EP1559170A1 - Reader or transmitter and/or receiver comprising a shrouded antenna - Google Patents

Reader or transmitter and/or receiver comprising a shrouded antenna

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Publication number
EP1559170A1
EP1559170A1 EP02787538A EP02787538A EP1559170A1 EP 1559170 A1 EP1559170 A1 EP 1559170A1 EP 02787538 A EP02787538 A EP 02787538A EP 02787538 A EP02787538 A EP 02787538A EP 1559170 A1 EP1559170 A1 EP 1559170A1
Authority
EP
European Patent Office
Prior art keywords
coils
group
turns
antenna
coil
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP02787538A
Other languages
German (de)
French (fr)
Other versions
EP1559170B1 (en
Inventor
Olivier Desjeux
Laurent Neveux
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EM Microelectronic Marin SA
Original Assignee
EM Microelectronic Marin SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by EM Microelectronic Marin SA filed Critical EM Microelectronic Marin SA
Publication of EP1559170A1 publication Critical patent/EP1559170A1/en
Application granted granted Critical
Publication of EP1559170B1 publication Critical patent/EP1559170B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/12—Supports; Mounting means
    • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/12—Supports; Mounting means
    • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
    • H01Q1/2208—Supports; Mounting means by structural association with other equipment or articles associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/12—Supports; Mounting means
    • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
    • H01Q1/2208—Supports; Mounting means by structural association with other equipment or articles associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems
    • H01Q1/2216—Supports; Mounting means by structural association with other equipment or articles associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems used in interrogator/reader equipment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q7/00—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
    • H01Q7/04—Screened antennas

Definitions

  • the present invention relates to a reader or transmitter and / or a receiver equipped with a shielded antenna.
  • the invention relates to such a device provided for communicating with transponders placed inside a communication volume defined by the antenna, in particular by the geometric dimensions thereof.
  • the communication volume is provided inside a rectangular cylinder or parallelepiped around which the antenna is arranged.
  • a central coil 2 defining inside its turns 4 a communication volume 6 and, on either side of this coil 2, two shielding coils 8 and 9.
  • the coils 8 and 9 are arranged at a certain distance of the coil 2.
  • the coils 8 and 9 are fed with a phase shift of 180 ° relative to the central communication coil.
  • a sharp decrease in the amplitude of the field of the shielded antenna occurs between the three regions dominated by the respective fields of the three coils under consideration.
  • regions 11 and 12 for decreasing the amplitude of the magnetic field thus result from the aforementioned 180 ° phase shift for feeding the shielding coils. It will be noted that, in regions 11 and 12, the decrease in the magnetic field is relatively large, so that communication between the reader or transmitter and / or receiver and transponders can not be ensured in these regions. Therefore, the active zone ZA of the shielded antenna shown in FIG. 1 is limited inside the geometrical dimensions of the coil 2. This represents a major disadvantage for such a device.
  • the shielded antenna of the prior art according to Figure 1 has a useful communication volume of a relatively small length ZA relative to the total length L of the shielded antenna.
  • An object of the present invention is to overcome the aforementioned major disadvantage by providing a reader or a transmitter and / or a receiver with a shielded antenna whose useful area of communication substantially corresponds to the total length of the shielded antenna.
  • the invention relates to a reader or transmitter and / or receiver for communication with transponders whose antenna is formed of several turns defining a central axis and a global interior volume, characterized in that this antenna comprises a first group of turns forming at least a first coil and a second group of turns forming at least a second coil, these first and second coils being supplied in phase quadrature and arranged to generate a communication field with a magnitude approximately constant over substantially the entire length of said antenna along its central axis and decreasing rapidly outside this antenna away from it.
  • the shielded antenna of the prior art shown in FIG. 1 by incorporating two compensation coils between the central coil and the two end coils respectively, these two compensation coils. being supplied with a phase shift of 90 ° relative to the other three coils. These two compensation coils are also supplied with a phase shift of 180 °, so as to rapidly cancel their resulting field out of the antenna, and are arranged relative to the first three coils shown in Figure 1 so as to compensate for the decrease in the field in the regions 11 and 12, that is to say between the central coil 2 and the end coils 8 and 9.
