EP2493017A1 - Method for producing an antenna assembly - Google Patents

Abstract

The method involves providing a basic geometry of an antenna arrangement (1) with an adjustable geometric antenna arrangement parameter, where a reading range of the Radio frequency identificationtransponder depends on the geometric antenna arrangement parameter. The material parameter of a cladding material is determined. The geometric antenna arrangement parameter is adjusted corresponding to the material parameter. An independent claim is also included for a computer program product, which comprises a computer program with instructions for manufacturing an antenna arrangement of a radio frequency identification transponder.

Description

The invention relates to a method for producing an antenna arrangement of an RFID transponder. Moreover, the invention relates to a corresponding computer program and a corresponding computer program product.

At the present time, items or persons may be provided with a so-called Radio Frequency Identification (RFID) transponder to identify the items or persons, monitor or the like. For example, an object in a production process can be provided with an RFID transponder in order to track the path of the object. In the RFID transponder, for example, data of the object or the person, such as identification data, access data, passwords or history data, stored and in particular be read without contact.

An RFID transponder has an antenna arrangement for transmitting and receiving data. The antenna arrangement may comprise at least one antenna and a matching network. For this purpose, the antenna and / or the matching network have a specific geometry, wherein different antenna types are characterized by different geometries.

Furthermore, an RFID transponder can have a circuit arrangement which can be electrically connected to the antenna arrangement. The circuit arrangement can be an analog Circuit for receiving and transmitting (transceiver) data, a digital circuit, such as a microcontroller, and a memory device.

Such an RFID transponder can be used in an RFID communication system. An RFID communication system may comprise at least one reading and / or writing device in addition to at least one RFID transponder. The reading and / or writing device can generate, for example, a high-frequency alternating electromagnetic field. If the passive or active RFID transponder arrives in this field, then the RFID transponder receives the signal via the antenna arrangement. The RFID transponder can be activated by the received alternating electromagnetic field. The information contained in the transmitted field can be decoded. Depending on the decoded information, the RFID transponder can execute corresponding instructions and, for example, send data to the reading and / or writing device by means of the antenna arrangement.

A performance criterion of an RFID transponder here represents the reading range. The reading range depends inter alia on the antenna arrangement and the circuit arrangement used. Furthermore, the reading range may depend on the proximity environment of the RFID transponder. In order to achieve good reading range, it is customary in the prior art to attach RFID transponders to outside areas of the corresponding objects in order to prevent influencing of the reading range of the RFID transponder by a wrapping material. For example, RFID Transponder can be purchased, which can be attached to an object and have a high reading range.

The problem with the RFID transponder of the prior art, however, is that when attached to an outside of an object there is a risk of mechanical destruction of the RFID transponder. The RFID transponder is usually unprotected on an outside and therefore can be easily damaged by impact or the like. In addition, consumables have the problem that it is not possible to monitor the material until it is finally consumed or disposed of, because attaching it to an outside such as the consumable packaging will result in the consumption of the consumable even before it is consumed the RFID transponder is no longer attached to the object and thus monitoring of the object is no longer possible.

From the US Pat. No. 7,323,977 B2 Transponders are also known, which allow an adjustment of the operating frequency band. The US Pat. No. 7,323,977 B2 discloses, in particular, a transponder with an antenna arrangement and with an integrated circuit which can be connected to the antenna arrangement. In order to adapt the operating frequency band of the transponder to different specifications of geographical regions (eg USA, Europe, Japan), it is possible to tune the transponder with the help of additional parasitic elements which can be arranged at a variable distance from the antenna.

The disadvantage of this is, on the one hand, that an adaptation of the antenna takes place only to fulfill legal requirements of different regions. An adaptation to Different shell materials do not occur, so that the reading range is significantly reduced when embedding a corresponding transponder in a tissue. In addition, on the other hand, it is necessary to provide additional elements for matching the antenna. In addition to the additional space required for the additional parasitic elements, the possibility of tuning in such an arrangement is limited, complicated and inflexible.

It is therefore the object of the present invention to provide a method for producing an antenna arrangement for an RFID transponder, which allows a simple adaptation of the antenna arrangement to different shell materials and the usual variations of their material parameters. The object of the invention is also to achieve a broadband reading range and a reduction in the geometric dimensions of the embedded RFID transponder.

The previously derived and indicated object is achieved according to a first aspect of the invention by a method for producing an antenna arrangement of an RFID transponder, the method comprising: providing a basic geometry of the antenna arrangement with at least one adaptable geometric antenna arrangement parameter, wherein at least one reading range of the RFID transponder of the at least one geometric antenna array parameter depends, determining at least one material parameter of a cladding material, and adapting the at least one geometric antenna array parameter as a function of the at least one material parameter.

In contrast to the prior art, according to the invention, no additional elements are arranged in order to meet legal requirements of different geographic regions, but at least one geometric antenna arrangement parameter is adjusted in order to optimize the reading range as a function of a material parameter of a shell material. It can be provided according to the invention that the at least one geometric antenna arrangement parameter is adjusted in dependence on the at least one material parameter such that the read range of the antenna arrangement is optimized, in particular increased.

