CN117039402A

CN117039402A - NFC loop antenna near metal structure and method for operating the same

Info

Publication number: CN117039402A
Application number: CN202310521182.6A
Authority: CN
Inventors: T·波特斯彻
Original assignee: STMicroelectronics Austria GmbH
Current assignee: STMicroelectronics Austria GmbH
Priority date: 2022-05-10
Filing date: 2023-05-10
Publication date: 2023-11-10

Abstract

NFC loop antennas in the vicinity of metallic structures and methods of operating the antennas are disclosed. In one embodiment, an apparatus includes a conductive structure, a Near Field Communication (NFC) reader includes a support to support an electrically conductive NFC loop antenna system positioned proximate to the conductive structure; and a component configured to excite the loop antenna system with a current, wherein the loop antenna system has a geometry configured to generate a plurality of electromagnetic fields in response to excitation of the current, the electromagnetic fields having NFC carrier frequencies and respective different field directions adapted to induce mutually cancelling respective eddy currents in the conductive structure.

Description

NFC loop antenna near metal structure and method for operating the same

Cross Reference to Related Applications

The present application claims the benefit of european patent application No. 22197935.4 filed at month 27 of 2022 and claims the benefit of european patent application No. 22172483.4 filed at month 5 of 2022, all of which are incorporated herein by reference.

Technical Field

The present application relates to wireless communication between elements, such as between a reader and a transponder, in particular between a Near Field Communication (NFC) contactless reader and a tag, a contactless integrated circuit card or a mobile phone emulated in card mode, typically using high frequency communication operating at 13.56MHz. The application relates more particularly to NFC antennas, such as readers, of such elements located in the vicinity of a metallic structure, located in the console of a vehicle and surrounded by metal, and intended to communicate with transponders or mobile devices/mobile phones placed on the console.

Background

Near field communication, or NFC, is a short-range high frequency wireless communication technology that is capable of exchanging data over short distances, e.g. 10 cm, between two contactless devices.

NFC is an open platform technology standardized in ISO/IEC 18092 and ISO/IEC 21481, but incorporates various pre-existing standards including ISO/IEC 14443 protocol type a and type B.

NFC devices have the capability to specifically support a reader/writer mode that can be used to read and write NFC transponders or tags.

The transponder may be passive, i.e. perform load modulation of the magnetic field generated by the reader.

The transponder may be an active transponder.

When the transponder is an active transponder, i.e. when information is transmitted to the reader using Active Load Modulation (ALM), the transponder generates a magnetic field simulating the load modulation of the reading device field performed by the passive transponder.

ALM is required if the signal strength produced by passive load modulation is not sufficient to be detected by the reader. This situation arises when the antenna of the transponder is small or in a challenging environment.

NFC transmission is a physical phenomenon based on electromagnetic inductive coupling. Both the reader and the tag are equipped with antenna coils, which generate a magnetic field each time electrons flow through the wire, and induce a current in the coil.

If the NFC antenna and its magnetic field are close to a conductive material such as a metal sheet, a circulating electron flow called eddy current will start to pass through the metal like the swirling water in a stream.

When the metal structure is located between the NFC reader and the receiver antenna system, the eddy currents flowing on the metal surface of the chassis will turn and generate their own magnetic field, which will interact with the coil and the communication will be negatively affected.

In other words, these eddy currents will cause losses, preventing the reader from generating a magnetic field strong enough to read or even power the card.

For example, when the antenna of the reader is surrounded by a metal structure, problems may occur in reading small tags placed at the outer periphery of the antenna.

A known solution is to shield the antenna of the NFC reader by using ferrite.

However, adding ferrite results in higher cost and accuracy during assembly of the reader.

Another known solution is to introduce a notch in the metal to prevent eddy currents from circulating around the antenna.

But the extra cut in the metal can lead to mechanical instability or manufacturing difficulties because the cut must be bonded with a non-conductive material.

Disclosure of Invention

Embodiments of the present application may be used with passive or active transponders.

Further embodiments provide improved performance of NFC readers in close proximity to conductive structures without incurring higher costs and precision during assembly of the reader or mechanical instability or manufacturing difficulties without requiring any additional items.

The various embodiments provide a completely different solution for improving the performance of NFC readers in close proximity to conductive structures. This new solution requires in particular neither additional material nor cutting in the electrical structure.

