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Title:
ANTENNA SYSTEM WITH TWO SOLENOID ANTENNAS, MAINLY FOR NFC RECEPTION AND TRANSMISSION
Document Type and Number:
WIPO Patent Application WO/2020/174385
Kind Code:
A1
Abstract:
The antenna system has a shorter first solenoid antenna (1) and longer second solenoid antenna (2), both with magnetic core. The first solenoid antenna (1) is placed against the second solenoid antenna (2) in such a way that they are mutually parallel and the center of the first solenoid antenna (1) is on the level of the first thread (3) of the second solenoid antenna (2). The distance "a" (mm) between the transverse axes a1 and a2 of the solenoid antennas (1, 2) is a=L/2 - x where L (mm) is the length of the core of the second solenoid antenna (1, 2) and x ranges from 1 mm to 4 mm. First and/or second solenoid antenna (1, 2) can have threads formed by multiple placement of the wound circular conductor side by side or it can have threads formed by the wire bonding. The exact mutual position of the solenoid antennas (1, 2) can be chosen pursuant to the electromagnetic influence of the surrounding environment. The ratio of the first solenoid antenna's (1) length to the second solenoid antenna's (2) length ranges from 1:1,1 to 1:4, preferably from 1:2 to 1:3.

Inventors:
HUBINÁK EMIL (SK)
TRÁVNÍČEK PAVEL (CZ)
Application Number:
PCT/IB2020/051588
Publication Date:
September 03, 2020
Filing Date:
February 25, 2020
Export Citation:
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Assignee:
LOGOMOTION SRO (SK)
International Classes:
H01Q1/52; G06K7/10; H01Q7/08; H04B5/00
Foreign References:
US20140333402A12014-11-13
US20150325918A12015-11-12
US20140176384A12014-06-26
Attorney, Agent or Firm:
PORUBČAN, Róbert (SK)
Download PDF:
Claims:
PATE N T C LA I MS

1. An antenna system with two solenoid antennas, mainly for an NFC reception and transmission, where both solenoid antennas (1, 2) have a magnetic core and they are placed in same base plane or in mutually parallel base planes, and where the solenoid antennas (1, 2) are designed for a connection to their own excitation elements, is characterized by the fact, that

the first solenoid antenna (1) is shorter than the second solenoid antenna

(2);

both solenoid antennas (1, 2) have parallel longitudinal axes;

a distance between the longitudinal axes is not more than four times a width of the core of the second solenoid antenna (2);

and a longitudinal center of the first solenoid antenna’s (1) core is on a level of a first thread (3) of the second solenoid antenna.

2. The antenna system with two solenoid antennas, mainly for NFC reception and transmission according to the claim 1 i s characterized by the fact, that length of the first solenoid antenna (1 ) is no more than 10 mm.

3. The antenna system with two solenoid antennas, mainly for NFC reception and transmission according to the claim 1 or 2 is characterized by the fact, that length of the second solenoid antenna (2) is no more than 30 mm.

4. The antenna system with two solenoid antennas, mainly for NFC reception and transmission according to any of the claims 1 to 3 i s characterized by the fact, that the first and/or the second solenoid antenna (1, 2) have threads formed by a multiple placement of a wound circular conductor side by side, preferably the number of wound conductors within a single thread ranges from 6 to 10, especially preferably it is 6 in case of the first solenoid antenna (1) and 9 in case of the second solenoid antenna (2).

5. The antenna system with two solenoid antennas, mainly for NFC reception and transmission according to any of the claims 1 to 4 i s characterized by the fact, that ratio of the first solenoid antenna’s (1) length to the second solenoid antenna’s (2) length ranges from 1:1,1 to 1:4, preferably from 1 :2 to 1 :3.

6. The antenna system with two solenoid antennas, mainly for NFC reception and transmission according to any of the claims 1 to 5 i s characterized by the fa ct , that ratio of the number of threads of the first solenoid antenna (1) to the number of threads of the second solenoid antenna (2) ranges from 1 :0,7 to 1:1,3.

