Tire RFID tag with segmented dipole antenna

Abstract

Tunable linear antenna transponders and methods of making and using the same are described. In some embodiments, the transponder includes two radiators made of an electrically conductive material, where the radiators may be the same or different. In some embodiments, the radiator is divided into a plurality of segments, where each segment is in the form of a linear segment, a helical spring segment, or a cylindrical segment. In some embodiments, the shapes and / or helical spring pitches of the two consecutive segments differ. Different transmission line segments provide additional degrees of freedom, allowing antenna resonance to have finer / improved tunability.

Description

Technical Field

[0001] The present invention relates to a highly durable radio frequency identification (RFID) tag for identifying a tire, the tag being embedded or otherwise integrated into the tire during its manufacture. Background Art

[0002] Identifying and tracking tires using radio frequency identification (RFID) technology enables automated and fully digital traceability throughout their entire life cycle. This technology automatically identifies data to optimize internal and external logistics process handling. In addition, RFID technology can provide supporting information about the different manufacturing steps at an early stage in the manufacturing process, helping to link process data and handle customer claims. The fully embedded transponder and its related information remain closely linked to the tire throughout the entire product life cycle. However, the embedding of the transponder in the tire must have absolutely no negative impact on the product life or its function. In particular, defects and airtight layers must be avoided, because in the worst case, they can cause the tire to be damaged or destroyed. Since the embedded transponder essentially constitutes a material defect, it should be integrated in a minimally intrusive manner, that is, the space occupied by the transponder inside the tire should be as small as possible.

[0003] The embedded transponder should have a minimal form factor; its resonant frequency can only be adjusted by shortening the antenna length. In particular, since the length of the helical antenna can only be reduced by reducing the number of windings, its tunability is limited by this approach. This approach results in large frequency steps for antenna tuning, especially in the case of high dielectric embedding media.

[0004] There is a need for more precise resonant tuning of RFID antennas to improve the overall performance of RFID transponders that are integrated into tires during the tire manufacturing process.

[0005] Thus, the present invention describes more precise resonance tuning of RFID antennas and structures incorporating the same that can improve the overall performance of RFID transponders that are integrated into tires during the tire manufacturing process. Summary of the invention

[0006] In order to solve the problem of insufficient tunability of linear antenna transponders, one embodiment of the present invention proposes to construct the antenna of a radio frequency identification (RFID) device in the manner described in the present invention. In one embodiment, the transponder is linear and contains or includes two radiators made of conductive material. In some embodiments, the two or more radiators are identical. In some embodiments, the radiator is divided into multiple or several transmission line segments, wherein each segment is in the form of a linear segment, a coil spring segment or a cylindrical segment. In some embodiments, the shape and / or the coil spring pitch of consecutive segments or adjacent segments are different.

[0007] The different transmission line segments provide additional degrees of freedom, allowing for finer / improved tunability of the antenna resonance. The electromagnetic signal creates small reflections at the transitions between the segments, and these reflections affect the resonant frequency. Since the amplitudes at which the reflections occur are small, the resonant frequency is less sensitive to changes in a single segment than to changes in the overall antenna length. This allows for fine tuning of the antenna. The final adjustment of the antenna is a combination of adjustments to the individual segments and to the overall antenna length.

[0008] In some embodiments, the antenna characteristics of a transponder with a normal matching network and a linear antenna can also be adjusted. The shape of the RFID antenna determines the specific radio frequency characteristics of the RFID tag. Similarly, the characteristics of a transponder with a regular matching network and a linear antenna can also be changed by introducing different antenna segments.

[0009] In some embodiments, one or more (or all) antenna segments are designed to meet the mechanical and geometric requirements of the intended application. For example, the characteristics of a single segment can be distinguished by its geometry (e.g., outer diameter or number of windings) and the material used (e.g., copper, bronze, steel and their alloys, wire with insulation, or other materials). Examples of the segments include, but are not limited to, cylindrical wire segments (called dipole segments); conical wire segments; hollow wires; helices with arbitrary pitches; helices or wires with an envelope curve forming a body of revolution; helices with contact windings (i.e., short-circuited windings); helices with contact windings made of insulated wire.

[0010] In some embodiments, spiral shapes or segments are advantageous because they can reduce the likelihood of antenna breakage, thereby minimizing the risk of tire damage. At the same time, such shapes or segments are open enough to allow rubber matrix penetration during the tire manufacturing process (such as vulcanization).

[0011] In some embodiments, each of the two identical conductive radiators is divided into at least three segments. The more segments a dipole antenna has, the greater the degree of freedom of antenna fine-tuning, thereby achieving adaptive adjustment that cannot be achieved in the prior art.

