Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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COIL ARRANGEMENT FOR RADIO-FREQUENCY TDENTIFICATION DEVICES, PROCESS AND
APPARATUS FOR MAKING SAID ARRANGEMENT
TITLE OF THE INVENTION
COIL ARRANGEMENT FOR RADIO-FREQUENCY
IDENTIFICATION DEVICES, PROCESS AND APPARATUS FOR MAKING
SAM E
FIELD OF THE INVENTION
[0001] The present invention relates to radio-frequency identification
devices. More specifically, the present invention is concerned with a coil
arrangement therefor and with a process and an apparatus for making such a
coil arrangement.
BACKGROUND OF THE INVENTION
[0002] Radio-frequency identification (RFID) technology is well
known in the art. RFID systems are usually made of two components, a reader
and a tag or card, which will hereinafter be referred.to as an RFID device.
The
RFID device generally comprises an antenna, in the form of an air coil, and a
microchip to which the antenna is connected. Since the operation of a RFID
system is believed well known in the art, it will therefore not be discussed
further herein.
[0003] The manufacturing of miniaturized RFID devices is generally
divided in two sequential steps: the winding of an ultra-fine magnet wire to
provide an air-coil and the subsequent electrical connection of the two
terminals of the coil to pads of the microchip.
[0004] One of the difficulties in the mass-production process of RFID
devices concerns the handling of the coil terminals and their precise
alignment
above the microchip pads. Indeed, since the wire used to form the air coil is
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ultra-fine, usually wire gage AWG 44 to AWG 50, it is difficult to handle and
to
properly align and maintain during the soldering operation. Accordingly, a
complicated dedicated apparatus is often used to connect the antenna to the
microchip. This apparatus increases the total cost of production of the RFID
device.
OBJECTS OF THE INVENTION
[0005] An object of the present invention is therefore to provide an
improved, coil arrangement for radio-frequency identification devices and
process and apparatus for making same.
SUMMARY OF THE INVENTION
[0006] The present invention provides a coil geometry, a winding
method and a winding apparatus that avoid the need to seize and align the coil
terminal during the coil to circuit assembly step described hereinabove. The
present invention also aims to increase the hardiness of the wire arrangement
allowing a very low amount of turns for a coil. Which is particularly useful
for
coils operating at higher frequencies (13.56MHz and above) as is sometimes
the case in RFID systems.
[0007] More specifically, ,in accordance with the present invention,
there is provided a coil arrangement for a radio-frequency identification
device
made of a wire; the coil arrangement comprising:
a first coil terminal made of one turn of the wire; the first coil
terminal having a first coil terminal geometry;
a active coil made of a predetermined number of turns of the
wire; the active coil defining a geometry of the coil arrangement;
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a second coil terminal made of one turn of the wire; the
second coil terminal having a second coil terminal geometry; and
wherein the coil arrangement geometry, the first coil
geometry and the second coil geometry are different.
[0008] According to another aspect of the present invention, there is
provided a process for making a coil arrangement for a radio-frequency
identification device from a wire; the method comprising:
making a first coil terminal by winding one turn of the wire;
the first coil terminal having a first coil terminal geometry;
making an active coil by winding a predetermined number of
turns of the wire; the active coil defining a coil arrangement geometry;
making a second coil terminal by winding one turn of the wire;
the second coil terminal having a second coil terminal geometry; and
making a supporting outer layer by winding at least one turn
of the wire;
wherein the coil arrangement geometry, the first coil
geometry and the second coil geometry are different.
[0009] According to third aspect of the present invention, there is
provided a process for making a coil arrangement for a radio-frequency
identification device from a wire; the method comprising:
providing a mandrel having a rotation axis, a first portion
having a predetermined cross-sectional profile, a second portion having a
predetermined cross-sectional profile and positioned axially adjacent to the
first
portion and a third portion having a predetermined cross-sectional profile and
positioned axially adjacent to the second portion;
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making a first coil terminal by winding one turn of the wire
orito the second portion of the mandrel;
making an active coil by winding a predetermined number of
turns of the wire onto the first portion of the mandrel; and
making a second coil terminal by winding one turn of the wire
onto the third portion of the mandrel.
