U.S. patent application number 12/440849 was filed with the patent office on 2009-09-10 for method and system for optimized reading of a radio frequency communication transponder with the aid of a passive resonant circuit.
This patent application is currently assigned to Gemalto SA. Invention is credited to Jean-Paul Caruana.
Application Number | 20090224888 12/440849 |
Document ID | / |
Family ID | 37882162 |
Filed Date | 2009-09-10 |
United States Patent
Application |
20090224888 |
Kind Code |
A1 |
Caruana; Jean-Paul |
September 10, 2009 |
METHOD AND SYSTEM FOR OPTIMIZED READING OF A RADIO FREQUENCY
COMMUNICATION TRANSPONDER WITH THE AID OF A PASSIVE RESONANT
CIRCUIT
Abstract
The invention relates to a method of reading RF transponders
disposed in one and the same magnetic interrogation field, in which
a magnetic coupling of the transponders is ensured with a passive
resonant circuit during reading. The method is distinguished in
that the passive antenna of the resonant circuit is associated with
at least one transponder antenna, and the passive resonant circuit
is tuned in such a way that the resonant frequency resulting from
the association corresponds to one of the frequencies of the
emission side bands of the transponder to be read. The invention
also relates to the system corresponding to the method, a
transponder structure and an object containing the transponder, in
particular a travel document.
Inventors: |
Caruana; Jean-Paul;
(Marseille, FR) |
Correspondence
Address: |
BUCHANAN, INGERSOLL & ROONEY PC
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
Gemalto SA
Meudon
FR
|
Family ID: |
37882162 |
Appl. No.: |
12/440849 |
Filed: |
September 11, 2006 |
PCT Filed: |
September 11, 2006 |
PCT NO: |
PCT/EP2006/066252 |
371 Date: |
April 8, 2009 |
Current U.S.
Class: |
340/10.2 ;
235/492 |
Current CPC
Class: |
G06K 19/07796 20130101;
G06K 19/025 20130101; G06K 19/07749 20130101; G06K 7/0008 20130101;
G06K 7/10178 20130101 |
Class at
Publication: |
340/10.2 ;
235/492 |
International
Class: |
H04Q 5/22 20060101
H04Q005/22; G06K 19/06 20060101 G06K019/06 |
Claims
1. A method for reading RF transponders disposed in one and the
same magnetic interrogation field, in which a magnetic coupling of
the transponders is ensured with a passive resonant circuit during
reading, wherein the passive antenna of the resonant circuit is
associated with at least one transponder antenna, and the passive
resonant circuit is tuned in such a way that the resonance
frequency resulting from the association corresponds to one of the
frequencies of the emission side bands of the transponder to be
read.
2. A method according to claim 1, wherein the association of the
passive antenna of the passive resonant circuit with at least one
transponder antenna is made negligible and the passive resonant
circuit is tuned to a resonance frequency corresponding to one of
the frequencies of the emission side bands of the transponder to be
read.
3. A reading method according to claim 2, wherein the method
further includes a step during which: the transponders are so
configured as to be negligible in the association with the passive
resonant circuit, by each drawing less magnetic field and/or by
interfering less with the other antennas of the transponder.
4. A reading method according to claim 3, wherein at least one
antenna format and one response from a transponder having a
behavior corresponding to such format are determined, and the
passive resonant circuit is so configured as to obtain a behavior
corresponding to such a format for each transponder.
5. A reading method according to claim 4, wherein the passive
antenna is defined between two rectangles respectively 81
mm.times.49 mm, and 64 mm.times.34 mm.
6. A reading method according to claim 1, wherein the side bands
are respectively selected approximately at 13.56 MHz.+-.847 Khz or
respectively 12.71 and 14.4 MHz, the interrogation frequency being
13.56 MHz rated at 847 Khz.
7. A reading method according to claim 5, wherein the antenna of
the passive resonant circuit includes between 3 and 6 turns.
8. A reading method according to claim 1, wherein the passive
resonant circuit has a quality factor with a value of less than
30.
9. A reading method according to claim 1, wherein the transponder
has a reduced format and has an antenna, the surface inside the
outer turn of which is greater than a 15.times.15 mm surface and
smaller than a surface of approximately 30.times.30 mm.
10. A reading method according to claim 9, wherein the transponder
antenna includes 13 to 18 turns.
11. A reading method according to claim 10, wherein the tuning
frequency is between 15 and 18 MHz.