  • FIG. 1 already described, represents a shielded antenna according to the prior art and resulting amplitude of the magnetic field along its central axis
  • FIG. 2 diagrammatically represents a first embodiment of a reader or transmitter and / or communication receiver according to the invention with a graph giving the amplitudes of the magnetic fields in the presence and the resulting magnetic field
  • Figure 3 shows a particular variant of the first embodiment
  • FIG. 4 shows an electrical diagram of the supply of the coils of the antenna of the first embodiment
  • FIG. 5 schematically represents a second embodiment of a reader or transmitter and / or receiver according to the invention. with a graph giving the amplitudes of the magnetic fields present and the resulting magnetic field.
  • the invention provision is made to arrange between the central coil 6 and the two end coils 8 and 9 of the antenna 14 two other coils 16 and 17 powered in quadrature phase with respect to the coils 6, 8 and 9 . More precisely, as in Figure 1, the coils 8 and 9 are fed by the supply and control means 20 of the reader 22 with a phase shift of 180 ° relative to the central coil 6. Then, the coils 16 and 17 are fed relative to each other with a phase shift also of 180 ° and with a phase shift of 90 ° relative to the other coils 6, 8 and 9.
  • the two coils 16 and 17 are arranged so that their magnetic field along the central axis 24 of the antenna 14 is maximum respectively in the two regions 11 and 12 where the resulting magnetic field for the three coils 6, 8 and 9 decreases or vanishes, as shown in the graph of the figure 2 which shows these amplitudes of the magnetic field H along the central axis 24 of the antenna.
  • Power phase shifts are described by a Cosine and Sinus (Sin) supply with one of the two +/- arithmetic signs placed in front.
  • each coil along the central axis 24 and the characteristics of each coil are determined so as to obtain a relatively constant amplitude of the magnetic field 30 within the volume 32 defined by the antenna, that is, that is to say by the set of coils defining a total length L on the axis 24.
  • the shielding of the main antenna that is to say of the central antenna 6, is arranged in such a way that the overall volume defined by the set of coils provided constitutes the Useful volume of communication with transponders.
  • the shielding is integrated into the antenna itself. Inside this antenna, no significant reduction or cancellation of the magnetic field takes place along the active zone ZA, so that the reader according to the invention can communicate with any transponder situated inside the volume 32 defined by the set of coils forming the antenna.
  • the cancellation of the magnetic field due to the counter-antennas fed with a phase shift of 180 ° is compensated by the arrangement of coils fed in quadrature phase.
  • the vector sum of all the fields generated by the set of coils corresponds to a quadratic sum between the resulting field of the first group of coils 6, 8 and 9 and the resulting field of the second group of coils 16 and 17.
  • Each coil is formed at least 1 turn.
  • the first group of coils constitutes a first group of turns while the second group of coils constitutes a second group of turns.
  • the two coils 16 and 17 are supplied with a phase shift of 180 ° so as to ensure mutual shielding out of the antenna.
  • the electrical diagram of the supply of the coils is given in FIG. 4. In order to obtain the phase shift of 180 ° between the coil 6 and the coils 8 and 9, respectively between the coils. coils 16 and 17, it is intended to wind the turns of each coil in a first direction for the coils 6 and 16 and in the other direction for the coils 8, 9 and 17.
  • FIG 3 is shown a variant of the arrangement of an antenna according to the invention.
  • the position of the five coils 6, 8, 9, 16 and 17 is shown schematically in the upper drawing.
  • the central spool 6 has 28 turns and extends along the axis 24 between -13.5 cm and 13.5 cm.
  • the coils 8 and 9 are each formed of 18 turns and are respectively at -70 cm and + 70 cm.
  • These three coils of the first group are traversed by a current of A.
  • the two coils 16 and 17 of the second group each comprise 15 turns and are placed respectively at -30 cm and + 30 cm.
  • the power supply of this second group is provided with 1.57 A.
  • FIG. 5 is shown schematically a second embodiment of the invention.
  • the antenna 42 is formed by only four coils, namely a first group consisting of coils 44 and 46 and a second group consisting of coils 48 and 50.
  • FIG. 5 shows the amplitudes 52 and 54 generated respectively by the first and the second group of coils.
  • the resulting total magnetic field is given by curve 56 which corresponds to the quadratic sum of curves 52 and 54.
  • the coils of the second group are energized in quadrature phase relative to the coils of the first group.
  • the two coils of the same group are supplied with a phase shift of 180 ° so as to generate mutual shielding.
  • the resulting amplitude 56 within the volume defined by the antenna 42 is substantially constant but has a slight variation.
  • this second embodiment allows the economy of a coil but must be satisfied with a certain variation of field within the volume of the antenna, that is to say the active zone ZA of communication with transponders.
  • such a relatively small variation with respect to the amplitude of the magnetic field H can be considered substantially constant.
