EP2377200A2 - Rfid antenna circuit - Google Patents

Abstract

The invention relates to an RFID/NFC antenna circuit, comprising an antenna (L) made of at least three turns (S) on a substrate, the antenna having a first end terminal (D) and a second end terminal (E), two access terminals (1, 2) for connecting a charge, a tuning capacitor (C1) at a predetermined tuning frequency, an intermediate connector (A) connected to the antenna (L) and separate from the terminals (D, E), a means (CON1A) for connecting the intermediate connector (A) to the terminal (1), and a means (CON2E) for connecting the end terminal (E) to the capacitor terminal (C1E). According to the invention, third means (CON31, CON32) are provided for connecting the capacitor terminal (C1X) and the second access terminal (2) to a first point (P1) of the antenna (L) and to a second point (P2) of the antenna (L) connected to the first point of the antenna (L) via at least one turn (S) of the antenna (L), respectively.

Description

 RFID antenna circuit

The invention relates to an RFID and NFC antenna circuit.

RFID is the abbreviation of radio frequency identification (in English: "radio frequency identification").

NFC is the abbreviation for near-field communication (in English: "near fîeld communication").

It is a technique that makes it possible to identify objects by using a memory chip or an electronic device capable, with the aid of a radio antenna, of transmitting information to a specialized reader.

RFID / NFC technology is used in many areas, for example in mobile phones, personal organizers called PDAs, computers, contactless card readers, cards themselves to be read without contact, but also passports, identification tags of articles or description of articles (in English: "tag"), USB keys and SIM cards and (U) SIM cards called "SIM card RFID or NFC", thumbnails for Dual or Dual Interface card (the sticker itself having an RFID / NFC antenna), watches.

In RFID / NFC technology, the antenna of a first RFID circuit (Reader) radiates electromagnetically at a distance a radio frequency signal comprising data to be received by the antenna of a second RFID circuit (transponder), which can, if necessary, respond to the first circuit by data by load modulation. Each RFID circuit has its antenna operating at its own resonant frequency.

In general, the problem of the RFID antenna circuit relates to the efficiency of the magnetic antenna of the transponder and the reader, or, on the efficiency of the coupling by mutual inductance between the two magnetic antennas, on the transmission energy and information between the party electronics and its antenna, on the transmission of energy and information between the two antennas of the RFID system.

The main objective is to gain in radio efficiency (power of the emitted or captured magnetic field, coupling, mutual inductance ...) by the antenna without losing on the quality of the signal (data distortions, bandwidth of the antenna ...) issued or received.

You see more and more appear antennas small areas (30 ^χ 30mm) or very low (5 ^χ 5 mm) for applications such as cards or μCartes, labels (in English: stickers), small players or optional drive or detachable, in mobile telephony, in USB keys, in SIM cards.

In addition to reduced surface area (<16cm ² ) or very small (<4cm ² ), very often there are very strong mechanical or electrical constraints such as the presence of a battery, a screen or display, a conductive support in the field very close to the antenna. These various constraints on the surface, electrical and mechanical then lead to a decrease in the efficiency of the antenna, a loss of the coupling efficiency and a loss of power in the signal transmitted or received by the antenna, a decrease in the possible distance of communication or the transmission of energy or information. For antennas of reasonable sizes (> 16 cm ² ) as for antennas with reduced surface area (<16cm ² ) or very small (<4cm ² ) antennas, one sees appearing ever more important needs on the necessity of power on the magnetic field transmitted or captured, over the bandwidth of the radio channel in order to meet the ever increasing data flow requirements and standards in force such as TISO14443 (example for transport, identity ...), ISO15693 (example for labels) and specifications for the RFID / NFC banking domain (EMVCO).

Thus, US-A-7,212,124 discloses a mobile phone information device comprising an antenna coil formed on a substrate, a sheet of magnetic material, an integrated circuit and resonance capacitors connected to the antenna coil. The integrated circuit communicates with an external device in that the antenna coil uses a magnetic field. A vacuum serving as a battery receiving section is formed on a portion of the housing surface and is covered by a battery cover. The battery, the antenna coil and the sheet of magnetic material are housed in the depression. A vacuum evaporated metal film or coating of conductive material is applied to the housing, while no vacuum evaporated metal film or coating of conductive material is applied to the battery cover. The antenna coil is disposed between the battery cover and the battery while the sheet of magnetic material is disposed between the antenna coil and the battery in the vacuum. The antenna coil has an intermediate tap, the resonance capacitors are connected to both ends of the antenna coil, and the integrated circuit is connected in the middle between one end of the antenna coil and the intermediate tap. .

This device has many disadvantages.

It only works in mobile phones. Due to the presence of a battery, the antenna must have a very high quality factor before integration. But a quality factor with such a high value is not suitable for RFID / NFC antenna circuits for readers or transponders (cards, labels, USB sticks). In a mobile phone, the reason for this very high value quality factor is that the electrical and mechanical constraints overwrite the original quality factor of the antenna. For conventional applications or without these constraints, this quality coefficient of the antenna would be too high and would then generate a bandwidth at -3 dB of the antenna very reduced, so a very severe filtering of the modulated RF signal emitted or received by load modulation (subcarrier 13.56 MHz to ± 847 kHz, ± 424 kHz, ± 212 kHz ...), and power transmitted or received too large. Furthermore, the coupling with such an antenna, still for conventional applications or without these constraints, would be such that at a short distance between the 2 antennas (<2 cm for example), the mutual inductance created would be such that it would detune totally tuning the frequency of the two antennas, would collapse the power radiated by the reader, could saturate the radio stages of the silicon chip or could lead to destruction transponder silicon, since silicon does not have an infinite heat dispersal capacity.

Thus, US-Al -2008 / 0450693 discloses an antenna device essentially for drive mode operation. There is a conventional arrangement of a series inductor, an arrangement of two parallel inductances and finally an arrangement of two series inductances with a third inductance parallel to one of the two series inductances. The proposed embodiments impose in particular two different surfaces, one large and one small, on either the same inductance or on two inductances. The purpose of the last two embodiments is to make it possible to amplify the signal emitted at the center of the antenna by a small parallel inductance and, in the third embodiment, to eliminate the radiation holes on a location between the arrangement of the two antenna surfaces.

One of the disadvantages of the antenna device according to US-Al-2008/0450693 is that it can not be integrated into an embossing card. Another disadvantage is that the coupling of this device in reader mode with another Antenna does not fulfill the ideal conditions for optimum coupling with a transponder.

Thus, the documents EP-A-1031 939 and FR-A-2777141 describe a device of an antenna circuit for operation in transponder mode having two independently electrically independent antenna circuits in the device described in the EP documents. -A- 1031 939 and FR-A-2777141, a first antenna circuit is composed of a conventional inductor and the transponder chip. A second antenna circuit is composed of a coil winding forming an inductance associated with a planar capacitance called "resonator". The objective of the two embodiments is to allow the amplification of the electromagnetic signal received by the arrangement of the "resonator" for the first antenna circuit comprising the transponder.

These devices according to EP-1031 939 and FR 2 777 141 have the disadvantage of a coupling that is much too strong, without guaranteeing the efficiency of increasing the reading distance. Worse, in the case of extremely high coupling efficiency, the RFID communication between the reader and the transponder is not done.

In addition, the same remarks as that made for US-A-7,212,124 can be made. Indeed, with a conventional "resonator" circuit coupled by mutual inductance with a first antenna circuit comprising the transponder, there is an almost linear relationship, by popularizing, between on the one hand the efficiency of reading distance or the efficiency of capture of the electromagnetic field and secondly the surface of the 2 antenna circuits, their proximity and their frequency agreements. The interest of the achievements described in the documents EP-A-1031 939 and FR-A

A-2777141 is to get the maximum efficiency between the 2 antenna circuits, so have the highest quality coefficient possible. It therefore falls on the same remarks of US-A-7 212 124.

Thus, document EP-AI 970 840 describes a device comparable to the two previous devices described in documents EP-A-1031 939 and FR-A-2777141, in the sense that two resonators are used for the amplification of the electromagnetic field. received. We thus find the same remarks as before. In addition, the constraints indicated for EP-A-1031 939 and FR-A-2777141 are all the higher and difficult to achieve that the two resonators are close to each other.

In order to increase the transmission of the energy transmitted or received by the antenna, it is possible to add an amplifier in the transmit or receive radio chain, but this adds a financial and energy cost available as well as a probable distortion on the modulated RF signal. It is also possible to increase the level of the signal emitted by silicon but it is often limited by integration, technological choices and its size.

It is also possible to reduce the internal consumption of silicon, but the current security needs by cryptography of the signal, of ever greater capacity in memory, and the speed of execution of the tasks make the tendency rather to increase the consumption of silicon. 'energy. In order to increase the magnetic field emitted or captured, the coupling, the mutual inductance, one could considerably increase the number of turns constituting the antenna. It would then increase the inductance of the antenna, the number of turns vis-à-vis with the antenna to be coupled, and therefore the mutual inductance and coupling. In distances very close to the 2 antennas (<2 cm), this is not an ideal solution either because the mutual inductance would be very high, and would lead to a malfunction of the RFID systems, by introducing a quality coefficient Q very high so a very low bandwidth. In long distance operation (>

15cm), it would be an almost ideal solution, but the modulated RF signal would be filtered for RFID / NFC systems.

Finally, we can play on the dimensions of the antenna but it is a rarely debatable variable and often a constraint.

The object of the invention is generally to obtain an antenna circuit having a transmission efficiency and improved transmission implementation conditions.

For this purpose, a first object of the invention is an RFID antenna circuit comprising an antenna formed by a number of at least three turns, the antenna having a first end terminal and a second end terminal. at least two access terminals for the connection of a load, at least one tuning capacity at a prescribed tuning frequency, having a first capacitance terminal and a second capacitance terminal, an intermediate tap connected to the antenna and separate end terminals, a first connection means of the intermediate tap at a first of the two access terminals, a second connection means of the second end terminal to the second capacitance terminal, characterized in it comprises third connection means of the first capacitance terminal and the second of the two access terminals to a first point of the antenna and at a second point of the antenna connected to the first point of the antenna by at least one turn of the antenna.

According to one embodiment of the invention, said intermediate tap (A) is connected to the first end terminal (D) of the antenna (L) by at least one turn (S) of the antenna (L) said intermediate tap (A) being connected to the second end terminal (E) of the antenna (L) by at least one turn (S) of the antenna (L).

According to one embodiment of the invention, (FIGS. 13, 14, 15, 16) the first point (P1) is connected to the intermediate tap (A) by at least one turn of the antenna. According to one embodiment of the invention, (FIGS. 13, 14, 15, 16) the first point (P1) is located at the intermediate tap (A).

According to one embodiment of the invention, the first point (P1) is connected to the first end terminal (D) of the antenna (L) by at least one turn (S) of the antenna (L). , the first point (Pl) being connected to the second end terminal (E) of the antenna (L) by at least one turn (S) of the antenna (L).

According to one embodiment of the invention, the first point (P1) is located at the first end terminal (D).

According to one embodiment of the invention, the second point (P2) is located at the first end terminal (D) of the antenna. According to one embodiment of the invention, the second point (P2) is located at the second end terminal (E) of the antenna.