In a first step, a basic geometry, ie a geometric standard shape or basic shape, of an antenna arrangement can be provided. This basic geometry can occur one-dimensionally as a "thread", two-dimensionally as an "area" or three-dimensionally as a "body". The basic geometry of the antenna array is determined by geometric antenna array parameters, such as the shape, length, height, width, thickness, or spacing of two sections. At least one of these geometric antenna arrangement parameters can be adaptable, ie variable or adjustable. In other words, at least one antenna arrangement parameter may be changed in the manufacture of the antenna arrangement for tuning the antenna arrangement. It is understood that the at least one adaptable antenna arrangement parameter can also remain unchanged during a customization in the special case.

According to the invention, the antenna arrangement is optimized with respect to a wrapping material with which at least the Surrounded antenna arrangement, in particular the entire RFID transponder or from which the antenna arrangement is enclosed. The wrapping material may be, for example, the object to be monitored itself. Thus, the antenna arrangement, in particular the entire RFID transponder, can be embedded in an enveloping material. The sheath material may preferably be a non-metallic solid material, such as fibrous materials, molding materials, rubber materials, organic insulating materials, potting compounds, fillers or animal tissue, or a liquid, but not gaseous substances, such as air. By embedding in a shell material on the one hand, the risk of mechanical destruction can be reduced. If the RFID transponder is embedded in a consumable material, monitoring of the consumable material can also be made possible until it is disposed of.

It has been recognized that the envelope materials reduce the reading range of conventional antenna arrangements or conventional RFID transponders. Furthermore, it has been recognized that a reading range can be optimized, ie increased, by a change of the geometric structure, in particular of at least one geometric parameter of the antenna arrangement. For this purpose, in particular the at least one geometric antenna arrangement parameter is adapted as a function of at least one determined material parameter of the envelope material. For example, a length parameter can be increased, shortened or, in the special case (if an optimal antenna arrangement parameter value for the shell material already exists) remain the same. Similarly, according to other variants of the invention other antenna arrangement parameters are adjusted.

In particular, the material parameter may be a parameter that influences the propagation velocity of electromagnetic waves.

It is understood that according to other variants of the invention, two or more antenna arrangement parameters can be adaptable and / or two or more material parameters can be taken into account.

According to the invention, an antenna arrangement for a covering material is adapted individually, at least with regard to the reading range, in a simple manner.

According to a first embodiment of the method of the invention, the basic geometry of the antenna arrangement may comprise an antenna. Alternatively or additionally, the basic geometry of the antenna arrangement may include an adaptation network. In particular, a basic geometry may include an adaptation network electrically connected to the antenna.

The at least one geometrically adaptable antenna array parameter may be a geometric parameter of the antenna or a geometric parameter of the matching network. This increases the number of possible customizable antenna array parameters from which suitable ones can be selected. It is understood that the antenna arrangement may also comprise more than one antenna.

In principle, any basic geometries of antennas and / or matching networks can be provided. According to According to one embodiment, the antenna may be a dipole antenna, in particular a bowtie antenna. Dipole antennas are due to their simple structure and operation in a particularly advantageous manner as antennas for RFID transponder. Basically, the use of a variety of different dipole antennas, such as a planar log-periodic antenna, a Vivaldi antenna, a spiral antenna or a differential elliptical antenna for a (broadband) antenna is possible. For use as a broadband antenna of an RFID transponder, a bowtie antenna is particularly suitable. A bowtie antenna is scalable and can be operated in different frequency ranges. In addition, it has a comparatively simple geometry compared to other dipole antenna, which can be adapted particularly easily.

Further, the matching network may be a T-matching network. In particular, a T-matching network may be an adapted T-matching network. An adapted T-matching network may comprise a coupling section for electrical coupling to an antenna and two legs or two connection conductors for electrical connection to a circuit arrangement. For example, a connection section can be provided between the legs and the coupling section. Here, the T-matching network may be formed axially symmetric. In addition to the symmetrical design, a T-fitting network is distinguished by a simple geometric structure. This structure has the advantage that an adaptation of geometric parameters is possible in a simple manner.

As already described, according to the method of the invention, a material parameter of a wrapping material is determined, which e.g. can affect the propagation of the radiated electromagnetic wave. According to a further embodiment of the method according to the invention, the at least one material parameter of the shell material may be a relative permittivity of the shell material or a relative permeability of the shell material or a material thickness of the shell material. These material parameters are related (directly) to the reading range of an antenna array and its geometrical dimensions. These material parameters are therefore particularly suitable to be taken into account when adapting the geometry of the antenna arrangement in order to optimize the reading range of the antenna arrangement or of the RFID transponder. It goes without saying that two or all material parameters can also be determined.

The determination of the at least one material parameter can be carried out in various ways. Thus, corresponding values may already be known from prior art tables. However, this information is usually inaccurate information, which was determined independently of the exact design of the shell material. For a more precise determination, according to an embodiment of the invention, the at least one material parameter of the enveloping material can be determined metrologically. Alternatively or additionally, the material parameter can be determined by calculation. In addition to a pure metrological determination is also possible to measure the material parameters in part and the missing Material parameters to be determined by a simulation calculation.