[0012] In other embodiments, the segment of each identical radiator adjacent to the integrated circuit chip is linear: the first segment is a linear dipole segment. In a dipole antenna, only the portion in the dipole direction will radiate. In a helical antenna, only the vector in the dipole direction will radiate, while the vector perpendicular to the dipole direction will not radiate. The linear segment can increase the effective length of the antenna.

[0013] In an alternative embodiment, the segment of each radiator immediately adjacent to the integrated circuit chip is in the form or shape of a helical spring with a greater pitch than the continuous segment. The larger pitch increases the proportion of the antenna portion parallel to the dipole. This can increase the effective length of the antenna while maintaining a stable helical spring form / shape.

[0014] In another embodiment, at least one segment on each radiator is a helical spring segment, and the pitch is small enough to allow the windings to be in electrical contact with each other. The windings can be made of uninsulated wire and shorted. Alternatively, a hollow cylinder can be used. The segments can form sharp transitions between antenna segments, causing signal reflections and thus impedance, as will be further described below. Alternatively, the windings can also be insulated from each other.

[0015] In other embodiments, all segments of the radiator in the RFID transponder device have the same length. In an alternative embodiment, the segments of the radiator in the RFID transponder device have at least two different lengths along the radiator.

[0016] In some embodiments, the RFID transponder device comprises an integrated circuit chip and a dipole antenna fixed to a main antenna, wherein the dipole antenna is an integral helical spring antenna and is capacitively or inductively connected to the integrated circuit chip via the main (coupled) antenna, and the chip is located at the midpoint of the length of the main (coupled) antenna, so that the parts of the antenna extending on both sides of the chip are of the same length, thus electrically forming two identical radiators. The embodiment may also include a dipole antenna divided into multiple segments. In a preferred version of the embodiment, the helical spring shape of two consecutive segments has a different pitch.

[0017] In another embodiment, the RFID transponder device comprises an integral dipole antenna divided into at least six segments. The six segments may be symmetrically distributed over the length of the antenna. In some embodiments, the integrated circuit chip is coupled through the main antenna in the middle of the integral antenna to form two electrically identical halves of the dipole antenna. In some embodiments, segments of similar shape are in the same relative position on each half. This arrangement may be referred to as mirror symmetry.

[0018] In other embodiments, the device is as described above, and the pitch of the segment immediately adjacent to the integrated circuit chip is larger than that of the adjacent segment. The larger pitch increases the proportion of the antenna portion along the dipole. This can increase the effective length of the antenna while maintaining a stable helical spring shape.

[0019] In other embodiments, the device is characterized in that the pitch of at least two segments is small enough to allow the windings to be in electrical contact with each other, wherein the segments are symmetrically distributed over the length of the antenna so that they are in the same relative position. In some embodiments, the windings can be made of uninsulated wire to electrically short the windings. Alternatively, hollow cylinders can be used. The segments can form sharp transitions between antenna segments, causing signal reflections and thus impedance, as further described below. Alternatively, the windings can also be insulated from each other.

[0020] The invention also describes a method for producing an RFID transponder device integrated into a tire.

[0021] In some embodiments, the method comprises the following steps:

[0022] (1) Use conductive materials to make two identical radiators;

[0023] (2) providing an integrated circuit chip suitable for UHF RFID, the chip having two antenna contacts;

[0024] (3) Fix one of the two identical radiators to each contact of the integrated circuit chip so that the radiator is in electrical contact with the contact of the integrated circuit chip.

[0025] In one embodiment, the conductive material may be a rod or a wire. In some embodiments, the radiator may include a plurality of segments, wherein each segment is in the shape of a line, a coil spring, or a cylinder. In other embodiments, two consecutive segments of the radiator have different shapes; if in the shape of a coil spring, the pitch of the coil spring is different.

[0026] In another embodiment, the radiator is divided into at least three sections. The more sections a dipole antenna has, the greater the degree of freedom for fine-tuning the antenna.

[0027] In some embodiments, the method is as described above, and includes forming a line shape on a segment of each radiator that is proximate to the integrated circuit chip.

[0028] In other embodiments, the method includes forming a segment of each radiator proximate to the integrated circuit chip into a helical spring shape with a greater pitch than an adjacent segment.

[0029] In other embodiments, the method includes forming at least one segment on each radiator in the form of a helical spring with a pitch small enough to allow the windings to be in electrical contact with each other, or in the form of a hollow cylinder.

[0030] As described above, applications of the RFID tags of the present invention include molded, formed or vulcanized rubber products, such as tires. In some embodiments, the transponder may be coated with a primer or coating material to increase adhesion between the transponder and the rubber. In some embodiments, an aqueous surface adhesive suitable for bonding elastomers may be used, for example, a mixture of mineral fillers, organic compounds, resins and polymer latex dispersed in an aqueous medium. The primer or coating may be applied by techniques known in the art, including spraying or dipping methods.

