Remote-inquiry surface acoustic wave component with optimum code space

ES 2 201 829 T3

DESCRIPTION

Surface wave component that can be queried by radio with optimal code spacing.

The present invention relates to a coded surface wave component that can be consulted by radio, as is known, in principle, from the state of the art (US-A-4 263 595, US-A-5469 170, 1995 IEEE Ultrasonics Symp., Pages 117-120, WO 96/14589, WO 97/42519, WO 97/26555).

A surface wave component comprises, with respect to its constructive structure, a substrate plate which is constituted by a piezoelectric or piezoelectrically coated material. At least one interdigital structure such as a piezoelectric transducer is arranged on or in its structure / layer with this piezoelectric property. By means of this transducer, an acoustic wave, generally referred to as a surface wave, can be generated with a corresponding electrical excitation of the elements of the transducer structure at the surface of the substrate. This acoustic wave has a direction / form of propagation there, which is determined, as is known, through the interdigital structure. Such a structure determines a main propagation direction of the waves in the plane of the surface.

According to a surface wave component that can be queried by radio, the mentioned surface wave in the component can be excited by radio excitation / power supply of the transducer. To this end, the transducer is equipped with a corresponding antenna for radio reception and, in general, also for radio retransmission of a response signal from this transducer to a receiver. A special transducer with antenna can also be provided for the inquiry signal.

The inquiry signal is transmitted by means of a transmitter, which can transmit with a minimum bandwidth to be predetermined. For this emission of the radio signal one can use, for example, a device, which can generate from thermal and / or mechanical energy, for example with the help of a non-linear electronic component, such as a spark gap, a high frequency impulse. Details are known in this regard.

The receiver provided for the radio response signal retransmitted by the mentioned component must be dimensioned, as is known, with respect to its bandwidth, in accordance with the specifications of the system that works with the surface wave component.

In the case of surface wave components, which are used for identification, it is required that it be ensured that a received signal can be clearly associated as a response signal to a predetermined surface wave component and individually coded accordingly, to Unless a system comprises a plurality of such components to be consulted, but coded differently from each other and / or unless other signals are received that arrive in any other way at the system receiver

Therefore, it is known and customary in practice to provide such surface wave components that can be queried by radio with a respective individual encoding, which makes the individual component within a plurality clearly distinguish from each other in the respective reception signal. of such surface wave components contained in the system.

As background, two examples of application possibilities are mentioned for such coded surface wave components that can be consulted by radio. One such example is that such a coded surface wave component is placed, for example, on an object, which must be identified in a corresponding way by means of this component or its coding. Such components are also known as ID tags. Another example is that the surface wave component has the additional property, or is equipped with such a property, of serving as a sensor, for example, for the measurement of a temperature, a force magnitude and / or other magnitudes. physical, chemical or similar status. Such applications and the corresponding configurations of a surface wave component are known.

Different principles are possible from which a coded radio response signal can be generated. An example consists in providing for the coding reflector elements which are arranged in a known manner adapted to the arrangement of the aforementioned interdigital structure of the transducer. Such reflective elements are, in general, fringe elements, which are provided in the course of the main direction of propagation of the surface waves on / on the surface of the substrate plate. Instead of the aforementioned reflector elements, as another example of coded elements, resonators can also be associated with the transducer (s), as is also described below.

An individual reflector element causes a response signal of the surface wave component that is offset in time with respect to the query signal, that is, with respect to the emission pulse. A component provided, instead, with resonators provides a response signal determined according to the (resonant) frequency. A respective plurality of reflectors arranged at different positions (relative to each other and relative to the transducer) provides a corresponding plurality of differently shifted impulse response signals, where the time shifts from each other depend on the positions of the reflectors respective to each other. The same applies in a corresponding way for a respective number of intended resonators different in frequency relative to different resonance response frequencies.