Furthermore, the adaptation of the at least one geometric antenna arrangement parameter can be carried out as a function of a transmission coefficient of the antenna arrangement. In particular, the transmission coefficient represents the relationship between the intensity of the electromagnetic waves in front of the circuit arrangement, such as an RFID chip (end of the matching network), and the interior of the circuit arrangement. It should be noted that the reflections occurring at a transition between air and covering material are low Permittivity values in general can be neglected. The transmission coefficient is thus a measure of "transmitted" intensity and assumes values between 0 and 1. The reading range of an antenna depends on the transmission coefficient (immediate). The transmission coefficient should preferably be maximized. The dependence of the transmission coefficient on the cladding material may, for example, be altered by a material parameter such as the relative permittivity of the cladding material or the relative permeability of the cladding material or the material thickness of the cladding material. An adaptation of the geometry of the antenna arrangement as a function of the transmission coefficient of the antenna arrangement leads to a particularly good match between the antenna and the RFID chip and thus an increase in the reading range.

According to a further embodiment of the invention, at least one output impedance of a circuit arrangement that can be electrically connected to the antenna arrangement may be preferred be determined. For example, the frequency-dependent and intensity-dependent output impedance can be measured. Thus, by means of a network analyzer, taking into account the protocol of the air interface, the output impedance can be determined. Alternatively, the value of the output impedance can also be read from a table or a data sheet of the circuit arrangement. The circuit arrangement may be an integrated circuit, such as an RFID chip.

In addition, according to a further embodiment, the at least one geometric antenna arrangement parameter can be adapted such that a complex impedance of the antenna arrangement at least in a predefinable frequency range substantially coincides with the complex conjugate output impedance of the circuit arrangement. The transmission coefficient of the antenna arrangement depends on the impedance of the antenna arrangement, in particular the antenna impedance, and the impedance of the circuit arrangement. A match of the complex impedance of the antenna arrangement with the complex conjugate output impedance of the circuit arrangement leads in a simple manner to a maximization of the transmission coefficient. This in turn increases the reading range of the antenna arrangement or of the RFID transponder.

In principle, the at least one geometric antenna arrangement parameter can be used to set a plurality of antenna parameters. According to one embodiment of the invention, the at least one antenna arrangement parameter may be used to set a resonant frequency of the antenna arrangement due to of a wrapping material can be adjusted. The resonance frequency can be optimized as a function of the enveloping material by the at least one geometric antenna arrangement parameter.

Alternatively or additionally, the at least one antenna arrangement parameter can be adapted to set an imaginary part of the complex impedance of the antenna arrangement. The imaginary part can also be influenced by the shell material. For example, the antenna array parameter may be changed such that the imaginary part of the complex impedance of the antenna array coincides with the imaginary part of the output impedance of the inverted-sign circuit.

In addition, alternatively or additionally, the at least one antenna arrangement parameter can be adapted to set a real part of the complex impedance of the antenna arrangement. Also, the real part can be influenced by the shell material. In particular, by means of the antenna arrangement parameter, the real part of the complex impedance of the antenna arrangement can be adjusted such that it agrees with the real part of the output impedance of the circuit arrangement.

Furthermore, alternatively or additionally, the at least one antenna arrangement parameter can be adapted to set an amplitude of the real part of the complex impedance of the antenna arrangement. This allows in particular a fine adjustment of the real part.

It has been recognized that, particularly in a matched and modified T-matching network including a coupling section and a connection section, the real part can be adjusted by changing the distance between a center of the coupling section of the matching network and a center of the connection section of the matching network. It should be noted that this antenna arrangement parameter exists only in a modified T-matching network including a coupling section and a connection section. In conventional customization networks, this parameter does not exist. In particular, a change of this antenna arrangement parameter (only) changes the real part, while the imaginary part remains almost unchanged, especially over a wide frequency range.

Furthermore, alternatively or additionally, the at least one antenna arrangement parameter can be adapted to set a reactance of the complex impedance of the antenna arrangement.

Essential antenna parameters of the antenna arrangement can be set and optimized in a simple manner by a corresponding adaptation of one or more geometrical antenna arrangement parameters to material parameters of the shell material.

In addition, basically, a plurality of geometric antenna arrangement parameters can be made adaptable. For an optimization of the reading range of a Bowtie antenna can according to one embodiment in an advantageous As a result, the at least one antenna arrangement parameter may be a length of the bowtie antenna. For example, in a first tuning step, this length can be adjusted. By changing the length of the bowtie antenna, for example, the resonant frequency of the antenna arrangement can be adjusted with regard to the shell material.

Alternatively or additionally, according to another embodiment, a distance between an outermost point of a leg of the matching network and an axis of symmetry of the antenna arrangement can also be adapted.

For example, this geometric antenna arrangement parameter (after the first step) can be adapted in a second step as a function of the at least one material parameter. For example, by geometrically changing the distance between the outermost point of a leg of the matching network and the axis of symmetry of the antenna array, an imaginary part of the complex impedance of the antenna array can be adjusted.