7. The antenna system with two solenoid antennas, mainly for NFC reception and transmission according to any of the claims 1, 2, 3, 5 and 6 is characterized by the fa ct , that the first solenoid antenna (1) and/or the second solenoid antenna (2) has the threads formed by a wire bonding, whereby the wire envelops the core placed on a board with small conductive surfaces.

8. The antenna system with two solenoid antennas, mainly for NFC reception and transmission according to any of the claims 1 to 7 i s characterized by the fact, that between the threads of the second solenoid antenna (2) on the core there are even gaps, whereby size of the gaps ranges from 0,2 mm to 0,7 mm, preferably 0,25 mm to 0,58 mm.

9. The antenna system with two solenoid antennas, mainly for NFC reception and transmission according to any of the claims 1 to 8 is characterized by the fact, that a distance of the longitudinal axes of the first and the second solenoid antenna (1, 2) is no more than 4 mm, preferably it is 2,6 mm ± 1 mm.

10. The antenna system with two solenoid antennas, mainly for NFC reception and transmission according to any of the claims 1 to 9 i s characterized by the fact, that a distance“a” (mm) between transverse axes“a1” and“a2” of the solenoid antennas (1 , 2) is a = L/2 - x, where L (mm) is a length of the core of the second solenoid antenna (2) and x ranges from 1 mm to 4 mm, preferably x = 3 mm.

11. The antenna system with two solenoid antennas, mainly for NFC reception and transmission according to any of the claims 1 to 10 is characterized by the fact, that resulting value of an inductance of the second solenoid antenna (2) ranges from 1,0 to 1,5 pH and quality Q = 20 to 25.

12. The antenna system with two solenoid antennas, mainly for NFC reception and transmission according to any of the claims 1 to 11 is characterized by the fact, that mutual position of the solenoid antennas (1 , 2) is chosen pursuant to an electromagnetic influence of surrounding environment, whereby a center of the first solenoid antenna (1) is set by tuning, at an NFC frequency, in an intersection of bands Aa - Ab.

13. The antenna system with two solenoid antennas, mainly for NFC reception and transmission according to any of the claims 1 to 12 is characterized by the fa ct , that the first solenoid antenna (1) is connected through a reception’s adaptation circuit (6) to an NFC controller (7) and the second solenoid antenna (2) is connected through a transmission’s adaptation circuit (5) to the identical NFC controller (7).

14. The antenna system with two solenoid antennas, mainly for NFC reception and transmission according to any of the claims 1 to 13 is characterized by the fa ct , that the first solenoid antenna (1) and/or the second solenoid antenna (2) are placed on a PCB (4) together with the adaptation circuits (6, 5).

AMENDED CLAIMS

received by the International Bureau on 12 Aug 2020 (12.08.20)

1. An antenna system with two solenoid antennas, mainly for an NFC reception and transmission, where both solenoid antennas (1, 2) have a magnetic core and they are placed in same base plane or in mutually parallel base planes, where the first solenoid antenna (1) is designed for receiving and the second solenoid antenna (2) is designed for transmitting, and where the first solenoid antenna (1) is shorter than the second solenoid antenna (2); is characterized by the fact, that

both solenoid antennas (1, 2) have parallel longitudinal axes;

a distance between the longitudinal axes is not more than four times a width of the core of the second solenoid antenna (2);

and a longitudinal center of the first solenoid antenna’s (1) core is on a level of a first thread (3) of the second solenoid antenna.

2. The antenna system according to the claim 1 i s characterized by the fact, that length of the first solenoid antenna (1 ) is no more than 10 mm.

3. The antenna system according to the claim 1 or2is characterized by the fact, that length of the second solenoid antenna (2) is no more than 30 mm.

4. The antenna system according to any of the claims 1 to 3 i s characterized by the fact, that the first and/or the second solenoid antenna (1, 2) have threads formed by a multiple placement of a wound circular conductor side by side, preferably the number of wound conductors within a single thread ranges from 6 to 10, especially preferably it is 6 in case of the first solenoid antenna (1) and 9 in case of the second solenoid antenna (2).

5. The antenna system according to any of the claims 1 to 4 i s characterized by the fact, that ratio of the first solenoid antenna’s (1) length to the second solenoid antenna’s (2) length ranges from 1:1,1 to 1:4, preferably from 1 :2 to 1 :3.