Therefore, the response signal to be obtained by the surface wave component on a radio inquiry signal is, in the case of reflectors, an additive superposition of partial response signals shifted in time to each other or in the case of resonators an additive superposition of a correspondingly large number of sinusoidal response partial signals, shifted in time (most of the time exponentially attenuated) with different frequencies from each other. Identifying a component of on3

The respective surface dashes are usually carried out in such a way that the reception instants are determined, which correspond to the selected positions of the individual reflectors of the respective component. The resonator principle results in amplitudes of the reception spectrum at frequency support points, which correspond to the selected resonance frequencies of the individual resonators. The coding or the printed code of a surface wave component coded with the respective reflector therefore consists, as regards the object / construction, in a coded position of the individual reflectors provided with respect to a reference reflector element or either with respect to the position of the transducer on the surface of the substrate plate. For the case of resonator coding, the different selected predetermined resonance frequencies of the individual resonators result in the code printed on the respective component.

A related problem is that the resolution of the structure of the corresponding measurement system is always limited. By resolution of the structure is understood here the capacity of the system (which is essentially made up of the emitter, the surface wave component and the receiver), for recognizing two partial response signals of reflection or resonance of two reflectors arranged immediately next to each other on the plate of the substrate or of two resonators with resonance frequencies immediately next to each other as two partial response signals separated from each other. In systems with time measurement (reflectors), the temporal resolution of the structure

At is inversely proportional to the spectral bandwidth B used of the system / measurement, that is, Δt prop. 1 B. In the system with frequency measurements (resonators), the relationships are, in principle, similar, that is, here the resolution of the structure Δf is determined through the quality of the system, that is, it is inversely proportional to the time duration t of the measurement signals (Δί prop. 1 / t). The proportionality factor is approximately 0.5 in the case of conventional measurement signals with a Gaussian-shaped envelope.

The resolution of the aforementioned structure, limited in principle, has the consequence that all the code elements in the reflectors must have a minimum distance from each other and in the case of the resonators they must have a corresponding minimum average frequency distance, since otherwise in the response signal the portions of the signal from neighboring elements in position or frequency (reflectors or resonators) would be superimposed, so that a reliable evaluation (identification) of a code of a respective component would no longer be possible.

For the sake of completeness, it should be noted that in the invention which is still described below, extensive coding possibilities can still additionally be provided. For example, instead of a binary system (reflector present / reflector not present), codes with a base greater than 2 can also be applied. One possibility in this regard is to provide several thresholds / amplitude stages for a respective code element. Another possibility is to (additionally) evaluate (in stages) the phase difference between two signals of two code elements.

The known type of coding consists in arranging in a distributed manner in terms of position, according to the required extension of the code, a greater or lesser number of reflector bands on the surface wave component along the main propagation direction of the waves. surface waves generated by the transducer. For example, for a 32-bit code extension, it is known as prior art to provide 32 places placed one behind the other in the main propagation direction of the waves for the 32 reflectors to be installed. In the case of a 1 μs resolution of the system structure (as the propagation time = path length s divided by the velocity v of the acoustic wave), therefore, double coding is needed for the arrangement of the reflectors have a length of the propagation time of 31 μs, that is, from the first to bit 32. This conditions a considerable length of the substrate plate necessary for the component. This is accompanied by technical problems, which are explained still below in connection with the invention. See also the detailed description given (below) regarding the use of resonators as code elements.

The object of the present invention is to achieve that, for a particularly high predetermined code extension, the size / length of the substrate plate is small (compared to the state of the art) and / or the fewest possible number of code components per code. individual. In other words, this means that a coding scheme is searched for a predetermined code length, which requires an optimally small number of code elements for each code, which are further individually selected arranged on a reduced length / area. of the substrate plate.

This task is solved by the measures of claims 1 and 2, respectively, and other configurations and developments of the invention are deduced from the dependent claims.