[0031] In another embodiment, the method for manufacturing the device of the present invention comprises the following steps:

[0032] (1) Using a conductive material to manufacture a coil spring; in a variation of the method, the conductive material may be a rod or a wire;

[0033] (2) providing an integrated circuit chip suitable for UHF RFID, the chip having two antenna contacts;

[0034] (3) Fix the main antenna or coupling antenna to the integrated circuit chip so that the main antenna couples the integrated circuit chip to the helical spring antenna through capacitance or inductance. The main antenna can be just a short loop antenna or a coil antenna suitable for the above coupling.

[0035] In a variation of the above method, the helical spring may comprise several or more segments, wherein the segments are symmetrically distributed or spaced along the length of the helical spring. In a further variation of the method, the helical spring pitch of two consecutive segments of the segments is different. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] 1 is a schematic diagram of an RFID device for tire marking made into a uniform spring antenna according to the prior art (a), and an embodiment of an RFID transponder device with a segmented spring antenna according to the present disclosure (b).

[0037] Figure 2 is a graph of the resonant behavior of a helical antenna by adjusting the number of windings in air (a) and embedded in tire rubber (b).

[0038] Figure 3 is a schematic diagram of different embodiments of RFID transponder devices. Figure 3(a) shows a transponder according to the prior art. Figure 3(b)-3(f) Different examples of RFID transponder devices according to the invention are shown.

[0039] Figure 4 It is a schematic diagram that approximates the dipole antenna as a pair of wires.

[0040] Figure 5are the complex impedance plots of (a) a lossless transmission line, (b) a lossy transmission line, and (c) a linear dipole antenna.

[0041] Figure 6 Schematic diagram of reflections generated during the transmission of waves through multiple antenna segments.

[0042] FIG. 7 is a graph showing impedance variation of the embedded helical antenna including five segments as shown in FIGS. 3( e ) and ( f ).

[0043] Figure 8 Schematic diagram of an antenna formed by a regular chain of two alternating elements.

[0044] Fig. 9 is a graph showing the results of a parametric study of a binary chain, where n = 3, a_1 = 0.4 mm, a_2 = 1 mm, l_1 = 40 mm and ε_r = 6. The figure shows the frequency curves of the propagation factor for different parameter configurations.

[0045] Fig.10 is a graph showing the results of a parametric study of a binary chain, where n = 3, a_1 = 0.4 mm, a_2 = 1 mm, l_1 = 40 mm and ε_r = 6. The figure shows the calculated resonant frequency as a function of the parameters.

[0046] Fig.11 Schematic diagram of an embodiment of the RFID transponder device according to the present invention, wherein non-conductive coupling is adopted between the integrated circuit and the antenna. DETAILED DESCRIPTION

[0047] For conventional receiver antennas, the impedance of the antenna is matched to the antenna transmission line or the load resistor of the receiver, which in both cases is typically 50 Ohms. Equal antenna and load impedances ensure that maximum power is transferred from the antenna to the load. However, if the antenna needs to be matched to a complex-valued load impedance, for example in the case of a (passive) RFID transponder integrated circuit, both resistance and reactance need to be considered. To ensure maximum power transfer, the complex-valued antenna impedance is matched in such a way that the resistances of the antenna and the integrated circuit remain the same as before and the reactances of the two elements cancel each other out. This process is known as complex conjugate matching of the antenna or matching for maximum power transfer. Due to their construction, (passive) transponder integrated circuits always exhibit a capacitive reactance. To compensate for this reactance, the transponder antenna needs to exhibit a conjugate reactance, i.e. an inductance. At the frequency at which compensation occurs, the transponder resonates and operates optimally. Typically, the complex conjugate matching with respect to the load impedance is established by an electrical matching circuit, which is added to the antenna but also requires additional space.

[0048] If the available space for embedding the transponder is strictly limited by the specific application, it may be difficult to find a properly designed matching circuit. Among all applications, this applies in particular to transponders that need to be embedded in a tire. In view of the huge safety risks posed by material defects and airtight layers, extremely narrow transponders are often used in tire applications. For these narrow transponders, finding enough space for a suitable matching network is a fundamental problem. Such transponders are referred to as linear transponders in the present invention. All transponders whose cross-section is not sufficient to accommodate a suitable matching network are referred to as linear transponders in the present invention. It does not matter if the transponder antenna is a simple wire, spiral or other structure.