6. The antenna system according to any of the claims 1 to 5 i s characterized by the fa ct , that ratio of the number of threads of the first solenoid antenna (1) to the number of threads of the second solenoid antenna (2) ranges from 1 :0,7 to 1:1,3.

7. The antenna system according to any of the claims 1, 2, 3, 5 and 6 i s characterized by the fact, that the first solenoid antenna (1) and/or the second solenoid antenna (2) has the threads formed by a wire bonding, whereby the wire envelops the core placed on a board with small conductive surfaces.

8. The antenna system according to any of the claims 1 to 7 i s characterized by the fact, that between the threads of the second solenoid antenna (2) on the core there are even gaps, whereby size of the gaps ranges from 0,2 mm to 0,7 mm, preferably 0,25 mm to 0,58 mm.

9. The antenna system with two solenoid antennas, mainly for NFC reception and transmission according to any of the claims 1 to 8 is characterized by the fact, that a distance of the longitudinal axes of the first and the second solenoid antenna (1, 2) is no more than 4 mm, preferably it is 2,6 mm ± 1 mm.

10. The antenna system according to any of the claims 1 to 9 i s characterized by the fact, that a distance “a” between transverse axes“a1” and“a2” of the solenoid antennas (1 , 2) is a = L/2 - x, where L is a length of the core of the second solenoid antenna (2) and x ranges from 1 mm to 4 mm, preferably x = 3 mm.

11. The antenna system according to any of the claims 1 to 10 is characterized by the fact, that resulting value of an inductance of the second solenoid antenna (2) ranges from 1,0 to 1,5 mH and quality Q = 20 to 25.

12. The antenna system according to any of the claims 1 to 11 is characterized by the fact, that mutual position of the solenoid antennas (1 , 2) is chosen pursuant to an electromagnetic influence of surrounding environment, whereby a center of the first solenoid antenna (1) is set by tuning, at an NFC frequency, in an intersection of bands Aa - Ab.

13. The antenna system according to any of the claims 1 to 12 is characterized by the fact, that the first solenoid antenna (1) is connected through a reception’s adaptation circuit (6) to an NFC controller (7) and the second solenoid antenna (2) is connected through a transmission’s adaptation circuit (5) to the identical NFC controller (7).

14. The antenna system according to any of the claims 1 to 13 is characterized by the fact, that the first solenoid antenna (1) and/or the second solenoid antenna (2) are placed on a PCB (4) together with the adaptation circuits (6, 5).

Description:
ANTENNA SYSTEM WITH TWO SOLENOID ANTENNAS, MAINLY FOR NFC RECEPTION AND TRANSMISSION

Field of technology

The invention concerns an antenna system which has one transmitting solenoid antenna and one receiving solenoid antenna, whereby both antennas have mutual spatial arrangement which produces their mutual electromagnetic isolation while they simultaneously transmit and receive the signal. The antenna system takes up little available space on the, for example, PCB (printed-circuit board) of the mobile phone, SiP (System in Package) module, SD memory card, USB stick and so on.

Prior state of the art

During communication by means of NFC platform, mainly according to ISO/I EC 14443 one preferably uses flat spiral antennas which take up large surface, which limits the design of the printed circuit board. With sufficiently large available space the flat antenna fulfills a function of transmitting as well as receiving antenna. The disadvantage of such solution lies in the mutual interference of the transmitting and receiving part of the NFC chip. The compromise between ideal transmission and ideal reception can be addressed by increase in the flat antenna’s dimensions.

The diminishment of the antenna’s surface leads to decrease of its transmitting and receiving power and to worsening of the quality of the communication channel. In passive mode initializer/receiver (PCD) provides a carrier field and energy for the production of the transponder/receiver (PICC, for example payment card), which responds by modulation of the carrier field (load modulation).

Instead of flat receiving antenna, one can use solenoid antenna, usually with ferrite core, during the diminishment of the available space. The problem with isolation of the receiving and transmitting antenna is addressed by the publication WO2017109681 A1 which discloses the solenoid antenna with ferrite core and flat spiral antenna, whereby they are placed in the same plane, whereby the are distanced in the groundplan from each other and the magnetic center of the flat spiral antenna lies in the transverse axial plane of the solenoid antenna. This solution achieves a good mutual isolation of the antennas, but it requires relatively larger space for placement.