According to one embodiment, an apparatus comprises:

an electrically conductive structure, such as a metal plate or a metal housing,

-a near field communication, NFC, reader comprising: a support, for example an electrically insulating support as a resin, eventually having glass fibers, supporting an electrically conductive NFC loop antenna system located in proximity to the electrically conductive structure; and a component, such as an NFC controller coupled to the impedance matching circuit, configured to energize the loop antenna system with current.

The antenna loop system has a geometry configured to generate a plurality of electromagnetic fields having NFC carrier frequencies and respective different directions in response to excitation of the current, the electromagnetic fields being adapted to induce respective eddy currents in the conductive structure that cancel each other.

According to one embodiment, a loop antenna system has a geometry configured to define a plurality of regions and generate an electromagnetic field in each region in response to an excitation of a current, the electromagnetic field having a first field direction perpendicular to the region or a second field direction opposite the first field direction, thereby inducing eddy currents in the conductive structure flowing in different current directions such that the eddy currents cancel each other out.

The number of regions may be an odd number, for example 3. However, in this case, it would be much more difficult to estimate or calculate the size of each individual region.

It is therefore preferable and much simpler to have an even number of regions.

The even number may be equal to 2, but may also be greater than 2, for example equal to 4, 6 or 8.

The loop antenna system is advantageously configured to define a loop antenna subsystem for each region.

Each loop antenna subsystem may include one or more turns (turns).

The loop antenna system may include one or more loop antennas.

According to one possible embodiment, the loop antenna system may include a loop antenna having a track including loop segments in each region for defining a loop antenna subsystem.

Each ring segment is for example configured to generate, in response to an excitation of a current, two respective electromagnetic fields having opposite first and second field directions in two adjacent regions having a common edge, thereby inducing two respective eddy currents flowing in opposite current directions in two portions of the conductive structure respectively located in the vicinity of the two adjacent regions.

According to another possible embodiment, the loop antenna system may comprise a plurality of loop antennas, e.g. two loop antennas, each loop antenna having a track comprising loop segments for defining at least one region of the respective loop antenna subsystem.

Each loop antenna may have a track comprising loop segments in a plurality of regions, e.g., two regions, for defining a respective loop antenna subsystem.

Each loop segment of the respective loop antenna is advantageously configured to generate, in response to excitation of a current, two respective electromagnetic fields having opposite first and second field directions in two adjacent regions, thereby inducing two respective eddy currents flowing in opposite current directions in two portions of the conductive structure respectively located in the vicinity of the two adjacent regions.

The loop antenna system includes a plurality of loop antennas having overlapping portions.

This allows to reduce or even eliminate the final blind spot.

The conductive structure may be located above or below or beside or around the loop antenna system.

The conductive structure may include an example metal shield surrounding the loop antenna system.

The conductive structure may also comprise, for example, a metal housing having an aperture closed by a support supporting the loop antenna system.

According to another embodiment, a communication system is proposed, comprising a device as described above and a near field communication NFC transponder, the transponder comprising a support supporting an electrically conductive NFC loop antenna system intended to face an NFC loop antenna system of an NFC reader, the antenna loop system of the NFC transponder having the same geometry as the antenna loop system of the NFC reader.

The geometry of the antenna loop system of the NFC transponder may be configured to extract the individual common NFC operating current in response to excitation of a plurality of electromagnetic fields generated by the NFC reader having an NFC carrier frequency and respective different field directions.

According to another embodiment, a near field communication, NFC, reader is presented comprising a support supporting an electrical NFC loop antenna system having the above-mentioned features, and a component configured to energize the loop antenna system with a current.

According to another embodiment, a near field communication NFC transponder is proposed, comprising a support for supporting an antenna loop system having the above-mentioned features.

According to another embodiment, a near field communication, NFC, transponder is presented comprising a cradle supporting an antenna loop system having a geometry configured to extract individual common NFC operating currents in response to excitation of a plurality of electromagnetic fields having NFC carrier frequencies and respective different field directions.

According to another embodiment, an NFC antenna assembly is proposed comprising a support for an electrical loop antenna system having the above-mentioned features.

The NFC antenna component may belong to an NFC reader.

According to another embodiment, an NFC antenna assembly of an NFC transponder is presented, comprising an electrical loop antenna system having a geometry similar to the geometry of the electrical loop antenna system of the antenna assembly of the NFC reader described above.

According to another embodiment, a method is presented comprising:

exciting a conductive NFC loop antenna system located in proximity to the conductive structure with a current,

-said loop antenna system being responsive to excitation of said current and due to its geometry generating a plurality of electromagnetic fields having NFC carrier frequency and respective different field directions, so as to induce mutually cancelling respective eddy currents in the conductive structure.