  • the antenna 42 is arranged as follows: the coil 46 extends from -70 cm to -39 cm and the coil 44 extends from -22 cm to 9 cm.
  • the spool 48 extends from -9 cm to 22 cm and the spool 50 extends from 39 cm to 70 cm. All the coils are formed of 15 turns and are powered by an electric current of 1 A. The amplitude curves given on the graph correspond to this numerical example.

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  • Near-Field Transmission Systems (AREA)

Abstract

The invention relates to a reader or transmitter and/or receiver (22) comprising a shrouded antenna which is formed by two groups of turns or coils (6, 8, 9; 16, 17). The first group of turns or coils forms a shrouded antenna. The second group comprises two coils (16, 17) which are disposed between the central coil (6) and respectively the two end coils (8, 9) of the first group. The second group of coils is powered in phase quadrature with respect to the first group of coils, the set of coils being arranged such as to obtain a magnetic field (H) having an amplitude (A) which is essentially constant along the length of the central axis (24) of the antenna inside the total internal volume of said antenna.

Description

LECTEUR OU EMETTEUR ET/OU RECEPTEUR EQUIPE D'UNE ANTENNE BLINDÉE READER OR TRANSMITTER AND / OR RECEIVER EQUIPPED WITH AN ARMORED ANTENNA
La présente invention concerne un lecteur ou un émetteur et/ou un récepteur équipé d'une antenne blindée. En particulier, l'invention concerne un tel dispositif prévu pour communiquer avec des transpondeurs placés à l'intérieur d'un volume de communication défini par l'antenne, notamment par les dimensions géométriques de celle-ci. A titre d'exemple, le volume de communication est prévu à l'intérieur d'un cylindre ou d'un parallélépipède rectangle autour duquel est agencé l'antenne.The present invention relates to a reader or transmitter and / or a receiver equipped with a shielded antenna. In particular, the invention relates to such a device provided for communicating with transponders placed inside a communication volume defined by the antenna, in particular by the geometric dimensions thereof. By way of example, the communication volume is provided inside a rectangular cylinder or parallelepiped around which the antenna is arranged.
Afin de blinder l'antenne, notamment pour que celle-ci ne perturbe pas son environnement, il est connu de l'homme du métier d'agencer, conformément à la figure , une bobine centrale 2 définissant à l'intérieur de ses spires 4 un volume de communication 6 et, de part et d'autre de cette bobine 2, deux bobines de blindage 8 et 9. Pour ne pas diminuer le volume de communication de l'antenne, les bobines 8 et 9 sont agencées à une certaine distance de la bobine 2. En effet, pour obtenir une annulation du champ magnétique hors de l'antenne, les bobines 8 et 9 sont alimentées avec un déphasage de 180° relativement à la bobine centrale de communication. Comme cela ressort du graphe inférieur de la figure 1 , une forte diminution de l'amplitude du champ de l'antenne blindée intervient entre les trois régions où dominent les champs respectifs des trois bobines considérées. Ces régions 11 et 12 de diminution de l'amplitude du champ magnétique résultent donc du déphasage de 180° susmentionné pour l'alimentation des bobines de blindage. On notera que, dans les régions 11 et 12, la diminution du champ magnétique est relativement importante, de sorte qu'une communication entre le lecteur ou émetteur et/ou récepteur et des transpondeurs ne peut être assurée dans ces régions. Par conséquent, la zone active ZA de l'antenne blindée représentée à la figure 1 est limitée à l'intérieur des dimensions géométriques de la bobine 2. Ceci représente un inconvénient majeur pour un tel dispositif.In order to shield the antenna, especially so that it does not disturb its environment, it is known to those skilled in the art to arrange, in accordance with the figure, a central coil 2 defining inside its turns 4 a communication volume 6 and, on either side of this coil 2, two shielding coils 8 and 9. In order not to reduce the communication volume of the antenna, the coils 8 and 9 are arranged at a certain distance of the coil 2. Indeed, to obtain a cancellation of the magnetic field out of the antenna, the coils 8 and 9 are fed with a phase shift of 180 ° relative to the central communication coil. As can be seen from the lower graph of FIG. 1, a sharp decrease in the amplitude of the field of the shielded antenna occurs between the three regions dominated by the respective fields of the three coils under consideration. These regions 11 and 12 for decreasing the amplitude of the magnetic field thus result from the aforementioned 180 ° phase shift for feeding the shielding coils. It will be noted that, in regions 11 and 12, the decrease in the magnetic field is relatively large, so that communication between the reader or transmitter and / or receiver and transponders can not be ensured in these regions. Therefore, the active zone ZA of the shielded antenna shown in FIG. 1 is limited inside the geometrical dimensions of the coil 2. This represents a major disadvantage for such a device.