For the new coding principle according to the invention, a new distribution of the positions or of the frequencies forming the respective codes is provided, which (will be explained in the first place below for the case of the distribution of the positions of the reflectors) enables, with a given resolution of the structure defined above, a large number of different codes. To remain in the example mentioned above, the invention with a resolution of the structure, for example, of 1 μs of the surface wave component and of its corresponding system (especially of the receiver that evaluates the signals) over the aforementioned length of 31 μs propagation time of the acoustic wave provides, instead of, as in the state of the art, 2³² Different encodings available, an encoding span increased by around 4000 times (17 167 680 177 565 encodings), which roughly corresponds to a 43-bit encoding according to the known encoding. In order to be able to apply, on the other hand, the previous code extension of the 32 bits with the measure according to the invention indicated below, only 23 reflectors (resonators) placed for each of the

ES 2 201 829 T3 codes, for which the substantially reduced length of the substrate plate, corresponding to a propagation time of

22.5 μ8. The above numerical comparison is only one example of the advantage that can be achieved with the invention. This can be selected even much higher by assuming an even lower inaccuracy of the measurement of the propagation time in reflectors (or of the measurement of the frequency in resonators) in the system, so that, for example, the coding can be generated 32-bit known only with a maximum of 20 reflectors placed per code then even over 19 μs in length.

Further details are given below first with respect to and with the aid of the embodiment of a component according to the invention with reflectors (= time slot coding) and further instructions for the embodiment with resonators (= = encoding in the frequency range).

As claimed, to the resolution of the known structure Δ, defined above, the property of the inaccuracy of the measurement δ of the system for the measurement of the propagation time or for the measurement of the frequency has been added or inserted here . The inaccuracy of the measurement designates the stochastic and systematic error, with which the value of the propagation time / frequency measured with the system deviates from the real value of the propagation time / frequency of the physical structure. The time position of a reflector or the frequency of a resonator can be accurately determined by virtue of the inaccuracy of the measurement made in or with the system only over a designated interval through the inaccuracy of the measurement. The measure of the inaccuracy of the measurement δ is, in general, in systems with a surface wave component, clearly less than the measure of the resolution of the structure. Measurement inaccuracy can also still be reduced in the case of stochastic measurement errors through the averaging of several measurements or in the case of systematic errors through calibration processes, which will be described further below.

According to the invention, with this measurement δ the respective position matrix with equidistant distances δ of the matrix or the frequency matrix with distances δf of the same frequency of the matrix is ​​formed for coding in accordance with the teachings of the invention.

The principle of the invention is to arrange, despite the resolution of the available structure Δ, for example from now on constantly large, given across the bandwidth, these reflectors according to the invention in such a position matrix, and to be able to clearly determine the position of a respective reflector, despite the limited resolution of the structure, foresee that in a matrix of positions the spaces of the matrix are only occupied in such a way that if there is no code, that is, if there is no configuration of code, the spaces close to each other of the matrix of positions are occupied. If, for example, the measurement inaccuracy of the propagation time measured in the time bound is half (for example δt = 0.5 μδ) than the resolution of the structure Δ (for example, 1 μ ») measured equally at the time limit, then the rule according to the invention provides for leaving unoccupied at least one place in the matrix between two occupied places in the matrix of positions. If, for example, the measure δt is only 1/3 of the structure resolution, then the position matrix should be distributed three times finer than a matrix with the structure resolution measure. According to the rule according to the invention, then, in effect, at least two places in the position matrix must remain unoccupied between two reflectors placed neighboring the code, namely, again conditioned by the limited resolution of the structure, but then, however, the extension of the code of the principle according to the invention is raised, for example with 32 occupied reflector positions for the individual code, to 5 x 10¹⁵ encodings. The code extension of the above 32-bit encoding could be generated in this case, by code, only still with a maximum of 20 placed reflectors, over a chip length of only still 19 μ8.

The above explanations apply to the invention in the correct sense also for resonators as code elements instead of the mentioned reflectors, which will be explained in detail further below.

According to a development of the invention, it is envisaged to provide for the individual codes / (coding possibilities) of the particular individual components within a group of components of a predetermined total length of the code always the same unit number of code elements, i.e. , reflectors or resonators, in each of the individual components. This means for the surface wave component that, seen from the transducer and for the propagation of the acoustic wave, an attenuation of constant magnitude of the wave is always present in a valid way and the recognition of an erroneous code is deduced from a divergent number of partial signals received. According to this development of the invention with constant number of code elements, these code elements for the respective codes are only arranged differently distributed in the position matrix. The entire array of positions has either an optimal short length - in comparison with the state of the art - or allows a short dimension of the component.