According to one embodiment of the invention, the second point (P2) is connected to the intermediate tap (A) by at least one turn of the antenna.

According to one embodiment of the invention, the second point (P2) is connected to the first end terminal (D) of the antenna (L) by at least one turn (S) of the antenna (L) , the second point (P2) being connected to the second end terminal (E) of the antenna (L) by at least one turn (S) of the antenna (L).

According to one embodiment of the invention, the first point (Pl) is located at the intermediate point (A) of the antenna (L) and the second point (P2) is located at the first terminal (D) of end of the antenna (L). According to one embodiment of the invention, said first and second points (P1, P2) are distinct from the first intermediate tap (A), the first point

(Pl) being connected to the first end terminal (D) of the antenna (L) by at least one turn (S) of the antenna (L), the first point (P1) being connected to the second terminal (E) end of the antenna (L) by at least one turn (S) of the antenna (L).

According to one embodiment of the invention, (FIGS. 13, 14) the second point (P2) is located at the first end terminal (D) of the antenna, the first point (P1) is connected to the socket intermediate (A) by at least one turn of the antenna.

According to one embodiment of the invention, said intermediate tap (A) forms a first intermediate tap (A), the first intermediate tap (A) being connected to the first end terminal (D) of the antenna (L). ) by at least one turn

(S) of the antenna (L), the first intermediate tap (A) being connected to the second end terminal (E) of the antenna (L) by at least one turn (S) of the antenna ( L), the second point (P2) is located at a second intermediate point (P2) of the antenna (L), the second intermediate point (P2) being connected to the first point

(D) end of the antenna (L) by at least one turn (S) of the antenna (L), the second intermediate tap (P2) being connected to the second terminal (E) of the end of the antenna (L) by at least one turn (S) of the antenna (L).

According to one embodiment of the invention, the capacitance comprises a first metal surface forming the first capacitance terminal (ClX), a second metallic surface forming the second capacitance terminal (ClE), at least one dielectric layer situated between the first metal surface and the second metal surface.

According to one embodiment of the invention, the capacitance comprises at least one dielectric layer having a first side and a second side remote from the first side, a first metal surface forming the first capacitance terminal (ClX) on the first side of the dielectric layer, a second metal surface forming the second capacitance terminal (ClE) on the second side of the dielectric layer, a third metal surface forming a third capacitance terminal (ClF) remote from the first metal surface on the first side of the dielectric layer, the first capacitance terminal (ClX) defining a first capacitance value (C2) with the second capacitance terminal (C2) capacitance terminal (ClE), the third capacity terminal (ClF) defining a second capacitance value (Cl) with the second capacitance terminal (ClE), the first capacitance terminal (ClX) defining a third value (C 12) coupling capacitance with the third capacitance terminal (ClF), means for connecting the third capacitance terminal (ClF) to one of the access terminals (1, 2).

According to one embodiment of the invention, the antenna (L) comprises at least a first turn (S1), at least a second turn and at least a third turn, which are consecutive, the first turn (S1) going from the second end terminal (E) in a first winding direction at a cusp point (PR) connected to the second turn, the second and third turns (S2, S3) running from said cusp point (PR) to the first end terminal (D) in a second reverse winding direction of the first winding direction, the first point (P1) of the antenna (L) and the second point (P2) of the antenna (L) being located on the second and third turns (S2, S3).

According to one embodiment of the invention, the antenna (L) comprises at least a first turn (S1) and at least a second turn (S2, S3) consecutive between two third and fourth points (E; D) of the antenna, the first turn (S1) being connected to the second turn (S2, S3) by a reversal point (PR), the first turn (S1) going from the third point (E) to the cusp point (PR) in a first winding direction, the second turn (S2, S3) from said reversal point (PR) to the fourth point (D) in a second reverse winding direction of the first winding direction.

According to one embodiment of the invention, (FIGS. 12, 31, 32) the antenna (L) comprises at least a first turn (Sl) and at least a second turn (S2,

S3) between two third and fourth points (E; D) of the antenna, the first turn (S1) being connected to the second turn (S2, S3) by a reversal point (PR), the first turn (S1) going from the third point (E) to the cusp point (PR) in a first direction of winding, the second turn (S2, S3) going from said cusp point (PR) to the fourth point (D) in a second reverse winding direction of the first winding direction, the first point (P1) is located at the intermediate point (A) of the antenna (L) and the second point (P2) is located at the first terminal (D) end of the antenna (L).

According to one embodiment of the invention, (FIGS. 15, 17) the antenna (L) comprises at least a first turn (S1) and at least a second turn (S2, S3) consecutive between two third and fourth points ( E; D) of the antenna, the first turn (S1) being connected to the second turn (S2, S3) by a reversing point (PR), the first turn (S1) going from the third point (E) to the point (PR) of reversal in a first winding direction, the second turn (S2, S3) from said reversal point (PR) to the fourth point (D) in a second direction of reverse winding of the first direction of winding, the first point (P1) is located at the first end terminal (D).

According to one embodiment of the invention, at least one turn (S2) of the antenna comprises in series a winding (S2 ') of turns of smaller surface area surrounded with respect to the surface surrounded by the remainder (S2 ") of said turn (S2) or with respect to the surface surrounded by other turns of the antenna (3).

According to one embodiment of the invention, the turns (S) of the antenna (3) are distributed over several distinct physical planes.

According to one embodiment of the invention, the tuning capacity (Cl) comprises a second capacitance (ZZ) formed by at least a third turn (SC3) comprising two first and second ends (SC31, SC32) and by at least a fourth turn (SC4) having two first and second ends (SC41, SC42), the third turn (SC3) being electrically separated from the fourth turn (SC4) to define at least the capacity (C1) of agreement between the first end (SC31) of the third turn (SC3) and the second end (SC42) of the fourth turn (SC4), the first end (SC31) of the third turn being further away from the second end (SC42) of the fourth turn (SC4) than from the first end (SC41) of the fourth turn (SC4), the second end (SC32) of the third turn (SC3) being farther away from the first end (SC41) of the fourth turn (SC4) than from the second end (SC42) of the fourth turn (SC4), the second capacity being defined between the first end (SC31) ) of the third turn (SC3) and the second end (SC42) of the fourth turn (SC4).

According to one embodiment of the invention, there is at least one turn (Sl) of the antenna between the intermediate tap (A) and the second capacitor. According to one embodiment of the invention, first coupling means are provided to ensure coupling (COUPL 12) by mutual inductance between on the one hand the at least one turn (S2) of the antenna electrically connected in parallel with the first and second terminals (1, 2) of access and the other at least one turn (Sl) of the antenna, second coupling means are provided to ensure coupling (COUPLZZ) mutual mutual inductance between said other at least one turn (S1) of the antenna and the at least one third and fourth turns (SC3, SC4) of the second capacitance (ZZ).

According to one embodiment of the invention, the first coupling means are made by the proximity between on the one hand the at least one turn (S2) of the antenna electrically connected in parallel with the first and second terminals (1, 2) access and the other at least one turn (Sl) of the antenna, the second coupling means are made by the proximity between the other at least one turn (Sl) of the antenna and the at least one third and fourth turns (SC3, SC4) of the second capacitance (ZZ). According to one embodiment of the invention, the third turn (SC3) and the fourth turn (SC4) are interleaved.

According to one embodiment of the invention, the third turn (SC3) comprises at least a third section adjacent to a fourth section of the fourth turn (SC4). According to one embodiment of the invention, the sections extend parallel to each other. According to one embodiment of the invention, the tuning capacitance (Cl) comprises a first capacitance (C1) comprising a dielectric between the first capacitance terminal (ClX) and the second capacitance terminal (ClE), the first capacitance (C1). (Cl) being made in the form of a wire element, engraved, discrete or printed.

According to one embodiment of the invention, (FIGS. 16, 18) another capacitor (C30) is connected between the second end terminal (E) and a point (PC1) of the antenna, which is connected to the second point (P2) by at least one turn of the antenna. According to one embodiment of the invention, (FIGS. 20, 22) the capacity

(Cl) agreement has a first capacitance (C30) in series with said second capacitance (Z).

According to one embodiment of the invention, (FIG. 22) the first capacitance (C30) is connected between the second end terminal (E) of the antenna and the second point (P2), which is connected to the first terminal (SC31) of the third turn (SC3), the intermediate point (A) being connected to the second terminal (SC42) of the fourth turn (SC4), which forms the first point (P1), the first point (SC41) of the fourth turn (SC4) forming the first end terminal (D) of the antenna.

According to one embodiment of the invention, (FIG. 20) the first capacitance (C30) is connected between the second end terminal (E) of the antenna and the second point (P2), which is connected to the first terminal (SC31) of the third turn (SC3) by at least one turn (SlO), the intermediate point (A) being connected to the second terminal (SC42) of the fourth turn (SC4), which forms the first point (Pl ), the first terminal (SC41) of the fourth turn (SC4) forming the first terminal (D) end of the antenna.

According to one embodiment of the invention, (FIG. 21) the first point (Pl) is located at the intermediate point (A), the second point (P2) is located at the second end point (E) of the 'antenna.

According to one embodiment of the invention, (FIG. 19) the first point (P1) is located at the first end terminal (D) and the second point (P2) is located at the second terminal (E) of end. According to one embodiment of the invention, the at least one third turn (SC3) and the at least one fourth turn (SC4) define a second sub-circuit having a second natural resonance frequency, the first and second terminals (1). , 2) of access define with a module (M) connected to them and with at least one turn (S2) connected to said first and second terminals (1, 2) of access a first sub-circuit having a first resonance frequency the turns being arranged so that the frequency difference between the first natural resonance frequency and the second own resonance frequency is less than or equal to 10 MHz and for example less than or equal to 2 MHz. According to one embodiment of the invention, the at least one third turn (SC3) and the at least one fourth turn (SC4) define a second sub-circuit having a second natural resonance frequency, the first and second terminals (1). , 2) of access define with a module (M) connected to them and with at least one turn (S2) connected to said first and second terminals (1, 2) of access a first sub-circuit having a first resonance frequency the turns being arranged so that the frequency difference between the first natural resonance frequency and the second natural resonance frequency is less than or equal to 500KHz.

According to one embodiment of the invention, the at least one third turn (SC3) and the at least one fourth turn (SC4) define a second sub-circuit having a second natural resonance frequency, the first and second terminals (1). , 2) of access define with a module (M) connected to them and with at least one turn (S2) connected to said first and second terminals (1, 2) of access a first sub-circuit having a first resonance frequency the turns being arranged so that the first natural resonance frequency and the second natural resonance frequency are substantially equal.

According to one embodiment of the invention, (FIGS. 29, 30) the antenna comprises a mid-point (PM) for fixing a potential to a reference potential, with an equal number of turns on the section going from the first terminal (D) end to the midpoint (PM) and the section from the midpoint (PM) to the second terminal (E) end. According to one embodiment of the invention, the antenna is on a substrate.

According to one embodiment of the invention, the antenna is a wire.

