U.S. patent application number 11/996349 was filed with the patent office on 2008-10-09 for field winding.
This patent application is currently assigned to WINSTEAD ASSETS LIMITED. Invention is credited to Georges Folcke, Eric Gout, Christophe Raoult.
Application Number | 20080246675 11/996349 |
Document ID | / |
Family ID | 37669187 |
Filed Date | 2008-10-09 |
United States Patent
Application |
20080246675 |
Kind Code |
A1 |
Folcke; Georges ; et
al. |
October 9, 2008 |
Field Winding
Abstract
The invention concerns an inductor comprising a plurality of
so-called first conductors (100 to 109) substantially parallel to
one another, at least three of said first conductors being
substantially mutually equidistant and distributed over a surface
(120), and an electric power supply (140) of said conductors
adapted to circulate an electric current in the same direction in
said conductors. Preferably, said conductors are more densely
distributed at the ends of the surface (120) comprising them.
Preferably, the inductor further comprises a plurality of second
substantially parallel conductors perpendicular to the first
conductors, the electric power supply circulating an electric
current in the same direction on said second conductors.
Preferably, the inductor further comprises a plurality of third
conductors forming closed turns, the electric power supply
circulating an electric current in the same direction in said third
conductors. Preferably, the electric power supply successively
powers the first, second and third conductors.
Inventors: |
Folcke; Georges; (Paris,
FR) ; Gout; Eric; (Igny, FR) ; Raoult;
Christophe; (Guyancourt, FR) |
Correspondence
Address: |
OSLER, HOSKIN & HARCOURT LLP (PROXiP)
1000 DE LA GAUCHETIERE STREET WEST, SUITE 2100
MONTREAL
QC
H3B-4W5
CA
|
Assignee: |
WINSTEAD ASSETS LIMITED
Roadtown, Tortola
VG
|
Family ID: |
37669187 |
Appl. No.: |
11/996349 |
Filed: |
July 24, 2006 |
PCT Filed: |
July 24, 2006 |
PCT NO: |
PCT/IB2006/002020 |
371 Date: |
June 2, 2008 |
Current U.S.
Class: |
343/741 |
Current CPC
Class: |
H01F 7/20 20130101; H01F
5/00 20130101; H01Q 1/2225 20130101; H01Q 1/2216 20130101; G06K
7/10316 20130101; G06K 19/073 20130101; G06K 7/0008 20130101; H01Q
7/08 20130101; G06K 19/0723 20130101 |
Class at
Publication: |
343/741 |
International
Class: |
H01Q 11/12 20060101
H01Q011/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 22, 2005 |
FR |
0507861 |
Jul 22, 2005 |
FR |
0507863 |
Aug 23, 2005 |
FR |
0508696 |
Aug 23, 2005 |
FR |
0508699 |
Nov 25, 2005 |
FR |
0512108 |
Nov 25, 2005 |
FR |
0512109 |
Nov 25, 2005 |
FR |
0512110 |
Feb 1, 2006 |
FR |
0600937 |
Claims
1- A device comprising an inductor having a plurality of so-called
first conductors substantially parallel to one another, at least
three of said first conductors being substantially mutually
equidistant and distributed over a surface, and an electric power
supply of said conductors adapted to circulate an electric current
in the same direction in said conductors.
2- The device according to claim 1, wherein said conductors have a
linear part, said linear parts being arranged in a plane.
3- The device according to claim 1, wherein said conductors are
more densely distributed at the ends of the surface comprising
them.
4- The device according to claim 1, wherein said conductors are
less densely distributed at the centre of the surface comprising
them.
5- The device according to claim 1, wherein at least some of the
first conductors are connected together by conductors forming with
them partially superimposed turns.
6- The device according to claim 1, wherein at least some of the
conductors connecting together said first conductors surround said
first conductors in said surface.
7- The device according to claim 1, wherein at least some of the
conductors connecting together said first conductors are on the
same side of a plane comprising said first conductors.
8- The device according to claim 1, wherein all of said first
conductors are symmetrical with respect to at least one of a plane
and a point.
9- The device according to claim 1, wherein at least some of the
conductors connecting together said first conductors have a
coplanar linear part on the same side of a plane comprising said
first conductors.
10- The device according to claim 1, further comprising a plurality
of second parallel conductors parallel to one another and
substantially perpendicular to the first conductors, said electric
power supply adapted to circulate an electric current in the same
direction in said second conductors.
11- The device according to claim 10, further comprising a
plurality of third conductors forming identical closed turns, said
electric power supply adapted to circulate an electric current in
the same direction in said third conductors.
12- The device according to claim 11, wherein the third conductors
surround said first conductors.
13- The device according to claim 11, wherein said electric power
supply is adapted to generate a current alternately on said first,
second and third conductors.
14- A product selected from a group consisting of a support, a
pallet, a container, a conveyor, a cash register, and a base
station, provided with a device comprising an inductor having a
plurality of so-called first conductors substantially parallel to
one another, at least three of said first conductors being
substantially mutually equidistant and distributed over a surface,
and an electric power supply of said conductors adapted to
circulate an electric current in the same direction in said
conductors.
Description
[0001] This invention concerns, firstly, an inductor. It presents,
in particular, a new antenna structure and applies, in particular,
to the base station antennas used to read electronic tags.
[0002] Antennas formed from flat coils representing a large number
of superimposed turns are known. The electromagnetic field
generated by these antennas is, on their surface or near their
surface, substantially perpendicular to this surface. Since
electronic tags, such as transponders or RFID (Radio Frequency
Identification) tags can only be read if the surface of their
antenna cuts a sufficient number of field lines, they cannot be
read when the plane of their antenna is oriented substantially
perpendicular to the plane of the read antenna.
[0003] Antennas arranged around a volume, for example on the sides
of a box through which tags pass to be read, are also known. These
boxes are bulky and cannot be used for the passage of large
objects.
[0004] Lastly, figure-8 shaped antennas display the following
disadvantages: [0005] the field is high in the immediate
neighborhood of the central wires but decreases quickly on moving
away; [0006] the antenna inductance may be relatively high since
all the turns are identical resulting in bulky strands around the
structure (300 to 400 pH for an antenna of 30 cm by 40 cm) [0007]
these antennas are poorly adapted to reading stacks of RFID tags (a
few dozen for example).
[0008] This invention aims to overcome these disadvantages.
[0009] This invention therefore relates, according to a first
aspect, to an inductor characterized in that it comprises a
plurality of so-called first conductors substantially parallel to
one another, at least three of said first conductors being
substantially mutually equidistant and distributed over a surface,
and an electric power supply of said conductors adapted to
circulate an electric current in the same direction in said
conductors.
[0010] Thanks to these arrangements, a magnetic field is generated
which is substantially perpendicular to the conductors and
substantially parallel to the surface containing them.
[0011] In addition the inductance is reduced, compared with a
figure-8 antenna, which means that the voltage across the terminals
of this antenna can be reduced in proportion. The electric power
supply is therefore easier (for example with a voltage divided by
two). Also the transmitter so formed is more reliable.
[0012] According to special characteristics, said conductors have a
linear part, said linear parts being arranged in a plane.
[0013] Thanks to these arrangements, a magnetic field is generated
parallel to said plane.
[0014] According to special characteristics, said conductors are
more densely distributed at the ends of the surface comprising
them.
[0015] According to special characteristics, said conductors are
less densely distributed at the centre of the surface comprising
them.
[0016] Thanks to each of these arrangements, the intensity of the
magnetic field generated is more constant than if the conductors
were uniformly distributed.
[0017] According to special characteristics, at least some of the
first conductors are connected together by conductors forming with
them partially superimposed turns.
[0018] According to special characteristics, at least some of the
conductors connecting together said first conductors surround said
first conductors in said surface.
[0019] According to special characteristics, at least some of the
conductors connecting together said first conductors are on the
same side of a plane comprising said first conductors. Thanks to
these arrangements, the magnetic field generated on the other side
of said plane is less disturbed by the magnetic field of these
conductors connecting together the first conductors than if they
were in the same plane.
[0020] According to special characteristics, all of said first
conductors are symmetrical with respect to a plane and/or with
respect to a point.
[0021] Thanks to these arrangements, it is easier to comply with
the applicable regulations concerning electromagnetic emissions,
for example the standards known as "ETSI ETS 300 330".
[0022] According to special characteristics, at least some of the
conductors connecting together said first conductors have a
coplanar linear part on the same side of a plane comprising said
first conductors.
[0023] Thanks to these arrangements, the intensity of the magnetic
field generated, on the edges of said plane closest to these
conductors connecting together the first conductors, is
increased.
[0024] According to special characteristics, the inductor as
outlined above comprises, in addition, a plurality of second
conductors parallel to one another and substantially perpendicular
to the first conductors, said electric power supply adapted to
circulate an electric current in the same direction in said second
conductors.
[0025] Thanks to these arrangements, by circulating an electric
current alternately in the first and second conductors, two
substantially perpendicular magnetic fields are generated
alternately in order to read at least all the electronic tags whose
antennas are perpendicular to said plane. In addition, by
circulating sinusoidal electric currents with a phase shift of
90.degree. on the first and second conductors, a rotary magnetic
field of substantially constant intensity is generated.
[0026] According to special characteristics, the inductor as
outlined above comprises, in addition, a plurality of so-called
third conductors forming identical closed turns, said electric
power supply adapted to circulate an electric current in the same
direction in said third conductors. Thanks to these arrangements,
by powering only said third conductors, a magnetic field is
generated which is substantially perpendicular to the surface of
these third conductors.
[0027] According to special characteristics, the third conductors
surround said first conductors. Thanks to these arrangements, at
least all the tags near said surface, whose antennas are
perpendicular to said surface or perpendicular to the first
conductors, can be read.
[0028] According to special characteristics, said electric power
supply is adapted to generate a current alternately on said first,
second and third conductors.
[0029] According to a second aspect, this invention relates to a
device chosen from a support, a pallet, a container, a conveyor, a
cash register or a base station comprising the inductor as outlined
above.
[0030] Since the advantages and purposes of this support, this
pallet, this container, this conveyor, this cash register or this
base station are similar to those of the inductor as outlined
above, they are not mentioned here.
[0031] This invention also relates to an electronic tag, a reading
method and a method to query such an electronic tag. It applies in
particular to radio frequency electronic tags.
[0032] The radio frequency electronic tags, known as "RFID" (Radio
Frequency IDentification), are well known for their ability to
supply an identification signal in response to base station query
signals, said signals modulating an electromagnetic field generated
by the base station.
[0033] However, in order to read a set of tags randomly orientated
in a given volume, it is often necessary to plan, in the base
station, a set of antennas which each cover parts of said volume
and particular tag orientations. Each antenna is implemented for a
time interval forming part of a complete read cycle, time interval
during which a tree structure of possible identifiers for the
electronic tags is browsed, at least partially. All tags whose
antenna axis is not perpendicular to the axis of the magnetic field
generated by the antenna are then likely to respond during the time
interval considered.
[0034] In this case, there is a risk that a large number of tags
are identified several times, during each time interval when a tag
receives requests from the base station. The tag antenna axes,
randomly oriented, are in fact rarely perpendicular to two, or even
to one of the axes of the magnetic fields generated
successively.
[0035] For example, when six antennas are implemented (two antennas
successively cover the entire given volume, for each of the three
axes), some tags are read two or three times during a complete
cycle.
[0036] Identification of all the tags is therefore slowed down by a
factor of two at least. The speed at which a group of tags is read,
however, is a key factor when selecting an electronic tag
technology.
[0037] This invention aims to overcome these disadvantages. This
invention therefore relates, according to a third aspect, to a
passive electronic tag designed to be read by a set of antennas of
a base station, successively generating magnetic fields during a
read cycle, characterized in that said electronic tag includes:
[0038] a means of transmitting responses to requests modulating
said magnetic field and [0039] an inhibition means adapted, even in
the absence of any electric power supply from the base station, to
inhibit the response transmission means at least for the duration
of a said read cycle.
[0040] Thanks to these arrangements, when the electronic tag has
been read, it is inhibited throughout the duration of the read
cycle and consequently cannot be read twice. The speed at which a
group of randomly oriented tags is read is therefore significantly
increased.
[0041] We observe that implementing this invention requires no
modifications to the base station, only the electronic tag is
modified to become inhibited for a duration several times longer
than the inhibition durations currently implemented, which only
concerns one of the above-mentioned time intervals.
[0042] According to special characteristics, the electronic tag as
outlined above comprises a means of determining the complete
identification of said electronic tag, said inhibition means
inhibiting the transmission means when the determination means has
determined that the electronic tag has been completely
identified.
[0043] According to special characteristics, the electronic tag
comprises a reception means for reception of an acknowledgement of
receipt from the base station and the means to determine the
complete identification of the electronic tag is adapted to
determine that an acknowledgement of receipt has been received by
the base station.
[0044] According to special characteristics, the transmission means
is adapted to successively transmit sections of the identifier of
said electronic tag and the determination means is adapted to
determine that all sections of the electronic tag identifier
sections have been transmitted by the transmission means.
[0045] According to special characteristics, the inhibition means
comprises a capacitor.
[0046] According to special characteristics, the inhibition means
comprises a transistor mounted as a diode to check the charge of
said capacitor.
[0047] Thanks to these arrangements, the inhibition duration can
last for several tens of seconds.
[0048] According to a fourth aspect, this invention relates to an
operating method of a passive electronic tag, characterized in that
it comprises: [0049] a step to answer requests from a base station
and [0050] once the tag has supplied its complete identification,
an extended inhibition step of duration at least equal to the
duration of a said read cycle, even in the absence of any electric
power supply from said base station.
[0051] According to special characteristics, the extended
inhibition step is executed after a step to receive an
acknowledgement of receipt of the complete identification of said
electronic tag.
[0052] According to special characteristics, the method as outlined
above comprises a step to exit the inhibition, in response to
reception of a request to exit extended inhibition, from said base
station.
[0053] According to a fifth aspect, this invention relates to a
method to query passive electronic tags, characterized in that it
comprises: [0054] a step to identify at least one electronic tag
during which a magnetic field is generated with at least one first
antenna, [0055] a step to transmit an extended inhibition request
for each electronic tag identified, [0056] a step to identify at
least one electronic tag during which a magnetic field is generated
with at least one second antenna different from each first antenna
and [0057] a step to transmit a request to exit extended inhibition
for each electronic tag identified during which a magnetic field is
generated with each said first antenna.
[0058] Since the advantages, aims and special features of this
method are similar to those of the electronic tag outlined above,
they are not described here.