[0010] According to another aspect of the present invention, there is
provided a spindle for making a coil arrangement comprising:
a flange rotatable about a rotation axis; the flange having a
flat and a mandrel a predeterminedheight; the mandrel
face of generally
defininga geometry of coil arrangementvia a peripheral coil
the winding
surface;the mandrel havinga first slot second slot separated
and a by an
intermediate wall having a height smaller than the height of the mandrel; the
mandrel being also provided with an external wall having a height smaller than
the height of the intermediate wall;
a counter-flange rotatable about the rotation axis; the
counter-flange having a flat face and a recess configured and sized to receive
at least a portion of the mandrel;
one of the flange and the counter-flange being so configured
as to be axially movable along the rotation axis to modify the portion of the
predetermined height of the mandrel received in the counter-flange, thereby
selectively allow a wire forming the coil to enter either the first and second
slots.
[0011] According to another aspect of the present invention,.there is
provided a spindle for making a coil arrangement comprising:
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a flange rotatable about a rotation axis; the flange having a
flat face and a mandrel; the mandrel generally defining a geometry of the coil
arrangement via a peripheral coil winding surface; the mandrel having:
- a central portion having a predetermined height;
- a first semi-circular wall portion separated from the first
semi-circular wall portion by a first slot; the first semi-circular
wall portion having a height smaller than the predetermined
height;
- a second semi-circular wall portion opposite the first semi-
circular wall portion; the second semi-circular wall portion
being separated from the central portion by a second slot and
having a height smaller than the predetermined height; the
first and second slots being generally parallel;
a counter-flange rotatable about the rotation axis; the
counter-flange having a flat face and a recess configured and sized to receive
at least a portion of the mandrel;
one of the flange and the 'counter-flange being so configured
as to be axially movable along the rotation axis to modify the portion of the
predetermined height of the mandrel received in the counter-flange, thereby
selectively allow a wire forming the coil to enter either the first and second
slots.
[0012] According to a final aspect of the present invention, there is
provided a spindle for making a coil arrangement, the spindle comprising:
a flange rotatable about a rotation axis; the flange having a
predetermined thickness; the flange having a first cross-sectional profile for
a
first portion of the predetermined thickness, a second cross-sectional profile
for
a second portion of the predetermined thickness and a third cross-sectional
profile for a third portion of the predetermined thickness;
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a counter-flange rotatable about the rotation axis; the
counter-flange having a flat face and a recess configured and sized to receive
at least a portion of the mandrel;
one of the flange and the counter-flange being so configured
as to be movable along the rotation axis to expose either the first, the first
and
second; and the first, second and third portions of the mandrel.
[0013] Generally stated, the present invention provides a coil
geometry, a winding method and a winding apparatus that avoid the need to
seize and align the coil terminal during the coil to circuit assembly step
described hereinabove. The present invention also aims to increase the
hardiness of the wire arrangement allowing a very low amount of turns for a
coil. Which is particularly useful for coils operating at higher frequencies
(13.56MHz and above) as is sometimes the case in RFID systems.
[0014] Other objects, advantages and features of the present
invention will become more apparent upon reading of the following non-
restrictive description of preferred embodiments thereof, given by way of
example only with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In the appended drawings:
[0016] Figure 1 is a side partly sectional view of a spindle according
to an embodiment of the present invention; the flange and counter-flange of
the
spindle being shown in one of their coil winding position;
[0017] Figure 2 is a front view of a flange of the winding spindle of
Figure 1;
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[0018] Figure 3 is a side partly sectional view similar to Figure 1
where the flange and counter flange are in a spaced apart position;
[0019] Figure 4 is a sectional enlarged view of a portion of Figure 3
during the winding of an inner layer of a coil arrangement;
[0020] Figure 5 is a front view of the flange during the winding of an
inner layer of a coil arrangement;
[0021] Figure 6 is a sectional view of the spindle during the winding
of a first coil terminal;
[0022] Figure 7 is a front view of the flange during the winding of the
first coil terminal;
[0023] Figure 8 is a sectional view of the spindle during the winding
of the main winding layer;
[0024] Figure 9 is a front view of the flange during the winding of the
main winding layer;
[0025] Figure 10 is a sectional view of the spindle during the winding
of the second coil terminal;
[0026] Figure 11 is a front view of the flange during the winding of
the second coil terminal;
[0027] Figure 12 is a sectional view of the spindle during the winding
of the outer layer of the coil;
[0028] Figure 13 is a front view of the flange during the winding of
the outer layer of the coil;
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[0029] Figure 14 is a front view of a coil arrangement according to a
first embodiment of the present invention;
[0030] Figure 15 is a front view of a coil arrangement according to a
second embodiment of the present invention;
[0031] Figure 16 is a front view of a flange used to obtain the coil
arrangement of Figure 15;
[0032] Figure 17 is a front view of a coil arrangement according to a
third embodiment of the present invention;
[0033] Figure 18 is a front view of a flange used to obtain the coil
arrangement of Figure 17;
[0034] Figure 19 is a front view of a coil arrangement according to a
fourth embodiment of the present invention;
[0035] Figure 20 is ~a perspective view of a flange used to obtain the
coil arrangement of Figure 19;
[0036] Figure 21 is a front view of a coil arrangement according to a
fourth embodiment of the present invention; and
[0037] Figure 22 is a front view of a flange used to obtain the coil
arrangement of Figure 20.