The electrical NFC loop antenna system used in the method may advantageously have the features defined above.

According to another embodiment, a method comprises:

exciting a conductive NFC loop antenna system with a plurality of electromagnetic fields having NFC carrier frequencies and respective different field directions,

-said antenna loop system generating individual common NFC operating currents in response to excitation of said plurality of electromagnetic fields and due to its geometry.

In other words, according to the features defined above, the loop antenna system advantageously has a geometry configured to generate a plurality of electromagnetic fields having NFC carrier frequencies and respective different field directions in response to excitation of the current.

The loop antenna system may have a geometry configured to define a plurality (preferably even) of regions and to generate an electromagnetic field in each region in response to excitation by a current, the electromagnetic field having a first field direction perpendicular to the regions or a second field direction opposite to the first field direction.

The even number is greater than or equal to 2, for example equal to 4.

The loop antenna system may be configured to define a loop antenna subsystem for each region.

Each loop antenna subsystem may include one or more turns.

The loop antenna system may include one or more loop antennas.

For example, a loop antenna system includes one loop antenna having a track including loop segments in each region for defining the loop antenna subsystem.

In such an embodiment, each ring segment may be configured to generate two respective electromagnetic fields having opposite first and second field directions in two adjacent regions having a common edge in response to an excitation of a current.

The loop antenna system may also include a plurality of loop antennas, each loop antenna having a track including a loop segment for defining at least one region of a corresponding loop antenna subsystem.

For example, each loop antenna has a track that includes loop segments in a plurality of regions for defining a respective loop antenna subsystem.

In such an embodiment, each loop segment of the corresponding loop antenna is configured to generate two respective electromagnetic fields having opposite first and second field directions in two adjacent regions in response to an excitation of a current.

The loop antenna system may include a plurality of loop antennas having overlapping portions.

The loop antenna system may operate in a differential mode or in at least one single-ended mode or sequentially in three different modes including a differential mode and two different single-ended modes.

Drawings

Other advantages and features of the application will appear in the following detailed description and accompanying drawings, which are not limiting, in which:

fig. 1 shows a device operating as an NFC reader;

FIG. 2 illustrates a method of generating mutually offset vortices;

fig. 3 shows a loop antenna system according to an embodiment;

FIG. 4 illustrates a loop antenna system in accordance with certain embodiments;

fig. 5 illustrates a loop antenna system in accordance with other particular embodiments;

fig. 6 shows a loop antenna system according to a further embodiment;

FIG. 7 illustrates a metal track according to an embodiment;

FIG. 8 illustrates a metal track according to other embodiments;

figures 9-11 illustrate loop antenna systems of other embodiments;

FIG. 12 illustrates different modes of operation according to an embodiment;

FIG. 13 illustrates a conductive structure according to an embodiment;

FIG. 14 illustrates an assembly according to an embodiment;

fig. 15 shows a metal plate according to an embodiment;

fig. 16 illustrates an NFC transponder including an electrically conductive NFC loop antenna system in accordance with one embodiment; and

fig. 17 schematically illustrates one embodiment of an NFC loop antenna system.

Detailed Description

In fig. 1, a communication device that operates as an NFC reader is designated with reference to APP.

Alternatively, the device may be a portable computer.

The device APP comprises a wireless component CMP of NFC type, for example an NFC microcontroller.

The microcontroller CMP comprises terminals RFO1, RFO2 for transmitting information to the transponder TG and two further terminals RFI1, RFI2 which can be used for receiving information from the transponder.

The reader APP is equipped with an NFC loop antenna system ANT comprising at least one coil CLO having an inductance value Lp, a resistance value rp_ant and a capacitance value Cp.

The or each coil CLO has two terminals B1 and B2, coupled to terminals RFO2 and RFO1, respectively, by a conventional matching circuit MC including an EMI filter (EMI: electromagnetic interference).

In fig. 1, the representation of the loop antenna system ANT is very straightforward. More precision in the design/geometry of the loop antenna system ANT will be given hereinafter.

Furthermore, for reasons of simplicity, the connection of the matching circuit MC to the terminals RFI1 and RFI2 is not shown.

The resistance, capacitance and inductance values of the different components of the antenna system ANT and the matching circuit MC are chosen such that the antenna system ANT forms a resonant circuit with a resonance frequency equal to the NFC carrier frequency, typically 13.56MHz.