12. A reading method according to claim 11, wherein the transponder
has a quality factor above 30.
13. A reading method according to claim 12, wherein each
transponder is positioned in a support in a random position, with
the support allowing several positions of the transponder which are
shifted with respect to each other.
14. A reading system with at least one RF transponder, with said
system including one reader able to emit an interrogation field on
at least one transponder and to collect a response from the
transponder, a passive resonant circuit to perform a magnetic
coupling with at least one transponder during the reading, wherein
the passive resonant circuit is tuned in such a way that the
resonant frequency resulting from the association M of the resonant
circuit with at least one transponder corresponds to one of the
frequencies of the emission side bands of the transponder to be
read.
15. A supporting object containing at least one main transponder,
one secondary transponder and an associated passive resonant
circuit associated with at least the main transponder, wherein the
passive resonant circuit is tuned in such a way that the resonant
frequency resulting from the association of the resonant circuit
with at least the main transponder corresponds with one of the
frequencies of the emission side bands of the secondary
transponder.
16. A supporting object containing at least one transponder and one
passive resonant circuit associated with at least one transponder,
wherein the passive resonant circuit is tuned to a resonance
frequency corresponding to one of the frequencies of the emission
side bands of the transponder.
17. A transponder including a flat antenna on a support defining an
outer turn, wherein: the surface inside the outer turn is greater
than a 15.times.15 mm surface and smaller than or equal to a
surface of approximately 30.times.30 mm, the antenna includes about
13 to 18 turns, the tuning frequency is between 15 and 18 MHz, a
quality factor is above 30.
18. A travel document including several pages between two covers
and a plurality of transponders between the pages, each transponder
being contained in a plane support separate from the pages or
covers but having substantially the format of a page, wherein the
transponders are configured as in claim 17.
19. A travel document according to claim 18, wherein the
transponders are positioned in the supports in various
positions.
20. An assembly of transponders according to claim 17, with each
transponder being positioned in a sheet having a greater format
than the latter, wherein the transponders are positioned in the
supports in various positions from one sheet to another.
Description
[0001] The invention relates to the field of methods and systems
for reading RF radio frequency transponders and the structure of
such radio frequency transponders.
[0002] More particularly, the invention relates to an improvement
in the reading and/or the communications between a transponder
liable to be surrounded by several transponders and a reader
provided for this purpose. The invention more particularly aims at
an application of such methods and systems to the contactless
reading of electronic travel documents such as electronic passports
and electronic visas in the form of transponders positioned
together. In particular, such documents and visas are compliant
with ICAO "International Civil Aviation Organization" specification
and the ISO7IEC 14443 standard.
[0003] The travel documents such as the electronic passports and/or
the electronic visas are composed on the one hand of a paper
document whereon information relative to the holder of said
document is noted and on the other hand a contactless electronic
chip which also contains secured information relative to the same
holder.
[0004] The unsolved problem arises as soon as the travel document
of the electronic passport type must also include several
electronic visas.
[0005] As a matter of fact, because of the variable principles used
by such contactless electronic chips, the increase in the number of
electronic visas in the document makes the simultaneous reading
more and more difficult when and as their number increases, which
can even make the operation thereof impossible as soon as the
number is greater than 4 or 5 visas.
[0006] The need expressed as regards electronic travel documents is
that said document may contain a maximum of contactless electronic
visas which are simultaneously operated when they are submitted to
a magnetic field from a contactless reader. The reader and the
travel documents must be compliant with the ISO/IEC 14443
standard.
[0007] The specifications of contactless electronic visa or visas
request that on the one hand each visa consumes as little as
possible magnetic field from the contactless reader and interacts
therewith as little as possible and on the other hand that each one
causes a variation of said magnetic field which is compatible with
the specifications imposed by the ISO/IEC 14443 standard during the
phases of responses from the visa to the reader.
[0008] The contactless technology resulting from the ISO/IEC 14443
standard describes the mechanisms making it possible to implement
the anti-collision principles between contactless products. Such
principles provide logical mechanisms which make it possible to
retrieve a contactless product among several others when they are
submitted to the same magnetic field. The condition required for a
correct operation of such principle is that the reader supplies all
the products existing in the field it generates and that it detects
them all.
[0009] More particularly, the contactless anti-collision mechanism
is limited by the consumption and the magnetic load induced by the
sum of several contactless transponders. This limits the number of
electronic visas which can be read in or out of an electronic
passport.