Moreover, according to another embodiment, alternatively or additionally, it may be provided that the antenna arrangement parameter is a length of a connection section of the matching network. Preferably, this parameter can be adjusted (after the second step) in a third step. For example, by changing the length of the connection section, a (rough) adaptation of the real part of the impedance of the antenna arrangement can take place.

According to a further embodiment of the method according to the invention, an antenna arrangement parameter may be a distance between a center of a coupling section of the matching network and a center of the connection section of the matching network. The two centers can be due to the axisymmetric configuration of the antenna array on the symmetry axis of the antenna array. Preferably, this antenna arrangement parameter (after the third step) can be adapted in a fourth step. For example, by changing the distance between the center of the coupling section of the matching network and the center of the connecting section of the matching network, the real part of the antenna impedance can be adjusted in amplitude. This feature of the matching network allows almost independent influence on the real part of the antenna impedance, without affecting (strongly) the reactance of the antenna. In particular, fine tuning of the real part of the antenna impedance is possible.

The antenna array parameter may be a diameter of a leg of the matching network according to another embodiment. In a fifth step (after the fourth step), for example, by changing the diameter of the limbs, that is to say the width of the connection lines of the circuit arrangement, the reactance of the antenna can be changed with little influence on the real part of the antenna impedance.

Preferably, according to an embodiment, the aforesaid antenna arrangement parameters can be changed in serial sequence. In this way, a particularly good adaptation of the antenna arrangement to a shell material can be achieved become. It is understood that according to other variants of the invention further or different antenna arrangement parameters can be adapted and the individual steps can also be carried out in a different order.

According to a further embodiment of the method according to the invention, an antenna arrangement with at least one adapted antenna arrangement parameter can be generated. For example, the geometric data of the adapted antenna arrangement can be forwarded (directly) from a data processing system to a device for the production of antenna arrangements. This can produce an antenna arrangement, for example by printing on a substrate, in accordance with the geometric data obtained. An antenna arrangement can be produced that is particularly suitable for use in a specific envelope material.

The object is achieved according to a further aspect of the invention by a computer program with instructions executable on a processor such that an antenna arrangement is produced by means of the previously described.

Furthermore, the object according to a further aspect of the invention is achieved by a computer program product comprising a computer program with instructions executable on a processor such that an antenna arrangement is produced by means of the method described above.

There are now a variety of possibilities, the inventive method, the inventive Computer program and the invention

Fig. 1

eine schematische Ansicht eines Ausführungsbeispiels einer Grundgeometrie einer Antenne gemäß der vorliegenden Erfindung;

Fig. 2

eine schematische Ansicht eines Ausführungsbeispiels einer Grundgeometrie eines Anpassungsnetzwerks gemäß der vorliegenden Erfindung für die Grundgeometrie einer Antenne gemäß Figur 1;

Fig. 3

eine schematische Ansicht eines Ausführungsbeispiels einer Grundgeometrie einer Antennenanordnung mit der Grundgeometrie einer Antenne gemäß Figur 1 und der Grundgeometrie eines Anpassungsnetzwerks gemäß Figur 2;

Figur 4

ein Flussdiagramm eines ersten Ausführungsbeispiels eines Verfahrens gemäß der vorliegenden Erfindung;

Figur 5

eine schematische Ansicht eines Ausführungsbeispiels einer Antennenanordnung angebracht an einer Papphülse; und

Figur 6

ein Flussdiagramm eines zweiten Ausführungsbeispiels eines Verfahrens gemäß der vorliegenden Erfindung.

Design and develop computer program product. For this purpose, reference is made, on the one hand, to the claims subordinate to the main claim, and, on the other hand, to the description of exemplary embodiments in conjunction with the drawing. In the drawing shows:

Fig. 1

a schematic view of an embodiment of a basic geometry of an antenna according to the present invention;

Fig. 2

a schematic view of an embodiment of a basic geometry of a matching network according to the present invention for the basic geometry of an antenna according to FIG. 1 ;

Fig. 3

a schematic view of an embodiment of a basic geometry of an antenna assembly with the basic geometry of an antenna according to FIG. 1 and the basic geometry of a matching network according to FIG. 2 ;

FIG. 4

a flowchart of a first embodiment of a method according to the present invention;

FIG. 5

a schematic view of an embodiment of an antenna assembly attached to a cardboard tube; and

FIG. 6

a flowchart of a second embodiment of a method according to the present invention.

The method according to the invention will be explained below using an example of a bowtie antenna with a suitable matching network, which is to be optimized for use in a cladding material. It is understood that the method according to the invention can be applied in a similar manner to other antenna types and other matching networks. In particular, a geometrically reduced, broadband and resonant antenna structure can be realized by a targeted embedding of an RFID transponder in a shell material.

FIG. 1 shows a schematic view of an embodiment of a basic antenna geometry according to the present invention. In the pictured

Exemplary embodiment is a bowtie antenna basic geometry 2. A bowtie antenna 2 is a dipole antenna 2 with two conductive split pole sections 4a and 4b. The pole sections 4a and 4b may be formed in particular (axes) symmetrical to each other. A bowtie antenna 2 has the advantage that due to the relatively simple and robust geometry high manufacturing tolerances can be allowed. As a result, the production rate can be increased, for example due to a faster printing process.