[0049] To solve the problem of appropriate matching components, discrete circuit components such as surface mount (SMD) inductors are often used. However, due to their inherent high losses, SMD inductors are often not suitable or cannot be used due to lack of space. However, in order to achieve at least partial matching between the antenna and the integrated circuit of a linear transponder, it is common practice to shorten the antenna length, depending on the integrated circuit used, the surrounding dielectric and / or the individual application. Although it is not actually possible to achieve a perfect complex conjugate match between the antenna and the integrated circuit by changing the antenna length alone, it is sufficient to properly adjust the resonance point of the transponder. This concept is based on the close relationship between antenna length, resonant frequency and impedance; in a simplified model, a linear wire dipole antenna is considered as a common signal transmission line. Its complex antenna impedance Z a It is roughly determined by the effective transmission line characteristics, namely the characteristic line impedance Z0, the geometric length of the line l and the phase velocity v of the conductive wave ph .

[0050] The two ends of the antenna behave as open transmission lines, and their characteristics can be explained by transmission line theory. In the case of a lossless transmission line, the input impedance is obtained by the following relationship:

[0051] Z a (ω)=-iZ0cot(ωl / v ph ), [A]

[0052] This expression is an approximation of the antenna impedance and adequately describes the antenna's resonant characteristics. "Lossless transmission" is a fairly simplistic assumption, since a proper antenna should always approximate a lossy line due to its radiation losses. That is, a lossy transmission line consists of fairly large values ​​of series resistance and parallel conductance, where different frequencies propagate at different speeds. The opposite is true for a lossless transmission line, where waves propagate at the same speed for all frequencies.

[0053] The periodic correlation of impedance, circular frequency ω, and antenna length l reflects the multiple harmonic modes of current distribution along the line. The poles and zeros of the imaginary part of the impedance indicate the series and parallel resonances of the antenna. The series resonance is characterized by the root of the imaginary part of the antenna impedance function, while the parallel resonance is characterized by the root of the imaginary part of the antenna admittance function. At these points, the antenna effectively acts as a series or parallel RLC (resistance, capacitance, and inductance) circuit.

[0054] In the range between series resonance and parallel resonance, the antenna has inductor-like characteristics and the capacitive impedance of the integrated circuit can be compensated by selecting an appropriate antenna length.

[0055] By adjusting the antenna length, the resonance of a linear transponder can in principle be tuned at will, but the window of length parameters may be severely limited. In particular, for linear transponders coated with dielectric materials, the resonant frequency in air is strongly detuned because the dielectric densifies the electric field lines inside it, thus changing the effective transmission line parameters of the antenna. This leads to a resonant antenna length of is the contraction of the coefficients, where ε r is the dielectric constant of the material. Therefore, parameter adjustment has a greater impact on more sophisticated embedded transponder structures.

[0056] Generally speaking, the higher the dielectric constant of the embedding material, the more precise and adaptable the antenna structure requires.

[0057] FIG. 1( a ) shows an RFID transponder device 100 implemented in a tire according to the prior art. An integrated circuit chip 102 is protected and connected to two identical radiators 105 via conductive connections 103, forming a helical spring dipole antenna 104. Due to the small size of the transponder, there is no matching network connected to it, so it is a linear transponder. In contrast, FIG. 1( b ) shows an RFID transponder device 150 according to an embodiment of the present disclosure. Two identical radiators 155 include helical spring segments 156, 157, 158, 159, 160 with different pitches.

[0058] As shown in Figure 2, for a helical spring antenna that will be embedded in a tire but can only be adjusted turn by turn, the concept of tuning the antenna length reaches its limit; trimming a single turn of the winding will cause a large frequency shift that cannot be compensated by any other degree of freedom.

[0059] Another aspect of this conventional setup is the impact on processing products of varying lengths. Each adjustment to the design, such as a customer-specific material or a specific integrated circuit, results in a different antenna length. Each specific length requires a set of production tools to be built and prepared, which increases the difficulty and cost of processing multiple personalized products. In both examples, the antenna cut range is between 1-7 turns. Assuming that Figure 2b In the figure, the ε of tire rubber r =6, the influence of the dielectric will cause a significant difference in the frequency offset of each winding.

[0060] FIG3 schematically shows different RFID transponder devices. FIG3(a) shows an RFID transponder device 200 according to the prior art. An integrated circuit chip 202 is provided in a protective package and connected to two identical radiators 205 via conductive connections 203, which together form a helical spring dipole antenna 204. FIG3(b) shows an RFID transponder device 250 with a segmented dipole antenna 254 according to an embodiment of the present invention, wherein the two radiators 255 include a linear dipole segment 256 and a helical spring segment 257. Although the linear dipole segment 256 functions the same as other standard linear antennas, reflections occur at the transition to the helical spring segment 257, thereby increasing the impedance. Therefore, the two consecutive segments 256, 257 of the antenna are different in form.