[0059] This invention also concerns an inductor to generate a
magnetic field, a base station and a conveyor comprising it. It
applies in particular to the base stations or electronic tag
readers used in the field of radio frequency identification known
as RFID (Radio Frequency Identification).
[0060] Numerous, generally flat, shapes of inductor or antenna are
known, intended for integration in portals, for example placed at
store exits or in storage areas in order to read electronic tags.
These inductors are unable to generate a sufficiently strong
magnetic field if the electronic tags are close to metal or organic
parts or water, and more generally materials which disturb
electromagnetic fields.
[0061] Solenoid-shaped inductors are also known, which can be used
to generate an intense electromagnetic field. However, solenoids
may not be adapted to manufacturing processes mainly involving
conveyors while respecting statutory constraints in terms of
electromagnetic radiation.
[0062] This invention aims to overcome these disadvantages.
[0063] This invention therefore relates, according to a sixth
aspect, to an inductor, characterized in that it comprises two
strands of electrical conductors forming two non-planar loops
through which current flows with opposite directions of
rotation.
[0064] Thanks to these arrangements, in a convexity area located
between said non-planar loops, the electromagnetic field is
increased in a direction going from one loop to the other.
[0065] According to special characteristics, each non-planar loop
is mostly contained in the junction of two planes.
[0066] According to special characteristics, said planes are
orthogonal.
[0067] According to special characteristics, each loop consists of
straight segments.
[0068] According to a seventh aspect, this invention relates to a
conveyor comprising a means of moving products bearing electronic
tags and at least one inductor as outlined above placed around the
path followed by said product.
[0069] According to special characteristics, the conveyor is
adapted to move products bearing electronic tags through an arch
formed by the inductor.
[0070] According to special characteristics, the conveyor is
adapted to position electronic tags near the inductor, with the
antenna axis of each electronic tag substantially parallel to an
axis going through the two loops.
[0071] Thanks to each of these arrangements, the mutual inductance
between the inductor and the electronic tag antenna is high as the
tag passes through the arch with its antenna substantially
perpendicular to the field lines.
[0072] According to an eighth aspect, this invention relates to a
base station comprising at least one inductor as outlined above and
electronic circuits to generate signals applied to each said
inductor and to process signals from each said inductor.
[0073] Since the advantages, aims and features of this conveyor and
of this base station are similar to those of the inductor outlined
above, they are not described here.
[0074] This invention also relates to a storage rack with automatic
tag reading device and a computer system comprising it. It applies,
in particular, to the storage of products and supplies and to the
replenishment of the stocks concerned.
[0075] A device to store and identify articles equipped with a bar
code described in document U.S. Pat. No. 4,636,634 is known. The
bar codes indicate the identity of the articles with which they are
associated. This device comprises at least one container adapted to
receive an article equipped with a code and, in each container,
presence detection means to detect the presence of an article in a
container, bar code reading means and circuits connected to the
presence detection means and to the reading means to provide an
indication of the presence and identity of articles in the
containers.
[0076] The manufacture of this device is complex since each
container must be equipped with two means, firstly to detect the
presence of an article and secondly, if an article is present, to
read its code. In addition, this device is unreliable since
incorrectly positioning the code in the container is sufficient to
prevent the code from being read.
[0077] This invention aims to overcome these disadvantages.
[0078] This invention therefore relates, according to a ninth
aspect, to a rack, characterized in that it comprises:
[0079] on at least one wall, at least one antenna comprising at
least two co-planar loops through at least one of which current
flows in the clockwise direction and, simultaneously, on at least
one other loop, the current flows in the anticlockwise
direction,
[0080] a signal generation circuit to generate signals transmitted
by each said antenna, to generate an electromagnetic field, and
[0081] a signal reception circuit modulating said magnetic
field.
[0082] Thanks to these arrangements, electronic tags within a
highly elongated volume with respect to the plane of said loops can
be read.
[0083] According to special characteristics, at least one said
antenna comprises two loops.
[0084] According to special characteristics, at least one said
antenna comprises three loops.
[0085] According to special characteristics, at least one said
antenna comprises four loops.
[0086] According to special characteristics, at least one wall
containing at least one of the antennas forms the back of the
rack.
[0087] According to special characteristics, at least one wall
containing at least one of the antennas forms a side wall of the
rack.
[0088] According to special characteristics, at least one wall
containing at least one of the antennas forms a central wall of the
rack.
[0089] According to special characteristics, the signal generation
circuit is adapted to successively generate signals for various
sets of antennas.
[0090] Thanks to these arrangements, antennas oriented along
different axes, possibly orthogonal to one another, can be read
successively.
[0091] According to special characteristics, the rack as outlined
above comprises products comprising at least one metallic part with
at least one narrow edge and an electronic tag with one antenna
positioned substantially perpendicular to a narrow edge of said
metallic part.
[0092] The inventors have in fact discovered that, with these
characteristics, the electronic tag could be read despite the
proximity of the metallic part and the electronic tag.
[0093] According to special characteristics, the electronic tag
antenna has a width, measured in the direction of the thickness of
the metallic part, greater than the thickness of the edge of the
metallic part opposite which the antenna is positioned.
[0094] According to special characteristics, the product has the
shape of a rectangular parallelepiped and comprises said electronic
tag on one of its four smallest sides.
[0095] According to special characteristics, the product has the
shape of a rectangular parallelepiped and comprises a paper label
positioned on one side of the product opposite to a side of the
product bearing said electronic tag.
[0096] According to special characteristics, the product has the
shape of a rectangular parallelepiped and comprises a paper label
positioned on one side of the product adjacent to a side of the
product bearing said electronic tag on one of its small sides.
[0097] Thanks to each of these arrangements, when the product is
stored, in a stack or vertically in a cabinet, the user is
encouraged to position it so that its paper label is visible. Due
to this position, the electronic tag is positioned toward an
antenna positioned so as to read the electronic tags.
[0098] According to special characteristics, said rack comprises a
user identification card reader.
[0099] Thanks to these arrangements, each product removed from the
rack can be associated with the identity of the person removing it,
a patient, a procedure, an operating theatre or a doctor, for
example.
[0100] According to special characteristics, the rack as outlined
above comprises warning means adapted to trigger a warning when a
minimum number of products of a particular reference has been
reached in said rack.
[0101] According to special characteristics, the rack as outlined
above comprises warning means adapted to trigger a warning on
approaching the use-by-date of a product present in said rack.
[0102] Thanks to these arrangements, product procurement is made
more secure.
[0103] According to a tenth aspect, this invention relates to a
computer system, characterized in that it comprises: [0104] in at
least one product user centre, at least one rack as outlined above,
containing products from at least one supplier; [0105] a server
having a database containing information about the products
contained in at least one said rack, this database being associated
with at least one microprocessor unit and with means of
communicating with said rack; [0106] a device located in each
product user centre including a microprocessor unit associated with
means of communicating with said server; [0107] a device located on
the premises of each supplier including a microprocessor unit
associated with means of communicating with said server; [0108]
said server comprising means of selective access to the database,
adapted to allow each product user centre to have access to all its
own stock of products contained in said racks, irrespective of the
product suppliers, and to allow each supplier to access, for all
product user centers, the stock level, in said racks, of its own
products.
[0109] Thanks to these arrangements, each product user centre can
find, in real time, the level and location of its stocks, each
supplier can program the future productions and deliveries and the
confidentiality of each party's data is guaranteed.
[0110] According to special characteristics, the server comprises a
computer program adapted to trigger warnings when a minimum number
of products of a particular reference has been reached in the stock
of a product user centre.
[0111] According to special characteristics, the server comprises a
computer program adapted to produce a sales report for each
supplier providing a summary of references by product user centre
and/or by territory.
[0112] Thanks to each of these arrangements, stock management is
simplified and efficient both for the product user centers and the
suppliers of these product user centers.
[0113] Since the advantages, aims and special features of this
computer system are identical to those of the rack outlined above,
they are not described here.
[0114] This invention also concerns an electronic tag and a base
station to query it. It applies, in particular, to the use of radio
frequency electronic tags associated with objects with metallic
parts or conducting materials, to identify these objects.
[0115] The radio frequency electronic tags, known as "RFID" (Radio
Frequency Identification), are well known for their ability to
supply an identification signal in response to base station query
signals, said signals modulating a magnetic field generated by the
base station.
[0116] When inserting this type of tag in an object comprising
metallic parts and in particular when the electronic tag must be in
contact or, at least partially, surrounded by a metallic part, the
disturbance produced by the metallic part on the tag antenna and
reader characteristics are likely to prevent its operation.
[0117] The presence of metal acts in various ways on the radio
frequency identification: [0118] firstly, in case of passive tags,
the tag is insulated by the metal and the magnetic field must
therefore be strong enough so that sufficient energy remains to
power the tag. [0119] secondly, for all tags, active or passive,
the metal reduces the intensity of the query signals which may
therefore not be detected by the tags, and [0120] lastly, the
metals present affect the base station reader antenna,
significantly reducing the magnetic field available.
[0121] The ability of a base station to query electronic tags is
therefore significantly reduced. This invention aims to overcome
these disadvantages.
[0122] According to an eleventh aspect, this invention therefore
relates to a device comprising at least one metallic part,
characterized in that it comprises an electronic tag which
comprises, opposite said metallic part: [0123] a reception means to
receive signals modulated at a first frequency: [0124] a processing
means to process said signals to identify a query signal to which
said electronic tag must reply and [0125] a transmission means to
transmit signals modulated at a second frequency different from
said first frequency.
[0126] The inventors have in fact discovered that by implementing
two different frequencies, although the sensitivity of the tag is
affected, its electrical characteristics are relatively
unchanged.
[0127] According to special characteristics, said first frequency
is less than 200 kHz. Thanks to these arrangements, penetration of
the magnetic field in the metallic parts is improved.
[0128] According to special characteristics, said second frequency
is equal to half the first frequency.
[0129] Choosing to use a non-resonating tag (whose product
LC.omega..sup.2 is not equal to 1, where L is the inductance, C the
capacitance and .omega. the angular frequency) rules out the use of
backscattering for the response from the tags. By choosing to reply
at half the frequency, this frequency is more easily detected on
the base station antenna. In addition, automatic tuning guarantees
that a maximum amount of energy will be available to power the
electronic tag.
[0130] According to special characteristics, the transmission means
modulates or charges one alternation out of two of the carrier of
the signal received by the reception means to obtain a signal of
half the frequency.
[0131] The tag therefore only cuts about 80% of the signal.
[0132] According to special characteristics, the transmission means
comprises at least two diodes adapted to guarantee a minimum signal
at the first frequency on the electronic tag antenna.
[0133] According to a twelfth aspect, this invention relates to a
base station to query electronic tags, characterized in that it
comprises: [0134] a transmission means to transmit signals
modulated at a first frequency: [0135] a reception means to receive
signals modulated at a second frequency different from said first
frequency, comprising an antenna and adapted to vary a read
frequency by controlling the amplitude of the voltage on the
antenna in order to constantly check that LC.omega..sup.2=1,
formula in which L is the antenna inductance, C the antenna
capacitance and .omega. the angular frequency, equal to 2pif, where
f is the frequency and [0136] a processing means to process said
signals modulated at the second frequency to identify a response
signal transmitted by said electronic tag.
[0137] According to special characteristics, said first frequency
is less than 200 kHz.
[0138] According to special characteristics, said second frequency
is equal to half the first frequency.
[0139] According to special characteristics, the reception means
comprises an antenna and is adapted to vary a read frequency by
controlling the amplitude of the voltage on the antenna in order to
constantly check that LC.omega..sup.2=1, formula in which L is the
antenna inductance, C the antenna capacitance and .omega. the
angular frequency, equal to 2pif, where f is the frequency.
[0140] The electronics therefore provide automatic tuning in order
to obtain the maximum magnetic field according to the metallic mass
and its position in front of the antenna.
[0141] According to special characteristics, the transmission means
and the reception means comprise a common antenna and the reception
means comprises an analogue to digital converter which transmits
the peak value present on the antenna to the processing means.
[0142] According to special characteristics, the analogue to
digital converter is connected to said antenna via a divider bridge
of high impedance adapted to keep the level of the setpoint between
0 V and 10 V and not disturb the tuning of the antenna.
[0143] According to special characteristics, the processing means
is adapted to compare said peak value with a voltage setpoint
acquired in the absence of metallic objects within the field of
said antenna.
[0144] According to special characteristics, the processing means
is adapted to vary the frequency to reach the level of the setpoint
by changing the inputs of a counter.
[0145] Since the advantages, aims and special features of this base
station are similar to those of the device outlined above, they are
not described here.
[0146] This invention also concerns a base station to query
electronic tags. It applies, in particular, to the querying of
radio frequency electronic tags and, especially, to the case where
objects with metallic parts or conducting materials are likely to
lie within the base station transmission field.
[0147] The radio frequency electronic tags, known as "RFID" (Radio
Frequency Identification), are well known for their ability to
supply an identification signal in response to base station query
signals, said signals modulating a magnetic field generated by the
base station.
[0148] When an electronic tag enters the transmission field of a
base station, its antenna disturbs this field and modifies the
resonance frequency of the base station antenna, possibly causing a
decrease in the gain of the base station antenna. When, in
addition, the electronic tag replies at the same frequency as the
signal transmitted by the base station, for the response as well,
the gain of the base station antenna may be lowered.
[0149] This problem is amplified if numerous electronic tags or
metallic parts are likely to enter the field of the base station.
For example, when inserting an electronic tag in an object
comprising metallic parts and in particular when the electronic tag
must be in contact or, at least partially, surrounded by a metallic
part, the disturbances caused by the metallic part on the gain of
the base station antenna may impair the communication between the
base station and the electronic tag.
[0150] The presence of metal acts in various ways on the radio
frequency identification: [0151] firstly, in case of passive tags,
the tag is insulated by the metal and the magnetic field must
therefore be strong enough so that sufficient energy remains to
power the tag. [0152] secondly, for all tags, active or passive,
the metal reduces the intensity of the query signals which may
therefore not be detected by the tags, and [0153] lastly, the
metals present affect the base station reader antenna,
significantly reducing the magnetic field available.
[0154] The ability of a base station to query electronic tags is
therefore significantly reduced. This invention aims to overcome
these disadvantages.