According to one embodiment of the invention, said terminals (D, E, 1, 2, ClE, ClX), said tap (A), said points (P1, P2) and the capacitance (C1, ZZ) define a plurality at least three nodes, the nodes defining at least one first group (Sl) of at least one turn between two first distinct nodes (1, ClE) between them and at least one second group of at least one other turn ( S2) between two second nodes (1, 2) which are distinct from one another, at least one of the first nodes being different from at least one of the second nodes, first coupling means are provided to ensure coupling (COUPL 12) by mutual inductance between on the one hand the first group (Sl) of at least one turn and on the other hand the second group of at least one other turn (S2) in that the first group

(S1) of at least one turn is positioned near the second group of at least one other turn (S2).

According to one embodiment of the invention, said terminals (D, E, 1, 2, ClE, ClX), said tap (A), said points (P1, P2) and the capacitance (C1, ZZ) define a plurality at least three nodes, the nodes defining at least one first group (Sl) of at least one turn between two first nodes (1, ClE) distinct from each other, and at least one second group of at least one other turn (S2) between two second nodes (1, 2) which are distinct from one another and at least one third group of at least one other turn (SC3, SC4) between two third nodes (E, ClX) which are distinct from each other, at least one of first nodes being different from at least one of the second nodes, at least one of the first nodes being different from at least one of the third nodes, at least one of the third nodes being different from at least one of the second nodes, first means coupling are provided to ensure coupling (COUPL12) by mutual inductance between on the one hand the first group (Sl ) of at least one turn and secondly the second group of at least one other turn (S2) in that the first group (Sl) of at least one turn is positioned near the second group of at least one other turn (S2), second coupling means are provided to ensure coupling

(COUPLZZ) by mutual inductance between on the one hand the first group (Sl) of at least one turn and on the other hand the third group of at least one other turn (SC3,

SC4) in that the first group (Sl) of at least one turn is positioned near the third group of at least one other turn (SC3, SC4).

According to one embodiment of the invention, the first group (Sl) of at least one turn is positioned between the second group of at least one other turn (S2) and the third group of at least one other turn ( SC3, SC3, SC4).

According to one embodiment of the invention, the spacing distance between the turns (Sl, S2, SC3, SC4) belonging to different groups is less than or equal to 20 millimeters.

According to one embodiment of the invention, the spacing distance between the turns (Sl, S2, SC3, SC4) belonging to different groups is less than or equal to 10 millimeters. According to one embodiment of the invention, the spacing distance between the turns (Sl, S2, SC3, SC4) belonging to different groups is less than or equal to 1 millimeter.

According to one embodiment of the invention, the spacing distance between the turns (Sl, S2, SC3, SC4) belonging to different groups is greater than or equal to 80 micrometers.

This is the distance between the groups of turns (Sl, S2).

According to one embodiment of the invention, at least one reader (LECT) as a load and / or at least one transponder (TRANS) as a load is connected to the access terminals (1, 2). According to one embodiment of the invention, the circuit comprises a plurality of first distinct access terminals (1) and / or a plurality of second access terminals (2) which are distinct from each other.

According to one embodiment of the invention, said at least one first access terminal (1) and said at least one second access terminal (2) are connected to at least one first load (Z1) having a first frequency tuned in a high frequency band and at least a second load (Z2) having a second tuning frequency prescribed in another ultra high frequency band.

Thanks to the invention, it is possible to maintain a reasonable quality factor or limit its increase (the quality factor being equal to the resonance frequency divided by the bandwidth at -3 dB), in order to keep a reasonable bandwidth or slightly increased while maintaining or increasing the power radiated or received by the antenna and maintaining or decreasing the mutual inductance generated during coupling with the second external RFID antenna circuit.

In particular, it eliminates the fact of having to limit the antenna to one or two turns as in the state of the art of RFID / NFC readers of reasonable sizes (> 16cm ² ) and be limited to 3 or 4 turns for antennas of reduced size (<16cm ² ). Indeed, in the state of the art of the RFID / NFC readers, a maximum of one or two turns was envisaged for the antennas of reasonable size (> 16cm ² ) and at most three or four turns for the antennas of reduced size (< 16cm ² ) to ensure both a power, radiated or received, greater than a minimum power and a bandwidth greater than a minimum band. In the state of the art of transponders, the number of turns is imposed by the compromise between the surface of the antenna and the silicon capacitance and the desired tuning frequency (around 13.56 MHz to 20 MHz). For the transponder, there is little freedom on the number of turns forming the antenna so little freedom on the radio efficiency of the antenna, so little freedom of action on the quality factor, the magnetic field captured, the coupling and the mutual inductance generated during coupling with the second external RFID antenna circuit.

The circuit according to the invention, in transmission or reception, makes it possible in particular to reduce the mutual inductance with the second antenna circuit

External RFID operating in reception or transmission, because the current density is mainly concentrated in the active part of the inductance of the antenna. Simplifying in a technical extension, the mutual inductance between two circuits is proportional to the number of turns of the circuits vis-à-vis. By decreasing the mutual inductance, the disturbing action is limited to the frequency agreements of the antenna circuits at short distances (<2 cm for example). This Decrease of the mutual inductance is not done to the detriment of the radiated or received power.

Consider these 3 rules, governing a RFID / NFC RF winding antenna system, known to those skilled in the art:

> The magnetic field (H) is defined by

+ x ² y for circular antennas. N is the number of turns of the antenna, R is the radius of the antenna and x is the distance from the center of the antenna in the direction x normal to the antenna.

> The mutual inductance (M) is defined by

where N1 is the number of turns of a first antenna and N2 is the number of turns of a second antenna. The mutual inductance is a quantitative description of the flux coupling two loops of conductors.

> The quality coefficient of the antenna (Q) is defined by

Q = L * 2π * Fo / Ra = Fo / Bandwidth at -3dB

> The coupling coefficient (K) is defined by

The coupling coefficient (K) introduces a qualitative prediction on the coupling of the antennas irrespective of their geometrical dimensions. Ll is the inductance of a first antenna and L2 is the inductance of a second antenna. Below are discussed possibilities of increasing the radio efficiency of a magnetic antenna.

To increase the magnetic field (H) transmitted or received, if we consider the radius R and the current in the antenna I as imposed, it is necessary to increase N, the number of turns of the antenna.

To increase the mutual inductance (M) between the 2 antennas, if we consider R1 and R2 as imposed, we must increase Nl and / or N2.

To decrease the quality coefficient (Q) of the antenna, it is necessary to decrease the inductance (L) of the antenna and / or to increase the resistance (Ra) of the antenna. To increase the coupling (k) between the 2 antennas, it is necessary to increase the mutual inductance (M) and / or to decrease the inductance Ll and L2 of the 2 antennas without decreasing the mutual inductance (M).

The problem and the related parameters are as follows.

It is difficult to increase the overall radio efficiency of the antenna without acting to the detriment of the magnetic field emitted or captured, the coupling, the mutual inductance and the bandwidth. For example, by increasing the number of turns, the inductance, the magnetic field and the mutual inductance are favorably increased, but the bandwidth is decreased by the increase in the coefficient of quality. In summary about the possible choices:

The magnetic field radiated or captured depends on the number of turns in the antenna. It is therefore necessary to increase the number of turns.

The coupling coefficient is inversely related to the inductances of the 2 antennas. By decreasing the inductance of the antennas, then the coupling coefficient between the 2 antennas increases. It is also necessary to either increase the mutual inductance or limit the loss on mutual inductance.

The mutual inductance is a function of the number of turns of the antennas. So by increasing the number of turns of the antenna, then the mutual inductance between the 2 antennas increases. Considering the coupling coefficient, ideally do not increase the inductances of the antennas. The bandwidth is a function of the inductance of the antenna and inverse function of the resistance of the antenna. It is therefore ideally to reduce the inductance and increase the resistance of the antenna.

In conclusion on the magnetic field, the number of turns must increase or be equal.

In conclusion on the coupling coefficient, the mutual inductance must increase or be equal and / or the inductance of the antenna must decrease.

In conclusion on the mutual inductance, the number of turns must increase or be equal. In conclusion on the coefficient of quality, the inductance of the antenna must decrease or be equal and / or the resistance of the antenna must increase.

The solution according to the invention gives the possibility of parameterizing, by the method of the invention, the distribution of the current in the antenna such as for example to have a different current density in at least two turns constituting the antenna therefore of do not have a uniform current in the antenna and therefore a different current in at least 2 different turns.

The fact of not having a uniform current in the antenna makes it possible to obtain a variation on the value of the inductance and of resistance between at least two turns constituting the antenna. One can then ideally favor or limit the general value of the inductance of the antenna with respect to the value of the general resistance of the antenna or vice versa.

By the non-uniform distribution of the current and the variations of the direct parameters, it is then possible to favor or limit the indirect parameters such as the magnetic field generated or received, the mutual inductance and the coupling and their distributions in the space of the antenna.

Thus, in embodiments, the circuit includes means for making the distribution of current between the two ends of the antenna nonuniform.

The fundamental difference with the prior art technique of "conventional" loop antennas is therefore well understood, where the antenna is composed of N windings of turns. In the conventional loop antenna, the current is considered as strongly uniform. There is therefore little way to parameterize or cross-vary the direct parameters (inductance, antenna resistance, bandwidth) with the indirect parameters (magnetic field emitted or sensed, coupling, mutual inductance). The solution according to the invention and the possible embodiments then introduce the concept of a particular arrangement of inductance and capacitances, of connection terminal, of so-called "active" inductance, of so-called "passive" inductance, of so-called "negative" inductance enabling an ideal implementation of the emitted or sensed magnetic field, the coupling, the mutual inductance and the bandwidth.

Finally, a particular arrangement of capacitances with the load or with the load plus the inductances or with the inductances or with a frequency tuning circuit participate in obtaining the proposed objective.

The invention will be better understood on reading the description which follows, given solely by way of non-limiting example with reference to the accompanying drawings, in which:

FIGS. 1A, 2A, 3A, 4A show embodiments of the transponder antenna circuit according to the invention,

FIGS. 1B, 2B, 3B, 4B represent equivalent electrical diagrams of the circuits of FIGS. 1A, 2A, 3A, 4A,

FIGS. 5A, 6A, 7A, 8A, 9A, 1A1 represent embodiments of the reader antenna circuit according to the invention,

FIGS. 5B, 6B, 7B, 8B, 9B, HB show equivalent electrical diagrams of the circuits of FIGS. 5A, 6A, 7A, 8A, 9A, 1A1, FIG. 10 is a view of FIG. an antenna in one embodiment,

- Figures 12 to 46 show embodiments of the circuit according to the invention.

In what follows, the antenna circuit may be a circuit for emitting electromagnetic radiation by the antenna, as well as a circuit for receiving electromagnetic radiation by the antenna. In a first case of application, the RFID antenna circuit is of the transponder type, to operate as a portable card, tag (in English: "tag"), to be integrated in a paper document, such as for example a document issued by an official authority, such as a passport, USB keys and SIM cards and (U) SIM cards called "RFID or NFC SIM card", thumbnails for Dual or Dual Interface card (the sticker itself having an RFID antenna / NFC), watches.

In a second case of application, the RFID antenna circuit is of the reader type to read, that is to say at least receive, the signal radiated by the RFID antenna of a transponder as defined in the first cases like mobile phones, personal organizers said "PDA", computers.