En effet, l'antenne blindée de l'art antérieur selon la figure 1 présente un volume utile de communication d'une longueur ZA relativement petite par rapport à la longueur totale L de l'antenne blindée.Indeed, the shielded antenna of the prior art according to Figure 1 has a useful communication volume of a relatively small length ZA relative to the total length L of the shielded antenna.
Un but de la présente invention est de pallier l'inconvénient majeur susmentionné en proposant un lecteur ou un émetteur et/ou un récepteur avec une antenne blindée dont la zone utile de communication correspond sensiblement à la longueur totale de cette antenne blindée.An object of the present invention is to overcome the aforementioned major disadvantage by providing a reader or a transmitter and / or a receiver with a shielded antenna whose useful area of communication substantially corresponds to the total length of the shielded antenna.
A cet effet, l'invention concerne un lecteur ou émetteur et/ou récepteur de communication avec des transpondeurs dont l'antenne est formée de plusieurs spires définissant un axe central et un volume intérieur global, caractérisé en ce que cette antenne comprend un premier groupe de spires formant au moins une première bobine et un deuxième groupe de spires formant au moins une deuxième bobine, ces première et deuxième bobines étant alimentées en quadrature de phase et agencées de manière à engendrer un champ de communication avec une amplitude environ constante sur sensiblement la longueur totale de ladite antenne le long de son axe central et diminuant rapidement à l'extérieur de cette antenne en s'éloignant de celle- ci.For this purpose, the invention relates to a reader or transmitter and / or receiver for communication with transponders whose antenna is formed of several turns defining a central axis and a global interior volume, characterized in that this antenna comprises a first group of turns forming at least a first coil and a second group of turns forming at least a second coil, these first and second coils being supplied in phase quadrature and arranged to generate a communication field with a magnitude approximately constant over substantially the entire length of said antenna along its central axis and decreasing rapidly outside this antenna away from it.
Dans un mode de réalisation particulier, il est prévu de modifier l'antenne blindée de l'art antérieur représenté à la figure 1 en incorporant deux bobines de compensation entre la bobine centrale et respectivement les deux bobines d'extrémité, ces deux bobines de compensation étant alimentées avec un déphasage de 90° relativement aux trois autres bobines. Ces deux bobines de compensation sont alimentées également avec un déphasage de 180°, de manière à annuler rapidement leur champ résultant hors de l'antenne, et sont agencées relativement aux trois premières bobines représentées à la figure 1 de manière à compenser la diminution du champ magnétique dans les régions 11 et 12, c'est-à-dire entre la bobine centrale 2 et les bobines d'extrémité 8 et 9.In a particular embodiment, it is planned to modify the shielded antenna of the prior art shown in FIG. 1 by incorporating two compensation coils between the central coil and the two end coils respectively, these two compensation coils. being supplied with a phase shift of 90 ° relative to the other three coils. These two compensation coils are also supplied with a phase shift of 180 °, so as to rapidly cancel their resulting field out of the antenna, and are arranged relative to the first three coils shown in Figure 1 so as to compensate for the decrease in the field in the regions 11 and 12, that is to say between the central coil 2 and the end coils 8 and 9.
La présente invention sera décrite plus en détail ci-après à l'aide du dessin annexé, donné à titre d'exemple nullement limitatif, dans lequel : - la figure 1 , déjà décrite, représente une antenne blindée selon l'art antérieur et l'amplitude résultante du champ magnétique le long de son axe central; la figure 2 représente schématiquement un premier mode de réalisation d'un lecteur ou émetteur et/ou récepteur de communication selon l'invention avec un graphe donnant les amplitudes des champs magnétiques en présence et le champ magnétique résultant; la figure 3 montre une variante particulière du premier mode de réalisation; la figure 4 montre un schéma électrique de l'alimentation des bobines de l'antenne du premier mode de réalisation, et - la figure 5 représente schématiquement un deuxième mode de réalisation d'un lecteur ou émetteur et/ou récepteur selon l'invention, avec un graphe donnant les amplitudes des champs magnétiques en présence et le champ magnétique résultant.The present invention will be described in more detail below with the aid of the appended drawing, given by way of non-limiting example, in which: FIG. 1, already described, represents a shielded antenna according to the prior art and resulting amplitude of the magnetic field along its central axis; FIG. 2 diagrammatically represents a first embodiment of a reader or transmitter and / or communication receiver according to the invention with a graph giving the amplitudes of the magnetic fields in the presence and the resulting magnetic field; Figure 3 shows a particular variant of the first embodiment; FIG. 4 shows an electrical diagram of the supply of the coils of the antenna of the first embodiment, and FIG. 5 schematically represents a second embodiment of a reader or transmitter and / or receiver according to the invention. with a graph giving the amplitudes of the magnetic fields present and the resulting magnetic field.
