 is mounted on the radiation plate so that
one end of the loop-shaped radiation electrode 36 faces the
capacitive coupling electrode 24a included in the functional
substrate 20 and the other end of the loop-shaped radiation
electrode 36 faces the capacitive coupling electrode 24b included
in the functional substrate 20.
[0085] As in the first and second preferred embodiments, a module
is obtained by mounting the wireless IC chip on the functional
substrate 20. The configuration of the functional substrate 20
according to the third preferred embodiment is substantially the
same as that of the functional substrates 20 according to the first
and second preferred embodiments.
[0086] Thus, if the wireless IC chip supplies electric power to the
radiation electrodes 32a and 32b via the functional substrate 20,
the radiation electrodes 32a and 32b operate as a magnetic field
antenna. As a result, the wireless IC device can communicate with a
reader/writer antenna for the wireless IC device using a magnetic
field.
Fourth Preferred Embodiment
[0087] FIGS. 8A to 8D and 9A to 9D are cross-sectional views
illustrating the configurations of some wireless IC devices
according to the fourth preferred embodiment of the present
invention. The configurations of the radiation plate 30 and the
wireless IC chip 1 according to the fourth preferred embodiment are
substantially the same as those of the radiation plates 30 and the
wireless IC chips 1 according to the first to third preferred
embodiments. In the fourth preferred embodiment, some examples of a
matching circuit included in a functional substrate will be
described.
[0088] In an example illustrated in FIG. 8A, a matching circuit is
defined by the inductors L1, L2, an inductor L3, and the capacitive
coupling electrodes 24a and 24b in a functional substrate 120. In
the example illustrated in FIG. 5, the mounting electrode 22b is
through-connected to the capacitor C2. In the matching circuit
according to the fourth preferred embodiment, the inductor L3 is
disposed at the through-connection portion. Accordingly, it is
possible to reduce the inductance values of the inductors L1 to L3
and easily provide the inductors L1 to L3 in a multilayer
substrate.
[0089] In an example illustrated in FIG. 8B, a matching circuit is
defined by the inductors L1 and L3, and the capacitive coupling
electrodes 24a and 24b in a functional substrate 121. In this
example, a shunt inductor is not disposed between the capacitive
coupling electrodes 24a and 24b. Accordingly, it is possible to
easily convert a small impedance. That is, if the above-described
shunt inductor has a small inductance value, it significantly
changes the impedance of an impedance matching circuit. In this
example, since such a shunt inductor is not used, such a problem
does not arise.
[0090] In an example illustrated in FIG. 8C, a matching circuit is
defined by the inductor L3 and the capacitive coupling electrodes
24a and 24b in a functional substrate 122. In this example, since
only the inductor L3 is used, it is possible to achieve the easy
configuration of the matching circuit.
[0091] In an example illustrated in FIG. 8D, a matching circuit is
defined by inductors L11, L12, L21, L31, and L32 and the capacitive
coupling electrodes 24a and 24b in a functional substrate 123. In
this example, since the inductors L12 and L32 are included, the
inductance values of the radiation electrodes 32a and 32b can be
reduced. Accordingly, the size of the radiation electrodes can be
reduced.
[0092] In an example illustrated in FIG. 9A, a matching circuit is
defined by the inductors L21, L31, and L32 and the capacitive
coupling electrodes 24a and 24b in a functional substrate 124. In
this example, since the inductors L11 and L12 illustrated in FIG.
8D are removed, it is possible to provide an easy configuration of
the matching circuit while enabling the matching circuit to have
the characteristic illustrated in FIG. 8D.
[0093] In an example illustrated in FIG. 9B, a matching circuit is
defined by the inductors L11, L21, and L32 and the capacitive
coupling electrodes 24a and 24b in a functional substrate 125. In
this example, the location of the inductor L31 illustrated in FIG.
9A is changed. Accordingly, it is possible to provide easy wiring
in the multilayer substrate while enabling the matching circuit to
have the same or substantially the same effect as that illustrated
in FIG. 9A.
[0094] In an example illustrated in FIG. 9C, a matching circuit is
defined by capacitors C11 and C31, inductors L22 and L23, and the
capacitive coupling electrodes 24a and 24b in a functional
substrate 126. In this example, since the matching circuit includes
the capacitors C11 and C31 connected in series to each other, it is
possible to achieve the impedance matching between each of the
radiation electrodes (antenna) having a capacitive impedance and
the wireless IC chip 1 having a capacitive impedance in a wide
frequency range.