In the case of still low measurement inaccuracy (for example 0.33 μs as mentioned above), the code length or the number of coding possibilities can be further increased with a predetermined number of code elements. code by code in reflectors for a predetermined length or for resonators on a predetermined surface of the component chip. Conversely, in the event of even lower measurement inaccuracy with a predetermined code length, the number of code elements required per code and / or the required length or surface area of ​​the component substrate plate can be reduced.

In other words, the idea of ​​the invention can be described as follows:

For the code elements of the individual codes of the code extension, a matrix is ​​formed according to the invention. It is a matrix of positions for reflectors and a matrix of frequencies for resonators as elements.

ES 2 201 829 T3 of code. The respective matrix has basic distances δg equidistant from each other (of the positions or of the frequencies) of the basic values ​​of the matrix.

These distances are dimensioned according to the inaccuracy of the system measurement, in which a propagation time or a delay can be measured with an error δ (δί for the measurement of the propagation time; δf for the measurement of the frequency). frequency.

In a matrix according to the invention, these distances are optimally dimensioned of the same magnitude or also greater than this measurement δ.

But, according to the invention, only those basic values ​​(positions / frequencies) are "occupied" with code elements, in which the distances between code elements arranged in this way are equal to or greater than the resolution of the structure Δ of all the system. If the measurement inaccuracy is δ = 0.5 μs or 0.33 μδ, these distances Δ required according to the invention between the reflectors placed as code elements with a structure resolution of 1 μ », measured at the elevation of time, they are in each case 1 μ8. The essential difference with respect to the state of the art is that through the use of the smallest position matrix, in terms of measurement, with respect to the resolution of the structure, a corresponding position matrix is ​​made available several times finer for occupation with reflectors as code elements. In the case of unchanged resolution of the Δ structure, a larger code length can be achieved in this way with a constant number of code elements per code or the code extension achievable hitherto with fewer code elements per code. The division ratio between the resolution of the structure and the selected measure of the matrix can also be a non-integer number (greater than 1).

If these teachings are applied to the technical activity of a resonator-encoded surface wave component, then the following analogy is obtained. Instead of R reflectors, the number of R resonators is provided and arranged on the substrate plate of the respective surface wave component (this belongs to the predetermined length of the code). These R resonators have respective resonant frequencies distinct from each other fi with i = 1 to R. The matrix for the selection of these frequencies fi is the frequency matrix according to the invention with its basic values ​​f, for example 1 to 46. These have an equidistant distance δf. This basic distance from the resonant frequencies that are available for coding (with a limitation indicated still below) is dimensioned such that it is greater or optimally equal to the measurement of the measurement inaccuracy δί, with the that an individual frequency can be measured in the system consisting of the emitter, the receiver and the component. In comparison with the reflectors, here again, starting from the frequencies of the basic values ​​of the matrix (for example 1 to 46), only those resonance frequencies fi for resonators a can be selected within the matrix according to the invention. used as code elements, in which the distances between neighboring selected resonance frequencies (fj, fj + 1) of two resonators are in each case greater or optimally equal to the resolution of the structure, that is, the resolution of the structure Δί of the entire system, including the natural bandwidth of these resonators, which it results from its quality.

For the calculation of the extension of the code, the following calculation law can be used. Suppose that P is the number of basic values ​​per interval of the resolution of the structure Δ (p · δ = Δ). For example, P = 2 for the above example with 0.5 μs of measurement inaccuracy and 1 μs of structure resolution. P = 3 applies for the mentioned example with 0.33 μs of measurement inaccuracy again with 1 μs resolution of the structure. The Cu coding extension is given for the number R of the respective code elements (hence Cu {R}) and for the number of code elements R + P - 1 (Cu [R + P - 1 }). The extension of the coding (Cu {R + P}) then results from the sum, that is, it applies (Cu {R + P} = (Cu {R} + (Cu {R + P-1} Therefore, if the coding extension is known for a number P of consecutive code elements (Cu {R}), Cu {R + 1}), ... (Cu {R + P -1}), then the code length can be calculated successively for all subsequent numbers of code elements.