Thus, when the antenna system ANT is supplied by the component CMP and is excited by a current having a frequency equal to said NFC carrier frequency (for example 13.56 MHz), it induces an electromagnetic field at the resonant antenna ANT.

And when the antenna system is located in the vicinity of the conductive structure, the NFC antenna system ANT, which is excited by a current having the NFC carrier frequency, generates an electromagnetic field in the conductive structure that induces eddy currents.

And in general, as shown in fig. 2, when the loop antenna system is excited by a current having a frequency equal to the NFC carrier frequency (step ST 20), the loop antenna system generates (step ST 21) a plurality of electromagnetic fields having the same power, the NFC carrier frequency, but respectively different directions due to its geometry.

These electromagnetic fields induce (step ST 22) respective eddy currents in the conductive structure that cancel each other out (step ST 23).

These eddy currents will therefore reduce or even not cause losses that prevent the reader from generating a sufficiently strong magnetic field to read the transponder.

The loop antenna system LANTS has a geometry configured to define an even number of regions and to generate an electromagnetic field in each region in response to excitation of a current, the electromagnetic field having a first field direction perpendicular to the region or a second field direction opposite the first field direction, thereby inducing eddy currents in the conductive structure flowing in different current directions such that the eddy currents cancel each other out.

The loop antenna system is configured to define a loop antenna subsystem for each region.

Each loop antenna subsystem includes one or more turns.

And the loop antenna system may include one or more loop antennas.

Referring now more particularly to fig. 3, fig. 3 diagrammatically shows a first embodiment of a loop antenna system LANTS.

In this embodiment, the loop antenna system comprises a loop antenna supported by an electrically insulating support or substrate SB and surrounded by a metal plate or shield MTST forming an electrically conductive structure.

The loop antenna has a metal track TRK, for example copper, meandered along the support SB on two metal layers for defining four areas AR1, AR2, AR3, AR4 here.

For example, a portion of the track TRK in the solid line is located on the metal layer 2, and a portion of the track TRK in the broken line is located in the metal layer 1. Conventional vias allow a connection to be established between the portion on metal layer 1 and the portion on metal layer 2.

The metal track comprises a loop segment in each region for defining a loop antenna subsystem LANTSB1-LANTSB4 for each region ARi.

Each annular segment has one turn.

Both ends of the metal track TRK form two terminals B1 and B2 of the loop antenna.

Here, the areas AR1 and AR2 have a common side (horizontal side in fig. 3).

The areas AR3 and AR4 have a common side (horizontal side in fig. 3).

The areas AR1 and AR4 have a common side (vertical side in fig. 3).

The areas AR2 and AR3 have a common side (vertical side in fig. 3).

The areas AR1 and AR4 have no common edge.

When the loop antenna is energized by a current CR, the current CR passes through the metal track from terminal B1 to terminal B2 according to the illustrated arrow.

And each ring segment is configured to generate two respective electromagnetic fields having opposite first and second field directions FDIR1, FDIR2 in two adjacent regions having a common side in response to an excitation of the current CR.

More precisely, in the region AR1, the generated electromagnetic field FLD1 has the second field direction FDIR2.

In the region AR2, the generated electromagnetic field FLD2 has the first field direction FDIR1.

In the region AR3, the generated electromagnetic field FLD3 has the second field direction FDIR2.

In the region AR4, the generated electromagnetic field FLD4 has the first field direction FDIR1.

The generated electromagnetic field FLD1 induces an eddy current ED1 flowing in the second current direction CDIR2 in the portion MTST1 of the metal plate MTST adjacent to the area AR 1.

The generated electromagnetic field FLD2 induces an eddy current ED2 in the portion MTST2 of the metal plate MTST adjacent to the area AR2, which eddy current ED2 flows in the first current direction CDIR1 opposite to the second current direction CDIR 2.

The generated electromagnetic field FLD3 induces eddy currents ED3 flowing in the second current direction CDIR2 in the portion MTST3 of the metal plate MTST adjacent to the area AR 3.

The generated electromagnetic field FLD4 induces an eddy current ED1 flowing in the first current direction CDIR1 in a portion MTST4 of the metal plate MTST adjacent to the area AR4.

These vortices cancel each other out.

It should be noted that in the part mtti of the metal plate adjacent to the region ARi there is an external electromagnetic field having a field direction opposite to the field direction of the field FLDi generated in this region ARi.

And the sum of all external electromagnetic fields is zero or approximately zero.