[0010] In addition, the ISO/IEC 14443 standard contains a
specification imposing that the contactless products be operated in
a range of magnetic field between 1.5 A/m and 7.5 A/m. This
specification makes it possible for contactless products to be
operated from a magnetic field of at least 1.5 A/m.
[0011] A standard compliant reader can thus generate only a 1.5 A/m
field in the presence of the travel document while being
conformable with the standard. The ISO/IEC 14443 standard also
imposes the minimum amplitude of the response of the contactless
product so that the reader can detect it.
[0012] Such minimum amplitude is worth at least 30/H.sup.1,2 (or
18.6 mV), with H amplitude of the magnetic field. Such value is
defined from the amplitude of the side bands generated because of
the amplitude modulation of the reader magnetic field, with the
frequency of 13.56 MHz by the contactless product at the rate of
the sub-carrier thereof, rated at 847 Khz.
[0013] If these conditions are complied with, the contact reader
complying with the standard should be capable of receiving the data
from the contactless chip.
[0014] The present state of the art makes it possible to comply
with all such conditions whenever a maximum number of a few
electronic visas are positioned in the travel document. At present,
5 visas seem to be a maximum as regards the curve of the
transponders response (FIG. 3 retrieved from the official document
N1088 from ISO/IEC JTC1/SC17/WG8).
[0015] The inventor noted that if more than five contactless
products which are individually standard compliant are used, when
they are grouped in the same travel document, because of the
electromagnetic coupling together, the assembly is no longer
compliant with the ISO/IEC 14443 standard. The conformable
contactless reader is no longer capable of supplying them or
detecting them.
[0016] This limitation to five as regards the number of
transponders is considered by the inventor as being potentially a
disadvantage in the development of an electronic passport and also
in a general way for the reading of several transponders positioned
together whatever the considered application.
[0017] Thus the inventor has considered improving in a general way
the contactless communication of a certain number of transponders
for a constant power of the reader.
[0018] As regards the known prior art making it possible to improve
the communication between the transponders and a reader, the
patents FR 2 777 141 or U.S. Pat. No. 6,172,608 are known.
[0019] Such patents make it possible to have a second oscillating
circuit which can be tuned on a frequency which is close to (or
equal to) the electromagnetic field, so that the modulation of the
field performed by the transponder is better detected by the
antenna of the reader. Such documents more particularly teach the
utilization of a passive resonant circuit for increasing the
communication distance between the reader and the transponder while
keeping a correct operation and without increasing the emission
power of the reader.
[0020] On the other hand, the document FR 2 812 482-A1 is known,
which uses a collective antenna which is closed to amplify the
communication from the reader with several transponders positioned
on the same support. The multiplicity of the transponders on a
support corresponds to the problem of increasing the storage memory
available on the support. The transponders have a more reduced
format than the passive antenna because of the manufacturing cost.
This document does not teach the optimization of the number of
legible transponders for a constant electromagnetic field
power.
[0021] In addition, the arrangement of a closed passive collective
antenna associated with several transponders having more reduced
dimensions than the passive antenna seems not to be operational, as
exposed in the present document in the present state of the art of
the person skilled in the art.
[0022] The invention more particularly relates to the solving of
the above-mentioned drawbacks.
[0023] It more generally aims at improving the reading of
transponders, such improvements being intended to lead to the
increase in the number of transponders which can be read together
in a determined electromagnetic field, whatever the dimension
thereof.
[0024] It also aims at providing the optimization of the number of
transponders which can be read together for the application to an
electronic passport, in compliance with specifications of the ICAO
and ISO/IEC14443, in particular. New transponders characteristics
are supplied for this purpose.
[0025] According to a first aspect, the invention aims at a method
for the contactless reading RF transponders positioned in one and
the same magnetic interrogation field, wherein a magnetic coupling
of the transponders is ensured with a passive resonant circuit
during reading.
[0026] The method is characterised in that the passive antenna of
the resonant circuit is associated with at least one transponder
antenna, and the passive resonant is tuned in such a way that the
resonant frequency resulting from the association corresponds to
one of the frequencies of the emission side bands of the
transponder to be read.
[0027] Such provisions make it possible to favor the amplitude of
the transponder return signal.