DETAILED DESCRIPTION
[0038] Turning to Figures 1 and 2 of the appended drawings, a
apparatus for forming a coil (herein after referred to as the spindle 10) will
be
described.
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[0039] The spindle 10 includes a flange 12 and a counter-flange 14
shown in sectional view in the appended drawings.
[0040] The flange 12 includes a shaft 16, a body 18, a face 20 and a
mandrel 24. As can be better seen from Figure 2, the center of the mandrel 24
includes a clutch fork male portion 22. The circular mandrel 24 defines a
generally cylindrical coil winding surface 26 having a predetermined height.
[0041] It is to be noted that the mandrel 24 is associated with a
retractable portion 17 of the shaft 16 to thereby allow the disengagement of a
finished coil from the mandrel 24, as will be described hereinbelow.
[0042] The mandrel 24 includes a first slot 30 defined by a wall 31
and an intermediate wall portion 32. It is to be noted that the height of the
intermediate wall 32 is less than the height of the mandrel 24 (see Figure 1
).
The mandrel 24 also includes a second slot 34 defined by the intermediate wall
32 and an external wall portion 36. The wall portion 36 has a semi-cylindrical
outer surface 40 defining a portion of the coil winding surface 26 of the
mandrel
24. It is to be noted that the height of the external wall 36 is less than the
height
of the intermediate wall 32.
[0043] In other words, the mandrel 24 is divided in three portions
defining different cross-sectional profiles and hence, the geometry of the
coil
arrangement as will be described hereinbelow.
[0044] A first portion of the height of the mandrel, extending from the
face 20 of the flange to the top of the external wall 36, has a generally
circular
cross-sectional profile.
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[0045] A second portion of the height of the mandrel 24, extending
between the top of the external wall 36 and the top of the intermediate wall
32,
defines a generally inverted D-shaped cross-sectional profile.
[0046] Finally, a third portion of the height of the mandrel, extending
between the top of the intermediate wall 32 and the top of the mandrel 24,
defines a smaller inverted D-shaped cross-sectional profile.
[0047] As is clearly seen from Figure 2, the slots 30 and 34 are each
provided with a respective wire outlet 42 and 44 and with a common wire inlet
46.
(0048] Conventionally, the flange includes grooves (not shown) used
to hold the end of the wire before it is would. Since this technique is
believed
well known in the art, it will not be discussed herein.
[0049] The shaft 16 of the flange 12 is associated with a motor (not
shown) that may be precisely controlled to rotate the flange 12 in the
direction
of arrow 47.
[0050] The counter-flange 14 includes a shaft 48, a body 50 and a
clutch fork female portion 52 configured to be engaged by the clutch fork male
portion 22 of the flange 12 so as to cooperate therewith. The face 54 of the
counter-flange 14 includes a circular recess 56 defining a cylindrical wall 58
having a diameter that is only slightly larger than the diameter of the
mandrel
24. As will be further discussed hereinbelow, the shaft 48 is free-wheeling,
i.e.
that it may rotate about an axis common to the rotation axis of the shaft 16
of
the flange 12. Furthermore, the shaft 48 is so associated with a displacement
mechanism (not shown) that the counter-flange 14 may axially be moved (see
double-arrow 60) to expose the first portion, the first and second portion or
the
first, second and third portion of the height of the mandrel.
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(0051] Figure 3, which is very similar to Figure 1, shows the counter-
flange 14 in an opened position, where the clutch fork portions 22 and 52 are
disengaged.