As shown in fig. 4, the loop antenna system LANTS of fig. 3 is used with a differential architecture.

More precisely, the matching circuit MC comprises an inductive element Lemc1 connected in series with the capacitor Cser1 between the terminal RFO1 and the terminal B1 of the antenna, and an inductive element Lemc2 connected in series with the capacitor Cser2 between the terminal RFO2 and the terminal B2 of the antenna.

The matching circuit further comprises two further capacitors Cemc1 and Cemc2 connected in series between the common node of Lemc1 and Cser1 and the common node of Lemc2 and Cser 2.

The common node of Cemc1 and Cemc2 is connected to ground GND.

The two capacitors Cp1 and Cp2 connected in series between the two antenna terminals B1 and B2 and having a common node connected to the ground GND represent the capacitance value of the antenna.

We now refer more specifically to fig. 5-8, which diagrammatically show a second embodiment of a loop antenna system LANTS.

In this embodiment, the loop antenna system LANTS comprises (fig. 5) two loop antennas ANT1 (solid line), ANT2 (dashed line) supported by an electrically insulating support or substrate SB and surrounded by a metal plate or shield MTST forming an electrically conductive structure.

The two antennas ANT1, ANT2 have overlapping portions, which allows reducing or even eliminating blind spots.

The two antennas again define four areas AR1-AR4.

As shown in fig. 6, the antenna ANT1 has a metal track TRK1, and the antenna ANT2 has a metal track TRK2.

Each track TRK1, TRK2, for example a copper track, meanders on two metal layers along the support SB for defining four areas AR1, AR2, AR3, AR4 therein.

For example, in fig. 6, portions of the solid line tracks TRK1, TRK2 are on the metal layer 2, and portions of the broken line tracks TRK1, TRK2 are in the metal layer 1. Conventional vias allow a connection to be established between the portion on metal layer 1 and the portion on metal layer 2.

Fig. 7 shows a diagram of the metal track TRK1 of the antenna ANT1, and fig. 8 shows a diagram of the metal track TRK2 of the antenna ANT 2.

The metal track TRK1 comprises loop segments in the areas AR1 and AR3 for defining loop antenna subsystems LANTSB1-LANTSB3 of the areas AR1 and AR 3.

Each loop segment has two turns.

The region AR1 and the region AR3 are adjacent regions of the loop antenna ANT 1.

Two ends of the metal track TRK1 form two terminals B1 and B3 of the loop antenna ANT 1.

The metal track TRK2 comprises loop segments in the areas AR2 and AR4 for defining loop antenna subsystems LANTSB2-LANTSB4 of the areas AR2 and AR4.

Each loop segment has two turns.

The region AR2 and the region AR4 are adjacent regions of the loop antenna ANT 1.

Both ends of the metal track TRK2 form two terminals B2 and B3 of the loop antenna ANT 1.

Terminal B3 is common to antennas ANT1 and AANT 2.

In fig. 6 to 8, arrows on the tracks TRK1 and TRK2 show currents flowing in the antenna when the antenna is excited by the currents.

Each loop segment of the corresponding loop antenna is configured to generate, in response to an excitation of a current, two respective electromagnetic fields having opposite first and second field directions in two adjacent regions, thereby inducing two respective eddy currents flowing in opposite current directions in two portions of the conductive structure respectively located in the vicinity of the two adjacent regions.

More precisely, each loop segment of the antenna ANT1 is configured to generate, in response to an excitation of a current, two respective electromagnetic fields FLD1, FLD2 having opposite second and first field directions FDIR2, FDIR1 in two adjacent regions AR1 and AR2, so as to induce, in two portions MTST1, MTST3 of the conductive structure located in the vicinity of the two adjacent regions AR1, AR3, respectively, two respective eddy currents ED1, ED3 flowing in opposite current directions CDIR2, CDIR 1.

Each loop segment of the antenna ANT2 is configured to generate, in response to an excitation of a current, two respective electromagnetic fields FLD2, FLD4 having opposite first and second field directions FDIR1, FDIR2 in two adjacent regions AR2, AR4, so as to induce, in two portions MTST2, MTST4 of the conductive structure located in the vicinity of the two adjacent regions AR2, AR4, respectively, two respective eddy currents ED2, ED4 flowing in opposite current directions CDIR1, CDIR 2.

These vortices cancel each other out.

As shown in fig. 9, the loop antenna system LANTS of fig. 3 is used with a differential architecture.