[0155] According to a thirteenth aspect, this invention therefore
relates to a base station to query electronic tags, characterized
in that it comprises: [0156] a transmission circuit comprising an
antenna for transmission of query signals and [0157] a slaving
means to slave the frequency Fr of the signal transmitted by said
antenna so that this frequency Fr respects the equation
L.times.C.times.(2.times.pi.times.Fr).sup.2=1, equation in which L
is the inductance of the transmission circuit comprising the
antenna and C is the capacitance of the transmission circuit
comprising the antenna.
[0158] Thanks to these arrangements, the frequency of the signal
transmitted by the antenna is the antenna resonance frequency, even
when the inductance of the transmission circuit is disturbed by the
presence of metallic parts or antennas, for example those of the
electronic tags, in the field of the base station antenna.
[0159] The gain of the transmission antenna therefore remains
substantially constant irrespective of the disturbances
encountered.
[0160] According to special characteristics, the base station as
outlined above comprises a reception circuit comprising the
transmission antenna.
[0161] Thanks to these arrangements, the reception circuit can take
into account the variations of the frequency Fr in detection of the
signal from electronic tags, especially in the general case where
the transmitted signal is much stronger than the received
signal.
[0162] According to special characteristics, the transmission
circuit comprises a capacitor in series with the antenna and an
image bridge comprising in series an inductor and a capacitor, the
capacitor in series with the antenna, the inductor and the
capacitor of the image bridge being adapted so that the voltage
between the antenna and the capacitor in series with the antenna is
substantially equal to the voltage between the inductor and the
capacitor of the image bridge.
[0163] Thanks to these arrangements, a signal received by the
antenna can be detected by difference between the voltage between
the antenna and the capacitor in series with the antenna and the
voltage between the inductor and the capacitor of the image
bridge.
[0164] According to special characteristics, the transmission
circuit comprises a transformer whose primary circuit is connected,
firstly, between the antenna and the capacitor in series with the
antenna and, secondly, between the inductor and the capacitor of
the image bridge.
[0165] Thanks to these arrangements, the signals received from the
electronic tags can be amplified.
[0166] According to special characteristics, the base station as
outlined above comprises a filtering and amplification circuit
connected to the secondary circuit of the transformer.
[0167] Thanks to these arrangements, the signals received from the
electronic tags are filtered and amplified before being processed
by the base station, for example to identify the electronic
tags.
[0168] According to special characteristics, the base station as
outlined above comprises an analogue to digital converter which
transmits the peak value present on the antenna to a processing
means to process the signals received by the base station from the
electronic tags.
[0169] According to special characteristics, the analogue to
digital converter is connected to said antenna via a divider bridge
of high impedance adapted to keep the level of the setpoint between
0 V and 10 V and not disturb the tuning of the antenna.
[0170] According to special characteristics, the processing means
is adapted to compare said peak value with a voltage setpoint
acquired in the absence of metallic objects within the field of
said antenna.
[0171] According to special characteristics, the base station as
outlined above comprises: [0172] a reception means to receive
signals modulated by electronic tags, comprising an antenna and
adapted to vary a read frequency by controlling the amplitude of
the voltage on the antenna in order to constantly check that
LC.omega..sup.2=1, formula in which L is the antenna inductance, C
the antenna capacitance and .omega. the angular frequency, equal to
2pif, where f is the frequency and [0173] a processing means to
process said signals modulated by the electronic tags to identify a
response signal transmitted by said electronic tag.
[0174] The electronics therefore provide automatic tuning in order
to obtain the maximum magnetic field according to the metallic mass
and its position in front of the antenna.
[0175] According to special characteristics, the transmission means
and the reception means comprise a common antenna.
[0176] This invention also concerns an electronic tag. It applies,
in particular, to radio frequency electronic tags and, especially,
to the case where objects with metallic parts or conducting
materials are likely to be present near the electronic tags
queries.
[0177] The radio frequency electronic tags, known as "RFID" (Radio
Frequency Identification), are well known for their ability to
supply an identification signal in response to base station query
signals, said signals modulating a magnetic field generated by the
base station.
[0178] When an electronic tag enters the transmission field of a
base station, its antenna disturbs this field and modifies the
resonance frequency of the base station antenna, possibly causing a
decrease in the gain of the base station antenna. When, in
addition, the electronic tag replies at the same frequency as the
signal transmitted by the base station, for the response as well,
the gain of the base station antenna may be lowered.
[0179] This problem is amplified if numerous electronic tags or
metallic parts are likely to enter the field of the base station.
For example, when inserting an electronic tag in an object
comprising metallic parts and in particular when the electronic tag
must be in contact or, at least partially, surrounded by a metallic
part, the disturbances caused by the metallic part on the gain of
the base station antenna may impair the communication between the
base station and the electronic tag.
[0180] The presence of metal acts in various ways on the radio
frequency identification: [0181] firstly, in case of passive tags,
the tag is insulated by the metal and the magnetic field must
therefore be strong enough so that sufficient energy remains to
power the tag. [0182] secondly, for all tags, active or passive,
the metal reduces the intensity of the query signals which may
therefore not be detected by the tags, and [0183] lastly, the
metals present affect the base station reader antenna,
significantly reducing the magnetic field available.
[0184] The ability of a base station to query electronic tags is
therefore significantly reduced. This invention aims to overcome
these disadvantages.
[0185] According to a fourteenth aspect, this invention therefore
relates to an electronic tag, characterized in that it comprises a
circuit for reception of signals from a base station, said
reception circuit comprising an antenna whose resonance frequency
is at least double the frequency of the signal received from the
base station.
[0186] Thanks to these arrangements, the gain of the electronic tag
antenna is close to 1 at the frequency transmitted by the base
station antenna.
[0187] According to special characteristics, the electronic tag
comprises: [0188] a reception means to receive signals modulated at
a first frequency: [0189] a processing means to process said
signals to identify a query signal to which said electronic tag
must reply and [0190] a transmission means to transmit signals
modulated at a second frequency different from said first
frequency.
[0191] The inventors have in fact discovered that by implementing
two different frequencies, although the sensitivity of the tag is
affected, its electrical characteristics are relatively
unchanged.
[0192] According to special characteristics, said first frequency
is less than 200 kHz. Thanks to these arrangements, penetration of
the magnetic field in the metallic parts is improved.
[0193] According to special characteristics, said second frequency
is equal to half the first frequency.
[0194] Choosing to use a non-resonating tag (whose product
LC.omega..sup.2 is not equal to 1, where L is the inductance, C the
capacitance and .omega. the angular frequency) rules out the use of
backscattering for the response from the tags. By choosing to reply
at half the frequency, this frequency is more easily detected on
the base station antenna. In addition, automatic tuning guarantees
that a maximum amount of energy will be available to power the
electronic tag.
[0195] According to special characteristics, the transmission means
modulates or charges one alternation out of two of the carrier of
the signal received by the reception means to obtain a signal of
half the frequency.
[0196] The tag therefore only cuts about 80% of the signal.
[0197] According to special characteristics, the transmission means
comprises at least two diodes adapted to guarantee a minimum signal
at the first frequency on the electronic tag antenna.
[0198] This invention also concerns a conducting product comprising
an electronic tag, a method and a device for identification of such
products. It applies, in particular, to remote identification of
metallic blisters implementing a radio frequency identification
known as RFID (Radio Frequency Identification).
[0199] Remote identification by electromagnetic waves implements a
reader, also known as a base station, and an electronic tag, also
known as a transponder, associated with each product to be
identified. Each electronic tag has a generally unique
identification code consisting, for example, of 64 bits, forming a
code of standardized structure and meaning. To read an electronic
tag, the base station transmits an electromagnetic field modulated
to carry a query signal and possibly to power the electronic tags.
On reception of this query signal, each electronic tag determines
whether it must reply and what it must reply. For example, only
electronic tags whose identification code starts with data
indicated, explicitly or implicitly, by the base station must reply
and they must reply providing one or more data items in addition to
their identification code. Other examples implement an
anti-collision protocol in which each electronic tag determines,
for example randomly, when it must reply in order to reduce the
risk that two electronic tags reply simultaneously, generating
interference between their response signals and preventing correct
reception of these signals by the base station.
[0200] As we can easily understand, the presence of conducting
parts, for example metallic parts or films or those comprising a
high proportion of water, disturb the electromagnetic fields used
and limit, or even prevent, communication between the base station
and the electronic tags.
[0201] This invention aims to overcome these disadvantages.
[0202] This invention therefore relates, according to a fifteenth
aspect, to a product comprising a substantially flat, at least
locally, metallic part, characterized in that it comprises an
electronic tag whose antenna is positioned near said metallic part,
the axis of said antenna being parallel to the local plane of said
metallic part.
[0203] Thanks to each of these arrangements, the magnetic field
parallel to the plane of the metallic part can be picked up by the
electronic tag antenna. Each electronic tag can therefore be read,
even when several similar products are stacked up.
[0204] According to special characteristics, the antenna of said
electronic tag is positioned near and parallel to an edge of said
metallic part.
[0205] Thanks to these arrangements, the disturbances due to the
presence of the metallic part are reduced near the electronic
tag.
[0206] According to special characteristics, said metallic part is
a metallic blister film.
[0207] Thanks to these arrangements, small blisters may
nevertheless be equipped with a practically invisible electronic
tag.
[0208] According to special characteristics, the product as
outlined above comprises a groove formed in a non-conducting
material, parallel and close to an edge of said metallic part, the
antenna of said electronic tag being positioned in said groove.
[0209] Thanks to these arrangements, the electronic tag can be
easily and automatically deposited in the blister at the same time
as the contents, for example tablets or capsules, stored in the
blister.
[0210] According to special characteristics, said electronic tag
comprises: [0211] a core of electrically-insulated material of
relative magnetic permeability above fifty, [0212] a coil
surrounding said core, coil forming an antenna adapted to receive a
query signal from a base station, [0213] a memory storing an
identification code and [0214] processing means adapted to process
the query signal from the base station to determine whether the
electronic tag must reply and, if yes, to command transmission of a
signal by said antenna.
[0215] Thanks to these arrangements, the antenna sensitivity is
multiplied according to the relative magnetic permeability of the
material forming the core, a value which may exceed 250, or even
650, for a ferrite core, compared with the same antenna without
ferrite core.
[0216] According to special characteristics, said core comprise a
ferrite. Thanks to these arrangements, the sensitivity gain may be
very high, ferrites having very high magnetic permeability's.
[0217] According to special characteristics, the coil wire is
thermo adherent. Thanks to these arrangements, the coil is easily
manufactured.
[0218] According to special characteristics, said tag is passive.
Thanks to these arrangements, its cost price, size and weight can
be reduced and its lifetime extended.
[0219] According to a sixteenth aspect, this invention relates to a
device to identify at least one product as outlined above, product
comprising a substantially plane metallic part, characterized in
that it comprises a transmitting antenna adapted to generate
magnetic field lines parallel to the axis of said antenna of the
electronic tag.
[0220] Thanks to these arrangements, the products can be identified
in a large volume.
[0221] According to special characteristics, the device as outlined
above comprises a presentation means to present one product at a
time opposite said transmitting antenna such that the plane of said
metallic part is perpendicular to the main plane of said
transmitting antenna and such that the core of the electronic tag
carried by said product is substantially parallel to the field
lines generated by said transmitting antenna.
[0222] According to special characteristics, the device as outlined
above comprises a presentation means to present a plurality of
products forming at least one stack opposite said transmitting
antenna such that the plane of each metallic part is perpendicular
to the main plane of said transmitting antenna and such that the
cores of the electronic tags carried by said products are
substantially parallel to the field lines generated by said
transmitting antenna.
[0223] According to special characteristics, said presentation
means is a conveyor.
[0224] Thanks to each of these arrangements, the products can be
identified in stacks. According to a seventeenth aspect, this
invention relates to a method to identify at least one product
comprising a substantially flat metallic part, characterized in
that it comprises: [0225] a step to mechanically associate said
product with an electronic tag whose antenna is perpendicular to
the plane of said mechanical part and a step to position said
product opposite a transmitting antenna of the base station so that
the transmitting antenna generates magnetic field lines parallel to
the axis of said electronic tag antenna.
[0226] Since the advantages, aims and special features of this
method are similar to those of the device outlined above, they are
not described here.
[0227] The various aspects of this invention, their main
characteristics and their special characteristics are intended to
be combined to form a universal electronic tag reading system. Each
main or special characteristic of each aspect of this invention
therefore forms a special characteristic of each other aspect of
this invention.