A pole section 4a, 4b of the illustrated bowtie antenna 2 comprises a first section 6a, 6b. The first portion 6a, 6b may have a substantially rectangular shape with have a width W4. A second section 8a, 8b may follow this first section 6a, 6b. The second section 8a, 8b can be formed essentially by an isosceles trapezoid. Here, the shorter side of the two parallel sides of the isosceles trapezium may have a length W4 corresponding to the width W4 of the first section 6a, 6b.

The basic antenna geometry shown can have a length L1. Here, the length L1 is the distance from an outer end of a second portion 8a to the opposite outer end of the other second portion 8b to understand. Further, the distance between an outer end of a first portion 6a to the opposite outer end of the other first portion 6b is denoted by L2.

In FIG. 2 an embodiment of a basic geometry of a matching network 10 is shown, which for the bowtie antenna 2 according to FIG. 1 suitable is. The mapped matching network 10 is an adapted and modified T-matching network. As will be explained in more detail below, such a modified T-matching network is characterized in particular by the antenna arrangement parameter M2.

First, the FIG. 2 it can be seen that the matching network 10 is formed axially symmetrical about an axis of symmetry 22.

The matching network 10 includes a coupling portion 12. This coupling portion 12 is for electrical Coupling of the matching network 10 with the antenna 2. In particular, the coupling portion 12 may be attached to the first portions 6a, 6b of the bowtie antenna 2. The coupling section 12 may be rectangular and correspond to the first sections 6a, 6b of the antenna 2. Here, the width W4 of the coupling portion 12 may substantially correspond to the width W4 of the first portions 6a, 6b of the divided pole portions 4a and 4b.

To the coupling portion 12, a connecting portion 14 may be arranged. From the connecting portion 14, two legs 16a and 16b and connecting lines 16a and 16b may extend. The connecting portion 14 may act as a transition region between the legs 16 a, 16 b and the coupling region 12. The connecting portion 14 has a length M1. Here, the length M1 is the distance between the beginnings of the two connecting lines 16a, 16b. Further, the center of the connecting portion 14, which lies on the axis of symmetry 22, from the center of the coupling portion 12, which is also on the symmetry axis 22, spaced by a distance M2.

The legs 16a, 16b are substantially axially symmetrical to each other. A leg 16a, 16b may be divided into a first section 18a, 18b connected to the connecting section 14 and a second section 20a, 20b. The leg 16a, 16b has a substantially constant diameter MD over substantially its entire length. The first portion 18a, 18b extends slightly arcuate to the longitudinal direction of the axis of symmetry 22 by a distance M3.

At this first portion 18a, 18b, a second section 20a, 20b connects. After a substantially 90 ° bend within a distance M5, the second section 20a, 20b extends in the direction of the axis of symmetry 22. In other words, the ends of the legs 16a, 16b each face in the direction of the axis of symmetry 22 and face each other.

The distance of the outermost point of a leg 16a, 16b (in this case is assumed by the center line of a leg) to the axis of symmetry 22 is denoted by M4. The ends of the legs 16a, 16b are spaced apart a distance from MDICY. Between these ends, a circuit arrangement (not shown), such as an integrated circuit, can be arranged. The circuitry may be electrically connected to the ends of the legs 16a, 16b. Then, an electromagnetic field can be emitted in the desired manner via the antenna arrangement.

FIG. 3 shows a schematic view of an embodiment of a basic geometry of an antenna assembly 1 with the basic geometry of an antenna according to FIG. 1 and the basic geometry of a matching network according to FIG. 2 ,

It has been recognized that the reading range of such an antenna array 1 depends on a (non-conductive) cladding material with which the antenna array may be surrounded. An RFID transponder may be completely surrounded, for example, by a solid material or a liquid material, wherein this enveloping material influences the near field of the antenna arrangement and in particular the

Reading range reduced. It is understood that at least partially an air gap can be present between the enveloping material and the RFID transponder. For example, the shell material may be fibrous materials, pressings, rubber materials, organic insulating materials, potting compounds, fillers or animal tissue. It is understood that an RFID transponder can be surrounded by different types of materials. By way of example, one side of the RFID transponder can be covered by a first enveloping material and the second side of the RFID transponder can be covered by another enveloping material.

FIG. 4 discloses an embodiment of a method according to the present invention for fabricating an antenna assembly that is geometrically matched with respect to the cladding material to optimize the read range. This method can be carried out, for example, by means of a suitable data processing system which has corresponding means for carrying out the individual method steps.

In a first step 401, a basic geometry of an antenna arrangement 1 with at least one adjustable geometric antenna arrangement parameter is provided. For example, a basic geometry of a bowtie antenna 2 with a suitable matching network 10 corresponding to FIGS. 1 to 3 to be provided. It is understood that other basic geometries of antenna arrangements for RFID transponders can be provided. The bowtie antenna 2 is particularly suitable for an ultra-high-frequency (UHF) RFID transponder (860 MHz to 960 MHz).

As already described, the basic geometry has at least one adjustable, that is to say adaptable, geometric antenna arrangement parameter. Basically, everyone in the FIGS. 1 to 2 used geometric parameters are used. This at least one adjustable geometric antenna arrangement parameter should be suitable for influencing, in particular optimizing, at least the reading range.