The code span can be further increased even further in the case of resonators as code elements, if the receiver unit is configured in such a way as to make it possible to determine the amplitude and / or the phase or the frequency position of the partial signals received from the individual resonators of the code elements. In this case, the amplitude or the phase or both pieces of information can additionally be used according to the principle known per se to further extend the length of the code.

If the structure of the code elements is to be used additionally also for measuring purposes with sensors (as already mentioned above), then it may also be advantageous not to arrange the possible positions of the reflectors or the frequencies of the resonators. exactly in the equidistant matrix according to the invention, but to introduce definite deviations of the position (frequencies) of the code element, so that the distances / frequencies distances between code elements are not exactly equal to the equidistant matrix. This prevents all reflectors or resonators from providing redundant sensor information. In this type of embodiment, it must be ensured, of course, as before, that all the distances in terms of position or frequency between the code elements are, according to the invention, at least not less than the resolution of the structure Δ (above, for example 1 μ «) of the entire sensor system. To this end, either the basic distance δ can then be greater than the measurement (at least) or fewer codes can be provided.

The type of coding according to the invention of a surface wave component offers, among other things, several advantages described below, for example also with regard to the technical implementation and implementation in the surface wave component. The type of coding according to the invention is, for example, as opposed to multi-phase coding, less dependent on limits of changes in the speed of propagation of the surface wave in the component. As a comparison, it uses, for example, an ID card with the average frequency 434 MHz, with a structure resolution of 1

ES 2 201 829 T3 μs and with a number P = 4 resonators per interval Δ. In this case, a 4-stage phase coding (4 PSK modulation) has a code extension comparable to the coding carried out according to the invention, which can be referred to as pulse position modulation. The minimum resolution of the structure with 1 μs is with this average frequency 434 x λ. In the known 4 PSK modulation, two close distances are separated by a phase of 90 °, that is, * 4λ. A variation of the temporal position of a reflector by only 0.25 λ: 434 λ = 1 μs: 1736, caused for example by an inaccuracy of the position during the manufacture of the component or due to a deviation of the wave speed The surface of the component therefore already leads to an unacceptable falsification of the response signal and thus to misidentification. In the case of a coded component according to the invention, an error of this type would only appear if the position of a reflector within the array were mispositioned 0.25 μδ. Only then, in the case of a surface wave component, would a comparable falsification of the signal appear encoded according to the invention. Therefore, this shows that a surface wave component with encoding made according to the invention is more insensitive by the factor 400 to surface wave velocity oscillations and / or position errors, compared to PSK modulation. known. On the other hand, this also shows that the type of coding according to the invention is an extremely robust multipurpose coding of a surface wave component. This goes hand in hand with great advantages, which also relate to the production of a respective component, coded according to the invention.

Previously, a measure δ for the inaccuracy of the measurement has been taken as a basis for the distances of the matrix ot and of, respectively, of the position matrix / frequency matrix used according to the invention, which is more or less less than the resolution of the Δ structure of the system. In this case, this measure of the δ value is selected, for example, on the basis of experiences and measurements, respectively, which have been obtained by working with surface wave elements. The purpose of a development of the invention is to indicate measures with which a (small) achievable measure of the inaccuracy of the measurement δ can be achieved in a selective predetermined manner, namely, in order to be able to use the invention in the most optimal way described above.