[0228] Other advantages, aims and features of this invention will
appear on reading the following description, given for a
non-limiting explanatory purpose and referring to the attached
drawings in which:
[0229] FIG. 1 is a diagrammatic plan view representation of a first
mode of realization of an inductor according to this invention;
[0230] FIG. 2 is a diagrammatic plan view representation of a
second mode of realization of an inductor according to this
invention;
[0231] FIG. 3 is a diagrammatic representation, in perspective, of
the intensity of a magnetic field generated by the second mode of
realization of this invention, as illustrated in FIG. 2;
[0232] FIG. 4 is a diagrammatic representation, in plan view, of a
third mode of realization of an inductor according to this
invention;
[0233] FIG. 5 is a diagrammatic representation, in plan view, of a
fourth mode of realization of an inductor according to this
invention;
[0234] FIG. 6 is a diagrammatic representation, in perspective, of
a fifth mode of realization of an inductor according to this
invention;
[0235] FIG. 7 is a diagrammatic representation, in plan view, of a
sixth mode of realization of an inductor according to this
invention;
[0236] FIG. 8 is a diagrammatic representation, in plan view, of a
seventh mode of realization of an inductor according to this
invention;
[0237] FIG. 9 is a diagrammatic representation, in perspective, of
a pallet according to this invention;
[0238] FIG. 10 is a diagrammatic representation, in perspective, of
a container according to this invention;
[0239] FIG. 11 is a diagrammatic representation, in cross-section,
of a conveyor according to this invention;
[0240] FIG. 12 is a diagrammatic representation, in cross-section,
of a cash register according to this invention;
[0241] FIG. 13 is a diagrammatic representation, in cross-section,
of a base station according to this invention;
[0242] FIG. 14 is a diagrammatic representation of an example of
implementation of this invention in a radio frequency electronic
tag reading system;
[0243] FIGS. 15A and 15B represent an electronic circuit integrated
in an electronic tag;
[0244] FIG. 16 represents a logic diagram showing the operation of
an electronic tag;
[0245] FIG. 17 represents a chronogram showing the operation of
electronic tags;
[0246] FIG. 18 is a diagrammatic representation, in perspective, of
a special mode of realization of an inductor according to this
invention;
[0247] FIG. 19 is a diagrammatic representation, in side view, of a
conveyor comprising an inductor illustrated in FIG. 18;
[0248] FIG. 20 is a diagrammatic representation, in side view, of a
base station comprising an inductor illustrated in FIG. 18;
[0249] FIG. 21 is a diagrammatic representation of a first mode of
realization of a rack according to this invention;
[0250] FIG. 22 is a diagrammatic representation of a second mode of
realization of a rack according to this invention;
[0251] FIG. 23 is a diagrammatic representation of a first shape of
antenna incorporated in a rack illustrated in FIG. 21 or 22;
[0252] FIG. 24 is a diagrammatic representation of a second shape
of antenna incorporated in a rack illustrated in FIG. 21 or 22;
[0253] FIG. 25 is a diagrammatic representation of a third shape of
antenna incorporated in a rack illustrated in FIG. 21 or 22;
[0254] FIG. 26 represents a product especially adapted to be stored
in a rack as illustrated in FIG. 21;
[0255] FIG. 27 represents, as a logic diagram, the operation on a
rack as illustrated in FIG. 21 or 22;
[0256] FIG. 28 represents a computer system according to this
invention and comprising a plurality of racks as illustrated in
FIG. 21 or 22;
[0257] FIG. 29 represents a flowchart showing the operation of the
computer system illustrated in FIG. 28;
[0258] FIG. 30 is a diagrammatic representation of an example of
implementation of this invention in a radio frequency electronic
tag reading system;
[0259] FIG. 31 represents a clock generation circuit integrated in
a base station;
[0260] FIGS. 32A and 32B represent a logic circuit integrated in a
base station;
[0261] FIG. 33 represents, in cross-section, the integration of an
electronic tag in a perfume bottle pump comprising metallic
parts;
[0262] FIG. 34 represents an electronic tag electronic circuit
according to this invention;
[0263] FIG. 35 represents the shape of a signal leaving the circuit
illustrated in FIG. 34;
[0264] FIG. 36 represents a signal spectrum present on the
electronic tag when it replies to a query signal;
[0265] FIG. 37 is a diagrammatic representation of the frequencies
preferably implemented by antennas of the device illustrated in
FIGS. 30 to 36;
[0266] FIG. 38 is a diagrammatic representation of a special mode
of realization of an electronic reception circuit of a base station
of the device illustrated in FIGS. 30 to 37;
[0267] FIG. 39 is a diagrammatic representation, in plan view, of a
special mode of realization of an electronic tag subject of this
invention;
[0268] FIG. 40 represents a group of curves used to determine a
true magnetic permeability according to a length/diameter ratio of
a ferrite and according to an asymptotic magnetic permeability;
[0269] FIGS. 41A and 41B are diagrammatic representations, in plan
view and in side view, of a special mode of realization of a
product according to this invention;
[0270] FIG. 42 is a diagrammatic representation of a special mode
of realization of an identification device subject of this
invention and
[0271] FIG. 43 represents, as a logic diagram, steps implemented in
a special mode of realization of the method subject of this
invention.
[0272] FIGS. 1 to 13 concern more specifically the first and second
aspects of this invention. In the entire description of FIGS. 1 to
13, the means used to demodulate signals from active or passive
electronic tags have not been represented, these means being well
known by those skilled in the art.
[0273] FIG. 1 shows first linear conductors 100 to 109 parallel to
one another and distributed over a plane surface 120, connected
together by connecting conductors 130 to form two electric circuit
strands, the ends of said strands being connected to an electric
power supply 140. The conductors are incorporated in a
non-conducting solid base 150 which can accommodate articles 160
equipped with electronic tags 170 whose antenna is in a plane
forming an angle of less than or equal to 45.degree. with the axis
of the first conductors.
[0274] When the electric power supply powers the circuit strands
forming the first conductors, the electric current flows in the
same direction in the first conductors, for example in the
direction indicated by the arrows placed on the first conductors.
The group of first conductors then generates a magnetic field,
above surface 120, which is, at the centre of this surface,
parallel to the arrow 180.
[0275] The electric current flowing through the top strand
therefore passes successively through the following points and
first conductors: A, B, 100, A, B, 101, A, B, 102, A, B, 103, A, B,
104 and A. The bottom strand is symmetrical with the top
strand.
[0276] The inductor illustrated in FIG. 1 therefore comprises a
plurality of first conductors parallel to one another, at least
three of the first conductors being substantially at the same
distance from each other and distributed over a surface, and an
electric power supply of the conductors which sends electric
current in the same direction through the conductors.
[0277] In the first mode of realization, illustrated in FIG. 1, the
first conductors are linear and uniformly distributed over the
surface 120, which is plane and the connecting conductors are
formed from turns partially superimposed over the first conductors,
on each half of the surface 120.
[0278] In variants, the first conductors are not uniformly
distributed over the surface 120 (see the second and fourth modes
of realization), are not linear, are not coplanar and/or do not
form turns with the connecting conductors (see the third and fourth
modes of realization).
[0279] FIG. 2 shows first linear conductors 200 to 209 parallel to
one another and distributed, in groups, over a plane surface 220,
connected together by connecting conductors 230 to form two
electric circuit strands, the ends of said strands being connected
to an electric power supply 240. The conductors are incorporated in
a non-conducting solid base 250 which can accommodate articles 260
equipped with electronic tags 270 whose antenna is in a plane
forming an angle of less than or equal to 45.degree. with the axis
of the first conductors.
[0280] When the electric power supply powers the circuit strands
forming the first conductors, the electric current flows in the
same direction in the first conductors, for example in the
direction indicated by the arrows placed on the first conductors.
The group of first conductors then generates a magnetic field,
above surface 220, which is, at the centre of this surface,
parallel to the arrow 280.
[0281] The electric current flowing through the top strand
therefore passes successively through the following points and
first conductors: A, B, 200, A, B, 200, A, B, 200, A, B, 200, A, B,
201, A, B, 201, A, B, 201, A, B, 202, A, B, 202, A, B, 202, A, B,
203, A, B, 203, A, B, 204, A, B, 204 and A. The bottom strand is
symmetrical with the top strand.
[0282] The inductor illustrated in FIG. 2 therefore comprises a
plurality of first conductors parallel to one another, at least
three of the first conductors being substantially at the same
distance from each other and distributed over a surface, and an
electric power supply of the conductors which sends electric
current in the same direction through the conductors.
[0283] In the second mode of realization, illustrated in FIG. 2,
the first conductors are grouped such that, near the edges of the
surface 220 and connecting conductors forming turns, the number of
first conductors is higher than towards the centre of the surface
220. In other words, the first conductors are more densely
distributed at the ends of the surface comprising them and less
densely distributed at the centre of the surface comprising
them.
[0284] In the example shown in FIG. 2, four first conductors are
grouped to form the smallest turns, then three conductors are
grouped to form the next turns, then three conductors are grouped
to form the next turns, then two conductors are grouped to form the
other turns.
[0285] This configuration in groups makes the magnetic field more
uniform near the surface 220 than near the surface 120.
[0286] In the second mode of realization, the first conductors are
linear and distributed over the surface 220, which is plane and the
connecting conductors are formed from turns partially superimposed
over the first conductors, on each half of the surface 220.
[0287] In variants, the first conductors are uniformly distributed
over the surface 220 (see the first and third modes of
realization), are not linear, are not coplanar and/or do not form
turns with the connecting conductors (see the third and fourth
modes of realization).
[0288] Compared with the third and fourth modes of realization
illustrated in FIGS. 4 and 5, the length of connecting conductors
implemented in the first and second modes of realization is
shorter, keeping the same dimensions of the surface 220.
[0289] Concerning the first and second modes of realization, due to
their symmetry, the electromagnetic coupling of the top and bottom
strands is only slight, thereby reducing energy losses.
[0290] FIG. 3 shows, in a 3D view, the intensity 300 of the
magnetic field component along the X-axis, i.e. the axis parallel
to the surface comprising the first conductors and perpendicular to
these first conductors. This intensity, represented by the height,
i.e. on the B-axis, is given for each point of the surface 220,
represented on the X- and Y-axes, at a constant distance from the
surface 220.
[0291] We see that the magnetic field intensity is substantially
uniform over a large part of the surface 220. For example, the line
of intensities equal to half the maximum intensity reaches all the
first conductors.
[0292] FIG. 4 shows first linear conductors 400 to 409 parallel to
one another and distributed over a plane surface 420, connected
together by connecting conductors 430 to form one electric circuit
strand, the ends of said strand being connected to an electric
power supply 440. The conductors are incorporated in a
non-conducting solid base 450 which can accommodate articles 460
equipped with electronic tags 470 whose antenna is in a plane
forming an angle of less than or equal to 45.degree. with the axis
of the first conductors.
[0293] When the electric power supply powers the circuit strand
forming the first conductors, the electric current flows in the
same direction in the first conductors, for example in the
direction indicated by the arrows placed on the first conductors.
The group of first conductors then generates a magnetic field,
above surface 420, which is, at the centre of this surface,
parallel to the arrow 480.
[0294] The electric current flowing through the strand therefore
passes successively through the following points and first
conductors: A, B, 400, C, D, 409, A, B, 401, C, D, 408, A, B, 402,
C, D, 407, A, B, 403, C, D, 406, A, B, 404, C, D, 405 and A.
[0295] The inductor illustrated in FIG. 4 therefore comprises a
plurality of first conductors parallel to one another, at least
three of the first conductors being substantially at the same
distance from each other and distributed over a surface, and an
electric power supply of the conductors which sends electric
current in the same direction through the conductors.
[0296] In the third mode of realization, illustrated in FIG. 4, the
first conductors are linear and uniformly distributed over the
surface 420, which is plane and the connecting conductors are
alternately connected to the ends of the surface such that they do
not form turns partially superimposed over the first
conductors.
[0297] In variants, the first conductors are not uniformly
distributed over the surface 420 (see the first, second and fourth
modes of realization), are not linear, are not coplanar and/or form
turns with the connecting conductors (see the first and second
modes of realization).
[0298] FIG. 5 shows first linear conductors 500 to 509 parallel to
one another and distributed over a plane surface 520, connected
together by connecting conductors 530 to form one electric circuit
strand, the ends of said strand being connected to an electric
power supply 540. The conductors are incorporated in a
non-conducting solid base 550 which can accommodate articles 560
equipped with electronic tags 570 whose antenna is in a plane
forming an angle of less than or equal to 45.degree. with the axis
of the first conductors.
[0299] When the electric power supply powers the circuit strand
forming the first conductors, the electric current flows in the
same direction in the first conductors, for example in the
direction indicated by the arrows placed on the first conductors.
The group of first conductors then generates a magnetic field,
above surface 520, which is, at the centre of this surface,
parallel to the arrow 580.
[0300] The electric current flowing through the strand therefore
passes successively through the following points and first
conductors: A, B, 500, C, D, 509, A, B, 501, C, D, 508, A, B, 502,
C, D, 507, A, B, 503, C, D, 506, A, B, 504, C, D, 505 and A.
[0301] The inductor illustrated in FIG. 5 therefore comprises a
plurality of first conductors parallel to one another, at least
three of the first conductors being substantially at the same
distance from each other and distributed over a surface, and an
electric power supply of the conductors which sends electric
current in the same direction through the conductors.
[0302] In the fourth mode of realization, illustrated in FIG. 5,
the first conductors are linear, are not uniformly distributed over
the surface 520, which is plane and the connecting conductors are
alternately connected to the ends of the surface such that they do
not form turns partially superimposed over the first
conductors.
[0303] In the fourth mode of realization, illustrated in FIG. 5,
the first conductors are closer to one another near the edges of
the surface 520 and farther away from one another other towards the
centre of the surface 520. In other words, the first conductors are
more densely distributed at the ends of the surface comprising them
and less densely distributed at the centre of the surface
comprising them.
[0304] The third and fourth modes of realization, illustrated in
FIGS. 4 and 5, offer the advantage of having low inductance with
respect to the first and second modes of realization illustrated in
FIGS. 1 and 2.
[0305] In variants, the first conductors are uniformly distributed
over the surface 520 (see the first and third modes of
realization), are not linear, are not coplanar and/or form turns
with the connecting conductors (see the first and second modes of
realization).
[0306] We see that, in the modes of realization where the
connecting conductors form turns with the first conductors, the
first conductors may, as in the mode of realization illustrated in
FIG. 5, be separated from one another by variable distances,
preferably more reduced at the ends of the surface that at its
centre.
[0307] Inversely, in the modes of realization where the connecting
conductors do not form turns with the first conductors, the first
conductors may, as in the mode of realization illustrated in FIG.
2, be grouped together with variable numbers of first conductors
per group, preferably higher at the ends of the surface that at its
centre.
[0308] FIG. 6 shows the first conductors (only the first conductors
601 to 606 are shown), connected by connecting conductors 612, 613
and 615. The first conductors are in one of the configurations
illustrated in FIG. 1, 2, 4 or 5, or in one of their variants. The
connecting conductors 612, 613 and 615 are on the same side of a
plane comprising the first conductors. The connecting conductors
have two linear parts, each side of the first conductors,
respectively 612 and 613. The linear parts 612 are coplanar and the
linear parts 613 are coplanar.
[0309] When an electric current is flowing through these parts 612
and 613, they generate underneath the first conductors a magnetic
field parallel to the magnetic field generated by the electric
current flowing through the first conductors. The total magnetic
field is therefore increased opposite the ends of the first
conductors.
[0310] FIG. 7 shows that, in a surface 720, first conductors 705,
parallel to one another, with current flowing through them in the
same direction when powered by the electric power supply (not
shown) and second conductors 710, parallel to one another, with
current flowing through them in the same direction when powered by
the electric power supply, the second conductors being
perpendicular to the first conductors and coplanar with them.
[0311] The electric power supply is adapted to generate a current
alternately on the first and second conductors, thereby alternately
generating, above the surface 720, magnetic fields illustrated by
arrows 780 and 785, respectively.
[0312] Electronic tags whose antennae are perpendicular to the
surface 720 can therefore always be read, when the first conductors
705 are powered and/or when the second conductors 710 are
powered.
[0313] FIG. 8 shows that, in a surface 820, first conductors 805,
parallel to one another, with current flowing through them in the
same direction when powered by the electric power supply (not
shown) and second conductors 810, parallel to one another, with
current flowing through them in the same direction when powered by
the electric power supply, the second conductors being
perpendicular to the first conductors and coplanar with them.
[0314] Third conductors 815 forming square turns powered by the
electric power supply are located around the surface 820.
[0315] The electric power supply is adapted to generate a current
alternately on the first, second and third conductors, thereby
alternately generating, above the surface 820, magnetic fields
illustrated by arrows 880, 885 and 890, respectively.