In a next step 402, at least one material parameter of a wrapping material which surrounds the RFID transponder is determined. For example, a relative permittivity and / or a relative permeability and / or a material thickness with which the enveloping material surrounds the RFID transponder can be determined. In principle, the material parameters can be determined by calculation or by measurement or from a previously stored table which has the corresponding values.

wobei ε'_r der Realteil der relativen Permittivität, ε"_r der Imaginärteil der relativen Permittivität und tanδ der dielektrische Verlustfaktor ist. Die relative komplexe Permittivität von Hüllmaterialien kann beispielsweise durch so genannte Resonanzmethoden messtechnisch ermittelt werden.Preferably, at least the relative complex permittivity can be determined. The relatively complex permittivity, which is also called complex, frequency-dependent dielectric constant, results from the following equation: $$\underset{}{\epsilon }={\epsilon }_r^{\text{'}}-j{\epsilon }_r^{"}={\epsilon }_r^{\text{'}}-j{\epsilon }_r^{\text{'}}\cdot \tan \delta .$$

where ε ' _{r is} the real part of the relative permittivity, ε " _{r is} the imaginary part of the relative permittivity, and tan δ is the dielectric loss factor Permittivity of encasing materials can be determined metrologically by so-called resonance methods, for example.

In addition, in step 402 optionally a (complex) output impedance of a circuit arrangement which can be electrically connected to the antenna arrangement 1, for example an RFID chip, can be determined. This output impedance can be determined, for example, from a previously determined table or metrologically.

In a next step 403, the at least one adaptable antenna arrangement parameter is then adapted as a function of the at least one material parameter. Depending on the at least one material parameter, the adaptable antenna arrangement parameter can be set to a value that is optimal with respect to the reading range. Preferably, two or more material parameters which have an influence on the reading range of the RFID transponder can be taken into account. Further, preferably two or more antenna arrangement parameters may be adjusted accordingly.

Optionally, in the last step 404, a corresponding antenna arrangement can be made. For example, a substrate with a corresponding antenna arrangement of a conductive material, such as a metal, such as copper, are printed. Furthermore, the circuit arrangement, such as an RFID chip, can be electrically connected to the antenna arrangement. The produced RFID transponder can then be arranged on / in the object in a known manner, in particular embedded. An automatic production one on one Sheath material individually tuned antenna arrangement can be achieved.

Hereinafter, a possible embodiment of the method according to the invention is illustrated with reference to a specific embodiment. In particular, a UHF RFID transponder is considered, which is to be embedded in a cardboard tube for decorative paper.

FIG. 5 shows a corresponding embodiment. The antenna arrangement 1 or the RFID transponder can be arranged on or in the cardboard sleeve 24. The cardboard sleeve 24 may be provided so that paper 26, such as decorative paper, can be wound on her. As can be seen, in the present case the RFID transponder with the antenna arrangement 1 is completely surrounded by the wrapping material, in the present case the cardboard tube 24 and the decorative paper 26.

The following is based on the FIG. 6 an embodiment of a method for producing an antenna assembly 1, which is adapted for use in a cardboard tube 24 with decorative paper 26, explained in more detail.

First, in a first step 601, a basic geometry of an antenna arrangement 1 is provided. In the present embodiment, it is a bowtie antenna structure 2 with a matched and modified T-matching network 10 according to the FIGS. 1 to 3 ,

In a next step 602, at least one material parameter of the wrapping material can be determined. Preferably, the relative permittivity of the cardboard tube 24 and the relative permittivity of the decor paper 26 are determined. For example, there is a relative permittivity of ε _{'r_papp} = 2.43 and a loss factor tans _Papp = 0.13 for the paper tube and a relative permittivity of ε' _{r_dek} of about 2.0 to 4.0 and a loss factor tans _dek of about 0.08 to 0.25 for the decor paper. The exact values of these decorative paper parameters depend, in particular, on the exact composition of the decorative paper and other factors, such as the moisture present in the decorative paper. It is understood that these are only exemplary approximate values. In addition, the respective material thickness can be taken into account.

Further, in a further step 603, optional non-geometric antenna array parameters, such as the antenna material, e.g. Copper or aluminum, and the thickness of the antenna, e.g. 20 μm (taking into account the skin effect).

In the next step 604, first of all the output impedance, in particular the complex conjugate output impedance, of the circuit arrangement can be determined. For example, the output impedance can be determined metrologically or tables are taken.

It has been recognized that an optimization of the reading range of the antenna arrangement 1 can be achieved in particular when adapting five adjustable geometric antenna arrangement parameters. It is understood that according to other variants also more or less geometric antenna arrangement parameters can be used and adapted.

In particular, the following antenna arrangement parameters may be adaptable to the basic geometry of the antenna arrangement: the length L1 of the bowtie antenna, the distance M4 between the outermost point of a leg 16a, 16b and the symmetry axis 22, the lengths M1 of the connection section 14, the distance M2 on the Symmetry axis 22 between the center of the coupling portion 12 and the center of the connecting portion 14 and the diameter MD of a leg 16 a, 16 b.