A l'aide des figures 2 à 4, on décrira ci-après un premier mode de réalisation de l'invention. Selon l'invention, il est prévu d'agencer entre la bobine centrale 6 et les deux bobines d'extrémité 8 et 9 de l'antenne 14 deux autres bobines 16 et 17 alimentées en quadrature de phase relativement aux bobines 6, 8 et 9. Plus précisément, comme à la figure 1 , les bobines 8 et 9 sont alimentées par les moyens d'alimentation et de commande 20 du lecteur 22 avec un déphasage de 180° relativement à la bobine centrale 6. Ensuite, les bobines 16 et 17 sont alimentées l'une relativement à l'autre avec un déphasage également de 180° et avec un déphasage 90° relativement aux autres bobines 6, 8 et 9. Finalement, les deux bobines 16 et 17 sont agencées de manière que leur champ magnétique le long de l'axe central 24 de l'antenne 14 soit maximal respectivement dans les deux régions 11 et 12 où le champ magnétique résultant pour les trois bobines 6, 8 et 9 diminue ou s'annule, comme cela est représenté sur le graphe de la figure 2 qui montre ces amplitudes du champ magnétique H le long de l'axe central 24 de l'antenne. Les déphasages à l'alimentation sont décrits par une alimentation en cosinus (Cos) et en sinus (Sin) avec l'un des deux signes arithmétique +/- placé devant. La position de chaque bobine le long de l'axe central 24 et les caractéristiques de chaque bobine sont déterminées de manière à obtenir une amplitude du champ magnétique 30 relativement constante à l'intérieur du volume 32 définit par l'antenne, c'est-à-dire par l'ensemble des bobines définissant une longueur totale L sur l'axe 24.With the help of Figures 2 to 4, will be described below a first embodiment of the invention. According to the invention, provision is made to arrange between the central coil 6 and the two end coils 8 and 9 of the antenna 14 two other coils 16 and 17 powered in quadrature phase with respect to the coils 6, 8 and 9 . More precisely, as in Figure 1, the coils 8 and 9 are fed by the supply and control means 20 of the reader 22 with a phase shift of 180 ° relative to the central coil 6. Then, the coils 16 and 17 are fed relative to each other with a phase shift also of 180 ° and with a phase shift of 90 ° relative to the other coils 6, 8 and 9. Finally, the two coils 16 and 17 are arranged so that their magnetic field along the central axis 24 of the antenna 14 is maximum respectively in the two regions 11 and 12 where the resulting magnetic field for the three coils 6, 8 and 9 decreases or vanishes, as shown in the graph of the figure 2 which shows these amplitudes of the magnetic field H along the central axis 24 of the antenna. Power phase shifts are described by a Cosine and Sinus (Sin) supply with one of the two +/- arithmetic signs placed in front. The position of each coil along the central axis 24 and the characteristics of each coil are determined so as to obtain a relatively constant amplitude of the magnetic field 30 within the volume 32 defined by the antenna, that is, that is to say by the set of coils defining a total length L on the axis 24.