[0052] The flange 12 of the spindle 10 is so configured as to
produce coils such as coil arrangement 100, as illustrated in Figure 14. The
coil arrangement 100 includes a plurality of turn of wire forming the main
winding 102 thereof and defining a geometry of the coil arrangement 100, in
this case a circle. The coil 100 also includes one turn of wire forming a
first coil
terminal 104 and defining a first coil terminal geometry, in this case an
inverted
D=shape having a straight portion and a curved portion. One turn of wire forms
a second coil terminal 106 having a second coil terminal geometry, in this
case
a smaller inverted D-shape having a straight portion and a curved portion. The
first and second coil terminals 102 and 104 defining an angle so that their
straight portions converge. As will be discussed hereinbelow, a supporting
inner layer of winding and a supporting outer layer of winding are also
provided.
[0053] Turning now to Figures 4 to 13 of the appended drawings, the
steps of the formation of a coil arrangement such as 100 from a single wire
will
be described.
[0054] The main steps are:
~ Formation of the supporting inner wire layer;
~ Formation of the first coil terminal;
~ Formation of the active coil;
~ Formation of the second coil terminal; and
~ Formation of the supporting outer layer.
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[0055] As will be understood by one skilled in the art, before the
winding of the coil arrangement, the end of the wire used must be secured to
the spindle 10 according to conventional manner.
[0056] It is also to be noted that a wire guide (not shown) is used to
guide the wire during the winding operation. This wire guide is operated in
translation along the rotational axis of the spindle 10 providing a precise
placement of the wire during winding. Since guides of this type are believed
well known in the art, they will not be further discussed herein.
[0057] Figures 4 and 5 illustrate the first step in the coil arrangement
formation process, the winding of the supporting inner wire layer. More
specifically, these figures illustrate the state of the spindle 10 after this
step is
done. It is to be noted that in the following figures the wire forming the
coil is
often shown in section, for clarity purposes.
[0058] As can be better seen from Figure 4, the distance separating
the faces 20 and 54 of the flange 12 and the counter-flange 14, respectively,
define the width of the coil. It is to be noted that during this step this
distance
between the faces 20 and 54 is slightly smaller than the height of the
external
wall 36 of the mandrel 24. Therefore, only the first portion of the height of
the
mandrel 24 is exposed.
[0059] It is to be understood that while the inner wire layer consists
of five turns of wire in the appended drawings, this number is arbitrary and
depends on the size of the wire used, the width of the desired coil and the
desired rigidity of the finished coil arrangement. For example, it would be
possible to provide an inner wire layer consisting of only one turn of wire
should
the faces 20 and 54 be positioned closer than they appear in the appended
drawings. Furthermore, in some instances it is possible to forego this step
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entirely, which would lead to a coil arrangement devoid of supporting inner
wire
layer.
[0060] As can be seen from Figure 5, the inner layer of wire follows
the winding surface 26 and the external surface 40 of the external wall 36,
thereby defining the coil arrangement geometry.
[0061] Figures 6 and 7 of the appended drawings illustrate the
winding of the first terminal 104 (see figure 14) of the coil arrangement.
More
specifically, these figures illustrate the state of the spindle 10 following-
this step
is done.
[0062] The counter-flange 14 has been moved (see .arrow 62) so
that the distance between the faces 20 and 54 is greater than the height of
both
the walls 32 and 36 but still smaller than the height of the mandrel 24.
Therefore, the first, second and third portions of the height of the mandrel
24
are exposed.
[0063] Since the guiding mechanism (not shown) guides the wire so
that it is adjacent to the face 54 of the counter-flange 14, upon rotation of
the
spindle 10, the wire will enter the slot 30 via the inlet 46, abut the wall 31
by
passing over the walls 32 and 36 and exit the slot 30 via the outlet 42.
[0064] Figure 7 illustrates the first coil terminal being wounded. As
can be clearly seen from this figure, the geometry of the coil terminal is
different
from the circular geometry of the inner layer since the first coil terminal is
wound onto the third portion of the height of the mandrel 24.
[0065] Once the first coil terminal is wound, the counter-flange 14
returns to the position illustrated in Figure 8 for the next step.
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[0066] Figures 8 and 9 illustrate the winding of the active coil of the
coil arrangement. More specifically, these figures illustrate the state of the
spindle 10 after this step is done.
[0067] As mentioned hereinabove, the counter-flange 14 has been
moved (see arrow 64) so that the distance between the faces 20 and 54 is back
to being slightly smaller than the height of the wall 36. Therefore, only the
first
portion of the height of the mandrel 24 is exposed.