[0028] According to a particular embodiment, the association of the
passive antenna of the resonant circuit with at least one antenna
of the transponder is made negligible and the passive resonant
circuit is tuned to a resonant frequency corresponding to one of
the frequencies of the emission side bands on the transponder to be
read.
[0029] Such provisions make it possible to further simplify the
reading method while favoring the amplitude of the return signal
delivered by the chip of the antenna module or transponder.
[0030] The invention also relates to a system for reading at least
one RF transponder, said system including a reader able to emit an
interrogation field on at least one transponder and to collect a
response from the transponder, a passive resonant circuit for
performing a magnetic coupling with at least one transponder during
the reading.
[0031] The system is characterised in that the passive resonant
circuit is tuned in such a way that the resonant frequency
resulting from the association of the resonant circuit with at
least one transponder corresponds to one of the frequencies of the
emission side bands of the transponder to be read.
[0032] Another aspect of the invention relates to a support object
containing at least one main transponder, at least one secondary
transponder and one passive resonant circuit associated with at
least a main transponder.
[0033] The object can be distinguished in that the passive resonant
circuit is tuned in such a way that the resonant frequency
resulting from the association of the resonant circuit with the
main transponder at least corresponds to one of the frequencies of
the emission side bands of the secondary transponder.
[0034] Another aspect of the invention relates to a support object
containing at least one transponder and a passive resonant circuit
associated with at least the transponder. It can be differentiated
in that the passive resonant circuit is tuned to a resonant
frequency corresponding to one of the frequencies of the emission
side bands of the transponder.
[0035] Another aspect of the invention relates to a transponder
including a flat antenna on a support defining an outer turn;
[0036] the transponder is characterised in that: [0037] the surface
outside the outer turn is greater than a 15.times.15 mm surface and
smaller than a surface of approximately 30.times.30 mm, [0038] the
antenna includes approximately between 13 and 18 turns, [0039] the
tuning frequency is between 15 and 18 MHz, [0040] a quality factor
is above 30.
[0041] Another aspect of the invention relates to a travel document
including several pages between two covers and a plurality of
transponders between the pages, with each transponder being
contained in a plane support distinct from the pages or covers, but
having substantially the same format of a page, with the
transponder having the above characteristics.
[0042] According to an advantageous provision making it possible to
have less interference or coupling between the transponders, the
latter are positioned in the support in various positions and
particularly in a random way.
[0043] Other characteristics and advantages of the invention will
appear upon reading the following description given as a non
limitative example and by referring to the appended drawings
wherein:
[0044] FIG. 1 illustrates an electronic passport reading system
according to the prior art;
[0045] FIG. 2 illustrates an electronic passport and the various
visas of the prior art;
[0046] FIG. 3 illustrates response curves in response to the number
of transponders of the prior art;
[0047] FIG. 4 illustrates a section in FIG. 5 along A-A;
[0048] FIG. 5 illustrates a transponder reading system complying
with one embodiment of the invention;
[0049] FIG. 6 illustrates an area for the possible dimensions of
the passive antenna according to one embodiment;
[0050] FIG. 7 illustrates a travel document which is compliant with
an embodiment of the invention;
[0051] FIG. 8 illustrates a travel document reading system
complying with the preceding Figure;
[0052] FIG. 9 illustrates a schematic view of the reading system of
the preceding Figure;
[0053] FIG. 10 illustrates a reading configuration for transponders
using an association of the passive resonant circuit with a main
transponder;
[0054] FIG. 11 illustrates a transponder according to one
embodiment of the invention;
[0055] FIGS. 12, 13 illustrate the transponder packaging according
to another embodiment of the invention.
[0056] In FIG. 1, an existing system 1 for reading electronics
passport and electronic visas in the form of transponders of the
radio frequency (RF) type includes a reader able to emit an
interrogation field via an emitting antenna 2 and to collect a
response from the transponder submitted to this field.
[0057] The passport 3 (PICI0) and each visa 4 (PCI1-PICI5) include
the same type of transponders, i.e. an electronic circuit (5a, 5b)
of the RF-ID (radio frequency identification) type connected to an
antenna (4a-4b).
[0058] In FIG. 2, the passport transponder is buried in the cover 6
of a passport 7 and each electronic visa transponder is buried in a
sheet 8.