[0061] FIG3( c ) shows an embodiment of the present disclosure, i.e., a schematic diagram of an antenna with a segmented radiator 255, wherein the segmented radiator 255 comprises two helical spring segments with different pitches: a helical spring segment 258 with a large pitch and a helical spring segment 259 with a narrow pitch, i.e., a first helical spring segment 258 with a first (large) pitch and a second helical spring segment 259 with a second (narrow) pitch, wherein the first pitch is greater than the second pitch. Therefore, the pitches of the two consecutive segments 258, 259 of the antenna are different.

[0062] In a helical spring antenna, only the portion of the antenna parallel to the length of the dipole radiator contributes to the effective antenna length. The antenna winding can be imagined as a vector consisting of a vertical and horizontal component, where the horizontal component points in the direction of the dipole radiator length and the vertical component points in the direction of the winding radius. The vertical components always cancel each other out because for each vertical vector in a winding, there is another vector pointing in the opposite direction, and the opposing electromagnetic fields cancel each other out. Only the portion of the vector parallel to the dipole does not cancel out and contributes to the effective length of the dipole. Therefore, the larger the pitch, the larger the portion of the vector parallel to the dipole radiator. The large pitch 258 provides stability, while the vector component parallel to the extended portion of the antenna is still large. Reflections occur at the transition to the narrow pitch portion 259. As shown in Figure 3(d), changing the pitch of the two segments allows greater freedom in antenna tuning. Here, segment 260 has a narrower pitch than segment 258 in Figure 3(c), and segment 261 is slightly shorter than segment 259 in Figure 3(c), causing antenna 254 to behave differently.

[0063] FIG. 3( e ) shows an embodiment of the present disclosure, namely a schematic diagram of an antenna with a segmented radiator 255 , wherein the segmented radiator 255 comprises segments 262 with a narrow pitch, alternating with segments 263 and 264 with a large pitch.

[0064] FIG3( f ) shows an embodiment of the present disclosure, namely a schematic diagram of an antenna comprising five segments 262, 265, 266, each of which has a different length, but the total length of the antenna is constant. The pitch of at least some of the segments 262 is small enough to allow the windings to be in electrical contact with each other. Three of the five segments 262 have electrically shorted windings and can be viewed as hollow cylindrical segments. Alternatively, the segments 262 can also be replaced by hollow cylinders.

[0065] The following will study the effect of partial reflection on the piecewise linear antenna. The explanation given here is mainly to help understand the principle of the present invention. Each line segment i=1,...,n of the piecewise dipole antenna is related to the characteristic impedance, effective phase velocity v ph,i And the segment length l i A linear or segmented dipole antenna can be simplified as a pair of wires with different diameters to simulate the different impedances of the segments. Figure 4 This is shown schematically.

[0066] Figure 5 The complex impedance plots for a lossless transmission line (top), a lossy transmission line (center), and a linear dipole antenna (bottom) are shown. The plots show that a dipole antenna of length L (measured from end to end) can be approximated as an open circuit uniform transmission line of length L / 2 (measured from the feed point to the end). The resonance points are nearly identical for all cases shown here, except for minor deviations. In the limit 0, the effective transmission line model does not apply.

[0067] Since the inductance and capacitance of each antenna length depends on its distance from the feed point, the characteristic impedance will change continuously. The reflections caused by this change are very small and will be ignored here, and only a qualitative explanation will be given.

[0068] Signal reflection occurs at the transition between two segments. The reflection amplitude depends on the line impedance difference at the transition, which can be expressed by the following formula:

[0069]

[0070] where ρ0 is the reflection coefficient of the transition between the first antenna segment and the measurement line; ρ n is the reflection coefficient of the open end of the antenna. Since the antenna can be regarded as an open transmission line, ρ n ≈1. The transition between antenna segments will produce multiple signal reflections. Therefore, the actual reflection coefficient at the antenna feed point is not equal to ρ0, but the coherent sum of all reflections along the line, see Figure 6 . Figure 6 The top figure shows the general situation where multiple reflections occur at transition points. The two figures below show some examples of first- and third-order reflections that occur during the transmission of a wave through four segments.

[0071] According to formula [B], reflection coefficient Γ=(Z A -Z0) / (Z A +Z0) and the actual measurable antenna impedance Z A Related.

[0072] In general, multiple signal paths cannot be summed in a closed-form expression. However, when the reflections at the transitions are small, that is, ρ1,…,ρ n-1 <<1, a simple approximation formula can be used. This approximation method is based on the assumption that the difference between the line segments is small due to the small geometric size. Considering the large reflection at the head and tail of the antenna, usually ρ n ≈1 and The reflection factor of the antenna feed point with n segments can be obtained by the following formula:

[0073]

[0074] Among them, the propagation factor RΠ n represents the coherent sum of all first-order reflections of the signal at the transitions between n segments (ignoring all higher-order reflections, the given result corresponds to the reflection coefficients ρ1,…,ρ n The first-order expansion of is as follows:

[0075]

[0076] This term refers to the property of the propagation constant as the coherent sum of n (free-wire) propagation factors and the reflection coefficient. Here, θ i =ωl i / v ph,i Represents the electrical phase of the i-th segment, with a geometric length of l i , the phase velocity is v ph,i , the angular frequency is ω.