Pursuant to publication WO2018198082 the antenna system is formed by two solenoid antennas and a flat antenna, whereby antennas have a geometrical arrangement which allows for placement of other electronic elements in the space between the two solenoid antennas. This improves the availability of the space, but it still leads to relatively large outer dimensions of PCB pursuant to the size of the flat antenna. Majority of the solutions with the independent transmitting and receiving antenna use a flat antenna with relatively large dimensions which correspond to a standard, which provides the possibilities of radiation (emission) of a sufficient power for excitation of the transponder/receiver (PICC). If the antenna system diminishes further, the diminishment of the flat antenna leads to problems with a sufficient emitting power, which is manifested by the decrease in the distance in which the NFC channel can stably communicate.

A solution is desired and not known, which will achieve, compared to the prior art, sufficiently strong isolation of the transmitting and receiving antenna so that the influence / interference of transmitting and receiving circuits of the controller does not take place, whereby it is possible to achieve additional transmitting and receiving power of the antenna system on the small available surface, and this during simultaneous transmission and reception. A requested feature of the new solution is also its capability to operate both in CE and RW mode on both ends of the communication channel.

Essence of the invention

The abovementioned deficiencies are significantly remedied by the antenna system with two solenoid antennas, designed especially for an NFC reception and transmission, where both antennas have a magnetic core and they are placed in the same base plane, according to this invention which essence lies in the fact that the first solenoid antenna is shorter than the second solenoid antenna, both solenoid antennas have parallel longitudinal axes and the longitudinal center of the first solenoid antenna’s core is at the level of the first thread of the second solenoid antenna. The parallel nature of the longitudinal antennas means that the solenoid antennas’ cores are parallel, whereby their mutual position can deviate from being exactly parallel within an allowed production margin of error, usually up to 5°.

The term“solenoid antenna” denotes a coil with multiple windings of the conductor on the core, for example on the core of the rectangular cross- section, where the length (longitudinal dimension) of the core is more than its transverse dimension; usually the length of the coil is more than five times the diagonal of the cross-section (for example, when the cross-section of the core is rectangular). The width of the core is a transverse dimension of the core by which the core is projected into the groundplan of the antenna’s carrier, that is, onto the plane of the base. In case of the oblong cross-section of the core the core’s width is a dimension in the direction parallel with the plane of the base; in case of the circular cross-section of the core the width of the core is its diameter. The core can be ferrite or from the material with similar magnetic features. The length of the solenoid antenna denotes an overall length of the core or the core’s length covered with the conductor’s threads.

The basic feature of the invention is the mutual parallel placement of two differently long solenoid antennas, whereby the first, shorter solenoid antenna is by its longitudinal center placed at the end of the second, longer solenoid antenna. The spatial and dimensional configuration according to this invention ensures a selective non-sensitivity of the receiving antenna, which is capable of receiving the outside signal from the alien source (PCD) during active transmission of the close antenna within a common antenna system. It is not necessary to complicatedly process and filter the received signal.

Usually both solenoid antennas will be connected to the respective circuits of a single NFC chip (controller) through its own adapting (binding) elements. The first, shorter solenoid antenna serves as a receiving antenna and it is connected by means of its adapting circuit to the receiving entry into an NFC chip (RX outputs, where R denotes receiving). The second, shorter solenoid antenna serves as a transmitting antenna which is connected by means of its adapting circuit to the transmitting output of an NFC chip (TX outputs, where T denotes transmitting).

The main advantage of the proposed invention is more effective use of the potential of the output circuit of a given NFC chip and achievement of the maximum possible radiating power without the decrease of the receiving capabilities of the NFC chip by low entry signal or by interference from the transmitting part. The first solenoid antenna and the second solenoid antenna are mutually coupled by air coupling (or similar coupling through a non- conductive environment); its parameters are affected by a distance of the longitudinal axes of the solenoid antennas. During miniaturizations, where the width of the second solenoid antenna is ca. 1 to 2 mm, the distance of the longitudinal axes of both solenoid antennas will be less than 8 mm, preferably less than 4 mm, for example 2,6 mm.