This task is solved by an advantageous type of realization of reading a respective code of a respective coded surface wave component. This embodiment of the reading provides for a consecutive multiple reading of the respective code, that is, a corresponding multiple measurement of the respective individual code elements. Therefore, the time measurement t of the position of the respective individual reflector or the frequency of the individual reflector is detected, ie measured according to the measurement technique by means of the interrogation signal. This multiple reading of the individual code elements is performed in the course of the corresponding multiple reading of this code in an extremely fast sequence. In this way, data sets are obtained, comprising the multiple measurement results of the respective individual code element. For each code element of the code read, a data set of the same type is obtained. These data sets are analyzed and the standard deviation measure or another measure that describes the statistics or the inaccuracy of the individual measurements within the respective data set is obtained. With a corresponding frequency of the measurements, a respective mean value (for the position of the reflector or for the frequency of the resonator) or also a mean value of the position / frequency representative of another type is obtained, with an inaccuracy of the measurement that is can be based on the inaccuracy of the δ measurement defined and used according to the invention.

If the previous multiple reading of the code elements of a respective code does not, for example, reach an inaccuracy of the predetermined measurement δ, that is, a predetermined measurement of the matrix ot and o'f, respectively, in a short determined, then the probability is raised that the respective code element, i.e. the position of the reflector / resonant frequency, is correctly measured, i.e. that all the code read has been read correctly. Through this configuration related to the performance of the reading with multiple reading and average an evaluation is achieved, in which all the stochastic inaccuracies, which are inherent in a respective measurement, are reduced to a (sufficiently) small measure.

On the average of the measurement values ​​described above, a calibration can also be carried out in a comparable way to eliminate possible systematic errors. To this end, it is necessary for the surface wave component to have at least two reference elements, perhaps for example the code elements. These can be reference reflectors and reference resonators, respectively, for example as a start element and / or a stop element in addition to the described code elements. These reference elements are arranged independently of the grating at known positions, or as resonators with known resonance frequencies, on the surface wave component. By comparing the measured values ​​and the measured values, if necessary, also still averaged of these reference elements with their known, predetermined values ​​in each case, for example by comparing the measured time difference / frequency difference between the starting element and the stopping element with the known difference predetermined by the design and / or by comparing the measurement values ​​of the positions / frequencies of the start element and the stop element with their respective known actual positions / frequencies, a scale factor and / or a deviation value can be derived, with which (with which) all time / frequency measurement values ​​of code elements can be corrected. Also in this case it is advantageous to carry out the calibration several times or to carry out an average over several respective measurements, until it is ensured that the inaccuracy (reduced) achieved in this way of the time or frequency values ​​of the position is less. to a certain extent that the / a predetermined measure of measurement inaccuracy δ.

ES 2 201 829 T3

The averaging described above or the calibration indicated above can be carried out or in a more advantageous manner various measures can also be applied as a further development of the invention.

For a still further explanation of the invention, the following description related to the corresponding figures also serves.

Figure 1 shows an example of a surface wave component configured according to the invention with reflectors.

Figure 1a shows the component in the radio consultation system.

Figure 2 shows a representation, with which the definition of the position matrix defined according to the invention is explained in a complementary manner.

Figure 3 shows an example of two surface wave components with different codes of a code span, respectively, with the same number of reflectors as code elements.

Figure 4 shows in projection view a constructional structure of a coded surface wave component according to the invention with resonators as code elements.

Figure 5 shows a defined frequency matrix according to the invention with its individual resonance frequencies that are available for selection (limited), and

Figure 6 shows an example of two different codes in the frequency matrix.

FIG. 1 shows the example of a surface wave component 1, comprising the teachings according to the invention, with a substrate plate 10, for example made of lithium novice, lithium tantalate and the like, or also quartz. These materials have the necessary piezoelectric property, on the surface 1 of the substrate plate 10, represented in the projection view, an electroacoustic transducer 12 is arranged on the one hand. This has, for example, an interdigital structure, comprising two comb-type structures, with two electrical connections 14. These are placed, so to speak, as terminals on a support base 101 of the substrate plate 10 and are connected electrically with the respective comb-shaped structure. The (dipole) antenna 114 provided for a component that can be consulted by radio can be electrically connected to these connections 14. With 15 the surface wave (indicated symbolically) to be generated, respectively, by means of the transducer 12 piezoelectrically on the surface of the substrate plate is designated 10. The double arrow 115 indicates the alignment of the main propagation direction of the waves. With 20 the structure of the code elements is briefly designated, which comprises code elements 21 arranged in alignment according to the direction of propagation of the waves 115. With the figures 1, 2, 3 ... 46, "basic values" of the matrix are mentioned numerically, which are described in detail still later. Of these, positions 1, 3, 6, 8, 10, 13 ... and 46 are occupied with a respective code element 21. In FIG. 1, reflectors 21 'are indicated for this purpose. The distribution of these code elements, for example, over the 46 base values, individually selected for a respective surface wave component from a group of such components, corresponds to a code or forms an individual code within the predetermined extent of the code , which can be prepared with this group of components.