[0077] Because all segments of the antenna work together, the coherent sum [D] represents a unique combination of the individual characteristics of each segment. Therefore, all characteristic transmission line characteristics of each segment (such as its line impedance Z i , geometric length l i , phase velocity v ph,i ) provides an additional degree of freedom for tuning the resonant frequency of the antenna. The characteristic impedance of a single segment affects the reflection coefficient at its ends. In addition, there is a direct relationship between the antenna impedance and the propagation factor [D]:

[0078]

[0079] The resonance of the antenna can be obtained through the zeros and poles of its impedance function. From this, the resonance condition of the propagation factor can be derived:

[0080] |RΠ n |=1,arg(RΠ n )=(2n+1)π,n∈N0(series resonance), [Fa]

[0081] |RΠ n |=1,arg(RΠ n )=2πn,n∈N0(parallel resonance). [Fb]

[0082] Since the propagation factor is complex, the conditions [Fa] and [Fb] contain the complex angle arg(RΠ n ) and modulus |RΠ n |Requirements.

[0083] Under ideal conditions, only a single parameter of the linear transponder antenna needs to be adjusted to tune the resonant frequency correctly. Typically, this parameter is the antenna length, which has a direct influence on the resonance point of the antenna. The following two examples will show how the effect differs from the case of simple tuning of the antenna length and how fine tuning of the antenna can be achieved. Thus, the simple case of a linear dipole antenna consisting of a single segment and the case of a periodic chain consisting of 2n+1 segments will be considered.

[0084] A linear dipole antenna consisting of only a single cylindrical wire segment is given by its electrical phase θ dip =ωl dip / c, where c is the speed of light. Equations [D] and [E] give the expression R∏ n =exp(-2iθ dip ), from which we know the known impedance [A] of the open transmission line. Then, as before, we can find the resonant point of the dipole antenna. Since the phase velocity v Ph,dip = c is constant and independent of the conductor geometry, so the antenna length l dip is still the only degree of freedom that can be used as a tuning parameter.

[0085] In Figure 7, the different curves show the Figure 7a ) and tire rubber ( Figure 7b ). The starting shift of the resonant frequency is much smaller than when a single winding is cut (see Figure 2). The results shown in the figure were obtained by simulation of an embedded antenna without simplifying assumptions about the effective transmission line parameters.

[0086] In non-simple cases, there are more degrees of freedom available for tuning. To illustrate this, we choose as an example a binary chain consisting of 2n+1 segments arranged in a regular pattern. The characteristic line properties of the two basic segments should be Z1,β1,l1 and Z2,β2,l2, see Figure 8 As in the case of the uniform dipole antenna, a closed-form expression for the propagation factor can be used. Due to the symmetry of the segment pattern, i.e., ρ2 = -ρ1, the expression [D] reveals the result:

[0087]

[0088] The result consists of two parts: The dominant contribution is of order O(1), i.e., independent of ρ1 and, as in the simple case, caused by reflections from the open end of the antenna. The electrical phase associated with this contribution is the sum of the electrical phases of all 2n+1 segments. Due to the mutual dependence of the dominant order term on the parameters n, θ1 and θ2, it is possible to match the antenna resonances beyond simple length adjustment. In addition, a smaller order term O(ρ1) is added to the result, which takes into account all first-order reflections. Since the contribution of this order term is much smaller than the dominant order term, it is less sensitive to changes in the antenna parameters. In order to be able to fine-tune the antenna, it is necessary to find a suitable parameter dependency that changes the first-order contribution but keeps the dominant order term constant.

[0089] As a specific example of such fine-tuning, a binary chain consisting of four dipole segments and six helical segments is considered (see Figure 8 ). Assuming that the windings of the spiral are in contact with each other, i.e., electrically short-circuited, the spiral segments can be regarded as hollow cylinders. Since the excitation frequency of these hollow cylinders is lower than their cutoff frequency, only the external field has an effect on the effective transmission line parameters. Therefore, the spiral segments can be regarded as dipole segments with an effective line diameter equal to the outer diameter of the spiral. Let a1 = 0.3 mm and a2 = 1 mm be the radii of each segment, l1 = 30 mm and l2 = 40 mm be the lengths of each segment, and ∈ r =6 is the dielectric constant of the surrounding medium. Fig. 9 and Fig.10 The results of the parameter study of the quantities a1 and l1 are shown. In both cases, the total antenna length is kept constant. Both parameter studies show that the resonance frequency is only weakly sensitive to the corresponding parameter. However, only the parameter a1 shows a unique reversible mapping in the evaluated frequency range and is therefore more suitable for adjusting the resonance frequency.