If the antenna is supposed to operate in CE (Card Emulation) mode as well as in RW (Read/Write) mode, that is, if it is supposed to be capable of communicating with a reader and in another communication case the identical antenna system should form a reader for a card, there are then opposite demands placed upon the design of the antenna system. The communication counterpart in the antenna system according to this invention is a reader (PCD) or a transponder (PICC), depending on whether the antenna system according to this invention operates in CE or RW mode. One demand allows to achieve a strong link between the antenna of the communication counterpart (PCD or PICC) and both solenoid antennas, so that the transfer of the signals in both directions is as effective as possible. The second demand is opposite: it demands weak link between first and second solenoid antenna so that the transmissions do not cancel themselves out and therefore the synchronization with the reader in case of CE mode is not lost, or that the inherent entry circuits in RW mode are not excited or overexcited, respectively.

The distance of the longitudinal solenoid antennas must be sufficiently small that the given antenna system can be effectively used with any type of PCD/PICC flat (planar) antenna of the communication counterpart, but also sufficiently large so that there are no great signal crosstalk between first solenoid antenna and second solenoid antenna. If the first solenoid antenna has a length up to 10 mm and second solenoid antenna has a length up to 30 mm, the middle optimal distance of the longitudinal axes of first and second solenoid antenna b = 2,6 mm ± 1 mm.

The longitudinal center of the first solenoid antenna’s core is at the level of the thread of the second solenoid antenna. This requires a position of the center of the first solenoid antenna at the end of the second solenoid antenna’s core. The level of the first thread denotes mainly a longitudinal center of the first thread in a projection onto the longitudinal axis of the second solenoid antenna. The level of the center of the first solenoid antenna can deviate from the level of the center of the first thread; it can be by its beginning or its end, where the second thread of the second solenoid antenna begins, as depicted in figure 11.

Slight shift of the longitudinal center of the first solenoid antenna’s core against the end of the second solenoid antenna’s core as well as small changes in the distance between the longitudinal axes of the solenoid antennas can serve the purpose of fine tuning the antenna system, whereby the influence of all components on the common PCB as well as other shielding elements, too, is taken into account. The optimal level of the first solenoid antenna (receiving antenna) can move within a tolerance of 4 mm in direction of longitudinal axes and in tolerance of 2 mm concerning the dimension of the distances of the longitudinal axes. These two bands of mutually perpendicular tolerances (or margins of error) produce a rectangle which delimits the possible positions of the centers of the first solenoid antenna against the position of the second solenoid antenna. Both solenoid antennas are preferably placed in a common substrate, that is, on the same surface, for example on a single surface of the PCB or on the opposite surfaces of a single PCB. A realization is also possible, though, where the antennas are on different planes or, eventually, on independent carriers; it is important, though, that the mutually parallel arrangement with a shift of the center of one solenoid antenna against towards first thread of the other solenoid antenna, is achieved. Such placement achieves preferable use of the available space; a sufficient isolation is produced even when the antennas are basically completely close to each other. Thanks to this, a good use is made of available building space, and the transmitting power (performance) is increased, respectively.

In a preferable arrangement the antenna system includes first solenoid antenna with a flat winding of the loops, whereby its length is up to 10 mm. First solenoid antenna can have cylindrical or rectangular cross-section of the core. The cross-section of the core in a preferable miniature realization can have dimension, for example, 0,6 mm x 0,8 mm (height x width). In order to simplify the winding up of the flat conductor onto the small core with a relatively large thread pitch, a flat cross-section of the conductor can be substituted for the multiply repeated placement of the circular conductor within a single thread.

The number of threads of first solenoid antenna is usually larger or smaller than the number of threads of second solenoid antenna. For example, if the first solenoid antenna has 21 threads, the second solenoid antenna can have between 21 to 26 threads. Pursuant to the particular features (mainly permeability) of the core, the second solenoid antenna can have smaller number of threads than first solenoid antenna, usually not less than 75% of the number of threads of the first solenoid antenna. In general it holds that the number of threads of first and second solenoid antenna is not directly proportional to the number of their lengths. For example, in an arrangement where the length of the second solenoid antenna is twice the length of the first solenoid antenna, both solenoid antennas can have identical number of threads. The number of threads and their ratio will depend mainly on the permeability of the core of the first and second solenoid antenna, whereby we strive to achieve the inductance of the second solenoid antenna with the range 1 ,0 to 1 ,5 pH.