In general, the circuit comprises an antenna 3 formed by at least three turns S of a conductor on an insulating substrate SUB. The turns S have an arrangement defining an inductance L having a determined value between a first end terminal D of the antenna 3 and a second end terminal E of the antenna 3.

In the embodiment shown in FIGS. 1A and 1B, the antenna 3 is formed by three consecutive turns S1, S2, S3 from the outer end terminal E to the inner end terminal D.

A first access terminal 1 is connected by a conductor CONlA to an intermediate point or point A of the antenna 3 between its end terminals D, E.

A capacity C according to a prescribed tuning frequency, that is to say at a resonance frequency, for example from 13.56 MHz up to 20 MHz, is provided in combination with the inductance L of the antenna 3.

The second end terminal E of the antenna 3 is connected by a conductor CON2E to the second terminal ClE of the capacitor C.

The first terminal ClX of the capacitor C is connected by a conductor CON31 to the intermediate socket A forming a first point P1 of the antenna 3.

A second access terminal 2 is connected by a conductor CON32 to the first end terminal D forming a second point P2 of the antenna 3. The point P2 is different from the point A.

The two access terminals 1, 2 are used to connect a load. According to the invention, there is at least one turn S between the first point A, P1 and the second point P2.

The intermediate tap A, P1 is connected to the end terminal D by at least one turn S of the antenna L, ie one turn S3 in FIG. 1. The intermediate tap A, P1 is connected to the second terminal E end of the antenna L by at least one turn S of the antenna L, ie two turns S1 and S2 in FIG. 1, where the intermediate tap A is located between the turns S3 and S2.

In a general way, according to the invention, the points D, E, 1, 2, A, ClE,

CIX, P1, P2 form electrical nodes of the circuit. The points directly connected to each other form the same node, for example when the connection means are electrical conductors. Two distinct nodes are connected by at least one turn.

In the equivalent diagram of FIG. 1B, the circuit of FIG. 1A has a first inductance L1, called active inductance, formed by the third turn S3, between the access terminals 1, 2. Between the intermediate tap A and the terminal E is a second inductance L2, called passive inductance, formed by the first turn

Sl and the second turn S2. The second inductor L2 is in parallel with the capacitor C between the intermediate tap A and the terminal E. The sum of the first inductance L1 and the second inductor L2 is equal to the total inductance L of the antenna 3. It is of course, the antenna 3 has a resistance in series with its inductance L as well as inter-turn coupling capacitors, which however have not been shown in all the figures.

The capacity C can be of any type of technology and method of production. In the example of FIG. 1A, the capacitor C is of planar type being disposed on the free zone of the substrate, present in the middle of the turns S. In FIG. 1A, the capacitor C is formed by a capacitor having a first surface SIX metal forming the first capacitance terminal ClX, a second metal surface SlE supported by the substrate and forming the second terminal ClE capacitance. One or more dielectric layers are located between the first metal surface S IX and the second metal surface SlE. The embodiment shown in FIGS. 1A and 1B makes it possible to increase the efficiency of the antenna 3.

The embodiment shown in Figures 2A and 2B is a variant of the embodiment shown in Figures IA and IB. In FIGS. 2A and 2B, the intermediate tap A, P 1 is located between the turns

Sl and S2. The intermediate tap A, P1 is connected to the end terminal D by at least one turn S of the antenna L, ie two turns S2 and S3. The intermediate tap A, P1 is connected to the second end terminal E of the antenna L by at least one turn S of the antenna L, ie a turn S1. Capacity C is formed by a capacitor having one or more dielectric layers having a first side and a second side remote from the first side. The first metal surface SIX forms the first capacitance terminal ClX on the first side of the dielectric layer. A second metal surface SlE forms the second capacity terminal ClE on the second side of the dielectric layer. The first metal surface SIX defines with the second metal surface SlE a capacitance value C2.

A third metal surface SlF forms a third terminal ClF of the capacitance C. The third metal surface SlF is situated on the same first side of the dielectric layer at a distance as the first metal surface SIX but at a distance from this first metal surface SIX. The third capacitance terminal ClF is connected by a conductor CON33 to the end terminal D. The third metal surface SlF defines with the second metal surface SlE a capacitance value C1.

The third metal surface SlF is coupled to the first metal surface SIX in that they share the same reference terminal ClE formed by the surface S1E, to form a coupling capacitor C12.

In the equivalent diagram of FIG. 2B, the circuit of FIG. 2A has a first inductance L1, called active inductance, formed by the second turn S2 and the third turn S3, between the access terminals 1, 2. intermediate A and the terminal E is a second inductor L2, called passive inductance, formed by the first turn S1. The sum of the first inductance L1 and the second inductance L2 is equal to the total inductance L of the antenna 3.

The second inductance L2 is in parallel with the capacitance C2 between the intermediate tap A and the terminal E. The first inductor L1 is in parallel with the coupling capacitor C 12.

The capacitor C1 is connected on the one hand to the terminal D and on the other hand to the terminal E.

The embodiment shown in FIGS. 2A and 2B makes it possible to further increase the radio efficiency of antenna 3, because of the arrangement of capacitors C1 and C2 and of the coupling between capacitors C1 and C2. The embodiment shown in FIGS. 3A and 3B is a variant of the embodiment shown in FIGS. 2A and 2B. In the embodiment shown in FIGS. 3A and 3B, the first point P 1 is distinct from the first intermediate tap A and is spaced from this first intermediate tap A by at least one turn S. The antenna 3 is formed by four turns S1, S2, S3, S4 consecutive from the outer end terminal E to the inner end terminal D. In addition, for example, in FIGS. 3A and 3B, the capacitor C is of the type of that of FIGS. 2A and 2B.

The first intermediate tap A is located between turns S2 and S3. The first intermediate tap A is connected to the end terminal D by at least one turn S of the antenna L, ie the two turns S3 and S4. The intermediate tap A is connected to the second end terminal E of the antenna L by at least one turn S of the antenna L, ie the two turns S2 and S1.

The access terminal 1 is connected to the first intermediate socket A by the conductor CONlA. The access terminal 2 is connected to the terminal D, which is not connected to the terminal ClF.

Between the access terminals 1, 2 is a load Z. The load Z is for example a chip generally designated by "silicon". This chip can also be present in general between the access terminals.

The terminal ClX is connected by the conductor CON31 to a first point P1 of the antenna 3, distinct from its terminals D, E. The first point P1 is located between the turns S3 and S4. The first point P1 is connected to the end terminal D by at least one turn S of the antenna L, ie the turn S4. The first point P1 is connected to the second end terminal E of the antenna L by at least one turn S of the antenna L, ie the three turns S3, S2 and S1. Terminal D forms the second point P2.

According to the invention, there is at least one turn S between the first point P1 and the second point P2, ie the turn S4.

The third capacitance terminal ClF is connected by a conductor CON33 to the access terminal 1. The terminal C IE is connected by a conductor CON2E to the terminal E.

In the equivalent diagram of FIG. 3B, the circuit of FIG. 3A has a first inductance L1, called active inductance, formed by the turn S4 between the terminal 2 and the point P1. Between the point P1 and the tap A is a second inductor LI l, also called active, formed by the turn S3. Between the intermediate tap A and the terminal E is a third inductor L3, called passive inductance, formed by the two turns S2 and S1. The sum of the first inductance L1, the second inductance LI1 and the third inductance L3 is equal to the total inductance L of the antenna 3.

The third inductance L3 is in parallel with the capacitance C1 between the intermediate socket A and the terminal E.

The second inductance LI1 is in parallel with the coupling capacitance C12.

The capacitor C2 is connected on the one hand to the point P1 and on the other hand to the terminal E.

Of course, the capacitance C could be of the type of that of FIG. 1A, that is to say having instead of Cl and C 12 only the capacitance C between Pl and E in FIGS. 3A and 3B.

The embodiment shown in FIGS. 3A and 3B makes it possible to increase the efficiency of antenna 3 because of the arrangement and combination of "active" and "passive" inductances and capacitors. The embodiment shown in Figures 4A and 4B is a variant of the embodiment shown in Figures IA and IB. In FIGS. 4A and 4B, the antenna 3 is formed from the second end terminal E to the first terminal D by a first turn S1, a second turn S2 and a third turn S3, which are consecutive. The turns S1 then S2 go from the second terminal E end to a point PR of a reversal in a first winding direction, corresponding to Figure 4A clockwise. The turn S3 goes from the recoiling point PR to the first end terminal D in a second direction of winding opposite to the first direction of winding, and therefore reverse clockwise in FIG. 4A. For example, the turn S3 is reversed direction inward with respect to the outer turns S2 and S3. The first point P1 forming the first intermediate tap A of the antenna connected to the access terminal 1 is located at the recoil point PR.

According to the invention, there is at least one turn S between the first point P1, A and the second point P2.

It is considered that the positive direction of the current in the antenna 3 is that going from the recoiling point PR to the terminal E, coinciding in this example with the greatest number of turns going in the same direction, as indicated by the arrows drawn on the antenna 3. The arrows drawn on the turns S1 and S2 correspond to this positive direction of the current.

In the equivalent diagram of FIG. 4B, the circuit of FIG. 4A has a second positive inductance + L2, called passive inductance, formed by the turns S2 and S1.

Due to the PR point of reversal, appears between the intermediate socket A, P1 and the terminal D a first negative inductance -Ll, called active inductance, formed by the third turn S3, between the points P1 and P2. The sum of the first inductance L1 in absolute value and the second inductance L2 is equal to the total inductance L of the antenna 3.

The negative inductance -L1 makes it possible to further reduce the mutual inductance generated by the antenna 3.

The embodiment shown in Figs. 5A and 5B is a variation of the embodiment shown in Figs. 1A and 1B. In FIGS. 5A and 5B, the antenna

3 is formed by three consecutive turns S1, S2, S3 of end terminal E outside the inner end terminal D forming the first point Pl of the antenna.

A first access terminal 1 is connected by a connection means CONlA to a first intermediate tap A of the antenna 3 between its end terminals D, E. The connection means CONlA is for example a capacitor ClO.

The second access terminal 2 is connected by a connection means CON32 to a second intermediate socket P2 forming a second point P2 of the antenna 3. The connection means CON32 is for example a capacitor C20. A capacity C according to a prescribed tuning frequency, that is to say at a resonance frequency, for example 13.56 MHz, is provided in combination with the inductance L of the antenna 3.

The second end terminal E of the antenna 3 is connected by a conductor CON2E to the second terminal ClE of the capacitor C. The first terminal ClX of the capacitor C is connected by a conductor CON31 to the terminal D, P1 of the antenna 3.

The two access terminals 1, 2 are used to connect a load.

According to the invention, there is at least one turn S between the first point P1 and the second point P2, ie the turn S3 and the turn S2 in the embodiment shown.

The intermediate tap A is located between the turns S3 and S2. The intermediate plug P2 is located between the turns S1 and S2. The intermediate terminal A is connected to the end terminal D by at least one turn S of the antenna L, ie the turn S 3 in the embodiment shown. The intermediate tap A is connected to the second end terminal E of the antenna L by at least one turn S of the antenna

L, two turns S1 and S2 in the embodiment shown.