More precisely, the same matching circuit MC as that disclosed with reference to fig. 4 is connected to the terminal B1 of the antenna ANT1 and the terminal B2 of the antenna ANT 2.

The common terminal B3 of the antennas ANT1 and ANT2 is connected to the ground GND.

As shown in fig. 10, the loop antenna system LANTS of fig. 3 may also be used with a single-ended architecture using an antenna ANT 1.

More precisely, in this case, only the terminal RFO1 of the microcontroller CMP cooperates (e.g. activates, operates, drives, … …) with the terminal B1 of the antenna ANT1 through the corresponding first portion Lemc1, cemc1, cser1 of the matching circuit, and the terminal B3 connects the antenna ANT1 to the ground GND.

Terminal RFO2 is in an inactive state.

As shown in fig. 11, the loop antenna system LANTS of fig. 3 may also be used with a single-ended architecture using an antenna ANT 2.

More precisely, in this case, only the terminal RFO2 of the microcontroller CMP cooperates with the terminal B2 of the antenna ANT2 through the respective second portions Lemc2, cemc2, cser2 of the matching circuit, and the terminal B3 connects the antenna ANT2 to the ground GND.

Terminal RFO1 is in an inactive state.

By using switches connected to these terminals and controlled by the microcontroller CMP, it is for example possible to implement activation or deactivation of the terminals RFO1/RFO2, to use a differential architecture or one of two possible single-ended architectures.

The component CMP may also have such a "switching" function built in. In this case, in a single ended architecture or mode, only one terminal RFOi is driven while the other RFO terminal is held at the supply voltage or ground.

These three possible architectures or modes (differential, single ended with RFO1, single ended with RFO 2) can be operated sequentially in order to increase the coverage of the generated electromagnetic field while reducing or even omitting blind spots in the differential structure.

An example of such a sequence is shown in fig. 12.

In step S120, the differential mode is operated.

In step S121, the single-ended mode with RFO1 is then operated.

In step S122, the single-ended mode with RFO2 is then operated.

Of course this order may be changed.

As shown in fig. 13, the conductive structure may be a metal plate MTST10 located above a substrate SB of the loop antenna system, and/or a metal plate MTST20 located around the substrate and/or a metal plate MTST40 located below the substrate and/or a metal housing MTST30 having a hole APT enclosed by the substrate, as shown more particularly in fig. 14.

In fig. 14, the components CMP of the reader may be located inside or outside the housing MTST 30.

As shown in fig. 15, the metal plate MTST20 may form a metal shield, which may further include a screen SCR and LEDs LD1-LD3.

In summary, embodiments provide an antenna loop system having a geometry configured to generate, in response to excitation of a current, several electromagnetic fields having NFC carrier frequencies and respective different field directions, the electromagnetic fields being adapted to induce respective mutually cancelling eddy currents in a conductive structure, which in particular allows reducing or even not causing losses, thereby preventing a reader from generating a sufficiently strong magnetic field to read a transponder TG (fig. 1).

We now turn to the operation of the near field communication NFC transponder TG in wireless communication with the NFC reader of these embodiments using antenna assemblies.

In the first case, the overall size of the NFC loop antenna system of the NFC transponder TG is much smaller than the size of the NFC loop antenna system LANTS of the NFC reader APP. For example, the size of the NFC loop antenna system of the NFC transponder TG is smaller than or about the size of the individual areas AR1-AR4 of the plurality of areas AR1-AR4.

In the first case, it is assumed that the NFC loop antenna system of the transponder faces only one area AR1-AR4 at a time (at least in most cases) when facing the NFC loop antenna system rants of the NFC reader APP.

Thus, when the sum of all external electromagnetic fields is zero or approximately zero, the NFC loop antenna system of the transponder is exposed to a local electromagnetic field having the first field direction FDIR1 or the second field direction FDIR2 without mutual compensation.

Thus, in the first case, the NFC transponder TG may comprise a conventional loop antenna. For example, a conventional loop antenna may include a single loop segment having at least one turn, typically several turns in a helical path.

In the second case, the overall dimensions of the NFC transponder TG and its NFC loop antenna system are approximately the same as the dimensions of the NFC loop antenna system LANTS of the NFC reader APP.

In the second case, it is considered that when facing the NFC loop antenna system LANTS of the NFC reader APP, the NFC loop antenna system of the transponder may face several of the plurality of areas AR1-AR4 simultaneously.

The NFC loop antenna system of the transponder can thus be exposed to at least two mutually canceling electromagnetic fields, having a first field direction FDIR1 and a second field direction FDIR2, respectively.