For example, in arrangement where the length of the second solenoid antenna is three times the length of the first solenoid antenna, the second solenoid antenna has 20% to 30% more threads compared to the number of threads of the first solenoid antenna. In order to effectively use the available space or surface for the placement of the antenna system, respectively, and in order to achieve the preferable ratio between the receiving features of the first solenoid antenna and the transmitting power of the second solenoid antenna, the ratio of length of the first solenoid antenna to the length of the second solenoid antenna will range from 1 :1 ,1 to 1 :4, preferably from 1 :2 to 1 :3. The ratio of the number of threads will range from 1 :0,7 to 1 :1 ,3.

The second solenoid antenna has, in preferable arrangement, flat winding of the threads, whereby there are gaps between the windings on the core. The length of the second solenoid antenna ranges up to 30 mm. During the optimization of the miniature second solenoid antenna a rectangular cross- section of the core with dimensions 0,6 mm x 1 ,6 mm (height x width) proved preferable. If the first solenoid antenna has a stable length up to 10 mm, the second solenoid antenna can - at the core’s permeability m = 80 - have dimensions and number of threads in following order:

The second solenoid antenna can have threads formed by a multistep winding of the wire, which produces a flat conductor of a single wire. In this way a conductor with a circular cross-section can achieve similar effect as is achieved in case of a wide flat conductor which is, however, problematically wound onto a small core. It is thus preferable if multiple conductors are wound by each other within a single winding; preferably the number of wound conductors within a single winding is 6 to 10, especially preferably they are 9. This achieves the desired ratio of the width of a single winding to the thickness (height) of the winding.

In the preferable arrangement a thin substrate is a component of the first and/or second solenoid antenna, whereby this substrate is wound to the bottom surface of the core during the winding of the conductor to the core. The small conductive surfaces (pads) are produced on the substrate on its ends, whereby the ends of the conductors are connected to them. The small conductive surfaces are subsequently used for connection to the PCB, preferably by means of SMD mounting (surface-mounting).

First and/or second solenoid antenna can in another arrangement have windings formed by wire bonding. The wire can be flat or one can reuse multiple wires with the standard circular cross-section within a single thread. The wire during bonding is surrounded by the core placed on the substrate with the small conductive surfaces. The bonding also binds the core to the substrate.

In the antenna system according to this invention the received signal from the initializer is only minimally interfered by the transmission of the transponder thanks to the isolation, and no additional external synchronization circuits are necessary. The signal received by the transponder in such a way is during the active modulation repeatedly transmitted back as a modulation carrier wave for the data modulation, which ensures that both signals are precise as far as their frequency is concerned. The identical antenna system according to this invention can effectively function on both sides of the NFC communication channel, both in CE and RW mode. The second, larger solenoid antenna is capable of radiating sufficient power for excitation of the passive card approaching the antenna system. The advantage of the invention is also the simple arrangement of the antenna system and simple connection of the respective circuits, whereby thanks to the physical binds between the transmitting and receiving antenna a high efficacy on small build-up surface is achieved.

Description of drawings

The invention is further disclosed by means of figures 1 to 11. The particular depicted solenoid antennas, the number and width of the threads, the examples of mutual dimensions - all these are for illustration purposes only and cannot by interpreted as limiting the scope of protection.

Figure 1 depicts the placement of the first solenoid antenna and the second solenoid antenna on the small PCB communication module with the adaptation circuits designed for the connection to the NFC controller. The axis marked as a1 is transverse axis of the first solenoid antenna and its marked position is at the level of the first thread of the second solenoid antenna. The depicted ratio of sizes of first and second solenoid antenna is for information purposes and the particular ratio was chosen for the purposes of clarity.

Figure 2 depicts the position of both antennas from the first figure, where the dimension “a” forms a distance of the transverse axes of the solenoid antennas.