The intermediate plug P2 is connected to the end terminal D by at least one turn S of the antenna L, ie the turn S2 and the turn S3 in the embodiment shown. The intermediate plug P2 is connected to the second end terminal E of the antenna L by at least one turn S of the antenna L, the turn S1 in the embodiment shown. In the equivalent diagram of FIG. 5B, the circuit of FIG. 5A has a first inductance L1, called active inductance, formed by the second turn S2, between points A and P2. Between the intermediate tap P2 and the terminal E is a second inductor L2, called passive inductance, formed by the first turn S1. Between the intermediate tap A and the terminal D is a third inductor L3, called passive inductance, formed by the third turn S3.

The sum of the first inductance L1, the second inductance L2 and the third inductance L3 is equal to the total inductance L of the antenna 3.

The embodiment shown in FIGS. 5A and 5B makes it possible to increase the efficiency of the antenna 3.

The embodiment shown in FIGS. 6A and 6B is a variant of the embodiment shown in FIGS. 5A and 5B. In FIGS. 6A and 6B, a fourth additional tuning capacitor C4 is connected between the intermediate tap A and the second tap P2, in parallel with the first inductor L1. The fourth capacitor C4 participates in the frequency tuning with C, particularly on the second inductor L2. The embodiment shown in FIGS. 6A and 6B makes it possible to increase the efficiency of the antenna 3.

The embodiment shown in FIGS. 7A and 7B is a variant of the embodiment shown in FIGS. 5A and 5B. In FIGS. 7A and 7B, the antenna 3 is formed by four consecutive turns S1, S21, S22, S3 from the outer end terminal E to the inner end terminal D.

According to the invention, there is at least one turn S between the first point P1 and the second point P2, ie the turn S21, the turn S22 and the turn S3, that is to say three second turns in the mode. embodiment shown. The first point P1 is formed by the terminal terminal D of the antenna.

Intermediate tap A is located between turns S3 and S22. The intermediate plug P2 is located between the turns S1 and S21. The intermediate terminal A is connected to the end terminal D by at least one turn S of the antenna L, ie the turn S3 in the embodiment shown. The intermediate tap A is connected to the second end terminal E of the antenna L by at least one turn S of the antenna

L, ie three turns S1, S21 and S22 in the embodiment shown. The catch intermediate P2 is connected to the terminal D end by at least one turn S of the antenna L, three turns S21, S22 and S3 in the embodiment shown. The intermediate plug P2 is connected to the second end terminal E of the antenna L by at least one turn S of the antenna L, the turn S1 in the embodiment shown.

In the equivalent diagram of FIG. 7B, the circuit of FIG. 5A has a first inductance L1, called active inductance, formed by the three second turns S21, S22 and S3, between the points P1 and P2. Between the intermediate tap P2 and the terminal E is a second inductor L2, called passive inductance, formed by the first turn S1. Between the intermediate tap A and the terminal D is a third inductor L3, called passive inductance, formed by the third turn S3.

The sum of the first inductance L1, the second inductance L2 and the third inductance L3 is equal to the total inductance L of the antenna 3.

The embodiment shown in FIGS. 7A and 7B makes it possible to increase the efficiency of the antenna 3 with a larger number of turns.

The embodiment shown in FIGS. 8A and 8B is a variant of the embodiment shown in FIGS. 5A and 5B. In FIGS. 8A and 8B, the antenna

3 is formed by six consecutive turns S1, S2, S31, S32, S33 and S34 from the outer end terminal E to the inner end terminal D. The first point P1 is formed by the end terminal D.

According to the invention, there is at least one turn S between the first point P1 and the second point P2, ie the turns S2, S31, S32, S33 and S34, that is to say five second turns in the mode. embodiment shown.

The intermediate tap A is located between the turns S2 and S31. The intermediate plug P2 is located between the turns S1 and S2. The intermediate tap A is connected to the end terminal D by at least one turn S of the antenna L, ie the four turns S31, S32, S33 and S34 in the embodiment shown. The intermediate tap A is connected to the second end terminal E of the antenna L by at least one turn S of the antenna L, ie the two turns S1, S2 in the embodiment shown. The intermediate tap P2 is connected to the end terminal D by at least one turn S of the antenna L, ie the five turns S2, S31, S32, S33 and S34 in the embodiment shown. The intermediate plug P2 is connected to the second end terminal E of the antenna L by at least one turn S of the antenna L, the turn S1 in the embodiment shown.

In the equivalent diagram of FIG. 8B, the circuit of FIG. 8A has a first inductance L1, called active inductance, formed by the second turns

S2, S31, S32, S33 and S34, between the points P1 and P2. Between the intermediate tap P2 and the terminal E is a second inductor L2, called passive inductance, formed by the first turn S1. Between the intermediate tap A and the terminal D is a third inductor L3, called passive inductance, formed by the four turns S31, S32, S33 and S34.

The sum of the first inductance L1, the second inductance L2 and the third inductance L3 is equal to the total inductance L of the antenna 3.

The embodiment shown in FIGS. 8A and 8B makes it possible to increase the efficiency of the antenna 3 with even more turns. The capacitor C is formed for example by a capacitor of the planar type as in FIG.

In transponder applications, the capacitance C, Cl, C2 is for example of the described planar type. In reader applications, the capacitance C may be in the form of an added capacitor component, instead of being of the planar type. The embodiment shown in FIGS. 9A and 9B is a variant of the embodiment shown in FIGS. 5A and 5B. In FIGS. 9A and 9B, the antenna 3 is formed from the second end terminal E to the first terminal D by a first turn S1, a second turn S2 and a third turn S3, which are consecutive. The turn S1 goes from the second end terminal E to a rewind point PR in a first winding direction corresponding to FIG. 9A clockwise. The turns S2 then S3 go from the reversal point PR to the first end terminal D in a second winding direction opposite to the first direction of winding, and therefore reverse clockwise in FIG. 9A. For example, the turn S1 is of direction reversed outside with respect to the internal turns S2 and S3.

The first point P1 is formed by the terminal D. The second point P2 forming the second intermediate point of the antenna connected to the access terminal 2, is located at the point PR of cusp.

According to the invention, there is at least one turn S between the first point P1 and the second point P2, ie the turn S2 and the turn S3 in the embodiment shown.

In the equivalent diagram of FIG. 9B, the circuit of FIG. 9A has a first positive inductance L1, called active inductance, formed by the second turn S2, between points A and P2.

Due to the recoiling point PR, there appears between the intermediate tap P2, PR and the terminal E a second negative inductance -L2, called passive inductance, formed by the first turn S1, considering that the positive direction of the current in the antenna 3 is the one going from the point PR, P2 to the point A, coinciding in this example with the greatest number of turns going in the same direction, as indicated by the arrows drawn on the antenna 3. The arrows drawn on the turns S2 and S3 correspond to this positive direction of the current.

Between the intermediate tap A and the terminal D is a third inductance + L3 positive, called passive inductance, formed by the third turn S3.

The sum of the first inductance L1, the second inductance L2 in absolute value and the third inductance L3 is equal to the total inductance L of the antenna 3.

The negative inductance -L2 makes it possible to further reduce the mutual inductance generated by the antenna 3.

The embodiment shown in FIGS. 1A and 1B is a variant of the embodiment shown in FIGS. 5A and 5B. The connection means CONlA is for example an electrical conductor.

The connection means CON32 is for example an electrical conductor. The capacitor C is of the type of that of FIG. 2A.

The second end terminal E of the antenna 3 is connected by a conductor CON2E to the second terminal ClE of the capacitor C. The first terminal D is connected to the terminal ClF of the capacitor C by the conductor CON33. The point P1 is formed by the terminal D.

The first terminal ClX of the capacitor C is connected by a conductor CON31 to the terminal D.

Terminal ClF is connected to terminal 2 access. According to the invention, there is at least one turn S between the first point P1 and the second point P2, ie the turn S3 and the turn S2 in the embodiment shown.

In the equivalent diagram of FIG. HB, the capacitance C1 is in parallel with the inductance L2 between the terminal E and the point P2. The capacitor C2 is connected between the terminals D and E. The coupling capacitor C 12 is connected between the second point P2 and the terminal D.

The embodiment shown in Figures HA and HB makes it possible to further increase the efficiency of the antenna 3, because of the coupling between the capacitors C1 and C2. Of course, one or more of the above embodiments may be combined with respect to the arrangement and arrangement of the inductors, capacitors, the one or more cusps, the number of turns.

In particular, the connection means, such as CONlA, CON32, terminals 1, 2 of access to the antenna can be capacitance, conductor or other, such as for example active elements, in particular of the transistor or amplifier type.

In general, any additional load or frequency or power matching circuit can be connected to the access terminals 1, 2, for example a chip, in particular a silicon-based chip, as well in the so-called transponder case. only in the case said reader.

In particular, the connection means of the antenna access terminals 1, 2 of FIGS. 5A, 6A, 7A, 8A, 9A may also be conductors. It is also possible to add an active or passive element, such as, for example, a capacitor, to terminals 1, 2 of access to FIGS. 1A, 2A, 3A, 4A. There can be provided a number of turns equal to one, two or more between the first point P1 and the second point P2. It can be expected a number of turns equal one, two or more between the first tap A and the end D. There may be provided a number of turns equal to one, two or more between the first tap A and the end E. A number of taps may be provided. turns equal to one, two or more between the first point P1 and the end D. It may be provided a number of turns equal to one, two or more between the first point P1 and the end E. It may be provided a number of turns equal to one, two or more between the second point P2 and the end D. It may be provided a number of turns equal to one, two or more between the second point P2 and the end E.

The antenna can be made of wire, engraved, printed (printed circuit board), copper, aluminum, silver particle or aluminum and any other electrical conductor and any other non-electrical conductor but chemically predicted to this effect.

The turns of the antenna can be made in multi-layers, superimposed or not, in whole or in part. As shown in FIG. 10, at least one turn S2 of the antenna may comprise in series a winding S2 'of turns of smaller surface area surrounded with respect to the surface surrounded by the remainder S2 "of the turn S2 or relative at the surface surrounded by the other turns of the antenna 3, in order to increase the resistance or the inductance of the turn S2 without accentuating the coupling, the mutual inductance and the general radiation of the antenna 3.

The capacity (s) can be in discrete element (component) or made in planar technology.

The capacitance (s) can be added to the antenna during the process of manufacturing the windings of turns as an element outside the printed circuit board and the antenna, especially in wire technology.

The capacitance (s) can be integrated in a module, in particular silicon.

The capacitance (s) can be integrated and realized on a printed circuit board. The turns S of the antenna 3 can be distributed over several different physical planes, for example parallel. The turns are formed of sections, for example rectilinear but may also have any other shape.

The turns of the antenna may be in the form of a wire which will then be heated to be embedded on or in an insulating substrate. The turns of the antenna can be etched on an insulating substrate.

The turns of the antenna may be on opposite sides of an insulating substrate.

The turns are for example in the form of parallel ribbons.

In the following figures is shown a load module M, such as for example a chip, the module M being connected between the first access terminal 1 and the second terminal 2 access.

In the embodiment shown in FIG. 12, the antenna L is formed by the turns S1, S2 situated between the first end terminal D and the second end terminal E. The first terminal D is connected to the second access terminal 2 forming the second point P2.

The tuning capacitance Cl at a prescribed tuning frequency comprises a first capacitance terminal ClX and a second capacitance terminal ClE.