Thus, as schematically illustrated in fig. 16, in the second case, the NFC transponder TG advantageously comprises a conductive NFC loop antenna system tg_lants which, when excited by several electromagnetic fields having an NFC carrier frequency and respectively different field directions (step ST 30) (from step ST 21-fig. 2), extracts (i.e. generates) a single common NFC operating current due to its geometry (step ST 31).

Fig. 17 schematically shows an embodiment of said advantageous NFC loop antenna system tg_lans for an NFC transponder TG, which is suitable for carrying out the steps ST30, ST31 shown in fig. 16.

In practice, this antenna loop system tg_lans of the NFC transponder TG is advantageously provided with the same geometry as the loop system lans of the NFC reader APP intended to face it for performing near field communication NFC.

Thus, in this example embodiment, the antenna loop system tg_lans of the NFC transponder TG has the same geometry as the first embodiment of the antenna loop system lans of the NFC reader APP disclosed with reference to fig. 3.

For the same subject matter, the same reference numerals as in fig. 3 are used, and the structural description of these common subject matters related to fig. 3 applies to fig. 17.

In an alternative embodiment, the NFC loop antenna system tg_lants of the NFC transponder TG may have the same geometry as the second embodiment of the antenna loop system LANTS of the NFC reader APP disclosed with reference to fig. 5-8.

Thus, when the NFC transponder TG faces the NFC reader APP, the transponder's antenna loop system tg_lants is exposed to said plurality of electromagnetic fields FLD1-FLD4 with respective different field directions FDIR1, FDIR2.

Since the geometry of the transponder antenna loop system tg_lans corresponds to the geometry of the reader antenna loop system lans, the respective electromagnetic fields FLD1-FLD4 each locally excite a respective region AR1-AR4 of the transponder antenna loop system tg_lans.

The respective opposite field directions FDIR1, FDIR2 thus each induce a current flowing in the respective directions, e.g. clockwise of the first field direction FDIR1 and counter-clockwise of the second field direction FDIRE2, by electromagnetic coupling.

Due to the geometry of the transponder's antenna loop system tg_lans, the respectively induced currents are all drawn in the same direction of the antenna system, which results in a separate common NFC operating current being drawn and flowing e.g. from terminal B1 to terminal B2.

That is, if the transponder TG is flipped or rotated 90 degrees (in this example), the resulting individual common NFC operating current tg_cr flows in the opposite direction, but in the same manner.

The NFC operating current tg_cr has a frequency equal to said NFC carrier frequency and can be used for powering the transponder TG and for example for back-modulating the electromagnetic field of the reader APP.

Thus, according to an embodiment of the loop antenna system tg_lans of the NFC transponder TG:

the loop antenna system tg_lants may be configured to define loop antenna subsystems LANTSB1-LANTSB4 for each region AR1-AR4.

Each loop antenna subsystem LANTSB1 to LANTSB4 may comprise one or more turns.

The loop antenna system tg_lans may comprise one or more loop antennas.

The loop antenna system tg_lans may comprise a loop antenna with a track TRK comprising loop segments in each of the areas AR1-AR4 for defining the loop antenna subsystem.

Each loop segment may be configured to draw said separate common NFC operation current tg_cr in two adjacent regions (e.g. regions AR3, AR 4) having a common edge in response to excitation of two respective electromagnetic fields (e.g. fields FLD3-FDIR2, FDL4-FDIR 1) having opposite first and second field directions.

In the alternative, for example with respect to the second embodiment shown in fig. 5-8:

the loop antenna system tg_lans may comprise a plurality of loop antennas ANT1, ANT2, each loop antenna having a track comprising loop segments in at least one region for defining a respective loop antenna subsystem.

Each loop antenna may have a track TRK1, TRK2 (fig. 6-8) comprising loop segments in several areas for defining the respective loop antenna subsystem.

Each loop segment of the corresponding loop antenna may be configured to draw said separate common NFC operating current tg_cr in two adjacent areas in response to excitation of two respective electromagnetic fields having opposite first and second field directions.

The loop antenna system tg_lans may comprise several loop antennas ANT1, ANT2 with overlapping portions OVLP (fig. 6-8).

The number of said areas AR1-AR4 may be an even number greater than or equal to 2, for example equal to 4.