[0059] In FIG. 3, a diagram of voltage response curve (10) of a
transponder with a ID1 format (the format of present passports) has
a peak beyond 35 volts whereas the voltage response of 5
transponders PICI positioned together is close to 5 volts. Beyond 5
transponders, the voltage dramatically drops and it is no longer
possible to detect and to read more than 5 transponders having a
frequency of 13.56 MHz.
[0060] Generally speaking, within the frame of the present
description, transponder means any identification electronic
circuit using detection or a communication using an electromagnetic
field. More particularly, electromagnetic fields are concerned and
they include a coil connected to a condenser and where an
integrated circuit or any other electronic components can be
found.
[0061] The transponders more particularly include an electronic
component such as an integrated circuit chip connected to an
antenna. They can be inserted into, or associated with any type of
support. They may, for example, have the shape of adhesive
electronic labels, contactless card; they can be buried in a
packaging, the cover of a document, a sheet or any other thing,
etc.
[0062] Transponders are used in various economics fields such as
bank (electronic purse), communications, transport, identity
(e-passport, ID card). More particularly as regards identity,
identifying a person through a radio frequency communication with a
contactless portable electronic object of the RFID type, is
known.
[0063] In a general way, reader means within the scope of the
following description, an emitter/receiver device provided with one
antenna which creates an electromagnetic field at a given
frequency. The antenna of the device also makes it possible to
modulate the electromagnetic field and to measure variations in the
electromagnetic field. The antenna of the device also makes it
possible to modulate the electromagnetic field and to measure the
variations in the electromagnetic field. The reader antenna is
generally composed of one or several coils.
[0064] The reader-transponder system is operated in a more or less
complex way according to the type of the transponder used. The
general operation principle consists in emitting an electromagnetic
field with a given frequency. When one transponder goes within the
electromagnetic field, it is supplied and it reacts. The reaction
of the transponder causes the variation of an electromagnetic field
which is detected by the reader.
[0065] For the simplest systems, the transponder being for example
composed of one coil and one condenser, the assembly is an
oscillating circuit tuned on the frequency of the electromagnetic
field. The presence of the transponder in the field makes the
oscillating circuit resonate and causes a modification of the field
which can be detected by the reader. Such systems which are very
simple are currently used as anti-theft devices in department
stores.
[0066] As regards the most complex systems, the transponder
includes for example an integrated circuit connected to a coil, the
coil and the integrated circuit forming among other things a tuned
resonant circuit. The presence of the transponder in the
electromagnetic field supplies the integrated circuit which
modulates the electromagnetic field to have the reader detect the
presence thereof. Then, a dialog can take place between the
transponder and the reader through the modulation of the
electromagnetic field.
[0067] In FIGS. 4 and 5, a reading system allows improvements in
the reading of several transponders 13-16 by implementing during
the reading, a magnetic coupling of the transponders with a passive
resonant circuit 17.
[0068] The reading system 12 includes the emission-reception
antenna 18 buried in a support 19 and the passive resonant circuit
17 is performed on a plane support 20 for example a paper sheet,
and includes an open antenna 21 the ends of which are connected to
plates 22, 23 of a capacitor. The antenna is in fact a double face
device made by screen printing with a conductive ink; on the inner
face the capacitor plate 24 is opposite two terminal plates 22, 23
connected to the turns.
[0069] The passive circuit is positioned in the above example of
the reader antenna, for example placed or glued on a support plane
close to the radio frequency antenna of the reader.
[0070] According to one implementation system, the passive antenna
of the resonant circuit is associated, at least during the reading,
with at least one transponder antenna. Association means a physical
bringing together of their positions so as to obtain a magnetic
coupling therebetween with or without a common support.
[0071] According to one step on the method, the passive resonant
circuit is tuned to a resonant frequency so that the resonant
frequency resulting from the association with at least one
transponder antenna corresponds to one of the frequencies of the
emission side bands of the transponder to be read.
[0072] The advantage consists in favoring the detection, by the
reader, of the variations in the field caused by the transponders
when they respond.
[0073] Preferably, the transponders are designed or configured so
as to be neglected in the association with the passive resonant
circuit, each more particularly by drawing less magnetic field
and/or by interfering less with the other transponder antennas. The
transponders, for this purpose, have a reduced format as compared
to the antenna of the passive resonant circuit. In the example, the
transponder is one or several of the transponders 13-16 with the
small dimension to be read as compared to the antenna. The reduced
format of the transponders is for example less than 1/10.degree.,
even 1/5.degree., the format of the passive resonant circuit
antenna.