[0095] In an example illustrated in FIG. 9D, a matching circuit is
defined by the inductors L22 and L23, the capacitor C31, and the
capacitive coupling electrodes 24a and 24b in a functional
substrate 127. In this example, since the capacitors C11 and C31
illustrated in FIG. 3C are integrated into the capacitor C31, it is
possible to achieve easy pattern formation in the multilayer
substrate while enabling the matching circuit to have the same or
substantially the same effect as that illustrated in FIG. 9C.
[0096] The circuit constant of each of the matching circuits
included in the functional substrates 120 to 127 is preferably
determined so that the relationship between the reactive component
of an impedance obtained by viewing the wireless IC chip from the
connecting portion connecting the wireless IC chip and the
functional substrate to each other and the reactive component of an
impedance obtained by viewing the radiation electrodes from the
connecting portion connecting the wireless IC chip and the
functional substrate to each other is a conjugate relationship.
Thus, a matching circuit including at least one inductance element
and at least one capacitance element as required.
Fifth Preferred Embodiment
[0097] FIG. 10 is a cross-sectional view of a main portion of a
wireless IC device according to the fifth preferred embodiment of
the present invention. As illustrated in FIG. 10, the wireless IC
chip 1 is mounted on the upper surface of the functional substrate
20, and the wireless IC chip 1 is covered with a resin 41 on the
upper surface of the functional substrate 20 so that a flat upper
surface is obtained. Other configurations are substantially the
same as those described in the first preferred embodiment.
[0098] Thus, when an electromagnetic coupling module obtained by
mounting the wireless IC chip 1 on the functional substrate 20 is
mounted on the radiation plate 30, it is possible to easily grasp
the electromagnetic coupling module by suction and chuck the
electromagnetic coupling module on the radiation plate 30. Since
the wireless IC chip 1 is embedded in the resin 41, the
environmental resistance of the wireless IC chip 1 is
increased.
[0099] A protection film may preferably be arranged on not only the
wireless IC chip 1 but also on the functional substrate 20 or the
radiation plate 30. Alternatively, a protection film may preferably
be arranged so as to cover all of the wireless IC chip 1, the
functional substrate 20, and the radiation plate 30. This is also
true for other preferred embodiments of the present invention.
Sixth Preferred Embodiment
[0100] FIGS. 11 and 12 are cross-sectional views of main portions
of wireless IC devices according to the sixth preferred embodiment
of the present invention. In an example illustrated in FIG. 11, a
functional substrate 128 includes the multilayer substrate 21, and
capacitive coupling electrodes 224a and 224b are arranged so that
they are exposed at the undersurface of the multilayer substrate
21.
[0101] The capacitive coupling electrodes 224a and 224b face the
internal ends of the radiation electrodes 32a and 32b,
respectively, via the adhesive 40. As a result, a large capacitance
can be generated between the capacitive coupling electrode 224a and
the internal end of the radiation electrode 32a and between the
capacitive coupling electrode 224b and the internal end of the
radiation electrode 32b.
[0102] In an example illustrated in FIG. 12, each of external
coupling electrodes 225a and 225b is arranged so as to extend from
the undersurface to the side surface of a functional substrate 129.
The coupling electrodes 225a and 225b are preferably connected to
the radiation electrodes 32a and 32b, respectively, via a
conductive joining material 42, such as solder, for example.
[0103] As a result, it is possible to achieve the direct electrical
connection between the coupling electrode 225a included in the
functional substrate 129 and the radiation electrode 32a provided
on the radiation plate 30 and the direct electrical connection
between the coupling electrode 225b included in the functional
substrate 129 and the radiation electrode 32b provided on the
radiation plate 30. Furthermore, it is possible to increase the
mechanical strength of the wireless IC device by increasing a
solder connecting area.
Seventh Preferred Embodiment
[0104] FIG. 13 is a cross-sectional view of a main portion of a
wireless IC device according to the seventh preferred embodiment of
the present invention. Referring to FIG. 13, a multilayer substrate
is included in a functional substrate 220. The multilayer substrate
includes inductance electrodes and capacitive coupling electrodes.