The first capacitance terminal ClX is connected to the first terminal 1 by means CON31 at the first access terminal 1.

The second capacity terminal ClE is connected to the second end terminal E.

The second point P2 is formed by the second access terminal 2.

The first point Pl of the antenna and the intermediate point A of the antenna are formed by the first terminal 1 access.

The second point P2, 2 of the antenna L is connected to the first point P1, 1, A of the antenna L by at least a first turn S1 of the antenna L.

The antenna L is formed by one or more second turns S1 between E and A, that is, for example, by two second turns S 1, connected by the point A to one or more turns S2 going from the point A to the terminal D, by example three turns S2. There is at least one turn of the antenna L between the first point P1 and the second point P2, namely the at least one turn S2 between P1 and P2.

The capacity Cl of agreement is formed by one or more third turns SC3 (for example five turns SC3) having two first and second ends SC31, SC32 and by one or more fourth turns SC4 (for example five turns SC4) comprising two first and second ends SC41, SC42.

The at least one third turn SC3 is distinct from the turns S1, S2 forming the antenna L and is connected to one E of the end terminals of the antenna L. The at least one fourth turn SC4 is distinct from the turns S1 , S2 forming the antenna L and is electrically separated from the third turns SC3, for example along the third turns SC3, so that the turns SC3 are arranged facing the turns SC4, for example by having parallel sections. The end SC31 forms the terminal ClE and is connected to the terminal E. The end SC32 is free and isolated from SC4. The SC41 end is free and isolated from SC3. The end SC42 forms the terminal ClX and is connected to the intermediate socket A, 1, Pl. The end SC31 is remote from the end SC42, while being close to and isolated from the end SC41. The end SC42 is remote from the end SC31, while being close and isolated from the end SC32.

The sections of the third turns SC3 located in front of the fourth turns SC4, which are not electrically connected to the fourth turns SC4, define the capacitor C1. Due to the third turns SC3 and the fourth turns SC4, which in themselves induce an inductance. the winding of the turns, the impedance ZZ located between the ends SC31, SC42 serving to connect the capacitor C1 to the rest of the circuit also reduce an inductance. The impedance ZZ between the connection ends SC31, SC42 can for example be seen as comprising a capacitive-inductive resonant parallel and / or series circuit according to FIG. 33, comprising two parallel branches, with in one branch the capacitance Cl and in the other branch a capacitance in series with an inductor. Therefore, the ZZ impedance seen between connection ends SC31, SC42 has the capacitance Cl. The value of the capacitance C1 of the impedance ZZ depends on the relation between the turns SC3 and SC4, and in particular of their mutual arrangement, for example adjacent.

In FIG. 12, there is at least one turn S1 between the intermediate tap A connected to the access terminal 1 of the module and the impedance ZZ formed by the at least one third turn SC3 and the at least one fourth turn SC4. .

The impedance ZZ formed by the at least one third turn SC3 and the at least one fourth turn SC4 is self-resonant, because a capacitance and a series and / or parallel inductance are contained in the impedance ZZ. The equivalent circuit diagram of the circuit shown in FIG. 12 is represented in FIG. 34. The at least one third turn SC3 and the at least one fourth turn SC4 make it possible to equalize the tuning frequency of the module M (for example chip) being in parallel with an inductor (turn (s) S2) on the tuning frequency of the circuit formed by the at least one third turn SC3 and the at least one fourth turn SC4, for example to have the tuning frequency prescribed at 13.56 MHz.

It is thus possible to obtain a large coupling between the self-resonant circuit ZZ, SC3, SC4 and the circuit formed by the module M being in parallel with the or turns S2, decreasing the mutual inductance between these two circuits. The inductance formed by the one or more turns S1 located between the module M and the turns SC3, SC4 forming the self-resonant circuit ZZ makes it possible to play on this mutual inductance between the self-resonant circuit ZZ, SC3, SC4 and the circuit formed by the module M being in parallel with the or turns S2.

Thus, by a clever arrangement of the value of the intrinsic currents and inductances of the turns, it is possible to parameterize the values of mutual inductances between the two aforementioned antenna circuits (M, S2) and (ZZ, S1) and to obtain two chords. in frequency quasi-independent of one another or two frequency agreements very close to one another, for example with tuning frequency differences <10 MHz, <2 MHz or <500 KHz or 2 chords frequency in the same frequency range, which makes it possible to obtain a large bandwidth with respect to the RFID transmission channel, while keeping a high efficiency of coupling and therefore energy transmission, even though the integration surface of the antenna circuit can be very small, for example <16cm ² or <8 cm ² .

One seeks in particular to have as much as possible the inductance of the turns S2 being in parallel with the module M in order to obtain a tuning frequency closest to the useful frequency, for example 13.56MHz.

In particular, the aim is to have the inductance contained in the self-resonant circuit ZZ, SC3, SC4 as small as possible in order to allow the integration of the antenna circuit into a small area <16 cm ^2, for example a tag (tag in English) or a sticker circuit (in English: sticker).

In addition, it can be seen that one of the advantages of the invention is the possibility of parameterizing the mutual inductance between the antenna circuits, for example, between, on the one hand, the antenna circuit comprising the transponder chip or reader and on the other hand a first and a second antenna part, so as to set the mutual final inductance of the transponder or reader system. Moreover, unlike the documents of the state of the art indicated above, it is possible to produce two frequency agreements that are almost independent of one another or two frequency agreements that are very close to one another, for example <10 MHz, <2 MHz or <500KHz or 2 frequency agreements combined in the same frequency range. According to embodiments of the invention, at least one electrical connection is provided between a first antenna circuit comprising the chip and at least one second (or more) antenna circuit comprising at least one capacitive element.

In particular, the devices according to the documents EP-A-1031 939 and FR-A-2777141 do not make it possible to produce two frequency agreements that are almost independent of one another or two frequency agreements that are very close to one another. other example <10 MHz, <2MHz or <500KHz or 2 frequency agreements combined in the same frequency range. In fact, the greater the mutual inductance between the 2 antenna circuits, the more the 2 so-called "natural" agreements of the 2 antenna circuits increase. If we want these two frequency agreements to be close, we must reduce the mutual inductance by, for example, decreasing strongly one of the antenna circuit surfaces relative to the other which induces a considerable loss in the transponder efficiency.

Means are provided for coupling COUPL 12 by mutual inductance between neighboring turns S1 and S2. Means are provided for coupling COUPLZZ by mutual inductance between the neighboring turns S1 and SC3, SC4 of the impedance ZZ. This coupling by mutual inductance is for example due to the arrangement of Sl close to S2 and to the arrangement of S1 close to SC3, SC4. For example, in FIG. 12, successively from the periphery to the center: S2, S1, SC3, SC4. The antenna circuit has at least two mutually intrinsic intrinsic inductances coupled between them: between Sl and S2, between Sl and ZZ.

It is thus possible to increase the reading distance of the circuit of FIG. 12.

Other embodiments of the invention are given in the table below, with reference to the figures below mentioned. In this table are indicated the electrically connected points together in the four corresponding columns (1, A), (ClE, E), (ClX, Pl) and (2, P2), as well as the number of turns. In FIGS. 12 and following mentioned below, the connecting means CONlA of the intermediate tap A with the first access terminal 1, the connecting means CON2E connecting the second end terminal E to the second terminal ClE of capacity the means CON31 connecting the first capacitance terminal ClX to the first point Pl of the antenna L and the connecting means CON32 connecting the second terminal 2 to the second point P2 are implemented by electrical conductors, without be necessarily indicated in the figures or in the table below. The column AE indicates the number of turns S1 between A and E. The column AD indicates the number of turns S2 between A and D. The column P1-P2 indicates the number N12 equal to at least one turn S of the antenna L between points P1 and P2. The last column on the right indicates either the presence of the impedance ZZ formed by the turns SC3 and SC4, indicating in this case the number of ZZ turns in parentheses, ie the presence of an additional capacitor C30, called the first capacitor, formed by a capacitive dielectric component between its terminals. The term "dielectric capacitive component" means any embodiment allowing the arrangement of a capacity. If necessary, this capacitive component may be formed by another circuit ZZ.

In Figures 16 and 18, two capacities C30 and ZZ are provided. The capacitance ZZ is formed by turns SC3, SC4 between SC42 and SC31 (for example 4 turns), with SC31 forming ClXZ. In addition to Z, another capacity C30 formed by a capacitive component is provided between E and ClXCl. The terminal ClXCl is connected to a point PC1 of the antenna L, which is at a distance of P2 from at least one turn, for example a turn to this figure. In Figures 16 and 18, ZZ is between ClXZ and ClE, and C30 is a capacitive component between E and ClXCl.

In FIG. 22, two capacitors C30 and ZZ are provided in series between the terminal ClE, E and the terminal ClX, Pl formed by the end SC42. The capacitance ZZ is formed by the turns SC3, SC4 between SC42 and SC31 (for example 4 turns), with SC31 forming PC1. In addition to Z, another capacity C30 formed by a capacitive component is provided between E and PCl. The terminal PC1 is connected to the point 2, P2 of the antenna L. The terminal ClE, E is formed by the end of the or turns Sl, remote from the terminal 2. In FIG. 20, two capacitors C30 and ZZ are provided in series between the terminal

ClE, E and the terminal ClX, Pl formed by the end SC42. The capacitance ZZ is formed by the turns SC3, SC4 between SC42 and SC31 (for example 4 turns), with SC31 connected in series with the point PC1 by one or more turns SlO (for example two turns SlO). In addition to Z, another capacity C30 formed by a capacitive component is provided between E and PCl. The terminal PCl is connected to the point 2, P2 of the antenna L. The terminal ClE, E is formed by the end of the or turns Sl, remote from the terminal 2.

In FIGS. 23 and 24 are provided two points PR1 and PR2 for reversing in the turns S1 between A and E. The point PR1 is away from A by at least one turn and E by at least one turn (for example two turns between A and PR1 and two turns between PR1 and E). The point PR2 is away from A by at least one turn and E by at least one turn (for example a turn between A and PR2 and three turns between PR2 and E).

In Figure 23, PR2 is away from P2 by at least one turn. In FIG. 25 are provided two points PR1 and PR2 for reversing in the turns S1 between A and E. The point PR1 is located in A. The point PR2 is away from A by at least one turn and E by at least one turn (for example a turn between A and PR2 and three turns between PR2 and E). In FIG. 26 are provided two points PR1 and PR2 for reversing in the turns S1 between A and E. The point PR1 is located in A. The point PR2 is away from A by at least one turn and from E by at least one turn (for example a turn between A and PR2 and four turns between PR2 and E).

In FIG. 27 are provided two points PR1 and PR2 for reversing in the turns S1 between A and D. The point PR1 is away from A by at least one turn and D by at least one turn (for example a turn between A and PR1 and two turns between PR1 and D). The point PR2 is away from A by at least one turn and D by at least one turn (for example two turns between A and PR2 and a turn between PR2 and D). In FIGS. 29 and 30, a mid-point PM for fixing a potential to a reference potential is provided on the antenna halfway between the two end terminals D and E of the antenna. In FIG. 29, where the number of turns of the antenna between D and E is even, the midpoint PM is distant from the other points 1, A, 2, P2, ClE, E, ClX, P1, D by at least a turn of the antenna. In FIG. 30, where the number of turns of the antenna between D and E is odd, the midpoint PM is remote from the other points 1, A, 2, P2, ClE, E, ClX, P1, D by at least a half-turn of the antenna and is for example on the other side with respect to the side having these points 1, A, 2, P2, ClE, E, ClX, Pl, D.