Grâce aux caractéristiques de l'invention, le blindage de l'antenne principale, c'est-à-dire de l'antenne centrale 6, est agencé de manière à ce que le volume global défini par l'ensemble des bobines prévues constitue le volume utile de communication avec des transpondeurs. En d'autres termes, le blindage est intégré dans l'antenne elle-même. A l'intérieur de cette antenne aucune diminution significative ou annulation du champ magnétique n'intervient le long de la zone active ZA, de sorte que le lecteur selon l'invention peut communiquer avec tout transpondeur situé à l'intérieur du volume 32 défini par l'ensemble de bobines formant l'antenne. L'annulation du champ magnétique dû aux contre-antennes alimentées avec un déphasage de 180° est compensée par l'agencement de bobines alimentées en quadrature de phase. La somme vectorielle de tous les champs générés par l'ensemble des bobines correspond à une somme quadratique entre le champ résultant du premier groupe de bobines 6, 8 et 9 et le champ résultant du deuxième groupe de bobines 16 et 17. Chaque bobine est formée d'au moins 1 spire. Ainsi, le premier groupe de bobines constitue un premier groupe de spires alors que le deuxième groupe de bobines constitue un deuxième groupe de spires.Thanks to the characteristics of the invention, the shielding of the main antenna, that is to say of the central antenna 6, is arranged in such a way that the overall volume defined by the set of coils provided constitutes the Useful volume of communication with transponders. In other words, the shielding is integrated into the antenna itself. Inside this antenna, no significant reduction or cancellation of the magnetic field takes place along the active zone ZA, so that the reader according to the invention can communicate with any transponder situated inside the volume 32 defined by the set of coils forming the antenna. The cancellation of the magnetic field due to the counter-antennas fed with a phase shift of 180 ° is compensated by the arrangement of coils fed in quadrature phase. The vector sum of all the fields generated by the set of coils corresponds to a quadratic sum between the resulting field of the first group of coils 6, 8 and 9 and the resulting field of the second group of coils 16 and 17. Each coil is formed at least 1 turn. Thus, the first group of coils constitutes a first group of turns while the second group of coils constitutes a second group of turns.
On remarquera encore que les deux bobines 16 et 17 sont alimentées avec un déphasage de 180° de manière à assurer un blindage mutuel hors de l'antenne. Le schéma électrique de l'alimentation des bobines est donné à la figure 4. Afin d'obtenir le déphasage de 180° entre la bobine 6 et les bobines 8 et 9, respectivement entre les bobines 16 et 17, il est prévu d'enrouler les spires de chaque bobine dans un premier sens pour les bobines 6 et 16 et dans l'autre sens pour les bobines 8, 9 et 17.It will also be noted that the two coils 16 and 17 are supplied with a phase shift of 180 ° so as to ensure mutual shielding out of the antenna. The electrical diagram of the supply of the coils is given in FIG. 4. In order to obtain the phase shift of 180 ° between the coil 6 and the coils 8 and 9, respectively between the coils. coils 16 and 17, it is intended to wind the turns of each coil in a first direction for the coils 6 and 16 and in the other direction for the coils 8, 9 and 17.
A la figure 3 est représentée une variante de l'agencement d'une antenne selon l'invention. La position des cinq bobines 6, 8, 9, 16 et 17 est représentée schématiquement sur le dessin supérieur. La bobine centrale 6 comporte 28 spires et s'étend le long de l'axe 24 entre -13,5 cm et 13,5 cm. Les bobines 8 et 9 sont formées chacune de 18 spires et sont situées respectivement à -70 cm et + 70 cm. Lorsqu'elles sont alimentées, ces trois bobines du premier groupe sont parcourues par un courant de A. Les deux bobines 16 et 17 du deuxième groupe comporte chacune 15 spires et sont placées respectivement à -30 cm et + 30 cm. L'alimentation électrique de ce deuxième groupe est prévue avec 1,57 A.In Figure 3 is shown a variant of the arrangement of an antenna according to the invention. The position of the five coils 6, 8, 9, 16 and 17 is shown schematically in the upper drawing. The central spool 6 has 28 turns and extends along the axis 24 between -13.5 cm and 13.5 cm. The coils 8 and 9 are each formed of 18 turns and are respectively at -70 cm and + 70 cm. When energized, these three coils of the first group are traversed by a current of A. The two coils 16 and 17 of the second group each comprise 15 turns and are placed respectively at -30 cm and + 30 cm. The power supply of this second group is provided with 1.57 A.
Sur le graphe inférieur donnant les amplitudes du champ magnétique le long de l'axe central 24, on constate que le champ résultant total 36 est sensiblement constant à l'intérieur de l'antenne sur toute la distance entre les deux bobines d'extrémité 8 et 9. Sur ce graphe sont encore représentées d'une part l'amplitude du champ magnétique 38 engendré par le premier groupe de bobines, et d'autre part l'amplitude du champ magnétique 40 engendré par le deuxième groupe de bobines.In the lower graph giving the amplitudes of the magnetic field along the central axis 24, it can be seen that the total resulting field 36 is substantially constant inside the antenna over the entire distance between the two end coils. and 9. On this graph are still represented on the one hand the amplitude of the magnetic field 38 generated by the first group of coils, and secondly the amplitude of the magnetic field 40 generated by the second group of coils.