[0090] exist Fig. 9 In the figure, the total length of the antenna remains constant for all parameter configurations. The diamond marks represent fixed frequency points, while the O-shaped marks represent ideal resonant points.

[0091] exist Fig.10The shape of the curve indicates that parameter a1 is suitable as a tuning parameter, while l1 is not suitable in the considered frequency range.

[0092] Fig.11 35 is a schematic diagram of an example of the RFID transponder device 350, which includes an integrated coil spring antenna 354. The integrated circuit chip 352 is not conductively coupled to two identical radiators, but is coupled to a main (or coupled) antenna (not shown). The main antenna is capacitively or inductively coupled to the coil spring antenna 354. As previously described, the coil spring antenna 354 is composed of a plurality of segments 356, 357, 358, wherein the pitch of the coil spring of two consecutive segments 356, 357, 358 is different. The main antenna can be directly connected to the integrated circuit chip 352, or the integrated circuit chip 352 can be fixed to a substrate and the main antenna is fixed to the integrated circuit chip 352 by conductive connection, so that the main antenna and the integrated circuit chip 352 are not placed together. However, due to limited space, it is usually preferred to use a compact solution. The main antenna can be located inside or outside the coil spring antenna 354. Therefore, the main antenna may be coaxial with the coil spring antenna 354. Ideally, the main antenna is coupled in such a way that the dipole produced by electromagnetic coupling has two identical radiators 355, so the dipole antenna can have segments 356, 357, 358 distributed in a mirror-symmetrical manner over the length of the integral dipole antenna 354. This occurs if the coupling is located in the middle of the integral helical antenna 354 (half the length). In special applications, other asymmetric variants can also be selected. As shown, the dipole antenna 354 can be divided into at least six segments 356, 357, 358. In some embodiments, the pitch of the segment adjacent to the integrated circuit chip 352 may be smaller than that of the continuous segment or adjacent segment. In an embodiment with six segments, such as Fig.11 As shown, the pitch of segment 356 immediately adjacent to integrated circuit chip 352 may be less than the pitch of the successive segment 357, but greater than the next segment 358. Thus, the pitch of the middle segment 357 is greater than any of its adjacent segments.

[0093] The present invention describes a tunable linear antenna transponder and methods of making and using the same. In some embodiments, the transponder includes two radiators made of conductive material, wherein the radiators can be the same or different. In some embodiments, the radiator is divided into a plurality of segments, wherein each segment is in the form of a linear segment, a helical spring segment, or a cylindrical segment. In some embodiments, two consecutive segments have different shapes and / or helical spring pitches. Different transmission line segments provide additional degrees of freedom, allowing for finer / improved tunability of the antenna resonance.

[0094] In the description and the scope of the invention claims of this specification, the words "include" and "comprise" and their variations mean "including but not limited to", and are not intended to (and do not) exclude other parts, additives, components, integers or steps. In the description and the scope of the invention claims of this specification, the singular includes the plural unless the context requires otherwise. In particular, when the indefinite article is used, this specification should be understood as taking into account both plural and singularity unless the context requires otherwise.

[0095] Features, integers, characteristics, compounds or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described in this specification, unless there is an incompatibility. All features disclosed in this specification (including any accompanying claims, abstract and drawings) and / or all steps of any method or process disclosed may be combined in any combination, except combinations in which at least some of the features and / or steps are mutually exclusive. The invention is not limited to the details of any foregoing embodiments. The scope of the invention extends to any novel feature or any novel combination of features disclosed in this specification (including any accompanying claims, abstract and drawings), or a novel step or novel combination of steps of any method or process disclosed.

[0096] The reader should pay attention to all the documents and files related to the present application filed with or before this specification, which are disclosed to the public for inspection together with this specification, and the contents of all these documents and files are made a part of the present invention by reference in the present invention.

Claims

1. A radio frequency identification transponder device (100, 150, 200, 250) integrated into a tire, comprising: An integrated circuit chip (102, 152, 202, 252) and a dipole antenna (104, 154, 204, 254) connected to the integrated circuit chip (102, 152, 202, 252), the dipole antenna (104, 154, 204, 254) comprising two identical radiators (105, 155, 205, 255) made of conductive material, the radio frequency identification transponder device (100, 150, 200, 250) being characterized in that: The radiator (105, 155, 205, 255) is divided into a plurality of segments (156, 157, 158, 159, 160, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266), wherein each segment is one of a linear, a helical spring or a cylindrical shape, wherein the shape or helical spring pitch of two consecutive segments is different.