[0074] The advantage consists in allowing the supply of as many
transponders as possible with the same field density.
[0075] Thus, in the example above, as this association is
negligible in so far as there is no significant influence of small
transponders on the resonant frequency resulting from the
association, the resonant circuit is tuned to a frequency
corresponding to one of the frequencies of the emission side band
of the transponder to be read.
[0076] The emission side bands are generated by any other
transponder submitted to an interrogation magnetic field that the
transponder modulates more particularly in amplitude, during its
response.
[0077] The side bands exist for other principles of modulations of
the communication between a reader and a transponder, more
particularly the phase modulation and frequency modulation.
[0078] In the example, an amplitude modulation of a sine-wave
signal having a 13.56 MHZ frequency by a 847 Khz modulating signal
corresponding to the sub-carrier generated by the transponder
creates, from a spectral point of view, a signal with two side
bands located at 13.56 MHz+/-847 KHz or 12.71 and 14.4 MHz
respectively.
[0079] Other side bands as other than those hereabove are also
generated but with less energy.
[0080] In order to favor as much as possible the detection by the
reader and reach the minimum level of retro-modulated field defined
by the ISO/IEC 14443 standard the resonance frequency of the
passive resonant circuit is selected at 14.4 MHz, i.e. 13.56
MHz+847 KHz.
[0081] Other examples of association will be subsequently
illustrated.
[0082] According to another implement, at least one format F of the
transponder antenna and one transponder response having a behavior
or characteristics corresponding to this format are determined and
then the passive resonant circuit is configured in such a way as to
obtain the behavior of the characteristics corresponding to such
format for each transponder.
[0083] The passive antenna has thus been voluntarily defined in an
area Z (FIG. 6) between two rectangles 25, 26 centered on each
other and in the ID1 format described in the ISO/IEC 14443
standard, respectively 81 mm.times.49 mm and 64 mm.times.34 mm.
[0084] The advantage consists in obtaining a response from small
transponders having the same characteristics as the big ones while
allowing a reading of more transponders with a constant
interrogation field.
[0085] This makes it possible to meet the specifications of the
ICAO in order to allow the reading to a greater number of
transponders, and a travel document 27 (FIG. 7) of the e-passport
or e-Visa is manufactured and includes the passive antenna (or
passive resonant circuit 17 composed of one or several conductive
tracks) more particularly in the cover of the passport.
[0086] This travel document can shelter one or several transponder
or transponders 13 to 16, each taking the part of the local field
induced by the passive resonant circuit submitted to the field of
the reader plus the part of the field which is radiated by the
antenna of the reader about the surface of the antenna module or
modules 13-16.
[0087] FIGS. 8 and 9 illustrate the system for reading the travel
document. It includes, as above, a reading support 19 containing an
emitting and receiving antenna 18 connected to means 28 for
processing and operating the signal received.
[0088] The resonant circuit 17 is here fixed under the reading
support. The advantage is to have a common circuit at the level of
the reader for all the passports whereas in the example in FIG. 7,
each document including such resonant circuit, it is not
indispensable to have it at the reading level.
[0089] In the example, conformably with the provisions of ICAO, the
amplitude of the magnetic field H of the reader is determined at a
value above or equal to 1.5 A/m and the amplitude of the
transponder response to a value above or equal to 30/H.sup.1,2.
[0090] The travel document includes a large dimensioned transponder
3 for example ID1 and several transponders 13-16 of smaller
dimensions such as electronic visas.
[0091] The antenna modules 13-16 are not necessarily positioned on
the same plane as those on which the passive antenna is
positioned.
[0092] In FIG. 8, the passive resonant circuit 17 is positioned out
of the travel document. It is associated with the reading system by
being fixed under the reading support.
[0093] However, it could be positioned close to it, more
particularly close to or stuck onto the reading support.
[0094] The passive resonant circuit can have the shape of a label
stuck on the document more particularly with an adhesive. It can be
integrated in the document more particularly in one of the pages or
the covers thereof.
[0095] The transponders to be read (13-16, 3) are in the travel
document 27B. In such a document, reduced dimensions, so-called
secondary transponders, and large dimensions, so-called main
transponders can be found. In this case, as indicated while
referring to FIG. 10 described infra, it is recommended to tune the
passive resonant circuit while considering the association with the
main circuit.