[0316] Irrespective of their antenna orientations, electronic tags
can therefore always be read, when the first conductors 805 are
powered, when the second conductors 810 are powered and/or when the
third conductors 815 are powered.
[0317] The mode of realization illustrated in FIG. 8 can be used to
produce a "3D" reader since the tags can be read irrespective of
their orientation or their position on the surface 820. This reader
is very flat and can easily be included in various supports (in
particular tables, shelves, partitions for stock management,
etc.).
[0318] Concerning the modes of realization illustrated in FIGS. 7
and 8, due to their symmetry, the strands comprising the first,
second and possibly third conductors are not electromagnetically
coupled. Consequently, there is no energy loss when associating
these three types of antenna.
[0319] The various modes of realization of this invention are
highly adapted to identification of stacks of a large number of
tags (especially tags not operating by resonance) which are
parallel and very close to each other. The comb structure due to
its highly uniform field allows optimum coupling of the energy to a
stack of tags, even very compact. The reader described above can be
used to identify a stack of 40 tags. A figure-8 shaped reader of
the same area cannot offer this type of performance.
[0320] In the remainder of the description, the seventh mode of
realization of the inductor illustrated in FIG. 8 has been
represented. However, this mode of realization is only given as an
example, the other modes of realization and their variants can be
integrated in a similar manner in pallets, containers, conveyors,
cash registers or base stations.
[0321] FIG. 9 shows a pallet 900 comprising, in its top surface, a
surface 820 equipped with the first, second and third conductors
and connected to the exterior of the pallet 900 by a connector 910
allowing an external electric power supply to power alternately
these first, second and third conductors.
[0322] The advantage of this pallet 900 is that the tags of the
objects it supports can be read, without having to move them
between antennas of a base station.
[0323] FIG. 10 shows a container or a box 1000 comprising, in its
bottom surface, a surface 820 equipped with the first, second and
third conductors and connected to the exterior of the container
1000 by a connector 1010 allowing an external electric power supply
to power alternately these first, second and third conductors.
[0324] The advantage of this container 1000 is that the tags of the
objects it contains can be read, without having to move them
between antennas of a base station.
[0325] FIG. 11 shows a conveyor 1100 comprising, underneath its
conveying surface, in this case represented by rollers 1110
supporting a flexible belt 1120, a surface 820 equipped with the
first, second and third conductors and connected to an electric
power supply 1140 which powers alternately these first, second and
third conductors.
[0326] The advantage of this conveyor 1100 is that the tags 1170 of
the objects 1160 it carries can be read, irrespective of the
orientation of their antennas and without obstructing the passage
of these objects 1160.
[0327] FIG. 12 shows a cash register 1210 comprising a display
screen 1220 and connected to a base comprising a surface 820
equipped with the first, second and third conductors and connected
to an electric power supply (not shown) incorporated in the cash
register, which powers alternately these first, second and third
conductors.
[0328] The advantage of this cash register 1210 is that the tags
1270 of the objects 1260 placed on the base can be read,
irrespective of the orientation of their antennas and without
restricting the size of these objects to particular dimensions.
[0329] This invention therefore allows automatic identification of
stacked products, especially at the checkout of a store.
[0330] FIG. 13 shows a base station 1310 connected to two vertical
surfaces 820 each equipped with first, second and third conductors
and connected to an electric power supply (not shown) incorporated
in the base station, which powers alternately these first, second
and third conductors in a correlated manner, so that the magnetic
field between the surfaces 820 is as uniform as possible.
[0331] The advantage of this base station 1310 is that the tags
1370 of the objects 1360 between the surfaces 820 can be read,
irrespective of the orientation of their antennas or their position
between the surfaces 820.
[0332] This invention can therefore be used to produce different
shapes of support comprising the inductor subject of this
invention. Since this support, used to read electronic tags whose
antenna is oriented in any direction, offers the significant
advantage of being very flat, it can be placed on or incorporated
in any work surface, counter, table, tray or shelf.
[0333] This invention is not limited to the modes of realization
described and represented or to their variants, but, quite on the
contrary, can be extended to the modes of realization of this
invention within the grasp of those skilled in the art.
[0334] When used with a signal frequency of 125 kHz crossing the
conductors, single-conductor standard building wire of
cross-section 1 mm.sup.2 can be used to form the conductors in
order to minimize the skin effect at said frequency.
[0335] We observe that the inductor subject of this invention is
especially intended to operate with frequencies below 30 MHz.
[0336] FIGS. 14 to 17 concern more specifically the third to fifth
aspects of this invention. FIG. 14 shows a group of antennae 1405
and 1410 of a base station (not shown) and passive electronic tags
1415, 1420, 1425 and 1430 placed between the group of antennae 1405
and 1410. The base station successively powers the antennae of the
group of antennae 1405 and 1410 to successively generate, during a
read cycle, a vertical magnetic field symbolized by the arrow 1440,
a lateral magnetic field symbolized by the arrow 1445 and a
longitudinal magnetic field symbolized by the arrow 1450.
[0337] The electronic tags are powered by the electromagnetic field
generated by the group of antennae 1405 and 1410 when their antenna
planes cut a sufficient number of magnetic field lines.
[0338] In the configuration shown, the electronic tag 1415 is
powered by the magnetic field 1440, tag 1420 by the magnetic field
1445, tag 1425 by the magnetic field 1450 and tag 1430 by each of
the magnetic fields 1440, 1445 and 1450.
[0339] Each of the tags 1415, 1420, 1425 and 1430 comprises a
communication means, respectively 1416, 1421, 1426 and 1431, to
communicate with the base station and an extended inhibition means,
respectively 1417, 1422, 1427 and 1432.
[0340] The communication means are adapted to reply to requests
transmitted, via successive magnetic fields, by the base station in
order to be identified by this base station. The extended
inhibition means 1417, 1422, 1427 and 1432 are adapted to inhibit
the reply to the query requests when the corresponding tag has been
fully identified, for a duration of at least one complete read
cycle, even when the corresponding electronic tag is not powered by
a magnetic field, such that there is no risk of an electronic tag
being successively identified by magnetic fields successively
generated by the group of antennae 1405 and 1410.
[0341] Thanks to this essential feature, each electronic tag can
only be read once per read cycle, which significantly increases the
number of electronic tags that can be identified per unit time.
[0342] On the contrary, in the prior art, when they were no longer
powered, the tags were quickly no longer inhibited and replied to
the identification requests from the base station as soon as they
were powered again, resulting in a plurality of successive
identifications of the same electronic tag during a given read
cycle and therefore a loss of time and reduced identification
rate.
[0343] In fact, apart from the special orientations of the
electronic tags 1415, 1420 and 1425, since the electronic tags are
randomly oriented, they can be read by several magnetic fields,
which is the case for electronic tag 1430.
[0344] FIGS. 15A and 15B show the assembly of a MOS transistor 1525
mounted as a diode, i.e. the drain is connected to the source and
the gate is connected to the substrate.
[0345] On power up, switch K1 1520 is closed, capacitor C 1530 is
discharged. As soon as the tag is identified, switch K11520 closes
allowing capacitor C 1530 to charge, across transistor 1525, at
constant current generated by the current source Ic 1515.
[0346] Switch K2 1535 can be used at any time to reset the extended
inhibition information stored in the capacitor 1530, i.e. exit the
extended inhibition state.
[0347] The level stored in capacitor C 1530 is present at point Vp
1540 in order to compare the potential Vp 1540 with a fixed
reference voltage Vref 1545. The signal present at output Vout 1555
of the comparator 1550 is the reshaping of the signal Vp 1540 and
represents the extended inhibition state of the electronic tag.
[0348] FIG. 16 shows the steps involved in the operation of an
electronic tag according to this invention.
[0349] The passive electronic tag wakes up when it receives a
magnetic field strong enough to power it, step 1605.
[0350] During a step 1610, it initializes, for example by resetting
counters. During a step 1615 it receives a reset signal from a base
station, via a read magnetic field, generally identical to the
power electric field.
[0351] During a step 1620, it replies to the requests transmitted
by the base station and supplies its identification, in one or more
parts. Possibly, during this step 1620, it becomes temporarily
inhibited so as not to reply to requests concerning the
identification of other electronic tags.
[0352] During a step 1625, the electronic tag determines whether it
has been fully identified, either according to the replies it has
transmitted, or after reception of an acknowledgement of receipt
signal from the base station, for example as a single pulse or as a
message repeating the entire identification of the tag
concerned.
[0353] If the result of step 1625 is negative, which may, for
example, happen if the tag did not correctly receive all the
requests transmitted for its attention by the base station or if
the base station did not correctly receive the replies transmitted
by the electronic tag, the tag returns to step 1615 and waits for a
new reset request.
[0354] If the result of step 1625 is positive, during a step 1630,
the electronic tag switches into extended inhibition until it
receives a request to exit extended inhibition, step 1635 or until
its extended inhibition means can no longer maintain the extended
inhibition signal, this extended inhibition being able to last for
a period of at least the duration of a said read cycle, even in the
absence of any electric power supply from said base station.
[0355] If it receives a request to exit extended inhibition, the
electronic tag exits extended inhibition state, step 1640 and
returns to step 1615. If the energy stored by the inhibition means,
for example by the capacitor 1530, is exhausted, the tag goes back
to sleep until a step 1605 occurs.
[0356] FIG. 17 shows, successively, on a time axis from bottom to
top, that the magnetic field 1450 is first transmitted to identify
electronic tags within said field. During this phase of the read
cycle, the electronic tag 1425 is fully identified and we assume in
this case that the electronic tag 1430, powered by the magnetic
field 1450, is not fully identified, for example because of its
orientation or communication faults between it and the base
station. The electronic tag 1425 then goes into extended inhibition
state which may last for at least the duration of a complete read
cycle implementing the various antenna combinations planned in this
cycle.
[0357] Once the base station has identified the electronic tags
capable of correctly communicating via the magnetic field 1450, the
magnetic field 1445 is transmitted and the electronic tag 1420 is
fully identified. Due to its extended inhibition, even if it is
powered by the magnetic field 1445 and it receives the requests
transmitted by the base station, the electronic tag 1425 does not
reply to these requests nor to the reset transmitted by the base
station.
[0358] We assume in this case that the electronic tag 1430 is also
fully identified during the transmission phase of magnetic field
1445.
[0359] As soon as they are fully identified, the electronic tags
1420 and 1430 go into extended inhibition state which may last for
at least the duration of a complete read cycle implementing the
various antenna combinations planned in this cycle.
[0360] Once the base station has identified the electronic tags
capable of correctly communicating via the magnetic field 1445, the
magnetic field 1440 is transmitted and the electronic tag 1415 is
fully identified. Due to their extended inhibition, even if they
are powered by the magnetic field 1440 and they receive the
requests transmitted by the base station, the electronic tags 1420,
1425 and 1430 do not reply to these requests nor to the reset
transmitted by the base station.
[0361] As soon as it is fully identified, the electronic tag 1415
goes into extended inhibition state which may last for at least the
duration of a complete read cycle implementing the various antenna
combinations planned in this cycle.
[0362] We assume in this case that the base station does not
transmit a request to exit extended inhibition as long as any tags
remain to be identified. The base station therefore performs a new
read cycle, successively implementing magnetic fields 1450, 1445
and 1440 and does not identify any new electronic tag.
[0363] The base station then transmits a request to exit extended
inhibition, via each of the magnetic fields 1450, 1445 and 1440 and
all tags exit extended inhibition and wait for a reset in order to
reproduce a read cycle. This step of transmission of a request to
exit extended inhibition is, for example, carried out to check that
the electronic tags are still within the range of the base station
or to deinhibit any electronic tag which could have come within the
range of the base station in an extended inhibition state, for
example under the effect of a read by another base station.
[0364] We observe that the tags exit extended inhibition state when
they receive the exit request. Due to their special orientations
therefore, the electronic tags 1420 and 1415 exit extended
inhibition state later than the electronic tags 1425 and 1430.
[0365] FIGS. 18 to 20 concern more specifically the sixth to eighth
aspects of this invention. FIG. 18 shows an inductor 1800
comprising two strands 1805 and 1825 in the shape of non-planar
loops and a product 1850 bearing an electronic tag 1855 comprising
a plane antenna 1860. Each loop of the strand 1805 comprises, for
each conductor, six line segments 1810 to 1815 and each loop of
strand 1825 comprises, for each conductor, six line segments 1830
to 1835. The combination of the two strands 1805 and 1825 is made
from a single conductor which successively goes through the loops
1805 and 1825. FIG. 18 only shows a given conductor going though
the strand three times so that the figure remains clear. However,
the number of times a conductor goes through each strand is
preferably much higher in order to generate a very strong
electromagnetic field.
[0366] In FIG. 18, the conductor first goes through strand 1805
three times then through strand 1825 three times. In variants, the
conductor goes alternately through strands 1805 and 1825, for
example to form a layer of conductors in one of the strands before
forming a layer of conductors in the other strand before going to
the next layer.
[0367] As we can easily understand, the current flows through the
two strands in opposite directions of rotation, at all times. For
example, in FIG. 18, when the current flows, as seen from above, in
the clockwise direction on strand 1805, it flows in anticlockwise
direction on strand 1825.
[0368] in FIG. 18, each non-planar loop of each strand is mostly
contained in the junction of two orthogonal planes, one horizontal
and the other vertical.
[0369] The product 1850 is of any type. It is associated with an
electronic tag or transponder 1855, for example RFID type. The
plane of the flat antenna 1860 of the electronic tag is oriented
substantially parallel to the line segments 1811, 1812, 1813, 1815,
1831, 1832, 1833 and 1835 and substantially perpendicular to line
segments 1810, 1814, 1830 and 1834. For example, the product 1850
is moved by a conveyor (see FIG. 19) or a conveyor belt parallel to
segments 1812, 1815, 1832 and 1835 such that it passes through the
arch formed by the inductor 1800.
[0370] The orientation of the axis of the antenna 1860 of each
electronic tag 1855 is substantially parallel to an axis 1865 going
through the two loops. The mutual inductance between the inductor
1800 and the antenna 1860 of the electronic tag 1855 is therefore
high as the electronic tag 1855 goes through the arch formed by the
inductor 1800, its antenna 1860 being substantially perpendicular
to the field lines, illustrated by the arrow 1870.
[0371] FIG. 19 shows, in side view, a conveyor 1900 comprising an
inductor 1800 as illustrated in FIG. 18 and electronic circuits
1905 to generate signals applied to the inductor 1800 and to
process signals from the inductor 1800 to identify the electronic
tags 1855 and the products 1850 and, possibly, write these
electronic tags 1855 in memory.