The aforementioned geometric antenna arrangement parameters can be adapted in the next step 605 in order to achieve the best possible reading range of an RFID transponder embedded in a cardboard tube 24 with decorative paper 26. In particular, this step 605 can be subdivided into a plurality of (serial) partial steps 606 to 609.

wobei λ die Wellenlänge der elektromagnetischen Welle ist, P_t die von einer Schreib/Leseeinrichtung übertragene Leistung, G_t der Antennengewinn der Leseantenne, G_r der Antennengewinn der Antenne des RFID Transponders, P_r__min die minimale Energie der Schaltungsanordnung, τ der Transmissionskoeffizient und p die Polarisationsverluste.Before discussing the individual sub-steps 606 to 609 in more detail, first some remarks on the read range of a dipole antenna are to be made. The reading range of an antenna is given by the following formula: $$r_{\mathit{read}}=\frac{\lambda }{4\pi }\sqrt{\frac{P_t\cdot G_t\cdot G_r\cdot p\cdot \tau }{P_{\mathit{r\_}\min }}}.$$

where λ is the wavelength of the electromagnetic wave, P _{t is} the power transmitted by a read / write device, G _{t is} the antenna gain of the read antenna, G _{r is} the antenna gain the antenna of the RFID transponder, P _r _ _min the minimum energy of the circuit, τ the transmission coefficient and p the polarization losses.

wobei Z_A=R_A+jX_A die Antennenanordnungsimpedanz, Z_C=R_C+jX_C die Ausgangsimpedanz der Schalungsanordnung, P_C die Versorgungsleistung, P_{C_max} die maximale Versorgungsleistung ist, R der Realteil der Impedanz Z und X der Imaginärteil der Impedanz Z ist.The reading range depends in particular on the frequency-dependent transmission coefficient τ of the energy, which describes the efficiency of the power matching between the circuit arrangement and the antenna arrangement. The transmission coefficient τ is given by the following equation $$\tau =\frac{P_C}{P_{\mathit{C\_}\mathrm{Max}}}=\frac{4\cdot R_A\cdot R_C}{{\left|Z_A+{\mathrm{<figure-callout\; id="2"\; label="Z\; C"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">Z\; </figure-callout>}}_C\right|}^2}.$$

where Z _A = R _A + jX _{A is} the antenna arrangement impedance, Z _C = R _C + jX _{C is} the output impedance of the formwork, P _{C is} the supply power, P _{C_max is} the maximum supply power, R is the real part of the impedance Z and X is the imaginary part of the impedance Z is.

The transmission coefficient τ is maximum when the ratio of the impedances Z _A and Z _{C is} conjugate complex with each other. In this case, however, the impedance Z _A depends on the enveloping material which surrounds the antenna arrangement.

In order to achieve an antenna arrangement which is optimally adapted to the wrapping material, it is possible, for example, to carry out the substeps 606 to 609. In a first substep 606, the antenna arrangement 1 can be adapted with the aid of the antenna arrangement parameter L1 to the wavelength of the global RFID frequencies in the envelope material, ie the surrounding material (cf. Fig. 7 ).

FIG. 7 shows the real part 28 of the antenna arrangement impedance and the imaginary part 30 of the antenna arrangement impedance. Furthermore, the courses for different values of L1 depending on the wrapping material are shown by way of example. For this purpose, the near surroundings of the RFID transponder can be integrated in the region of the reactive and radiating near field of the antenna. With the aid of the parameter L1, the resonance of the impedance of the transponder antenna can be adjusted to the desired frequency range.

For example, the maximum of the real part of the antenna impedance can be set to about 910 MHz.

Then, in the (subsequent) second step 607, the imaginary part of the antenna impedance may be transmitted via the

Antenna arrangement parameters M4 are set to the amount of the imaginary part of the output impedance of the circuit arrangement (see. Fig. 8 ). In FIG. 8 For example, the real part 28 of the antenna arrangement impedance and the imaginary part 30 of the antenna arrangement impedance are shown. Furthermore, the curves for different values of M4 depending on the enveloping material are shown by way of example. By changing the length of the serial inductances of the matching network (parameter M4), the imaginary part of the antenna can be easily adapted to the impedance of the circuit arrangement. In this case, the real part of the impedance can be influenced.

Furthermore, a rough adjustment of the real part of the antenna impedance can be made by the parameter M1 (cf. Fig. 9 ). This can be done in an additional step or simultaneously with the setting of parameter M4. FIG. 9 shows the real part 28 of the antenna arrangement impedance and the imaginary part 30 of the antenna arrangement impedance. Furthermore, the curves for different values of M1 as a function of the enveloping material are shown by way of example.

Subsequently, fine tuning of the real part of the antenna impedance can be done (step 608). For example, this can be done by means of the antenna arrangement parameter M2. In this tuning, it is advantageous that the maximum of the real part is set to approximately 135% of the real part of the circuit arrangement (cf. Fig. 10). FIG. 10 represents the real part 28 of the antenna array impedance and the imaginary part 30 of the antenna array impedance. Further, the waveforms for various values of M2 depending on the cladding material are exemplified.