Claims

1. An apparatus, comprising:

a conductive structure;

a near field communication, NFC, reader comprising a support supporting an electrically conductive NFC loop antenna system located in proximity to the electrically conductive structure; and

a component configured to energize the loop antenna system with a current,

wherein the loop antenna system has a geometry configured to generate a plurality of electromagnetic fields in response to excitation of the current, the electromagnetic fields having NFC carrier frequencies and respective different field directions adapted to induce respective eddy currents in the conductive structure that cancel each other.

2. The apparatus according to claim 1,

wherein the geometry of the loop antenna system is configured to:

defining a number of regions, and

in response to the excitation of the current, an electromagnetic field is generated in each region, the electromagnetic field having a first field direction perpendicular to the respective region or a second field direction opposite to the first field direction, thereby inducing the eddy currents flowing in the conductive structure in different current directions such that the eddy currents cancel each other.

3. The apparatus of claim 2, wherein the loop antenna system is configured to define a loop antenna subsystem for each region.

4. The apparatus of claim 3, wherein each loop antenna subsystem comprises one or more turns.

5. The apparatus of claim 4, wherein the loop antenna system comprises one or more loop antennas.

6. The apparatus of claim 5, wherein the loop antenna system comprises a plurality of loop antennas having overlapping portions.

7. The apparatus of claim 2, wherein the number is an even number greater than or equal to 2.

8. The apparatus of claim 7, wherein the even number is equal to 4.

9. The apparatus of claim 1, wherein the loop antenna system comprises one loop antenna having a track comprising loop segments in each region.

10. The apparatus of claim 9, wherein each ring segment is configured to generate, in response to excitation of the current, two respective electromagnetic fields having opposite first and second field directions in two adjacent regions having a common edge, thereby inducing two respective eddy currents in two portions of the conductive structure located respectively in the vicinity of the two adjacent regions that flow in opposite current directions.

11. The apparatus of claim 1, wherein the loop antenna system comprises a plurality of loop antennas, each loop antenna having a track comprising loop segments in at least one region.

12. The apparatus of claim 11, wherein the track comprises annular segments in a plurality of regions.

13. The apparatus of claim 12, wherein each loop segment of a corresponding loop antenna is configured to generate two respective electromagnetic fields having opposite first and second field directions in two adjacent regions in response to excitation of the current, thereby inducing two respective eddy currents in two portions of the conductive structure located respectively in the vicinity of the two adjacent regions that flow in opposite current directions.

14. The apparatus of claim 1, wherein the conductive structure is located above or below the loop antenna system.

15. The apparatus of claim 14, wherein the conductive structure comprises a metal shield surrounding the loop antenna system.

16. The apparatus of claim 14, wherein the conductive structure comprises a metal housing having an aperture closed by the loop antenna system.

17. A communication system, comprising:

the apparatus of claim 1; and

an NFC transponder comprising a support supporting an electrically conductive NFC loop antenna system of the NFC loop antenna system facing the NFC reader,

wherein the antenna loop system of the NFC transponder has the same geometry as the antenna loop system of the NFC reader.

18. The communication system of claim 17, wherein a geometry of the antenna loop system of the transponder is configured to induce a separate common NFC operational current in response to excitation of the plurality of electromagnetic fields with the NFC carrier frequency and respective different field directions produced by the NFC reader.

19. A near field communication, NFC, reader comprising:

a support supporting the conductive NFC loop antenna system; and

a component configured to energize the loop antenna system with a current,

20. A near field communication, NFC, transponder comprising:

a support supporting a loop antenna system having a geometry configured to induce a separate common NFC operational current in the NFC transponder in response to excitation of a plurality of electromagnetic fields having an NFC carrier frequency and respective different field directions.

21. A method, comprising:

exciting a conductive near field communication, NFC, loop antenna system with a current, the NFC loop antenna system being located in proximity to a conductive structure; and

a plurality of electromagnetic fields having NFC carrier frequencies and respective different field directions are generated by the loop antenna system in response to excitation of the current and due to geometry of the loop antenna system, thereby inducing respective eddy currents in the conductive structure that cancel each other.

22. The method of claim 21, wherein the loop antenna system operates in a differential mode or in at least one single-ended mode, or wherein the loop antenna system is operated in three different modes, including a differential mode and two different single-ended modes.

23. A method, comprising:

exciting a conductive NFC loop antenna system with a plurality of electromagnetic fields having a near field communication NFC carrier frequency and respective different field directions; and

a separate common NFC operating current is induced in the NFC transponder in response to excitation of the plurality of electromagnetic fields and due to the geometry of the conductive NFC loop antenna system.