Of course, in the foregoing, the number of turns between the points mentioned on the antenna (1, A, 2, P2, ClE, E, ClX, P1, D, as well as the cusp point (s)) can be whatever, for example by being greater than or equal to one. These numbers of turns may be integers, for example as shown in the figures, or not integers such as for example in FIGS. 31 and 32.

In FIGS. 12, 13, 14, 19, 21, 25, 26 is provided a point PR3 of reversal at point 1, A, that is to say an inversion of the winding direction of the turns of the antenna to the passage 1, A from D to E. In Figures 15, 16, 17, 18, 22, 23, 24, 27, 28, 29, 30, 31 and 32, we go through the point 1, A going from D to E keeping the same winding direction of the turns of the antenna. However, one or more changes in winding direction of the turns are made at a point PR2, PR1 other than 1, A in FIGS. 23, 24, 26, 27. The first access terminal is distinct from the second terminal of FIG. access in that the first access terminal is separated from the second access terminal by one or more turns.

Only one first access terminal 1 and only one second access terminal 2 are for example provided. In one embodiment, a transponder TRANS as load Z is connected to the first terminal 1 and the second terminal 2, as for example in FIG.

Figures 35 to 46 correspond to any of the embodiments described above, where the capacities ClO, C20 present where appropriate have not been represented.

In another embodiment, a reader LECT as load Z is connected to the first terminal 1 and the second terminal 2, as for example in FIG.

Several charges can be provided. In another embodiment, several separate charges Z can be connected to the same first access terminal 1 and to the same second access terminal 2.

For example, a transponder TRANS as the first load Z1 and a reader LECT as the second load Z2 can be connected to the same first terminal 1 and the same second terminal 2, as shown for example in FIGS. 37 and 38, the TRANS transponder and the reader LECT being electrically in parallel with FIG.

In another embodiment, the antenna may comprise, for the connection of several separate loads, a plurality of first distinct access terminals 1 and / or a plurality of second access terminals 2 distinct from each other. First distinct access terminals 1 are separated from each other by minus one turn of the antenna. Separate second terminals 2 are separated from each other by at least one turn of the antenna.

For example, in FIG. 39, a transponder TRANS as the first load Z1 is connected between the first access terminal 1 and the second access terminal 2, while an LECT reader as the second load Z2 is connected. between another first access terminal 11 and another second access terminal 12.

For example, in FIG. 40, a transponder TRANS as the first load Z1 is connected between the first access terminal 1 and the second access terminal 2, while an LECT reader as the second load Z2 is connected. between another second access terminal 12 and the second access terminal 2 (successive access terminals).

In another embodiment, a plurality of RFID applications, and / or RFID reader and / or RFID transponder may be connected between the first and second identical access terminals 1, 2 or between first and second access terminals 1, 2 distinct, as for example the applications designated by APPLl, APPL3 in Figure 41 between first and second terminals 1, 2, access distinct 1, 2, 12, 13 successive.

Of course, in the foregoing, the role of the first access terminal 1 and the role of the second access terminal 2 can be inverted. In the foregoing, the load Z connected to the access terminals 1, 2 has, for example, a prescribed tuning frequency, as shown in FIG. 42. This tuning frequency is fixed.

This prescribed tuning frequency is for example in a high frequency band (HF), the high frequency band covering frequencies greater than or equal to 30 kHz and less than 80 MHz. This tuning frequency is for example 13.56 MHz.

The tuning frequency may also be in an ultra high frequency (UHF) band, the ultra high frequency band covering frequencies greater than or equal to 80 MHz and less than or equal to 5800 MHz. For example, in this case, the tuning frequency is 868 MHz or 915 MHz. In one embodiment, said at least one first access terminal 1 and said at least one second access terminal 2 are connected to at least one first load Z1 having a first prescribed frequency of agreement and to at least one second charge Z2 having a second prescribed tuning frequency different from the first prescribed tuning frequency.

In one embodiment, a first load Z1 having the first prescribed tuning frequency in the high frequency band and a second load Z2 having the second tuning frequency prescribed in the ultra high frequency band are connected to the terminals 1, 2 d. 'access. In the embodiment of Fig. 43, the first load Z1 having the first tuning frequency prescribed in the high frequency band and a second load Z2 having the second tuning frequency prescribed in the ultra high frequency band are connected to the same first terminal 1 access and the same second terminal 2 access. In the embodiment of FIG. 44, the first load Z1 having the first tuning frequency prescribed in the high frequency band is connected between the first access terminal 1 and the second access terminal 2, while the second Load Z2 having the second tuning frequency prescribed in the ultra high frequency band is connected between another first access terminal 11 and another second access terminal 12.

In the embodiments of Figures 45 and 46, the first load Z1 having the first tuning frequency prescribed in the high frequency band is connected between the first access terminal 1 and the second access terminal 2, while the second load Z2 having the second tuning frequency prescribed in the ultra-high frequency band is connected between another second access terminal 12 and the second access terminal 2 (successive access terminals), the number of turns between the two terminals being different between the two figures.