In a fourth step 609, the antenna arrangement parameter MD can be used to set the antenna reactance at approximately 910 MHz to the amount of the reactance of the circuit arrangement (cf. Fig. 11). FIG. 11 represents the real part 28 of the antenna array impedance and the imaginary part 30 of the antenna array impedance. Further, the waveforms for various values of MD depending on the cladding material are exemplified.

It is understood that according to further variants of the present invention, the previously described sub-steps 606 to 609 can also be processed in a different order or even individual sub-steps can be omitted. However, tests have shown that particularly good results can be achieved in the above described sequence of steps 606-609.

For example, the following antenna arrangement parameters can result in millimeters for optimizing the reading range. L1 L2 W1 W4 M1 M2 M3 M4 M5 M10 MDICY MD 78 20 25 3 14 2.6 6.8 9 1 5.4 5 2

In the last step 610, the previously determined values may for example be transferred from the data processing system to a machine for the production of antenna arrangements. This can then produce an antenna arrangement in accordance with the geometric data. Basically, various manufacturing methods are known. Thus, the antenna assembly can be printed on a non-conductive substrate.

It should be noted that the reading range of an RFID transponder in addition to the transmission coefficient also depends on the directional characteristic of the antenna gain and the frequency. The antenna gain of a UHF RFID transponder antenna can also be influenced by the surrounding material. The antenna gain concentrates in the direction in which there is more material with a corresponding permittivity. To determine the possible reading range, this influence can also be taken into account, as equation 2 can be found.

The particular in the FIG. 5 presented RFID transponder, was measured in reality in an absorber room and thus validated the simulation results. In addition, practical tests confirmed the high performance of the embedded RFID transponder.

Claims (13)

Method for producing an antenna arrangement (1) of an RFID transponder comprising: Providing a basic geometry of the antenna arrangement (1) with at least one adaptable geometric antenna arrangement parameter, wherein at least one reading range of the RFID transponder depends on the at least one geometric antenna arrangement parameter, Determining at least one material parameter of a wrapping material (24, 26) and - Adapting the at least one geometric antenna arrangement parameter as a function of the at least one material parameter. Method according to claim 1, wherein the basic geometry of the antenna arrangement (1) comprises an antenna (2) and / or the basic geometry of the antenna arrangement (1) comprises a matching network (10). Method according to claim 2, wherein the antenna (2) is a dipole antenna, in particular a bowtie antenna, and / or
the matching network (10) is a T-matching network. Method according to one of the preceding claims, wherein the at least one material parameter of the wrapping material (24, 26) has a relative permittivity of the wrapping material (24, 26) or a relative permeability of the wrapping material (24, 26) or a material thickness of the enveloping material (24, 26). Method according to one of the preceding claims, wherein the determination of the at least one material parameter of the enveloping material (24, 26) takes place by means of metrology and / or computation. Method according to one of the preceding claims, wherein the adaptation of the at least one geometric antenna arrangement parameter in dependence on a transmission coefficient of the antenna arrangement (1) is performed. Method according to one of the preceding claims, further comprising determining an output impedance of a with the antenna assembly (1) electrically connectable circuit arrangement. The method of claim 7, wherein the at least one geometric antenna arrangement parameter is adjusted such that a complex impedance of the antenna arrangement (1) at least in a predefinable frequency range substantially coincides with the complex conjugate output impedance of the circuit arrangement. Method according to one of the preceding claims, wherein the at least one antenna arrangement parameter is adapted for setting a resonant frequency of the antenna arrangement (1), and / or
wherein the at least one antenna arrangement parameter is for adjusting an imaginary part of the complex impedance the antenna arrangement (1) is adapted, and / or wherein the at least one antenna arrangement parameter for adjusting a real part of the complex impedance of the antenna arrangement (1) is adjusted, and / or wherein the at least one antenna arrangement parameter for adjusting an amplitude of the real part of the complex impedance of the antenna arrangement (1) is adjusted, and / or
wherein the at least one antenna arrangement parameter is adjusted to adjust a reactance of the complex impedance of the antenna arrangement (1). Method according to one of the preceding claims, wherein the at least one antenna arrangement parameter is a length (L1) of the bowtie antenna, or
wherein the at least one antenna arrangement parameter is a distance (M4) between an outermost point of a leg (16a, 16b) of the matching network (10) and an axis of symmetry of the antenna arrangement (1), or wherein the at least one antenna arrangement parameter has a length (M1) of a connecting section ( 14) of the matching network (10), or
wherein the at least one antenna arrangement parameter is a distance (M2) between a midpoint of a coupling section (12) of the matching network (10) and a midpoint of the connecting section (14) of the matching network (10), or
wherein the at least one antenna arrangement parameter is a diameter (MD) of a leg (16a, 16b) of the matching network (10). Method according to one of the preceding claims, further comprising generating the antenna arrangement (1) with at least one adapted antenna arrangement parameter. Computer program with instructions executable on a processor such that an antenna arrangement by means of the method according to one of the claims 1 to 11 is produced. Computer program product comprising a computer program with instructions executable on a processor such that an antenna arrangement is produced by the method according to one of the claims 1 to 11.

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