[0068] Once this is done, a predetermined number of turns may be
wound onto the previously wound inner layer and first terminal. Of course, the
number of turns of wire depends on the desired characteristics of the antenna.
For example, up to 1200 turns of wire may be wound to yield the active coil,
depending on the requirements of the microchip, the diameter and thickness of
the air coil. It is believed to be within the reach of one skilled in the art
to
determined the number of turns of wire required for a particular application.
[0069] As can be seen from Figure 9, the active coil follows the
winding surface 26 and the external surface 40 of the external wall 36,
thereby
following the coil arrangement geometry.
[0070] Turning now to Figures 10 and 11, the formation of the
second coil terminal 106 (see Figure 14) will be described. These figures
illustrate the state of the spindle 10 after this step is done.
[0071] As can be seen from Figure 10, the counter-flange 14 has
been moved (see arrow 66) so that the distance separating the faces 20 and 54
is greater than the height of the external wall 36 but smaller than the height
of
the intermediate wall 32. Therefore, only the first and second portions of the
height of the mandrel 24 are exposed.
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[0072] Since the guiding mechanism (not shown) guides the wire so
that it is adjacent to the face 54 of the counter-flange 14, upon rotation of
the
spindle 10, the wire will enter the slot 34 via the inlet 46, abut the
intermediate
wall 32 by passing over the wall 36 and exit the slot 34 via the outlet 42.
[0073] Figure 11 illustrates the second coil terminal being wounded.
As can be clearly seen from this figure, the geometry of the coil terminal is
different from the circular geometry of the inner layer, the active coil and
of the
geometry of the first terminal.
[0074] Once the second coil terminal is wounded, the counter-flange
14 returns to the position illustrated in Figure 12 for the next step.
[0075] Figures 12 and 13 illustrate the winding of the supporting
outer layer of the coil arrangement.
[0076] The counter-flange 14 has been moved (see arrow 68) so
that the distance between the faces 20 and 54 is again slightly smaller than
the
height of the external wall 36. Therefore, only the first portion of the
height of
the mandrel 24 is exposed.
[0077] It is to be understood that while the supporting outer wire
layer consists of five turns of wire in the appended drawings, this number is
arbitrary and depends of the size of the wire used and of the width of the
finished coil.
[0078] As can be seen from Figure 13, the outer layer of wire follows
the winding surface 26 and the external surface 40 of the external wall 36,
thereby following the coil arrangement geometry.
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[0079] Once the outer layer of wire has been wound, the wire can be
cut and the completed coil 100 is ready to be unloaded from the spindle 10.
The counter-flange 14 throws out of gear as illustrated in Figure 3. The
retractable portion 17 of the shaft 16 is then moved back (see arrow 70),
pulling
with it the mandrel 24, forcing the finished coil out of the mandrel 24 since
it
abuts the face 20 of the flange 14.
[0080] It is to be noted that while the description hereinabove states
that the flange 12 is connected to a motor (not shown) and that the counter-
flange 14 is driven by the engagement of the clutch elements 22 and 52, it
would be within the reach of one skilled in the art to connect the counter-
flange
14 to a motor instead and let the flange 12 be driven:
[0081] Similarly, the counter-flange 14 could be axially fixed and the
flange 12 could move axially to selectively expose the first, first and
second, or
first second and third portions of the height of the mandrel 24.
[0082] It is to be noted that while the above description specifies that
the first coil terminal goes through slot 30 and the second coil terminal goes
through slot 34, this is not essential to the present invention. Indeed, the
first
coil terminal could be wound into slot 34 and the second coil terminal could
be
wound into slot 30.
[0083] Similarly, while the appended drawings illustrate that the first
and second terminals are would near the face 54 of the counter-flange 14, it
is
not necessarily so.
[0084] Turning now to Figures 15 to 22 of the appended drawings,
other possible configurations of coil arrangements made according to
embodiments of the present invention will be described. It is to be noted that
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other configurations and geometries, not shown herein, are possible within the
scope of the present invention.
[0085] Figure 15 illustrates a coil arrangement 200 also having a
circular geometry but where the geometry of the first and second coil
terminals
202 and 204 is different. Indeed, while being generally D-shaped, instead of
converging as illustrated in Figure 14, the straight portions of the terminals
202
and 204 are parallel and located on the same side of the coil arrangement.