On the upper surface of the multilayer substrate, a chip inductor
51 that is preferably a discrete component is mounted. A matching
circuit is defined by the internal electrodes included in the
functional substrate 220 and the external chip component.
[0105] In a wireless IC device having the above-described
configuration, it is possible to reduce the size of the functional
substrate by mounting a chip inductor having a large inductance
value or a chip capacitor having a large capacitance value on the
functional substrate so as to reduce the inductance or capacitance
value of an element included in the functional substrate.
Eighth Preferred Embodiment
[0106] A wireless IC device according to the eighth preferred
embodiment of the present invention will be described with
reference to FIGS. 14 to 16B. FIG. 14 is a cross-sectional view of
a main portion of a wireless IC device according to the eighth
preferred embodiment. In a radiation plate 130, the radiation
electrodes 32a, 32b, and 32c are provided on the upper surface of
the base material 31. A functional substrate 221 includes a
loop-shaped external coupling electrode 226. An electromagnetic
coupling module obtained by mounting the wireless IC chip 1 on the
functional substrate 221 is mounted on the radiation plate 130 so
that the magnetic field of the loop-shaped external coupling
electrode 226 and the magnetic field of the radiation electrode 32c
are coupled to each other.
[0107] FIG. 15 is a plan view of radiation electrodes provided on
the upper surface of the radiation plate 130 and a loop-shaped
external coupling electrode included in the functional substrate
221. The radiation electrodes 32a and 32b, which are relatively
long, are connected to each other by the loop-shaped radiation
electrode 32c. The loop-shaped external coupling electrode 226
included in the functional substrate is preferably spirally wound
with a plurality of turns and a size that is about the same as the
loop-shaped radiation electrode 32c.
[0108] Thus, the winding axis of the loop-shaped external coupling
electrode 226 that is an inductance element that is spirally wound
with a plurality of turns crosses an area in which the radiation
electrode 32c is provided. As a result, a magnetic field is
generated at the loop-shaped external coupling electrode 226 in a
direction that is parallel or substantially parallel to the winding
axis and is vertical or substantially vertical to the radiation
electrode 32c, and a magnetic field is generated around (in and out
of) the radiation electrode 32c. Accordingly, a magnetic field loop
generated at the functional substrate 221 is interlinked with a
magnetic field loop generate at the radiation electrode 32c, so
that the degree of coupling between the loop-shaped external
coupling electrode 226 and the radiation electrode 32c can be
further increased.
[0109] In the examples illustrated in FIGS. 14 and 15, the
loop-shaped radiation electrode 32c is provided. However, instead
of a loop-shaped radiation electrode, for example, a dipole
electrode may preferably be used as the radiation electrode 32c.
Such a dipole electrode can also be strongly coupled to the
loop-shaped external coupling electrode 226, since the magnetic
flux of the loop-shaped external coupling electrode 226 passes
around the radiation electrode 32c and is then coupled to the
magnetic field of the radiation electrode 32c.
[0110] Furthermore, in the examples illustrated in FIGS. 14 and 15,
the loop-shaped external coupling electrode 226 that is spirally
wound is provided. However, a loop-shaped external coupling
electrode that is wound with a single turn may preferably be used
as the loop-shaped external coupling electrode 226.
[0111] FIGS. 16A and 16B are impedance circuit diagrams of the
above-described wireless IC chip, the above-described functional
substrate, and the above-described radiation plate. Referring to
FIG. 16A, an inductor La on the side of the radiation plate is an
inductor at the radiation electrode 32c, and an inductor Lb on the
side of the functional substrate is an inductor at the loop-shaped
external coupling electrode 226. One terminal of the wireless IC
chip 1 is connected in series to an inductor Lc.
[0112] If the mutual inductance between the inductors La and Lb
between which a magnetic field coupling is achieved is represented
by M, the circuit illustrated in FIG. 16A can be changed to a
circuit illustrated in FIG. 16B. The inductors La, Lb, and Lc
illustrated in FIG. 16A are determined so that the relationship
between X.sub.IC and X1 illustrated in FIG. 16B is a conjugate
relationship.