[0372] The conveyor 1900 comprises, above its conveying surface,
represented here by rollers 1910 supporting a flexible belt 1920,
the inductor 1800. The conveyor carries the product 1850 such that
the orientation of the axis of the antenna 1860 of each electronic
tag 1855 is substantially parallel to an axis going through the two
loops. The electronic tag 1855 is therefore read as it goes under
the inductor 1800, its antenna 1860 then being substantially
perpendicular to the field lines generated by the inductor
1800.
[0373] The advantage of this conveyor 1900 is that the tags 1855 of
the products 1850 it carries can be read as they go under the
inductor 1800.
[0374] FIG. 20 shows a base station 2000 comprising an inductor
1800 as illustrated in FIG. 18 and electronic circuits 2005 to
generate signals applied to the inductor 1800 and to process
signals from the inductor 1800 to identify the electronic tags 1855
and the products 1850 and, possibly, write these electronic tags
1855 in memory.
[0375] The base station 2000 comprises, underneath and around a
support 2010 of products 1850, the inductor 1800 turned upwards.
The products 1850 to be identified are positioned, for example by a
warehouseman, a salesman, a customer or a security officer, on the
support 2010 such that the orientation of the antenna 1860 axis of
each electronic tag 1855 is substantially parallel to an axis going
through the two loops. The electronic tag 1855 is therefore read
when the products 1850 are placed on the support 2010 and above the
inductor 1800, the antenna 1860 of the electronic tag 1855 then
being substantially perpendicular to the field lines generated by
the inductor 1800.
[0376] This invention can therefore be used to produce different
shapes of support comprising the transducer subject of this
invention. This support, used to read electronic tags whose antenna
is oriented in any direction, offers the significant advantage that
it can be incorporated in a work surface, a counter or a shelf.
[0377] This invention also allows automatic identification of
stacked products whose electronic tag antennae are parallel.
[0378] This invention is not limited to the modes of realization
described and represented or to their variants, but, quite on the
contrary, can be extended to the modes of realization of this
invention within the grasp of those skilled in the art.
[0379] FIGS. 21 to 29 concern more specifically the ninth and tenth
aspects of this invention. FIG. 21 shows a rack 2100 comprising, in
or on its back wall 2105, an antenna 2110, in its upper part,
electronic tags 2115, shelves 2120 supporting products 2125
equipped with electronic tags 2160, a communication means 2155, a
reader 2135 to read an identification card 2140 and a display
2145.
[0380] The rack 2100 and the shelves 2120 are made from rigid
materials, for example wood, glass or plastic.
[0381] The antenna 2110 is connected to the back wall 2105, for
example by gluing, stapling or inclusion. The antenna 2110 has one
of the antenna shapes illustrated in FIGS. 23 to 25.
[0382] The electronic tags 2160 and the electronic circuits 2115
are of type known in the field of radio frequency identification
(RFID). They comprise, in a known manner, a signal generation
circuit adapted to successively generate signals for each antenna
or group of antennae incorporated in the rack (see also FIG. 22)
and a signal reception circuit modulating said magnetic field.
[0383] The electronic circuits 2115 consist, for example, of a
computer and circuits specific to the field of RFID electronic
tags. They are adapted to supply to the antenna 2110, at
predetermined times, a signal enabling it to generate an
electromagnetic field. This electromagnetic field is used to power
the electronic tags 2160 and transmit messages, requests or
instructions to the tags 2160. The electronic circuits 2115 are
also adapted to detect the signals transmitted by the electronic
tags 2160, by modulation of the magnetic field transmitted by the
antenna 2110, to process these signals, to identify the electronic
tags and to transmit these identifiers to the communication means
2155.
[0384] The electronic circuits 2115 are also adapted to process the
signals from the card 2140 reader 2135 to identify a user and
command the contents of the display 2145.
[0385] The operation of the electronic circuits 2115 is detailed
with reference to FIG. 27.
[0386] The communication means 2155 allows remote communication
with a computer, a server or a computer system comprising a
network, according to known techniques, on wired or wireless
support. The communication means 2155 is, for example, a modem.
[0387] The identification card 2140 reader 2135 is, for example, of
type known in the field of radio frequency identification. In this
case, each card 2140 comprises a transponder, or electronic tag and
the reader 2135 comprises an antenna for transmission and reception
of magnetic fields modulated for the data exchanges required to
identify the cards 2140.
[0388] As a variant, the reader 2135 is replaced by a biometric
identification device of known type, to identify the users
accessing the content of the rack 2100.
[0389] The display 2145 is of known type, for example a Liquid
Crystal Display (LCD screen) and used to display visible messages
to users, for example instructions for their identification, for
the positioning of products 2125 in the rack 2100 and to display
warnings if the number of products of a given reference reaches a
predetermined value or if one of the products is approaching its
use-by-date.
[0390] Preferably, when the back wall supports an antenna,
arrangements are made so that the electronic tags cannot be placed
in the immediate vicinity of this antenna. For example, the back
wall in front of each antenna is made slightly thicker, projecting
into the rack.
[0391] FIG. 22 shows, in a rack 2200, the same elements as in FIG.
21, the shelves and the products not being shown for clarity
reasons, as well as an antenna 2205, in or on the back wall 2105 of
the rack 2200, and antennae 2210, 2215, 2220, 2225, 2230 and 2235,
placed two by two in or on the side walls 2240 and 2245 and central
2250 wall of the rack 2200. In this case, the electronic circuits
2115 are adapted to multiplex the uses of the antennae to
successively query the electronic tags 2160 whose antennae are
positioned according to orthogonal axes.
[0392] FIG. 23 shows that a first shape of antenna 2300
incorporated in a rack illustrated in FIG. 21 or 22 consists of a
figure-8, i.e. two coplanar loops 2305 and 2310, the conductor
forming this antenna going alternately through one or the two
loops, with opposite directions of rotation. In this figure, only
one coil has been represented, it being understood that the antenna
actually comprises a large number of superimposed coils.
[0393] Consequently, when the current flows through the two
coplanar loops, in one of the loops it flows in the clockwise
direction and, simultaneously, in the other loop it flows in the
anticlockwise direction. This configuration generates an
electromagnetic field over an extended volume near the back wall
2105 of the rack.
[0394] FIG. 24 shows that a second shape of antenna 2400
incorporated in a rack illustrated in FIG. 21 or 22 consists of
three coplanar loops 2405, 2410 and 2415, the conductor forming
this antenna going alternately through the three loops, with
directions of rotation alternately clockwise and anticlockwise. In
this figure, only one coil has been represented, it being
understood that the antenna actually comprises a large number of
superimposed coils.
[0395] Consequently, when the current flows through the three
coplanar loops, in at least one of the loops it flows in the
clockwise direction and, simultaneously, in at least one other loop
it flows in the anticlockwise direction. This configuration
generates an electromagnetic field over an extended volume near the
back wall 2105 of the rack.
[0396] FIG. 25 shows that a third shape of antenna 2500
incorporated in a rack illustrated in FIG. 21 or 22 consists of
four coplanar loops 2505, 2510, 2515 and 2520, the conductor
forming this antenna going alternately through the four loops, with
directions of rotation alternately clockwise and anticlockwise. In
this figure, only one coil has been represented, it being
understood that the antenna actually comprises a large number of
superimposed coils.
[0397] Consequently, when the current flows through the four
coplanar loops, in two of these loops it flows in the clockwise
direction and, simultaneously, in the other two loops it flows in
the anticlockwise direction. This configuration generates an
electromagnetic field over an extended volume near the back wall
2105 of the rack.
[0398] In the case of the rack illustrated in FIG. 22, for example,
the back wall supports both an antenna as illustrated in FIG. 23
and an antenna as illustrated in FIG. 24 and each side or central
wall supports an antenna as illustrated in FIG. 23. The inventors
discovered, in fact, that this configuration covered the entire
interior volume of the rack 2200 without leaving any dead areas,
with the electromagnetic fields successively transmitted by the
various antennae.
[0399] As a variant of the various modes of realization of the rack
subject of this invention, at least one antenna is incorporated in
a shelf. This antenna comprises at least two coplanar loops through
at least one of which the current flows in the clockwise direction
and, simultaneously, through at least one other loop the current
flows in the anticlockwise direction, For example, this antenna is
one of the antennae illustrated in FIGS. 23 to 25 or a combination
of such antennae. The signal generation circuit 2115 is adapted to
successively generate signals for various antennae related to
various shelves.
[0400] FIG. 26 shows a product 2125 comprising a paper label 2165
and the electronic tag 2160. The product comprises a metallic part
2610 (in this case a metallic or metal bag) which is thin, in other
words of thickness less than one quarter of its largest dimension,
on at least one of its edges 2605. The electronic tag 2160 has an
antenna 2615 which is positioned substantially perpendicular to a
thin edge of the metallic part 2610.
[0401] The antenna 2615 preferably has a width, measured in the
direction of the thickness of the metallic part 2610, greater than
the thickness of the edge 2605 of the metallic part opposite which
the antenna is positioned.
[0402] The inventors have discovered that, with these
characteristics, the electronic tag could be read despite the
proximity of the metallic part and the electronic tag.
[0403] In FIG. 26, the product 2125 has the shape of a rectangular
parallelepiped and comprises the electronic tag on one of its four
smallest sides. The product 2125 also comprises a paper label 2165
positioned on a side of the product opposite the side of the
product bearing said electronic tag. In this case, the paper label
2165 shows the reference "duo M8H".
[0404] As a variant, the paper label 2165 is positioned on one side
of the product adjacent to a side of the product bearing said
electronic tag 2160 on one of its small sides.
[0405] Consequently, when the user stores the product 2125, in a
stack or vertically in the rack 2100 or 2200, he is encouraged to
position it so that its paper label 2165 is visible. Due to this
position, the electronic tag 2160 is positioned towards the back
wall of the rack or towards one of its shelves, allowing the
electronic tags 2165 to be read by an antenna positioned on or in
the back wall or a shelf, respectively.
[0406] The inventors discovered, in fact, that with this
configuration: [0407] the user could read the text shown on the
paper label 2165, without moving the product 2125, and [0408] the
electronic tags 2160 were positioned near to and opposite the
antenna supported by the back wall 2105 of the rack or by a shelf
in the rack.
[0409] When the product 2125 is flat, for example with a thickness
of 10 mm to 12 mm, the electronic tag 2160 preferably comprises an
elongated antenna 2615, for example measuring 8 mm.times.80 mm.
[0410] As show in FIG. 27, an initialization step 2702 is first
carried out, during which associations are defined between: [0411]
electronic tag identifiers and product references, [0412]
electronic tag identifiers and product use-by-dates, [0413] minimum
numbers of products of each reference below which products with
this reference must be reordered and [0414] card identifications
with user identifications.
[0415] This step 2702 can be carried out by reading data in a local
and/or remote database, as indicated with reference to FIG. 29.
[0416] The rack circuits then perform a first read of the
electronic tags present in the rack by successively generating
magnetic fields on the various groups of antennae incorporated in
the rack, step 2704, associating them with product references, step
2706, transmitting this information remotely, step 2708, and
displaying, on the display, the rack use instructions.
[0417] When the user comes to open the rack he is identified, step
2710 and his identifier is stored, step 2712.
[0418] Whenever a user is identified, there is a predetermined
timeout, for example two minutes, step 2714, then the electronic
tags of the products present in the rack are read, step 2716,
successively implementing the rack antennae.
[0419] At regular time intervals, for example every hour, intervals
measured during a step 2722, the electronic tags of the products
present in the rack are read, step 2724, successively implementing
the rack antennae.
[0420] After each read, the identifiers of the electronic tags are
associated with product references, step 2732, and this information
is transmitted remotely, step 2734.
[0421] The list of products present is then compared with the list
of products previously present, step 2736, and the user
identification is associated with the references and identifiers of
the products which have been added to or removed from the rack,
step 2738, and this information is transmitted remotely, step
2740.
[0422] During a step 2742, a check is then carried out to
determine, for one or more product references, whether the number
of products present in the rack is less than or equal to a
predetermined value. If yes, during a step 2744, a local warning is
triggered, this information is transmitted remotely and the
references of the missing products are shown on the display.
[0423] Then, if the result of step 2742 is negative or after step
2744, during a step 2746, a check is carried out to determine
whether the use-by-date of at least one product present in the rack
lies within a future of predetermined duration, for example one
month. If yes, during a step 2748, a local warning is triggered,
this information is transmitted remotely and the references of the
products concerned are shown on the display.
[0424] Then, if the result of step 2746 is negative or after step
2748, the rack circuits display the rack use instructions on the
display, before returning to step 2710.
[0425] FIG. 28 shows a computer system 2800 comprising a plurality
of racks 2802 to 2810, as illustrated in FIG. 21 or 22 and
connected together and to local workstations 2815, 2820 and 2825,
by local networks respectively 2830, 2835 and 2840, a server 2845
connected to said local networks, by an external network 2850 and
external workstations 2855 and 2860 connected, via the external
network 2850, to the server 2845.
[0426] The workstations 2815, 2820, 2825, 2855 and 2860, as well as
the server 2845 are of known type and each comprises a
microprocessor and communication means, for example a modem,
enabling them to communicate with the networks to which they are
directly connected.
[0427] The local workstations implement several user interfaces to
find and manage the stock of products available, reorder new stocks
or manage the parameters triggering these reorders or access
catalogues of products proposed by the various suppliers and place
orders with them.
[0428] The external network 2850 is, for example, the Internet.
[0429] In addition, the server 2845 comprises a database 2875,
means of selective access 2880 to the database by the workstations
2815, 2820, 2825, 2855 and 2860, a warning computer program 2890
and a monitoring computer program 2895.
[0430] The database 2875 contains information concerning the
products contained in the racks 2802 to 2810.
[0431] The workstations 2855 and 2860 are implemented by suppliers
of products likely to be stored in racks subject of this invention,
preferably equipped with paper labels and electronic tags placed on
opposite sides of these products.
[0432] The workstation 2815 and the racks 2802 and 2804 are located
in a first product user centre and contain products from suppliers
implementing the workstations 2855 and 2860.
[0433] The workstation 2820 and the racks 2806 and 2808 are located
in a second product user centre and contain products from suppliers
implementing the workstations 2855 and 2860.
[0434] The workstation 2825 and the rack 2810 are located in a
third user centre and contain products from suppliers implementing
the workstations 2855 and 2860.