[0096] The energy and coupling balance of such a solution cannot be
compared with the balance obtained by ID1 dimension transponders
which are compatible with ISO/IEC14443. Each antenna-module is
separately perceived by the reader as having a format and thus an
action on the magnetic field of the reader which corresponds to
that of the passive antenna which is itself in compliance with the
standard ID1 for the travel documents.
[0097] The geometric and electric characteristics, on the one hand,
of the passive resonant circuit and the antenna-module preferably
corresponding to the following description, on the other hand,
exist.
[0098] As regards the reader and also the test devices such as
those described in the test methods for contactless products:
ISO/IEC 10373-6, the travel document including several electronic
visas must be considered as only one contactless product.
[0099] The following preferable principles aiming at making a
passive resonant circuit to be included in the travel document of
the electronic passport type are the results thereof.
[0100] The passive resonant circuit must be such that the couple
thereof with the reader causes an effect complying with the
contactless card equipped with a ID1 format antenna.
[0101] It must cause a low load on the electromagnetic field
generated by the reader. Such load must correspond to that caused
by the reference PICC, appendix D of the ISO/IEC 10373-6 standard
adjusted on 6 Volt for Hmin. The loading induced by the transponder
corresponds to an ID1 antenna tuned on 13.56 Mhz and including a
resistive part of 1.8 k.OMEGA. and the continuous voltage of which
is the result of an interrogation field of less than 6V at the load
terminals.
[0102] This results in the resonant circuit having the following
geometric characteristics.
[0103] As described hereabove, the passive antenna has thus been
voluntarily defined in a zone Z between two rectangles 25, 26
centered on each other and on the ID1 format described in the
ISO/IEC 14443 standard, respectively 81 mm.times.49 mm and 64
mm.times.34 mm (FIG. 6).
[0104] In order not to limit too much the field generated by the
contactless reader, the quality factor on the passive resonant
circuit is voluntarily limited to a value of less than 30.
[0105] The optimum quality coefficient of such resonant circuit for
meeting the conditions described hereabove is between 10 and 20.
The optimum value of the quality factor of the passive resonant
circuit is 20. This allows drawing technologies for an antenna with
a strong electric resistance such as screen printing using silver
ink or carbon ink. Because of the necessity for an overvoltage
factor, the passive resonant circuit must be composed of an antenna
composed of several terms and connected to a capacitor.
[0106] The passive resonant circuit must supply to the
electromagnetically coupled antenna-modules, the additional energy
which they require because of their small coupling surfaces with
the reader. The passive resonant circuit must generate an
additional local field as a complement to that delivered by the
reader which supplies the antenna modules.
[0107] On the other hand (FIG. 11) the transponder 13 can be made
in the form of an antenna module complying with the chip card
technology. It includes a flat antenna 29 on an isolating support
30 (dielectric film) in a plane and is connected to an integrated
circuit chip 31. The chip may include a protective coating resin 32
or not. The assembly may have a global thickness of less than 1
mm.
[0108] The antenna 29 is preferably made of a metal wire or copper
etching so as to have a good quality factor.
[0109] The transponder will advantageously have a reasonable size
for example 25 mm in length, 15 mm in width and include an antenna
of about fifteen turns for example between 13 and 18 turns. The
number of turns will slightly depend on the selected chip.
[0110] Each turn for example made of copper has for example a width
of the order of 50 to 300 .mu.m with a spacing between two
contiguous turns of the order of 50 to 200 .mu.m.
[0111] A compromise or optimization between the surface ratio is
still to be reached. A module-antenna having too small a surface
for example of less than 10 mm by 10 mm would require a very
accurate positioning with respect to the passive resonance circuit
in order to allow a correct operation which a priori excludes the
devices based on antennas directly made on the surface of the
chip.
[0112] A contrario, a module-antenna having dimensions above 30 mm
by 30 mm would consume too much magnetic field and would be too
coupled to the other modules having an antenna to allow the
operation of several integrated circuit chips or electronic
visas.
[0113] The ideal solution is a resonance frequency of transponders
amounting to 17 MHz.
[0114] Considering the geometry of the transponders, the resonance
frequency and the number of the turns, the number of the passive
resonance circuit turns is optimum for 4 turns. The surface of the
capacitor plates is so calculated as to make the frequency tuning,
as mentioned hereabove.