[0086] Figure 16 illustrates, in a perspective view, a flange 206
provided with a mandrel 208 used to wind the coil arrangement 200. The
mandrel 208 is very similar to the mandrel 24 discussed hereinabove. The
slots 210 and 212 are parallel and are separated by two intermediate wall
portions 214a and 214b. An external wall 216 completes the circular cross-
section of the first portion of the height of the mandrel 208.
[0087] As can be clearly be seen from this figure, the intermediate
wall is not full length and the main portion of the mandrel 208 includes a
generally U-shaped clearance 218. These features are intended to reduce the
surface of contact between the straight portions of the first and second
terminals 202 and 204 and thereby to reduce the friction between the straight
portions and the mandrel 208 when the finished coil 200 is removed from the
flange 206. In turn, this reduced friction provides terminals that remain
straight.
[0088] One skilled in the art will have no difficulty in transposing
these features to the other embodiments of mandrels described herein.
[0089] Figure 17 illustrates a coil arrangement 300 also having a
circular geometry but where the geometry of the first and second coil
terminals
302 and 304 is different. Indeed,. instead of being close apart as illustrated
in
Figure 15, the straight portions of the terminals 302 and 304 are parallel and
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located on opposite sides of the coil arrangement. The coil arrangement 300 is
especially adapted to the ultra small coils for which the terminal spacing is
about their diameter.
[0090] Figure 18 illustrates a flange 306 provided with a mandrel 308
used to wind the coil arrangement 300 of Figure 17. The mandrel 308 includes
two slots 310 and 312 separated by wall portions 314, 316 and 318. The
height of the wall portion 318 is smaller than the height of the wall portion
314
which itself is smaller than the height of the wall portion 316. The winding
of
the coil arrangement 300 follows generally the same steps as the winding of
the coil arrangement 100 describe hereinabove.
[0091] One skilled in the art will easily understand that the height of
the wall portions 314 and 318 could be equal. If this is the case, the
terminals
would be wound by turning the flange 306 by half a turn.
[0092] Figure 19 illustrates a circular geometry coil arrangement 400
provided with coil terminals 402 and 404 extending outside the circular
geometry.
[0093] Figure 20 illustrates, in a perspective view, a flange 406
provided with a mandrel 408 used to wind the coil 400 of Figure 19. The
mandrel 408 is circular and is used to wind the supporting inner and outer
layers and the active layer of the coil arrangement 400. The face 410 of the
spindle 406 is generally flat but includes the slots 412 and 414 axially
recessed
therein. A front wall 418 and an intermediate wall 420 define the slot 412
while
the intermediate wall 420 and a rear wall 422 define the slot 414.
[0094] The winding steps of the coil arrangement 400 are very
similar to the winding steps of the coil arrangement 100 described in detail
hereinabove. However, the coiling of the first and second terminals 402 and
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404 is done by moving either the flange 406 or the wire guide (not shown) so
that the wire is wound in a corresponding slot.
[0095] To remove the finished coil arrangement from the flange 406,
the mandrel 408 is retracted as discussed with respect to the mandrel 24,
thereby allowing the terminals 402 and 404 to exit their respective slot.
[0096] Figure 21 illustrates a fourth variant for a coil arrangement
500. The geometry of the coil arrangement 500 being generally trapezoid. The
geometry of the coil terminals 502 and 504 being generally rectangular and
extending outside the geometry of the coil arrangement 500.
[0097] Figure 22 illustrates a flange .506 very similar to the flange
406 discussed hereinbelow. The main difference between these flanges being
the cross sectional shape of the mandrel 508 designed to yield the trapezoid
shape of the coil arrangement 500. The other features being identical to the
features of the flange 406.
[0098] As will easily be understood by one skilled in the art, the coil
arrangements made according to the present invention are interesting since
they are self-supporting and since the terminals are always indentically
positioned from one coil to the next, therefore simplifying the connection of
the
terminals to the microchip. For example, thermo-compression and ultrasonic
welding techniques could be used.
[0099] It is to be noted that the present invention is very useful for
the RFID tags operating at 13.56MHz and above. In this case, the active coil
is
formed by no more than 5 or 6 turns. Without the additional wire inner and
outer layers, the resulting coil would have been both very difficult to handle
and
would hardly resist the product lifetime.
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[00100] Although the present invention has been described
hereinabove by way of preferred embodiments thereof, it can be modified,
without departing from the spirit and nature of the subject invention as
defined
in the appended claims.