For the above-described special embodiment of the reading with calibration to eliminate possible systematic errors, the reflectors K1 and K2 serve as the starting and stopping reference code elements as reference elements.

For completeness, reference must still be made to other elements of the structure, such as reflectors, which belong in a manner known per se to a sensor structure 221, which serves, for example, for temperature measurement, for a force measurement or the like. 17 designate wave sinks for the surface wave.

Figure 1a shows an overview of the system, comprising the surface wave component 1 and the sensor S and the receiver E that are necessary for radio consultations.

Figure 2 shows, from the view of the embodiment of figure 1, only the substrate plate 10 and the interdigital structure 12 of the transducer (because this determines the main propagation direction of the waves 115 on the surface of the plate substrate 10). Instead of the structure of code elements 20 (not indicated here yet) of FIG. 1, the matrix of positions 30 according to the invention is indicated, defined for the invention for reflectors with its basic values ​​130 of the positions, which are designated as in FIG. 1 with 1, 2, 3 .... The individual limit values ​​130 are represented in each case by a line (mean). This matrix 30 according to the invention is defined in such a way that it is aligned, on the one hand, in the main propagation direction 115 of the wave 15 generated with the transducer 12. Due to the linear propagation direction of the waves, the matrix of positions 30 is a linear matrix. In special cases another configuration may also be present, but the matrix always follows the propagation of the waves, in such a way that the reflectors can act as code elements on the occupied positions of the basic values ​​130 in a manner known per se by reflecting on surface wave 15.

The linear array 30 has as many basic values ​​130 as the predetermined code scope taking into account another distribution condition according to the invention for the individual code elements. According to the definition given with the invention, the equidistant distances "a" of the basic values ​​130 from each other are dimensioned such that the measure of the respective distance of neighboring basic values ​​(1 and 2, 2 and 3, .. .) is equal to the path ot, which the acoustic surface wave 15 travels within a defined time limit. This time limit is for the measurement of the propagation time with reflectors as code elements the inaccuracy of the measurement δ of the system, measured in time as defined above or determined through a time indication, in which it is contained the surface wave component 1 along with the emitter S and the receiver E.

As stated with the teachings of the invention, the basic values ​​130 of the position matrix 30 can only be occupied in resolving the structure at distances Δt corresponding to a respective code element. With ó'l <* / 2 At, one or more values ​​130 are kept free between two basic values ​​130 occupied with code elements.

ES 2 201 829 T3

As an illustrative example of claim

3, Figure 3 shows two arrays of positions 30 'and 30 "represented adjacent with (comparatively only) 13 basic values ​​130 per array. Of these values, in both matrices, preferably the same number, namely six basic values, are positions of the respective matrix occupied with code elements 21, that is, with reflectors 21 '. However, the distribution of the occupation is different according to the different code in both matrices,

Figure 4 shows as an example an embodiment with resonators instead of reflectors as shown in the preceding figures.

Figure 4 shows in projection view a component 1 'of surface waves with resonators 220. With 10' is designated the substrate plate, on whose surface 11 are arranged transducers 212, the aforementioned resonators 220, connections 14 for the dipole antenna 114 and wave sinks 17 for attenuation of the waves. Shown in the second line of Figure 4 is a transducer 212, and the two resonator portions 2201 'and 2201 "that form a resonator 2201. 115 indicates the main propagation direction of the waves and 15 indicates the corresponding surface wave. The resonator 2201 is constituted in its two portions by spaced apart resonator bands, usual for an element of this type, and is adapted through the selection of the distance between the bands, for example at the selected frequency f1. This resonator 2201 is a first code element of this coded component 1 'shown in the figure