A la figure 5 est représenté schématiquement un deuxième mode de réalisation de l'invention. Dans la partie supérieure de cette figure, on remarque que l'antenne 42 est formée par seulement quatre bobines, à savoir un premier groupe constitué des bobines 44 et 46 et un deuxième groupe constitué des bobines 48 et 50. Sur le graphe inférieur de la figure 5 sont représentées les amplitudes 52 et 54 engendrées respectivement par le premier et le deuxième groupe de bobines. Le champ magnétique résultant total est donné par la courbe 56 qui correspond à la somme quadratique des courbes 52 et 54.In Figure 5 is shown schematically a second embodiment of the invention. In the upper part of this figure, it is noted that the antenna 42 is formed by only four coils, namely a first group consisting of coils 44 and 46 and a second group consisting of coils 48 and 50. On the lower graph of FIG. FIG. 5 shows the amplitudes 52 and 54 generated respectively by the first and the second group of coils. The resulting total magnetic field is given by curve 56 which corresponds to the quadratic sum of curves 52 and 54.
Comme dans le premier mode de réalisation, les bobines du deuxième groupe sont alimentées en quadrature de phase relativement aux bobines du premier groupe. De plus, les deux bobines d'un même groupe sont alimentées avec un déphasage de 180° de manière à engendrer un blindage mutuel. L'amplitude résultante 56 à l'intérieur du volume défini par l'antenne 42 est sensiblement constante mais présente une légère variation. Ainsi, ce deuxième mode de réalisation permet l'économie d'une bobine mais doit se satisfaire d'une certaine variation de champ à l'intérieur du volume de l'antenne, c'est-à-dire de la zone active ZA de communication avec les transpondeurs. Toutefois, dans le cadre de la présente invention, une telle variation relativement petite par rapport à l'amplitude du champ magnétique H peut être considérée comme sensiblement constante. A titre d'exemple, l'antenne 42 est agencée de la manière suivante : la bobine 46 s'étend de -70 cm à -39 cm et la bobine 44 s'étend de -22 cm à 9 cm. La bobine 48 s'étend de -9 cm à 22 cm et la bobine 50 s'étend de 39 cm à 70 cm. Toutes les bobines sont formées de 15 spires et sont alimentées par un courant électrique de 1 A. Les courbes d'amplitude données sur le graphe correspondent à cet exemple numérique.As in the first embodiment, the coils of the second group are energized in quadrature phase relative to the coils of the first group. In addition, the two coils of the same group are supplied with a phase shift of 180 ° so as to generate mutual shielding. The resulting amplitude 56 within the volume defined by the antenna 42 is substantially constant but has a slight variation. Thus, this second embodiment allows the economy of a coil but must be satisfied with a certain variation of field within the volume of the antenna, that is to say the active zone ZA of communication with transponders. However, in the context of the present invention, such a relatively small variation with respect to the amplitude of the magnetic field H can be considered substantially constant. By way of example, the antenna 42 is arranged as follows: the coil 46 extends from -70 cm to -39 cm and the coil 44 extends from -22 cm to 9 cm. The spool 48 extends from -9 cm to 22 cm and the spool 50 extends from 39 cm to 70 cm. All the coils are formed of 15 turns and are powered by an electric current of 1 A. The amplitude curves given on the graph correspond to this numerical example.
Bien évidemment l'homme du métier pourra optimiser l'agencement du lecteur selon l'invention, en particulier des bobines de son antenne pour obtenir au mieux le résultat recherché par la présente invention, à savoir un champ sensiblement constant à l'intérieur du volume géométrique de l'antenne de manière à permettre une communication efficace avec des transpondeurs placés à l'intérieur de celle-ci. Of course, those skilled in the art will be able to optimize the arrangement of the reader according to the invention, in particular the coils of its antenna, in order to obtain at best the result sought by the present invention, namely a substantially constant field inside the volume. geometry of the antenna so as to allow efficient communication with transponders placed therein.

Claims

REVENDICATIONS
1. Lecteur ou émetteur et/ou récepteur (22; 42) de communication avec des transpondeurs et comprenant une antenne formée d'une pluralité de spires définissant un axe central (24) et un volume intérieur global, caractérisé en ce que cette antenne comprend un premier groupe de spires formant au moins une première bobine (6, 8, 9) et un deuxième groupe de spires formant au moins une deuxième bobine (16, 17), ces premier et deuxième groupes de spires étant alimentés en quadrature de phase et agencés de manière à engendrer un champ magnétique total d'amplitude environ constante sur sensiblement la longueur totale (L) de ladite antenne le long de son axe central et diminuant rapidement à l'extérieur de cette antenne en s'éloignant de celle- ci.A reader or transmitter and / or receiver (22; 42) for communicating with transponders and comprising an antenna formed of a plurality of turns defining a central axis (24) and a global interior volume, characterized in that said antenna comprises a first group of turns forming at least a first coil (6, 8, 9) and a second group of turns forming at least a second coil (16, 17), these first and second groups of turns being supplied in phase quadrature and arranged to generate a total magnetic field of approximately constant amplitude over substantially the total length (L) of said antenna along its central axis and rapidly decreasing outside this antenna away from it.
