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)

Applications Claiming Priority (1)

Publications (2)

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ID=32241232

Family Applications (1)

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• 2002
  • 2002-10-31 US US10/533,444 patent/US7098866B2/en not_active Expired - Lifetime
  • 2002-10-31 EP EP02787538.4A patent/EP1559170B1/de not_active Expired - Lifetime
  • 2002-10-31 WO PCT/EP2002/012195 patent/WO2004040698A1/fr not_active Ceased
  • 2002-10-31 AU AU2002351813A patent/AU2002351813A1/en not_active Abandoned

Non-Patent Citations (1)

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