[0113] Thus, since a matching circuit includes the inductor at the
radiation electrode 32c, the impedance matching between an antenna
defined by the radiation electrodes 32a and 32b and the wireless IC
chip can be achieved.
[0114] According to the eighth preferred embodiment, since both of
the radiation electrode 32c on the side of the radiation plate and
the loop-shaped external coupling electrode 226 on the side of the
functional substrate are loop-shaped electrodes, the mounting
direction of the module, which is obtained by mounting the wireless
IC chip 1 on the functional substrate 221, with respect to the
radiation plate 130 has substantially no effect on the
characteristics. That is, if the module is mounted on the radiation
plate 130 in any orientation, a predetermined characteristic can be
obtained.
Ninth Preferred Embodiment
[0115] FIG. 17 is a cross-sectional view of a main portion of a
wireless IC device according to the ninth preferred embodiment of
the present invention. In this example, a functional substrate 222
includes a double helix external coupling electrode 227. The
magnetic field of the double helix external coupling electrode 227
and the magnetic field of the loop-shaped radiation electrode 32c
provided on the radiation plate 130 are coupled to each other.
[0116] The double helix external coupling electrode 227 has a
double helix configuration in which two different linear electrodes
are adjacent to each other and ends of these linear electrodes are
electrically connected to each other. The pattern of the radiation
electrodes provided on the radiation plate 130 is substantially the
same as that illustrated in FIG. 15.
[0117] FIG. 18 is an impedance circuit diagram of the wireless IC
chip illustrated in FIG. 17. Inductors Lb1 and Lb2 included in a
functional substrate are inductors at the double helix external
coupling electrode 227. Capacitors Ca and Cb are capacitors
included in the multilayer substrate included in the functional
substrate 222. The inductor La at a radiation substrate is an
inductor at the loop-shaped radiation electrode 32c. The magnetic
field of the inductor La is coupled to the magnetic fields of the
inductors Lb1 and Lb2 at the double helix external coupling
electrode.
[0118] The constants of circuit elements of the matching circuit
included in the functional substrate are determined so that the
relationship between a reactance component X.sub.IC of an impedance
obtained by viewing the wireless IC chip from a connecting portion
connecting the wireless IC chip and the functional substrate to
each other and a reactance component X1 of an impedance obtained by
viewing the radiation electrodes 32a and 32b from the connecting
portion connecting the wireless IC chip and the functional
substrate to each other is a conjugate relationship.
[0119] Thus, by using an external coupling electrode having a
double helix shape, the degree of coupling between the external
coupling electrode and a radiation electrode can be increased.
Furthermore, since the two lines included in the double helix
external coupling electrode have different lengths, the two lines
can have different resonance frequencies. Accordingly, it is
possible to increase a frequency band used by the wireless IC
device.
Tenth Preferred Embodiment
[0120] FIG. 19 is a plan view illustrating the configuration of a
functional substrate used in a wireless IC device according to the
tenth preferred embodiment of the present invention. In this
example, an electrode pattern is provided on only the upper surface
of a functional substrate 223. As illustrated in FIG. 19, a double
helix external coupling electrode 228 is provided on the upper
surface of the functional substrate 223, and the inner ends of the
double helix external coupling electrode 228 define the mounting
electrodes 22a and 22b for the wireless IC chip 1. Other mounting
electrodes 22c and 22d are provided near the mounting electrodes
22a and 22b. An electromagnetic coupling module is obtained by
mounting the wireless IC chip 1 on the mounting electrodes 22a to
22d.
[0121] The configuration of a radiation electrode on the side of a
radiation plate is substantially the same as that illustrated in
FIG. 15. The electromagnetic coupling module illustrated in FIG. 19
is preferably arranged so as to face the loop-shaped radiation
electrode 32c as illustrated in FIG. 15. As a result, the double
helix external coupling electrode 228 is electromagnetically
coupled to the loop-shaped radiation electrode 32c. Thus, an
impedance matching circuit can be obtained without using a
multilayer substrate.
[0122] In the above-described preferred embodiments, various
typical examples of a wireless IC device have been described.
However, a wireless IC device may be obtained by combining
configurations described in any of the above preferred
embodiments.
[0123] While preferred embodiments of the present invention have
been described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing the scope and spirit of the present invention. The scope
of the present invention, therefore, is to be determined solely by
the following claims.
* * * * *