2. Lecteur ou émetteur et/ou récepteur selon la revendication 1 , dans lequel ledit premier groupe de spires est constitué de trois bobines (6, 8, 9) dont une bobine centrale (6) et deux bobines d'extrémité (8, 9) placées respectivement aux deux extrémités de l'antenne, ladite bobine centrale étant alimentée avec un déphasage de 180° relativement aux deux bobines d'extrémité, caractérisé en ce que ledit deuxième groupe de spires est constitué de deux bobines de compensation (16 et 17) agencées entre ladite bobine centrale et respectivement les deux bobines d'extrémité, de manière à compenser la diminution ou l'annulation du champ magnétique entre la bobine centrale et les deux bobines d'extrémité servant au blindage de cette bobine centrale, les deux bobines de compensation étant alimentées avec un déphasage de 180°.Reader or transmitter and / or receiver according to claim 1, wherein said first group of turns consists of three coils (6, 8, 9) including a central coil (6) and two end coils (8, 9). ) respectively placed at both ends of the antenna, said central coil being fed with a phase shift of 180 ° relative to the two end coils, characterized in that said second group of turns consists of two compensation coils (16 and 17). ) arranged between said central coil and respectively the two end coils, so as to compensate for the decrease or the cancellation of the magnetic field between the central coil and the two end coils used for the shielding of this central coil, the two coils compensation being fed with a phase shift of 180 °.
3. Lecteur ou émetteur et/ou récepteur selon la revendication 1 , caractérisé en ce que ledit premier groupe de spires est constitué de deux bobines (44 et 46) alimentées avec un déphasage de 180°, et en ce que ledit deuxième groupe de spires est constitué de deux bobines (46 et 48) également alimentées avec un déphasage de 180°, les deux bobines du premier groupe étant placées à une certaine distance l'une de l'autre, cette distance étant sensiblement égale à celle séparant les deux bobines dudit deuxième groupe, ces premier et deuxième groupes étant positionnés l'un relativement à l'autre de manière à ce que chacun de ces groupes compense la diminution ou l'annulation du champ magnétique entre les deux bobines de l'autre groupe.3. Reader or transmitter and / or receiver according to claim 1, characterized in that said first group of turns consists of two coils (44 and 46) supplied with a phase shift of 180 °, and in that said second group of turns consists of two coils (46 and 48) also supplied with a phase shift of 180 °, the two coils of the first group being placed at a certain distance from one another, this distance being substantially equal to that separating the two coils said second group, these first and second groups being positioned relative to each other so that each of these groups compensates for the decrease or cancellation of the magnetic field between the two coils of the other group.
4. Lecteur ou émetteur et/ou récepteur selon la revendication 2, caractérisé en ce que le premier groupe de spires est alimenté avec un courant électrique d'une valeur inférieure à celle du courant circulant dans le deuxième groupe de spires, le nombre de spires de chaque bobine étant prévu de manière que ledit champ magnétique total est sensiblement constant à l'intérieur dudit volume intérieur global de l'antenne.4. Reader or transmitter and / or receiver according to claim 2, characterized in that the first group of turns is supplied with an electric current of a value less than that of the current flowing in the second group of turns, the number of turns each coil being provided so that said field total magnetic flux is substantially constant within said overall interior volume of the antenna.
5. Lecteur ou émetteur et/ou récepteur selon la revendication 3, caractérisé en ce qu'une bobine (44) du premier groupe de spires est partiellement superposée à une bobine (48) du deuxième groupe de spires. 5. Reader or transmitter and / or receiver according to claim 3, characterized in that a coil (44) of the first group of turns is partially superimposed on a coil (48) of the second group of turns.
EP02787538.4A 2002-10-31 2002-10-31 Reader or transmitter and/or receiver comprising a shrouded antenna Expired - Lifetime EP1559170B1 (en)

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US7098866B2 (en) 2006-08-29
WO2004040698A1 (en) 2004-05-13
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AU2002351813A1 (en) 2004-05-25
US20060044208A1 (en) 2006-03-02

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