Four. A code element j shows the underlying line with the resonator 220j which is again constituted by two portions and its transducer 212j necessary for the generation of wave 15. Also the frequency fj is selected from the frequency matrix according to the invention. The R code element of component 1 'is shown on the fourth line. Again, the resonator is made up of two 220R portions. The resonator 220R is tuned to the frequency fR, which is also selected from the predetermined frequency matrix according to the invention. These resonators are therefore surface wave structures tuned in a manner known per se with respect to their resonance frequency with the different frequencies f1 to fR relative to each other. These selected frequencies give rise to the general code of the individual surface wave component. The transducers 2121 and 212R can be connected in a known way in series or also in parallel. A constructionally unique transducer structure may also be provided, comprising, however, the main propagation directions of the represented waves 1151 to 115R. Usually, the bandwidth of such a transducer 12 is so great that also identical made transducers can form the transducer chain.

The frequency matrix 230 according to the invention of FIG. 5, which is relevant for the embodiment with resonators, is similar to the position matrix of FIG. 2. The distance of the matrices δt relevant to the invention as claimed in the frequency range is given through the inaccuracy of the measurement of the system, consisting of emitter, receiver and component, or through the inaccuracy of the measurement that is can be achieved with multiple measurements or with the average, comparable to the distance of the basic values ​​130, given through the inaccuracy of temporal measurement in figure 2. In connection with the embodiments of Figures 1 and 2, also in Figure 5 are indicated, for example 46 frequencies . The number of such frequencies fi which are necessary for the component 1 'for the selection of the number R of resonant frequencies of its resonators 2201 to 220R is here also set according to the predetermined extension of the code. (In order to keep a component 1 or 1 'according to FIG. 1 and according to FIG. 4, respectively, as small as possible from the geometric point of view, the large minimum R number is also selected here, which can be achieved with the invention with reduced inaccuracy of the δ measurement, for example with approximate unaltered Δ structure resolution).

According to the invention, for the "occupation" of the possible basic values ​​of the frequency matrix according to FIG. 5, the limitation is applied that between two adjacent frequencies fj and fj + 1 (j = from 1 to R), used as resonators, the distance of the frequency must be Δί, where Δί is at least of the same magnitude as the resolution of the given structure through the quality of the system. This structure resolution is the frequency distance Δί, which is necessary to be able to distinguish between two different resonance frequencies in the system. For example, compared to component 1 described above with reflectors with a minimum allowable distance between the positions according to the time magnitude At, in an embodiment with resonators an occupation of the positions of the frequency f1 to f46 of the matrix can be used according to figure 5 with a minimum distance between the frequencies ΔΓ = 2 x o'f, when the inaccuracy of the system frequency measurement is twice less than the resolution of the structure ΛΓ in terms of frequency.

The resonators R11 and R12 are used as starting elements and as stopping elements in the component with resonators as reference elements for carrying out the reading with calibration.

Figure 6 shows in comparison to figure 3 the frequency scheme of two different codes from a predetermined code extension with six resonators provided as code elements. For example, these are the different codes of components 1 (n) and 1 (n + 1) of a number N of surface wave components 1 'encoded of a predetermined code length.

The application of the invention also achieves advantages, which result with respect to the performance of the manufacturing process. For example, during the manufacture of a coded component according to the invention, the illumination time for the manufacture of the code elements (reflectors / resonators) is reduced, for example by half. This is the case where, for example, two reflectors are always placed on the illumination mask, which are illuminated in common. These two reflectors must be provided for this purpose at different distances from each other and in particular at minimum distances according to the specification according to the invention on the illumination mask. For example, if the resolution of the structure is 1 μs and the number of code elements is P = 4 per interval Δ of

ES 2 201 829 T3 the resolution of the structure, then lighting masks must be provided, respectively, with two reflectors to illuminate at the same time for the distances between the reflectors 1.00, 1.25, 1.50, 1.75 and 2.00 μβ if necessary.