RU168220U1 - ANTI-COLLISION RADIO FREQUENCY IDENTIFICATION LABEL ON SURFACE ACOUSTIC WAVES - Google Patents

Abstract

The utility model relates to radio electronics, in particular to piezoelectric devices, and can be used in radio frequency identification tags (RIM) on surface acoustic waves (SAWs) to automatically control the movement of many objects simultaneously through the radio frequency control zone. The technical result of the claimed utility model is to increase the size of the location area of the labels (identifiable objects) ΔR, in which errors in the definition of codes are eliminated. The specified technical result is achieved by the fact that the anti-collision radio frequency identification tag on surface acoustic waves, designed to be placed within an acceptable range of distances ΔR from the reader antenna in a group of k similar identifiable tags from a set of N tags, includes a transceiver interdigital transducer and a reflector located on the substrate, according to the solution, the distance L between the transceiver and the interdigital transducer and the code reflector is selected from the conditions ia: L = V / 2 (t + n (τ + 2ΔR / c)), where V is the speed of surface acoustic waves, t is the initial delay of the code pulse, τ is the duration of the radio pulse of the reader polling, s is the speed of light, n∈ [ 1; N] - label number in the set. 3 ill.

Description

ANTI-COLLISION RADIO FREQUENCY IDENTIFICATION LABEL ON SURFACE ACOUSTIC WAVES

The utility model relates to radio electronics, in particular to piezoelectric devices, and can be used in radio frequency identification tags (RIM) on surface acoustic waves (SAWs) to automatically control the movement of many objects simultaneously through the radio frequency control zone.

Radiofrequency identification systems with RIM to SAW have recently become widespread due to their many advantages over RIM on integrated circuits, namely resistance to external influences in the form of intense flows of ionizing radiation, powerful electromagnetic fields, the inability to fake or erase the code, and operability at high temperatures (up to 800K) with large information capacity, high reading speed and large identification distances - up to tens of meters for passive constructions.

The design of a SAW RIM consists of a piezoelectric substrate, an interdigital transducer (IDT), a system of reflectors and an antenna. The electromagnetic request pulse received by the antenna tag is converted by means of IDT into a surfactant pulse, which propagates along the piezoelectric substrate to a system of reflectors located at different distances from IDT. The reflected surfactant pulses are returned to the IDT at various points in time. IDT converts acoustic pulses into electromagnetic pulses that are emitted by an antenna tag. The described design is the most common for currently used SAW tags (S. Harma and VP Plessky. Surface Acoustic Wave RFID Tags. Development and Implementation of RFID Technology. I-Tech Education and Publishing. 2009, VP Plessky, LM Reindl. Review on SAW RFID Tags. IEEE Trans. Ultrason. Ferroelectr. Freq. Control, vol. 57, pp. 654–668, 2010; S. Baghdasaryan, Yu. Gulyaev. Surfactant technologies in radio frequency identification // Chip news - 2005 - No. 3 (96)).

Labels of this design operate at frequencies from 800 MHz to 2450 MHz. The advantages of such labels, as already noted, is the possibility of their use in a wide temperature range (from -100 ºC to 500 ºC), as well as an almost unlimited service life.

However, such marks cannot be applied when several marks are simultaneously located in the irradiation zone of the code reader (reader). When responding to a reader request impulse, each label emits its own packet of code pulses and a mixture of code pulses is formed at the input of the reader receiver, from which it is impossible to extract codes of individual labels. This phenomenon is called code collision.

In anti-collision ROMEs for surfactants, currently there are two ways to eliminate code conflicts - the correlation method (see RF patent for IZ No. 2486665, IPC Н03Н9 / 145, G06К7 / 01, published June 27, 2013), and the method of discrete-time encoding (see RF patent for IZ No. 2344437, IPC G01S13 / 00, published on January 20, 2009).

The correlation method consists in using not a single pulse as a request signal, but a code packet of pulses. Then the label, the code of which coincides with the code packet of the request, responds with the maximum amplitude of the autocorrelation signal, and if it does not match, then it responds with a cross-correlation signal of much smaller amplitude. The number of simultaneously recognized marks is determined by the excess of the autocorrelation signal over the cross-correlation one and does not exceed 40 marks (Brown, P. Asset Tracking on the International Space Station Using Global SAW Tag RFID Technology [Text] / P. Brown, P. Hartmann, A. Schellhase, A Powers, T. Brown, C. Hartmann, D. Gaines // inProc. IEEE International Ultrasonics Symposium - 2007. - P. 72-75) when they are close, but significantly reduced when they are removed from each other by distances exceeding 1-3 electromagnetic wavelengths due to violation of the time condition for the minimum of cross-correlation signals to correspond to the moment generation of an autocorrelation signal (Suchkov, S. G. On the issue of anti-collision protection of spatially remote radio frequency identification tags on surface acoustic waves [Text] / S. G. Suchkov, S. A. Nikitov, S. S. Yankin, V. A. Nikolayevtsev, S.V. Komkov, A.A. Pilovets, D.S. Suchkov, and Yu.A. Shatrova // Radio Engineering and Electronics - 2016. V. 61, No. 8. –C. 806-810).