[0435] The means of selective access 2880 to the database are of
known type, for example authentication software (for example with
user name and password or with card or biometric recognition) or
signature software and are adapted to allow each product user
centre to access to all its own stock of products contained in the
racks 2802 to 2810, irrespective of the product suppliers.
[0436] The means of selective access 2880 are also adapted to allow
each supplier to access, for all product user centers, the stock
level, in the racks 2802 to 2810, of its own products.
[0437] The warning computer program 2890 is adapted to trigger
warnings when a minimum number of products of a particular
reference has been reached in the stock of a product user centre.
This warning can be used to increase the number of products to be
renewed to avoid further warnings.
[0438] The monitoring computer program 2895 is used to produce a
sales report for each supplier, giving a summary of the references
by product user centre and/or by territory.
[0439] Since each workstation of a product user centre can be
connected by the Internet to the server 2845, it can be identified
and receive information concerning the products in stock, i.e.
entering a rack or leaving a rack in the product user centre
concerned. Each workstation of a product user centre can also
consult the delivery delays for the products stored in order to
manage their renewal.
[0440] As shown on FIG. 29, an initialization step 2902 is carried
out to initialize the various computer devices, during which the
database of the product references and suppliers, and the means of
authenticating the users and/or the various workstations likely to
access the database, are created.
[0441] Then, during a step 2904, each rack supplies a first list of
products it contains, this list being automatically renewed after
each read of electronic tags in these racks and completed by
warning and user identifications, as explained previously.
[0442] During a step 2906, the server aggregates the data received
by product user centre, by supplier and by user.
[0443] During a step 2908, the server determines whether a request
to access the database has been received. If not, return to step
2904. If the result of step 2908 is positive, during a step 2910,
the user and/or the workstation attempting to access the database
are identified.
[0444] If the identification fails, return to step 2904. If the
identification succeeds, during a step 2912, a check is carried out
to determine whether the user and/or the workstation attempting to
access the database is a product user centre workstation or a
supplier workstation.
[0445] If it is from a product user centre, access is allowed to
all its own stock of products contained in the racks of this
product user centre, irrespective of the product suppliers, step
2914.
[0446] It is also allowed, step 2916, to renew products with the
suppliers, in which case the renewal request is sent to the
suppliers concerned. During this step 2916, it is also allowed to
select from catalogue and order products from the supplier, in
which case the order is sent to the suppliers concerned. The
product user centre therefore selects, in the database, the product
references and quantities, the renewal or order forms being
automatically distributed between the suppliers of the references
concerned.
[0447] If, during step 2912, a supplier is found to be accessing,
during a step 2918, this supplier is allowed to access,
simultaneously for all the product user centers, the stock level,
in said racks, of its own products.
[0448] The supplier is also allowed, step 2920, to update its
catalogue, its product references, prices and delivery delays and
to consult the renewal or order forms sent to it. The server can
therefore be used to produce a sales report for each supplier,
giving a summary of the references by product user centre and/or by
territory, according to known techniques.
[0449] After step 2916 or 2920, a check is carried out to determine
whether a warning has been received from a rack, step 2922, and, if
yes, this warning is transferred to the workstation of the product
user centre concerned, step 2924. Then, if the result of step 2922
is negative or after step 2924, return to step 2904.
[0450] As can be seen from the above, the invention is a
significant improvement over the existing technique by providing an
installation which can be used to manage simply and efficiently the
stock in the product user centers and to manage the flow of
equipment between the suppliers and these product user centers
while allowing the suppliers to manage their stock stored in each
product user centre.
[0451] FIGS. 30 to 38 concern more specifically the eleventh to
fourteenth aspects of this invention.
[0452] Throughout the description, the communication protocol
between a base station and an electronic tag is described, without
describing: [0453] the elements used to manage the query requests
allowing the base station to select the requests to be transmitted
and each electronic tag to select the requests concerning it (for
example, by following a tree of the possible electronic tag
identifiers), [0454] the elements used to manage the replies from
the electronic tags allowing them to decide when and how to reply
to the requests from the base station and which allow the base
station to manage the replies from the electronic tags (writing in
databases, electronic tag temporary or permanent inhibition
commands, triggering of alarms, etc.)
[0455] These elements are in fact well known by those skilled in
the art of electronic tags, especially RFID, and are described in
numerous published patents.
[0456] FIG. 30 shows an object 3005 associated with an electronic
tag 3010 which comprises: [0457] an antenna 3030, [0458] a
reception means to receive signals modulated at a first frequency
3015, [0459] a processing means 3020 to process the signals
received by the reception means to identify a query signal to which
said electronic tag must reply and [0460] a transmission means to
transmit signals modulated at a second frequency different from
said first frequency 3025.
[0461] FIG. 30 also shows a base station 3040 to query electronic
tags 3010, which comprises: [0462] at least one antenna 3045,
[0463] a transmission means to transmit signals modulated at a
first frequency 3060. [0464] a reception means to receive signals
modulated at a second frequency different from said first frequency
3055 and [0465] a processing means to process said signals
modulated at the second frequency 3050 to identify a response
signal transmitted by said electronic tag 3010.
[0466] The object 3005 can be of any type. It is assumed here that
it comprises metallic parts which affect the magnetic field
surrounding the electronic tag 3010. The antenna 3030 is of known
type. It is for example circular and equipped with numerous turns
to increase its sensitivity to the magnetic fields generated by the
antenna 3045. The reception means 3015 and the transmission means
3025 implement the antenna 3030 to communicate with the base
station 3040. The transmission means is described with reference to
FIGS. 34 to 36.
[0467] FIG. 30 shows only one antenna 3045. However, in numerous
modes of realization of this invention, a set of antennae oriented
differently or with different geometries is implemented so that any
electronic tag present within a predetermined volume can be
identified, irrespective of its position or orientation in this
volume.
[0468] The transmission means 3060 is partially illustrated in
FIGS. 31, 32A and 32B.
[0469] By implementing a non-resonating tag, although the
sensitivity of the tag is affected, its electrical characteristics
are relatively unchanged, compared with the same tag used in
resonance.
[0470] Preferably, the first frequency is less than 200 kHz and the
second frequency is equal to half the first frequency. Implementing
a first low frequency results in better penetration of the magnetic
field in the metallic parts of the object 3005. In addition, by
choosing to reply at a second frequency half of the first
frequency, this frequency is more easily detected on the antenna of
the base station 3045. In addition, automatic tuning may guarantee
that a maximum amount of energy will be available to power the
electronic tag 3010.
[0471] As can be seen with reference to the electronic diagrams in
FIGS. 31, 32A and 32B, the base station electronics provide
automatic tuning in order to receive the maximum magnetic field
according to the metallic mass and its position in front of the
antenna. To do this, the read frequency is varied by controlling
the amplitude of the voltage on the antenna in order to check
constantly that LC.omega..sup.2=1.
[0472] Using a quartz 3105, oscillating for example at 14.13838
MHz, a clock is generated at this frequency (FIG. 31) on the output
CLK 3110, with a traditional electronic circuit.
[0473] Then, using the logic circuit illustrated in FIGS. 32A and
32B, the second working frequency and its double corresponding to
the first frequency are created according to the position of the
four pre-positionable binary inputs 3125 of a programmable counter
3115 (inputs E1, E2, E3 and E4). The values of the inputs E1, E2,
E3 and E4 are selected to maximize the voltage V (see FIG. 37).
[0474] N being a number chosen on the four inputs of the counter
3115 and
[0475] F being the frequency of the quartz 3105, thus:
F 0 min = F 4 ( 33 - N ) = 14.31818 4 ( 33 - 0 ) = 108.47 kHz
##EQU00001## and ##EQU00001.2## F 0 max = F 4 ( 33 - N ) = 14.31818
4 ( 33 - 15 ) = 198.863 kHz ##EQU00001.3##
[0476] F0min is the minimum value of the first frequency and F0max
is the maximum value of the first frequency.
[0477] The first frequency can therefore be positioned from 108.470
Hz to 198.863 Hz in variable steps of average value 3.389 Hz.
According to the frequency variation and the required resolution,
the quartz can be changed (for example with a 10 MHz quartz, the
first frequency can be positioned from 75.757 Hz to 138.888 Hz in
variable steps of average value 2.367 Hz.)
[0478] FIG. 32A shows the wiring of the counters 3115 and 3120. At
the output of the counter 3120, the frequency is four times the
first frequency. Component 3140 is an "XOR" gate and component 3145
is an inverter. The output 3130 "B" of a flip-flop "D" is twice the
first frequency, for example 125 kHz, the latter being on the
signal present at output 3135 "C" of a second flip-flop "D". By
using the circuit shown in FIG. 32A, we obtain the first frequency
at output 3135. The output 3130 supplies the double frequency,
which is only used as a synchronization signal in the base
station.
[0479] The components 3115 and 3120 are used to divide a frequency
from a quartz according to the formula described (preloadable
reversible counter). The minimum frequency (F0min) and the maximum
frequency (F0max) can be adjusted by changing the quartz.
[0480] The base station is equipped with a slaving means to slave
the frequency Fr of the signal transmitted by the antenna 3045 so
that this frequency Fr respects the equation
L.times.C.times.(2.times.pi.times.Fr).sup.2=1, equation in which L
is the inductance of the transmission circuit comprising the
antenna and C is the capacitance of the transmission circuit
comprising the antenna.
[0481] To provide the slaving, an analogue to digital converter
3150 is used to download to a digital signal processor (DSP) 3155
the peak value present on the transmission antenna. This value is
taken after a divider bridge 3160 of high impedance adapted to keep
the level of the setpoint between 0 V and 10 V and not disturb the
tuning of the antenna 3165. This value is compared, by the digital
signal processor 3155, with the voltage setpoint acquired in the
absence of a metal bottle then the digital signal processor 3155
varies the frequency Fr to reach the level of the setpoint by
changing the four inputs of the counter 3115.
[0482] If an electronic tag 3010 is associated with a pump 3200 for
perfume bottle, as illustrated in FIG. 33, the RFID electronic tag
3010 is positioned at the centre of the pump structure, surrounded
by the metallic parts 3205 of the pump, which are represented by
dark areas in FIG. 33.
[0483] The tag response principle consists in modulating the
response signal at a second frequency less than the first frequency
and equal in this case to half the first frequency.
[0484] This second frequency, equal to half the first frequency, is
preferred since this frequency carries the most energy and can
easily be produced by the electronic tag 3010.
[0485] To do this, the transmission means 3025 of the electronic
tag 3010 modulates, or "charges" one alternation out of two of the
carrier (first frequency) to obtain a signal of half the frequency.
Since the clock is preserved, the electronic tag only cuts 80% of
the signal.
[0486] FIG. 34 shows the assembly used to modulate the tag antenna
formed by the inductor L2 3305, a series resistor R1 3310 of the
antenna 3030 and a spurious capacitor C1 3315 of the antenna 3030,
and two diodes D1 3320 and D2 3325 guaranteeing at least a minimum
signal at the first frequency F0 on the antenna of the electronic
tag 3010. The modulation transistor M1 3330 operates as a switch
and the control voltage V1 3335 is, in time, as represented in FIG.
35, with a frequency equal to the second frequency, i.e. 62.5
kHz.
[0487] The signal V.sub.L2 3400 represented in FIG. 35 shows the
charge of the voltage V.sub.L2 when V1 is 1.
[0488] FIG. 36 shows the spectrum of the signal present on the
electronic tag 3010 when it replies: a line of smaller density is
present at the second frequency. This second frequency is detected
by the reception means 3055, via the antenna 3045 of the base
station 3040.
[0489] Note that an antenna behaves as an RLC circuit comprising an
inductor in series with a resistor, the inductor and the resistor
being in parallel with a capacitor. The resonance frequency is such
that L.times.C.times.(2.times.pi.times.Fr).sup.2=1. The antenna
gain varies according to the frequency transmitted starting from
value 1 for zero frequency, increasing up to the resonance
frequency Fr then decreasing afterwards. For example, this gain
reaches a value of 30 for the resonance frequency Fr.
[0490] To adjust the resonance frequency to the required
transmission frequency, a capacitor is added in parallel with the
antenna.
[0491] FIG. 37 shows, at the top, the curve 3705 of gain against
the frequency of the signal supplied to the base station
antenna.
[0492] According to an aspect of this invention, the power supply
circuit of the base station antenna is adapted to compensate for
the inductance variations due to the presence of metal or of
electronic tag antennae within the antenna transmission field by
modifying the transmission frequency in order to maintain the
relation L.times.C.times.(2.times.pi.times.Fr).sup.2=1. The gain of
the transmission antenna therefore remains substantially constant
irrespective of the disturbances encountered.
[0493] The antenna therefore always transmits a signal at the
resonance frequency, indicated by the vertical broken line and the
reference 3710.
[0494] According to another aspect of this invention, the resonance
frequency of the electronic tag antenna is shifted with respect to
the frequency of the signal transmitted by the base station.
Preferably, the resonance frequency of the electronic tag antenna
is greater than the frequency of the signal transmitted by the base
station. Preferably, the resonance frequency of the electronic tag
antenna is equal to at least double the frequency of the signal
transmitted by the base station. FIG. 37 shows, at the bottom, the
curve 3715 of the gain of the electronic tag antenna against the
frequency of the signal received. We see that the resonance
frequency indicated by the reference 3720 is more than twice the
frequency received, corresponding to the reference 3710.
[0495] For example, for signals transmitted by the base station of
frequency between 125 kHz and 225 kHz, the resonance frequency of
the electronic tag antennae is between 400 kHz and 700 kHz.
[0496] Thanks to these characteristics, the gain of the electronic
tag antenna is close to 1 at the frequency transmitted by the base
station antenna and, consequently, at the electronic tag response
frequency which is, for example, half the frequency of the signal
transmitted by the base station, as described with reference to
FIGS. 30 to 36.
[0497] FIG. 38 shows an electronic diagram of a base station
reception circuit in which the transmission signal enters the
circuit via the input 3800 and crosses the antenna 3805 in series
with a capacitor 3810. In parallel with this branch of the circuit
formed by the antenna 3805 and the capacitor 3810, an image bridge
is used to supply the same intermediate voltage as the voltage
present between the antenna 3805 and the capacitor 3810. The image
bridge comprises an inductor 3815 and a capacitor 3820. The values
of the inductor 3815 and of the capacitor 3820 are adapted so that
the current flowing through this image bridge is much lower, for
example ten times lower, than the current flowing through the
antenna 3805.