2. The radio frequency identification transponder device (100, 150, 200, 250) according to claim 1, wherein: Each of the two identical radiators (105, 155, 205, 255) is divided into at least three segments (156, 157, 158, 159, 160, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266).

3. The radio frequency identification transponder device (100, 150, 200, 250) according to claim 1 or 2, wherein: The segment (156, 157, 158, 159, 160, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266) of each radiator (105, 155, 205, 255) adjacent to the integrated circuit chip (102, 152, 202, 252) is linear.

4. The RFID transponder device (100, 150, 200, 250) according to claim 1 or 2, wherein: The segment (156, 157, 158, 159, 160, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266) of each radiator (105, 155, 205, 255) adjacent to the integrated circuit chip (102, 152, 202, 252) is in the shape of a spiral spring, and the pitch is greater than that of the continuous segment.

5. The RFID transponder device (100, 150, 200, 250) according to any one of claims 1 to 4, wherein: At least one segment (156, 157, 158, 159, 160, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266) on each radiator (105, 155, 205, 255) is in the shape of a helical spring with a pitch small enough to enable the windings to be in electrical contact with each other, or is a hollow cylinder.

6. A radio frequency identification transponder device (350) integrated into a tire, comprising an integrated circuit chip (352) fixed to a main antenna and a dipole antenna (354) in the form of an integral helical spring antenna, wherein the dipole antenna (354) is capacitively or inductively connected to the integrated circuit chip (352) via the main antenna, wherein the integrated circuit chip (352) is located at half the length of the antenna, wherein the radio frequency identification transponder device (350) is characterized in that: The dipole antenna is divided into a plurality of segments (356, 357, 358), wherein: The helical spring pitches of two consecutive sections (356, 357, 358) are different.

7. The RFID transponder device (350) of claim 6, wherein: The integrated dipole antenna (354) is divided into at least six sections (356, 357, 358), which are distributed in a mirror-symmetrical manner along the length of the integrated dipole antenna (354).

8. The RFID transponder device (350) according to claim 6 or 7, wherein: The pitch of the segments (356, 357, 358) immediately adjacent to the integrated circuit chip (352) is narrower than that of the consecutive segments.

9. The RFID transponder device (350) according to any one of claims 6 to 8, wherein: At least one pair of segments (356, 357, 358) has a pitch small enough to allow the windings to be in electrical contact with each other, or is a hollow cylinder, wherein the pair of segments (356, 357, 358) are distributed in mirror symmetry over the length of the integrated dipole antenna (354).

10. A method for manufacturing a radio frequency identification transponder device (100, 150, 200, 250) integrated into a tire, the method comprising the steps of: - manufacturing two identical radiators (105, 155, 205, 255) using conductive material; - providing an integrated circuit chip (102, 152, 202, 252) suitable for ultra-high frequency radio frequency identification, the chip having two antenna contacts; - connecting each of two identical radiators (105, 155, 205, 255) to each contact of an integrated circuit chip (102, 152, 202, 252) so that the radiator (105, 155, 205, 255) is in electrical contact with the contact of the integrated circuit chip (102, 152, 202, 252), the method being characterized in that - using wires or rods of conductive material to form radiators (105, 155, 205, 255); - dividing the radiator (105, 155, 205, 255) into a plurality of segments (156, 157, 158, 159, 160, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266), wherein each segment is one of a linear, a helical spring or a cylindrical shape; - The segments (156, 157, 158, 159, 160, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266) are made so that the shape or the helical spring-shaped winding width of two consecutive segments is different.

11. The method of claim 10, comprising dividing the radiator (105, 155, 205, 255) into at least three segments (156, 157, 158, 159, 160, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266).

12. The method according to claim 10 or 11 includes making the segment (156, 157, 158, 159, 160, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266) of each radiator (105, 155, 205, 255) adjacent to the integrated circuit chip (102, 152, 202, 252) into a linear shape.

13. The method according to claim 10 or 11 includes making the segment (156, 157, 158, 159, 160, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266) of each radiator (105, 155, 205, 255) adjacent to the integrated circuit chip (102, 152, 202, 252) into a spiral spring shape with a pitch greater than that of the continuous segment.

14. The method according to any one of claims 10 to 12, comprising making at least one segment (156, 157, 158, 159, 160, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266) on each radiator (105, 155, 205, 255) in the shape of a helical spring with a pitch small enough to enable the windings to be in electrical contact with each other, or in the shape of a hollow cylinder.

15. The method according to any one of claims 10 to 14, comprising applying a coating or a primer to the RFID transponder device (100, 150, 200, 250) after all other method steps have been completed, wherein: The coating or primer is a mixture of mineral fillers, organic compounds, resins and polymer latex dispersed in an aqueous medium.

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