Claims

An RFID antenna circuit, comprising an antenna (L) formed by a number of at least three turns (S), the antenna having a first end terminal (D) and a second terminal (E) of at least two terminals (1, 2) of access for the connection of a load, at least one capacity (C1, ZZ) according to a prescribed tuning frequency, having a first terminal (ClX) of capacitance and a second terminal (ClE) of capacitance, an intermediate tap (A) connected to the antenna (L) and distinct from the end terminals, a first means (CONlA) for connecting the intermediate tap (A) to a first (1) of the two access terminals, a second means (CON2E) connecting the second terminal (E) end to the second terminal (ClE) capacity, characterized in that it comprises third means ( CON31, CON32) connecting the first terminal (ClX) capacity and the second (2) of the two access terminals to a first point (Pl) of the antenna (L) and at a second point (P2) of the antenna (L) connected to the first point of the antenna (L) by at least one turn (S) of the antenna (L). 2. Circuit according to claim 1, characterized in that said intermediate tap (A) is connected to the first end terminal (D) of the antenna (L) by at least one turn (S) of the antenna ( L), said intermediate tap (A) being connected to the second end terminal (E) of the antenna (L) by at least one turn (S) of the antenna (L). 3. Circuit according to any one of claims 1 and 2, characterized in that the first point (Pl) is connected to the intermediate point (A) by at least one turn of the antenna. 4. Circuit according to any one of claims 1 and 2, characterized in that the first point (Pl) is located at the intermediate point (A). 5. Circuit according to any one of claims 1 to 4, characterized in that the first point (Pl) is connected to the first terminal (D) of the end of the antenna (L) by at least one turn (S ) of the antenna (L), the first point (Pl) being connected to the second end terminal (E) of the antenna (L) by at least one turn (S) of the antenna (L). 6. Circuit according to any one of claims 1 and 2, characterized in that the first point (Pl) is located at the first terminal (D) end. 7. Circuit according to any one of claims 1 to 5, characterized in that the second point (P2) is located at the first terminal (D) end of the antenna. 8. Circuit according to any one of claims 1 to 5, characterized in that the second point (P2) is located at the second terminal (E) end of the antenna. 9. Circuit according to any one of claims 1 to 6, characterized in that the second point (P2) is connected to the intermediate hold (A) by at least one turn of the antenna. 10. Circuit according to any one of claims 1 to 6, characterized in that the second point (P2) is connected to the first terminal (D) of the end of the antenna (L) by at least one turn (S ) of the antenna (L), the second point (P2) being connected to the second end terminal (E) of the antenna (L) by at least one turn (S) of the antenna (L). Circuit according to Claim 2, characterized in that the first point (P1) is located at the intermediate point (A) of the antenna (L) and the second point (P2) is at the first point (D). end of the antenna (L). Circuit according to Claim 1, characterized in that the said first and second points (P1, P2) are distinct from the first intermediate tap (A), the first point (P1) being connected to the first tap (D) of end of the antenna (L) by at least one turn (S) of the antenna (L), the first point (P1) being connected to the second end terminal (E) of the antenna (L) by at least one turn (S) of the antenna (L). Circuit arrangement according to Claim 1, characterized in that the second point (P2) is located at the first end terminal (D) of the antenna, the first point (P1) is connected to the intermediate point (A). by at least one turn of the antenna. 14. Circuit according to claim 1, characterized in that said intermediate tap (A) forms a first intermediate tap (A), the first intermediate tap (A) being connected to the first end terminal (D) of the antenna. (L) by at least one turn (S) of the antenna (L), the first intermediate tap (A) being connected to the second end terminal (E) of the antenna (L) by at least one turn (S) of the antenna (L), the second point (P2) is located at a second intermediate point (P2) of the antenna (L), the second intermediate point (P2) being connected to the first terminal (D). ) end of the antenna (L) by at least one turn (S) of the antenna (L), the second intermediate tap (P2) being connected to the second terminal (E) of the antenna end (L) by at least one turn (S) of the antenna (L). 15. Circuit according to any one of the preceding claims, characterized in that the capacitance comprises a first metal surface forming the first capacitance terminal (ClX), a second metal surface forming the second capacitance terminal (ClE), at least one dielectric layer between the first metal surface and the second metal surface. Circuit according to one of Claims 1 to 14, characterized in that the capacitance comprises at least one dielectric layer having a first side and a second side remote from the first side, a first metal surface forming the first terminal (ClX ) on the first side of the dielectric layer, a second metal surface forming the second capacitance terminal (ClE) on the second side of the dielectric layer, a third metal surface forming a third terminal (ClF) of capacitance to distance from the first metal surface on the first side of the dielectric layer, the first capacitance terminal (ClX) defining a first capacitance value (C2) with the second capacitance terminal (ClE), the third capacitance terminal (ClF) defining a second capacitance value (C1) with the second capacitance terminal (ClE), the first capacitance terminal (C1X) defining a third coupling capability value (C12) with the third capacitance terminal (ClF) means for connecting the third capacitance terminal (ClF) to one of the access terminals (1, 2). 17. Circuit according to any one of the preceding claims, characterized in that the antenna (L) comprises at least a first turn (Sl), at least a second turn and at least a third turn, which are consecutive, the first turn (S1) from the second end terminal (E) in a first winding direction to a cusp point (PR) connected to the second turn, the second and third turns (S2, S3) from said point ( PR) to the first end terminal (D) in a second reverse winding direction of the first winding direction, the first point (P1) of the antenna (L) and the second point (P2) of the antenna (L) being located on the second and third turns (S2, S3). 18. Circuit according to any one of the preceding claims, characterized in that the antenna (L) comprises at least a first turn (S1) and at least a second turn (S2, S3) consecutive between two third and fourth points ( E; D) of the antenna, the first turn (S1) being connected to the second turn (S2, S3) by a reversing point (PR), the first turn (S1) going from the third point (E) to the point (PR) of reversing in a first winding direction, the second turn (S2, S3) from said reversal point (PR) to the fourth point (D) in a second reverse winding direction of the first winding direction. 19. Circuit according to claim 1, characterized in that the antenna (L) comprises at least a first turn (S1) and at least a second turn (S2, S3) consecutive between two third and fourth points (E; D). of the antenna, the first turn (S1) being connected to the second turn (S2, S3) by a reversal point (PR), the first turn (S1) going from the third point (E) to the point (PR) of creep in a first winding direction, the second turn (S2, S3) going from said reversal point (PR) to the fourth point (D) in a second reverse winding direction of the first winding direction, the first point (P1) is located at the intermediate point (A) of the antenna (L). ) and the second point (P2) is located at the first end terminal (D) of the antenna (L). 20. Circuit according to claim 1, characterized in that the antenna (L) comprises at least a first turn (S1) and at least a second turn (S2, S3) consecutive between two third and fourth points (E; D). of the antenna, the first turn (S1) being connected to the second turn (S2, S3) by a reversal point (PR), the first turn (S1) going from the third point (E) to the point (PR) of in a first winding direction, the second winding (S2, S3) running from said reversal point (PR) to the fourth point (D) in a second reverse winding direction of the first winding direction, the first point ( Pl) is located at the first end terminal (D). 21. Circuit according to any one of the preceding claims, characterized in that at least one turn (S2) of the antenna comprises in series a winding (S2 ') of turns of smaller area surrounded with respect to the surrounding surface. by the remainder (S2 ") of said turn (S2) or with respect to the surface surrounded by other turns of the antenna (3). 22. Circuit according to any one of the preceding claims, characterized in that the turns (S) of the antenna (3) are distributed over several distinct physical planes. 23. Circuit according to any one of the preceding claims, characterized in that the tuning capacitance (Cl) comprises a second capacitance (ZZ) formed by at least a third turn (SC3) comprising two first and second ends (SC31, SC32) and by at least a fourth turn (SC4) having two first and second ends (SC41, SC42), the third turn (SC3) being electrically separated from the fourth turn (SC4) to define at least the capacitance (Cl ) in agreement between the first end (SC31) of the third turn (SC3) and the second end (SC42) of the fourth turn (SC4), the first end (SC31) of the third turn being further away from the second end (SC42) of the fourth turn (SC4) than the first end (SC41) of the fourth turn (SC4), the second end (SC32) of the third turn (SC3) being further away from the first end (SC41) of the fourth turn (SC4) than the second end (SC42) of the fourth turn (SC4), the second capacitance being defined between the first end (SC31) of the third turn (SC3) and the second end (SC42) of the fourth turn (SC4). 24. Circuit according to the preceding claim, characterized in that there is at least one turn (Sl) of the antenna between the intermediate tap (A) and the second capacitor. 25. Circuit according to any one of claims 23 and 24, characterized in that first coupling means are provided to ensure a coupling. (COUPL 12) by mutual inductance between on the one hand the at least one turn (S2) of the antenna electrically connected in parallel with the first and second terminals (1, 2) access and the other at least one turn (Sl) of the antenna, second coupling means are provided for coupling (COUPLZZ) by mutual inductance between said other at least one turn (S1) of the antenna and the at least one third and fourth turns (SC3, SC4) of the second capacitance (ZZ). 26. Circuit according to the preceding claim, characterized in that the first coupling means are formed by the proximity between on the one hand the at least one turn (S2) of the antenna electrically connected in parallel with the first and second terminals ( 1, 2) and on the other hand at least one turn (Sl) of the antenna, the second coupling means are formed by the proximity between the other at least one turn (S1) of the antenna and the at least one third and fourth turns (SC3, SC4) of the second capacitance (ZZ). 27. Circuit according to any one of claims 23 to 26, characterized in that the third turn (SC3) and the fourth turn (SC4) are interleaved. 28. Circuit according to any one of claims 23 to 27, characterized in that the third turn (SC3) comprises at least a third section, the fourth turn (SC4) comprises a fourth section, the third section being adjacent to the fourth section. . 29. Circuit according to claim 28, characterized in that the sections extend parallel to each other. 30. Circuit according to any one of claims 23 to 29, characterized in that the tuning capacitance (Cl) comprises a first capacitance (C1) comprising a dielectric between the first capacitance terminal (ClX) and the second terminal ( ClE) of capacity, the first capacitance (Cl) being in the form of a wire element, engraved, discrete or printed. 31. Circuit according to any one of claims 23 to 30, characterized in that another capacitor (C30) is connected between the second end terminal (E) and a point (PCl) of the antenna, which is connected to the second point (P2) by at least one turn of the antenna. 32. Circuit according to any one of claims 23 to 30, characterized in that the capacity (Cl) of agreement comprises a first capacitance (C30) in series with said second capacitance (Z). Circuit according to the preceding claim, characterized in that the first capacitance (C30) is connected between the second end terminal (E) of the antenna and the second point (P2), which is connected to the first terminal ( SC31) of the third turn (SC3), the intermediate tap (A) being connected to the second terminal (SC42) of the fourth turn (SC4), which forms the first point (P1), the first terminal (SC41) of the fourth turn (SC4) forming the first end terminal (D) of the antenna. Circuit according to Claim 32, characterized in that the first capacitance (C30) is connected between the second end terminal (E) of the antenna and the second point (P2), which is connected to the first terminal ( SC31) of the third turn (SC3) by at least one turn (SlO), the intermediate point (A) being connected to the second terminal (SC42) of the fourth turn (SC4), which forms the first point (P1), the first terminal (SC41) of the fourth turn (SC4) forming the first terminal (D) of the end of the antenna. 35. Circuit according to any one of claims 23 to 30, characterized in that the first point (Pl) is located at the intermediate point (A), the second point (P2) is located at the second terminal (E) d end of the antenna. Circuit according to one of Claims 23 to 30, characterized in that the first point (P1) is located at the first end terminal (D) and the second point (P2) is located at the second terminal ( E) end. Circuit according to one of Claims 23 to 36, characterized in that the at least one third turn (SC3) and the at least one fourth turn (SC4) define a second sub-circuit having a second own resonance frequency, the first and second access terminals (1, 2) define with a module (M) connected to them and with at least one connected turn (S2) at said first and second access terminals (1, 2) a first sub-circuit having a first natural resonance frequency, the turns being arranged so that the frequency difference between the first natural resonance frequency and the second resonance frequency clean is less than or equal to 10 MHz. Circuit according to one of Claims 23 to 36, characterized in that the at least one third turn (SC3) and the at least one fourth turn (SC4) define a second sub-circuit having a second resonance frequency of its own. the first and second access terminals (1, 2) define with a module (M) connected to them and with at least one turn (S2) connected to said first and second access terminals (1, 2) a first slot circuit having a first natural resonance frequency, the turns being arranged so that the frequency difference between the first natural resonance frequency and the second natural resonance frequency is less than or equal to 500 KHz. Circuit according to one of Claims 23 to 38, characterized in that the at least one third turn (SC3) and the at least one fourth turn (SC4) define a second sub-circuit having a second resonance frequency of its own. , the first and second access terminals (1, 2) define with a module (M) connected to them and with at least one turn (S2) connected to said first and second terminals (1, 2) access a first sub-circuit having a first natural resonance frequency, the turns being arranged so that the first resonance frequency and the second own resonance frequency are substantially equal. 40. Circuit according to any one of the preceding claims, characterized in that the antenna comprises a mid-point (PM) for fixing a potential to a reference potential, with an equal number of turns on the section going from the first terminal (D) end to the midpoint (PM) and the section from the midpoint (PM) to the second terminal (E) end. 41. Circuit according to any one of the preceding claims, characterized in that the antenna is on a substrate. 42. Circuit according to any one of the preceding claims, characterized in that the antenna is a wire. 43. Circuit according to any one of the preceding claims, characterized in that said terminals (D, E, 1, 2, ClE, ClX), said tap (A), said points (P1, P2) and the capacitance (C1 , ZZ) define a plurality of at least three nodes, the nodes defining at least one first group (Sl) of at least one turn between two first nodes (1, ClE) distinct from each other and at least one second group of at least one other turn (S2) between two second nodes (1, 2) which are distinct from each other, at least one of the first nodes being different from at least one of the second nodes, first coupling means are provided for coupling ( COUPL 12) by mutual inductance between on the one hand the first group (S1) of at least one turn and on the other hand the second group of at least one other turn (S2) in that the first group (S1) ) at least one turn is positioned near the second group of at least one other turn (S2). 44. Circuit according to any one of the preceding claims, characterized in that said terminals (D, E, 1, 2, ClE, ClX), said tap (A), said points (P1, P2) and the capacitance (C1 , ZZ) define a plurality of at least three nodes, the nodes defining at least a first group (Sl) of at least one turn between two first nodes (1, ClE) distinct from each other, and at least one second group of at least one other turn (S2) between two second nodes (1, 2) which are distinct from one another and at least one third group of at least one other turn (SC3, SC4) between two distinct third nodes (E, ClX) between them, at least one of the first nodes being different from at least one of the second nodes, at least one of the first nodes nodes being different from at least one of the third nodes, at least one of the third nodes being different from at least one of the second nodes, first coupling means are provided to ensure coupling (COUPL12) by mutual inductance between on the one hand the first group (S1) of at least one turn and on the other hand the second group of at least one other turn (S2) in that the first group (S1) ) at least one turn is positioned near the second group of at least one other turn (S2), second coupling means are provided for coupling (COUPLZZ) by mutual inductance between on the one hand the first group (Sl) of at least one turn and on the other hand the third group of at least one other turn (SC3, SC4) in that the first group (Sl) of at least one turn is positioned near the third group of at least one other turn (SC3, SC4). 45. Circuit according to the preceding claim, characterized in that the first group (Sl) of at least one turn is positioned between the second group of at least one other turn (S2) and the third group of at least one other spire (SC3, SC4). 46. Circuit according to any one of claims 43 to 45, characterized in that the spacing distance between the turns (Sl, S2, SC3, SC4) belonging to different groups is less than or equal to 20 millimeters. 47. Circuit according to any one of claims 43 to 45, characterized in that the spacing distance between the turns (Sl, S2, SC3, SC4) belonging to different groups is less than or equal to 10 millimeters. 48. Circuit according to any one of claims 43 to 45, characterized in that the spacing distance between the turns (Sl, S2, SC3, SC4) belonging to different groups is less than or equal to 1 millimeter. 49. Circuit according to any one of claims 43 to 48, characterized in that the spacing distance between the turns (Sl, S2, SC3, SC4) belonging to different groups is greater than or equal to 80 micrometers. Circuit according to one of the preceding claims, characterized in that at least one reader (LECT) as a load and / or at least one a transponder (TRANS) as a load is connected to the access terminals (1, 2). 51. Circuit according to any one of the preceding claims, characterized in that it comprises a plurality of first distinct access terminals (1) between them and / or a plurality of second access terminals (2) which are distinct from one another. 52. Circuit according to any one of the preceding claims, characterized in that said at least one first access terminal (1) and said at least one second access terminal (2) are connected to at least a first load ( Zl) having a first tuning frequency prescribed in a high frequency band and at least a second charge (Z2) having a second tuning frequency prescribed in another ultra high frequency band.