Figure 3 continues to mark possible positions of the first solenoid antenna, where Aa is a range of the positioning of the transverse axes of the solenoid antennas and Ab is a range of the positioning of the longitudinal axes of the solenoid antennas.

Figure 4 depicts the connection of both solenoid antennas to the NFC controller.

Figure 5 depicts the coupling between the antennas during the creation of the communication channel with the reader and card in the position of the counterpart. Coefficient k1 expresses the coupling between the antenna of the communication counterpart and the first solenoid antenna (RX). Coefficient k2 expresses the coupling between the antenna of the communication counterpart and second solenoid antenna (TX). Coefficient k3 expresses the coupling between the first solenoid antenna (RX) and second solenoid antenna (TX).

Figure 6 depicts the construction of the second solenoid antenna. N is the number of threads; L is the length; s is the size of the gap between threads; n denotes a single thread.

Figure 7 is a graph of dependence of the number of threads of the second solenoid antenna on its length. Figure 8 is a graph of the dependence of the size of the gap between the threads of the second solenoid antenna on its length.

Figure 9 is a view of the edge of the core of the first solenoid antenna with six conductors of the circular cross-section within a single thread, where one can see that the thread on the edge has an increased pitch, so that the group of the conductors of a single thread is separated for the purposes of connection to the small conductive surface. The letter“n” denotes a single thread.

Figure 10 is an axonometric view of the communication module with the adapting circuits and both solenoid antennas.

Figure 11 depicts the detail of the position of the center of the first solenoid antenna against the first thread of the second solenoid antenna. The hatched strip denotes various points of the position at the level of the first thread. The dashed line depicts the edge of the winding on the opposite side of the core. For the purposes of clarity the slope (angle) of the winding on the sides of the core is not depicted. Examples of realization

Example 1

In this example according to figures 1 to 9 the antenna system has first solenoid antenna 1 and second solenoid antenna 2. Both have a ferrite core. The first solenoid antenna 1 has a core length 9 mm, the core’s permeability m=80, and it has 21 threads, whereby each thread is formed by six conductors of the circular cross-section placed side by side. There is no gap between the threads. The cross-section of the core of the first solenoid antenna 1 has dimensions 0,6 mm x 0,8 mm. The conductors of the threads are wound in the even slope (angle) except for the ends of the first and last thread, whereby the ends have an increased slope in order to achieve the distance of the group of conductors for their connection to the small conductive surfaces on the substrate.

The second solenoid antenna 2 has 18 mm long core, permeability m=80 and it has 21 threads, where each thread is formed by nine conductors placed side by side. Between the neighboring threads on the second solenoid antenna’s 2 core there is 0,25 mm gap. The second solenoid antenna’s 2 core has cross-section 0,6 mm x 1 ,6 mm. Both antennas are placed on a single surface of a common carrier. They are placed in parallel and the center of the first solenoid antenna 1 is at the level of the first thread 3 of the second solenoid antenna 2. The distance a (in mm) between transverse axes a1 and a2 of the solenoid antennas 1_, 2 is a=L/2 - 3 mm, where L (in mm) is the length of the core of the second solenoid antenna 2. The distance of the longitudinal axes of the solenoid antennas 1, 2 in this case is 2,6 mm. The windings are from copper wire with the circular cross-section. The multiple placement of the conductor side by side within a single thread produces an effect of the flat conductor.

Each solenoid antenna 1_, 2 has its own adaptation circuit 5, 6 and these are connected to the common NFC controller 7.

The resulting inductance value of the second solenoid antenna 2 in this example ranges from 1 ,0 - 1 ,5 pH, usually 1 ,26 pH, and its quality (measured at actual transmitting current) Q = 20 - 25, usually 23.

The antenna system suppresses the interference with the need for active suppression of active circuits. This removes the problem in case of miniature NFC antennas which require active load modulation, where the active signal from the point of view of the receiver manifests itself as interference, and as a result the quality of reception decreases. Antenna system is suitable for use in the mobile phone, SiP modules of various devices, SD cards, and it is suitable both for read/write mode and Card Emulation mode.