[0115] In FIG. 10, the passive resonant circuit 17 is associated
with a transponder having an antenna, the dimensions of which can
be compared to those of the passive circuit. The importance thereof
is such that it must be considered within the tuning in frequency
of the passive resonant circuit.
[0116] As a matter of fact, the resultant resonance frequency of
two circuits is defined by the following relation:
fres , 2 = fres 1 + k ##EQU00001##
[0117] where k: the coupling coefficient between the transponders
(equal to 1 if the coupling is the maximum one)
[0118] fres.2: resonance frequency resulting from the association
of two transponders having the same resonance frequency "fres".
[0119] This could be for example the ID1 format transponder such as
presently positioned in the cover of the electronic passport of the
prior art or one of the electronic visas in the ID1 format as in
FIG. 2.
[0120] The passive resonant circuit is so tuned that the resonance
frequency resulting from the association M corresponds to one of
the frequencies of the emission side bands of the transponder to be
read.
[0121] The two associated elements can be grouped together in the
same support, for example a cover 6A of the travel document.
[0122] Due to the extension of this principle, the association may
concern several transponders so long as the number thereof gives
them a non-negligible importance.
[0123] According to an advantageous provision illustrated in FIGS.
12 and 13, each electronic visa is positioned in a support 33, 34,
for example a sheet which is substantially of the same format as
the document or slightly smaller. In the application to the
passport, the support is in the ID1 format or slightly smaller. The
important thing is not leaving the choice to the user when it is
applied into the document.
[0124] This transponder support 33 must be placed in the document
or stuck onto a page more particularly using a self-adhesive
coating.
[0125] The transponder 13 is positioned in a random position inside
the support upon the manufacturing of the visa more particularly
through lamination. In FIG. 12, it is positioned along the left
side edge 35 whereas it is positioned along the right side edge 36
in FIG. 13. Thus, when both sheets are superimposed, the
transponders get less coupled together.
[0126] An embodiment of the transponders must include, for this
purpose, a step and means for the random or varied position of the
transponder on the surface of a transporter support sheet for
example during the lamination of sheet sandwiching the
transponder.
[0127] Thus, when it is copied in the travel document, it is
distributed also in a random way with respect to the other
transponders. The result is that the labels are all different as
regards the magnetic point of view and they can be more easily
operated even though they are superimposed.
[0128] Thus, thanks to the invention, it is possible to make the
application of an electronic Visa with a more important number of
electronic visas possible. The preferred characteristics, as
mentioned hereabove, make it possible to read up to 15 transponders
complying with the ICAO specifications.
[0129] The reading method can implement an anti-collision mechanism
or protocol of a known type more particularly the one described in
the standard. The mechanism can be triggered by the reader
processing means.
[0130] According to another aspect, the invention makes it possible
to produce an electronic travel document. This document is supposed
to include a plurality of transponders complying with constraints
or specifications more particularly resulting from the standard
(ICAO) which impose at least one ID1 format of transponder antenna,
a minimum amplitude of the magnetic field H for the reading and a
minimum amplitude for the response from the transponders.
[0131] According to this other aspect, the transponder is made with
an antenna format smaller than the ID1 format and said transponder
is so arranged with a passive resonant circuit and a capacitor and
a passive antenna with an ID1 format, so that the transponder is
seen by the reader as a ID1 format transponder.
[0132] The travel document according to the invention may include
several pages and a plurality of transponders between the pages,
with each transponder being contained in a plane support separate
from the pages but substantially having the format of a page of the
document.
[0133] This document can easily be read by all the transponders in
so far as the transponders are positioned in the supports in
various positions.
[0134] Consequently, the invention is also characterised by an
assembly or a set of transponders, more particularly for electronic
visas, in that each transponder is positioned in a sheet (33, 34)
having a bigger format than the format and in that the transponders
are positioned in the sheets (33, 34) in various positions from one
sheet to another.
[0135] Although the invention has mainly been described in relation
with a travel document, it can be applied to any object supporting
a passive resonant circuit associated to at least one transponder
such as for example an electronic label, a chip card including a
module-antenna associated with a passive resonant circuit the
antenna of which has the dimensions of the contactless chip
ID1.
[0136] Such objects are preferably portable devices such as a chip
card or a cell phone.
[0137] The passive antenna can be included in the body of the chip
card, more particularly about the module antenna inserted in a
standard cavity of the chip card. The passive antenna together with
the resonant circuit can also be integrated in the reader.
* * * * *