[0498] The primary circuit of a transformer 3825 is connected
firstly between the antenna 3805 and the capacitor 3810 and
secondly between the inductor 3815 and the capacitor 3820. The
secondary circuit of the transformer 3825 is connected to a
filtering and amplification circuit 3830 whose output is connected
to the base station processing circuits which process the signal
from the electronic tags.
[0499] Thanks to the image bridge, since the signals received,
which have the electronic tag transmission frequency, in this case
half the base station transmission frequency, are only present
between the antenna 3805 and the capacitor 3810, they can be
detected by the filtering and amplification circuit 3830. However,
the signals having the base station transmission frequency which,
as we have seen above, can be variable, do not modify the equality
of the voltages across the terminals of the primary circuit of the
transformer 3825 and therefore do not disturb detection of the
signals received from the electronic tags.
[0500] FIGS. 39 to 43 concern more specifically the fifteenth to
seventeenth aspects of this invention. FIG. 39 shows a passive
electronic tag 3900 comprising: [0501] a core 3905 of
electrically-insulating material of relative magnetic permeability
above fifty, [0502] a coil 3910 surrounding the core 3905, coil
3910 forming an antenna adapted to receive a query signal from a
base station (see FIG. 42), [0503] an electronic circuit 3915
comprising a memory 3920 storing an identification code and
processing means 3925 adapted to process the query signal from the
base station to determine whether the electronic tag 3900 must
reply and, if yes, to command transmission of a signal by the
antenna 3910.
[0504] The core 3905 is, for example, cylindrical with circular
base. Preferably, the core 3905 consists of and comprises a
ferrite. Consequently, in the remainder of the description, the
insulating material of high magnetic permeability forming the core
will be called "ferrite", without this being limiting.
[0505] The conducting wire forming the coil 3910 is, for example,
thermoadherent.
[0506] The sensitivity of the antenna 3910 is therefore multiplied
according to the relative magnetic permeability of the material
forming the core, a value which may exceed 250, or even 650, for a
ferrite core, compared with the same antenna without ferrite
core.
[0507] Note that the sensitivity of a traditional RFID tag formed
from a coil of N turns of conducting wire, coiled on an average
area S, is given by the traditional relation:
B min = V p . supply .omega. NS .apprxeq. 3 .omega. NS ( 1 )
##EQU00002##
where .omega.=2.pi.f f being the base station working
frequency.
[0508] According to this invention, the sensitivity of the antenna
3910 of the electronic tag 3900, of miniature dimensions to save
space on products of small dimensions (see FIGS. 41A and 41B) is
increased by winding the antenna 3910 on a core 3905, also known as
a rod, of electrically-insulating material of relative magnetic
permeability above fifty, preferably a ferrite. The magnetic
permeability .mu. of this type of material is much higher than that
of non ferromagnetic metals since this permeability consists of two
terms:
.mu.=.mu..sub.0.mu..sub.r (2)
Where .mu..sub.0 is the magnetic permeability in vacuum
4.pi.10.sup.-7 and where .mu..sub.r is the relative magnetic
permeability of the material which takes values of up to several
hundred (typically 250 or 550).
[0509] A ferrite also exhibits the characteristics of an
electrically-insulating medium since the electrical conductivity of
a ferrite is equal to zero.
[0510] The magnetic field lines are therefore focused in the
ferrite core, as though the area of the ferrite core was multiplied
by the relative magnetic permeability .mu..sub.r. The magnetic
field is therefore guided by the ferrite core.
[0511] The base station antenna or inductor (see FIG. 42) can be
defined by the radius R.sub.1 of its assumed circular antenna and
by the number of turns N.sub.1 of the base station antenna.
[0512] In the presence of ferrite surrounded by a coil of radius
R.sub.2 with a number of turns N.sub.2, placed at a distance D from
the base station antenna, the mutual coupling inductance M.sub.21
or M.sub.12 between the two antennae is given by the following
relation:
M 12 = .mu. 0 .mu. r .pi. R 1 2 R 2 2 N 1 N 2 ( D 2 + R 1 2 ) 3 2
##EQU00003##
[0513] The mutual coupling inductance between the two coils is
therefore, due to the presence of the core 3905, multiplied by the
relative magnetic permeability .mu..sub.r.
[0514] The area of an antenna depends on the tag's geometric
parameters:
S = .pi. 12 ( 3 D 2 - 3 D N b .PHI. 2 + N 2 b 2 .PHI. 4 )
##EQU00004##
where
[0515] N: number of turns
[0516] b: coil thickness
[0517] .PHI.: diameter of the wire used to make the coil
The inductance of a coil without a core is given by the following
relation to within .+-.5%:
L = .mu. 0 .pi. a 2 N 2 b + c + R F ' F '' ##EQU00005## F = 10 b +
12 c + 2 R 10 b + 10 c + 1.4 R ##EQU00005.2## F '' = 0.5 log ( 100
+ 14 R 2 b + 3 c ) ) ##EQU00005.3##
where R is the outer radius of the coil. b its thickness. a the
average radius. c is the inner radius. For a long coil, F' and F''
are approximately equal to 1.
[0518] When the antenna is formed from a coil on a core of
insulating material of relative magnetic permeability .mu..sub.r,
of diameter D.sub.1 and length L.sub.2, n turns are wound over a
length L.sub.1. The outer diameter of the turns is called
D.sub.2.
The coil area is A. We can therefore write:
A = .pi. D 2 2 4 ##EQU00006## R m = L 1 .mu. A ##EQU00006.2## L = n
2 R m = n 2 .mu. A L 1 ##EQU00006.3##
[0519] In the mode of realization tested by the inventors, the wire
used is thermoadherent, type 51/62 .mu.m (copper diameter 51 .mu.m,
sheathed diameter 62 .mu.m) or 20/25 .mu.m.
[0520] The number of turns is the product of the number of turns
per layer by the number of layers. For a wire of sheath diameter d,
the number of layers of wire is equal to L.sub.1/d. The number of
turns per layer is equal to (D.sub.2-D.sub.1)/(2d).
[0521] In practice, the parameters are all related to each other
and are not independent. The reluctance Rm and the magnetic
permeability .mu. are therefore difficult to measure.
[0522] For a highly permeable core 3905 of length L.sub.2 plunged
into a magnetic field, the field lines will go through this core
3905 if the path in air is equal to the length of the core 3905.
All field lines whose distance from the axis of the core 3905 is
less than L.sub.2/2 will go through the core 3905.
[0523] This can also be expressed by "the equivalent area of a
ferrite antenna of diameter D and length L is equivalent at best to
L/D times the sensitivity of a tag of diameter D."
[0524] The true magnetic permeability .mu. is highly dependent on
the ratio between the length of the core 3905, the diameter of the
core 3905 and the relative magnetic permeability .mu..sub.r of the
core 3905. The value of .mu..sub.r provided by the manufacturer of
the core, for example of the ferrite, is the asymptotic value
.mu..sub.asymptotic for a very long ferrite whose length tends to
infinity.
[0525] In practice, an effective magnetic permeability
.mu..sub.effective of the core 3905 can be calculated after
defining the length of the core 3905, its diameter and the
permeability corresponding to the asymptotic value
.mu..sub.asymptotic.
[0526] The network of curves illustrated in FIG. 40 can be used to
quickly estimate the effective value of pr, knowing l and d. The
example marked by perpendicular arrows shows the transfer from
asymptotic ferromagnetic permeability .mu..sub.asymptotic to
effective magnetic permeability .mu..sub.effective with a ratio
l/d=10.
[0527] The effective magnetic permeability .mu..sub.effective can
also be calculated by measuring the inductance of a coil wound on
ferrite core and measuring or calculating the inductance of an
identical coil without ferrite core. The ratio gives the value of
the magnetic permeability .mu. directly.
[0528] For example, for a long coil with and without ferrite with
the following characteristics:
Length b of the coil=7 mm. Outer diameter of the turns=1.7 mm,
radius R=0.85 mm. Inner diameter=1 mm. Diameter of wire used=22
.mu.m. Number of turns in the coil=1800.
[0529] To calculate the inductance in air, we determine that the
inner diameter is equal to the difference a-c/2, where c is equal
to the difference between the outer radius and the inner
radius.
Consequently, c=175 .mu.m And a=325 .mu.m. The number of layers of
copper wire is 6, the number of layers is 300. These figures are
compatible with a number of turns equal to 1800.
[0530] The inductance of the coil without core is approximately 172
.mu.H.
[0531] The inventors have measured an inductance of the coil with
ferrite core and found a value of 16 mH.
[0532] We can therefore estimate that, for this coil wound on a
ferrite of length 8 mm, the effective magnetic permeability
.mu..sub.effective is approximately 93. The magnetic permeability
.mu..sub.asymptote given by the manufacturer is approximately
650.
[0533] The sensitivity of an electronic tag without core can be
evaluated at approximately 3.6 mT. In practice, we have observed a
value close to 500 .mu.T. The gain of the antenna equipped with a
ferrite core is therefore very close to 7, which confirms the
advantage of implementing this invention.
[0534] We observe that the weight of an antenna made on ferrite
may, in the current situation of commercial offers, drop down to 35
milligrams.
[0535] FIGS. 41A and 41B show a product 4100 comprising a metallic
part 4105 and an electronic tag 4110.
[0536] When an electronic tag is to be associated with a metallic
part, for example the metallic film of a blister, the film, placed
perpendicular to the transmitting antenna of a base station
disturbs the tuning of this transmitting antenna and behaves like a
loss generator weakening the electric current powering the
electronic tag. An electronic tag placed flat on a blister can be
read at a short distance, but it would be quite unrealistic to
attempt to read a stack of blisters marked in this way.
[0537] According to an aspect of this invention, the electronic tag
4110 is similar to the electronic tag 3900 detailed with reference
to FIG. 39. Preferably, the antenna of the electronic tag 4110 is
positioned near and parallel to one edge 4115 of the metallic part
4105.
[0538] In the mode of realization described and represented, the
metallic part 4105 is a metallic blister film comprising, apart
from a film of insulating material, generally, a plastic
thermoformed material, the metallic film and the film of insulating
material enclosing a content, for example medications. The product
4100 then consists of this blister and, possibly, of its
non-metallic packaging, made for example of card or plastic.
[0539] The blisters are, roughly speaking, equivalent to a metallic
plate with, all around the blister, a groove formed in a film made
from insulating material, generally, a plastic thermoformed
material. The groove is therefore, all around the product, parallel
and near to one edge of the metallic part formed from the metallic
film.
[0540] Preferably, the antenna of the electronic tag is positioned
in this groove.
[0541] Thanks to the implementation of this invention, the
electronic tag 4110 can be read despite the presence of metallic
parts, even when several similar products are stacked.
[0542] The sixteenth aspect of this invention consists in
implementing an electronic tag comprising an antenna of very small
dimensions made by forming a coil on a core of insulating material
of high relative magnetic permeability, for example a ferrite and,
preferably, in positioning said antenna parallel and near to one
edge of the metallic part.
[0543] The electronic tag placed in the groove around the blister
can be used to mark all types of blister irrespective of their
content. The electronic tag can be easily and automatically
deposited in the blister at the same time as the contents, for
example tablets or capsules, stored in the blister.
[0544] FIG. 42 shows an identification device 4200 to identify at
least one product 4100, which comprises a base station 4205 and a
presentation means 4210 to present products 4100. The base station
4205 comprises a transmitting antenna 4215 with a main plane. For
example, the transmitting antenna 4215 is flat.
[0545] According to an aspect of this invention, the main plane of
the transmitting antenna 4215 is placed perpendicular to the plane
of the metallic part 4105 and the transmitting antenna 4215 is
adapted to generate magnetic field lines parallel to the core of
the antenna of the electronic tag 4110 carried by the product
4100.
[0546] In a first variant, the presentation means 4210 is adapted
to present one product 4110 at a time opposite the transmitting
antenna 4215 such that the plane of the metallic part 4105 is
perpendicular to the main plane of the transmitting antenna 4215
and such that the core of the antenna of the electronic tag 4110
carried by the product 4100 is substantially parallel to the field
lines generated by the transmitting antenna 4215.
[0547] In a second variant, the presentation means 4210 is adapted
to present, at the same time, a plurality of products 4110 forming
a stack opposite the transmitting antenna 4215 such that the plane
of each metallic part 4105 is perpendicular to the main plane of
the transmitting antenna 4215 and such that the core of the antenna
of the electronic tag 4110 carried by each product 4100 is
substantially parallel to the field lines generated by the
transmitting antenna 4215.
[0548] For example, the presentation means 4215 is a manipulator
arm, for example a robotized arm or a conveyor.
[0549] If the products 4100 comprise blisters, they are placed
perpendicular to the transmitting antenna 4215, thereby creating
only very little disturbance to the field emitted by the
transmitting antenna 4215.
[0550] The electronic tag 4110 of each product 4100 is of very
small dimensions but can be easily powered by the transmitting
antenna 4215 perpendicular to the blisters.
[0551] A stack of blisters can therefore be easily identified.
[0552] FIG. 43 shows steps of a method for identifying at least one
product comprising a substantially flat metallic part.
[0553] During a mechanical association step 4305, an electronic tag
positioned near and parallel to one edge of said metallic part is
associated with the product, said electronic tag comprising a core
of electrically-insulating material of relative magnetic
permeability above fifty, a coil surrounding said core, coil
forming an antenna adapted to receive a query signal from a base
station, a memory storing an identification code and processing
means adapted to process the query signal from the base station, to
determine whether the electronic tag must reply and, if yes, to
command transmission of a signal by said antenna.
[0554] When the product is of blister type, during step 4305, the
electronic tag is automatically deposited in the groove of the
blister at the same time as the contents, for example tablets or
capsules, stored in the blister.
[0555] During a positioning step 4310, the product is positioned
opposite a transmitting antenna such that the main plane of the
transmitting antenna is placed perpendicular to the plane of said
metallic part and such that the core is placed parallel to the
magnetic field lines generated by said transmitting antenna.
[0556] During a step 4315, the identifications of the electronic
tags associated with the products are read, with a base station,
simultaneously, according to known deterministic or anti-collision
techniques.
[0557] As described with reference to FIGS. 39 to 42, this method
can be used to identify products despite the presence of a metallic
part inside them, despite the small dimension imposed on the
electronic tag and, possibly, despite the presentation of the
products in stacks.
[0558] The various aspects of this invention, their main
characteristics and their special characteristics are intended to
be combined to form a universal electronic tag reading system. Each
main or special characteristic of each aspect of this invention
therefore forms a special characteristic of each other aspect of
this invention.
* * * * *