The shifting (deviation) of mutual geometrical axes of the solenoid antennas 1, 2 within the field delimited pursuant to figure 3 as Aa - Ab one can fine tune the antenna system in such a way that it takes into account the effects of the production irregularities as well as the effects of the components and shielding in the vicinity of the antenna system. Example 2

In the second example the second solenoid antenna 2 has the length of a core 20 mm, it has 22 threads and each thread is formed by nine conductors placed side by side. The gap between the neighboring threads on the second solenoid antenna’s 2 core is 0,35 mm. The second solenoid antenna’s 2 core has a cross-section 0,6 mm x 1 ,6 mm. The resulting inductance value of the second solenoid antenna 2 in this example is 1 ,26 pH and its quality (measured at actual transmitting current) Q = 23.

Example 3

Second solenoid antenna 2 has a length of a core 23 mm; it has 23 threads. The thread is formed by nine conductors placed side by side. The gap between neighboring threads is 0,45 mm. The core’s cross-section is 0,6 mm x 1 ,6 mm. The resulting inductance value is 1 ,40 pH and its quality (measured at actual transmitting current) Q = 23.

Example 4

Second solenoid antenna 2 has a length of a core 25,5 mm; it has 24 threads. The thread is formed by nine conductors placed side by side. The gap between neighboring threads is 0,52 mm. The core’s cross-section is 0,6 mm x 1 ,6 mm. The resulting inductance value is 1 ,40 pH and its quality (measured at actual transmitting current) Q = 23. Example 5

Second solenoid antenna 2 has a length of a core 28 mm; it has 28 threads. The thread is formed by nine conductors placed side by side. The gap between neighboring threads is 0,58 mm. The core’s cross-section is 0,6 mm x 1 ,6 mm. The resulting inductance value is 1 ,47 pH and its quality (measured at actual transmitting current) Q = 23.

Example 6

The first solenoid antenna 1 has identical construction as in previous examples and its length is 9 mm. The second solenoid antenna 2 has a core’s length chosen pursuant to the largest available space in a given PCB 4, whereby the number of threads and the size of the gaps between threads is chose pursuant to graphs in figures 7 and 8. The course of the graph pursuant to figure 7 can be approximated by linear function y = 0,42x + 13,35. The course of the graph according to figure 8 can be approximated by linear function y = 0,031x - 0,287.

Example 7

First solenoid antenna 1 has a ferrite core and the threads are formed by a multiple placement of the copper wire in a single thread. The longitudinal cross-section of the core has dimensions 0,6 mm - 0,8 mm and length 9 mm.

The second solenoid antenna 2 is formed by bonding. The conductive loops envelop the core placed on the non-conductive substrate; part of the conductive substrate is formed by the flat circuit on the board where the group of conductive strips placed side by side is produced, whereby the core is placed on these strips. The core can be placed directly onto the board or onto the substrate. The conductive strips overhang thorugh the core’s groundplan; the ends of the conductive strips overhanging on both sides of the core form a little connecting surfaces. Wires shaped for the enveloping of the core are connected to the connecting surfaces, whereby the wire connects the connecting surface of a single conductive strip with the connecting surface on the opposite end of the neighboring conductive strip. The conductive strip and the wire form conductors of the individual loops; the loops envelop the core of the antenna. The wire in this example has flat cross-section.

Industrial applicability

The industrial applicability is obvious. According to this invention it is possible to industrially and repeatedly compose and use antenna system with two solenoid antennas for transmission and reception of the signal, whereby the antenna system is effective in both CE and RW mode.

List of symbols

1 - first solenoid antenna

2 - second solenoid antenna

3 - first thread

4 - PCB (printed circuit board)

5 - transmission’s adaptation circuit

6 - reception’s adaptation circuit

7 - NFC controller a1 - transverse axis of the first solenoid antenna

a2 - transverse axis of the second solenoid antenna

a - distance of transverse axes

b - distance of longitudinal axes

Aa - scope of positioning of transverse axes of the solenoid antennas Ab - scope of positioning of longitudinal axes of the solenoid antennas

NFC - Near field communication

PCB - printed circuit board

SiP - System in Package

SMD - Surface Mount Devices