The method of discrete-time coding is to determine the code by the delay time of a single response pulse of the ROME. For this, for example, 100 time intervals are set, starting from t ₀ = 1 μs from the moment of emission of the radio polling pulse (RIO) and ending with t ₁₀₀ = 1 + 100 × Δt, where Δt is the temporary code position. Each temporary code position corresponds to a spatial code position on the surface of the crystalline substrate along which the surfactant propagates. The SAW code reflector is located in the middle of the spatial code position. In this design, it is possible to simultaneously recognize 100 RIM located at a distance of no more than 2-3 electromagnetic wavelengths.

Closest to the claimed useful model is a SAW mark, which is a delay line (LZ) with a transceiver interdigital transducer (IDT) and with only one reflecting IDT. In different LZs of the identifiable group of tags, the reflectors are located at distances from the corresponding transceiver IDTs that differ from each other by the same value (code position length) L _c = V _s τ, where V _s is the speed of the SAW, τ is the duration of the radio pulse survey (see RF patent for IZ No. 2344437, IPC G01S13 / 00, published January 20, 2009). In this design, the discrete-time coding method described above is implemented. Temporary code point has a duration equal to two times the duration of the interrogation pulse, that is Δt = 2τ, and the spatial position of the code has a length L _C. The code that the label generates has the number n corresponding to the nth code position and is determined by the reader by the delay time of the response radio pulse, which is the sum of the propagation time of the electromagnetic signal from the reader to the tag and vice versa, and the delay time in the LZ itself, determined by the distance IDT to the n-th reflector L _n . Typically, the duration of the RIO in the allowed frequency ranges of 860-960 MHz and 2400-2483 MHz is about 40 ns and about 20 ns, respectively. If the marks are located at a distance of, for example, 3 m, the delay on the electromagnetic channel is 20 ns, which is comparable to the value of the temporary code position. This leads to an error in the definition of the code.

The disadvantage of this prototype is that the proposed design of tags can only be used for closely spaced (not further than 1 m) tags and, accordingly, objects marked by them.

The technical result of the claimed utility model is to increase the size of the location area of the labels (identifiable objects) ΔR, in which errors in the definition of codes are eliminated.

The specified technical result is achieved by the fact that the anti-collision radio frequency identification tag on surface acoustic waves, designed to be placed within an acceptable range of distances ΔR from the reader antenna in a group of k similar identifiable tags from a set of N tags, includes a transceiver interdigital transducer and a reflector located on the substrate, according to the solution, the distance L _n between the transceiver interdigital transducer and the code reflector is selected from the conditions ovium: L _n = V _S / 2 (t ₀ + n (τ + 2ΔR / c)), where V _S is the speed of surface acoustic waves, t ₀ is the initial delay of the code pulse, τ is the duration of the radio pulse of the reader polling, s is the speed light, n∈ [1; N] is the number of the label in the set.

The utility model is illustrated by drawings, where in FIG. 1 shows the location area of identifiable objects. In FIG. Figure 2 shows the discrete-time coding RFID tags with an extended time code position for the three nearest code positions. In FIG. 3 - extended temporary code position.

The positions in the drawings indicate:

1 - reader; 2 - group of identifiable tags; 3 - substrate; 4 - transceiver IDT surfactant; 5 - reflector surfactant.

Device description

Anticollision radio frequency identification tag on surface acoustic waves, designed to be placed within the acceptable range of distances from the reader 1 ΔR = R _P - R ₁ , where R ₁ is the minimum distance, R _P is the maximum distance, as one of the group containing k similar identifiable tags 2 (Fig. 1). A group of k tags is chosen at random from a set of N tags, in which the maximum number of tags N is limited by the signal loss in the tag, depending on the frequency range of the tags (k and N are any positive integer, k is not more than N). Moreover, the entire group of k tags is identified simultaneously. In FIG. 2 shows a LZ consisting of a substrate 3, which can be made of a piezoelectric crystal, for example, lithium niobate, with metallized structures of IDT 4 deposited on its surface, and a SAW 5 reflector, which can consist of a system of metal strips or grooves on the surface of the substrate.

Figure 3 shows a time chart that shows the start time of the time code zone T _d = t ₀ (minimum delay time in LZ, usually 1 μs), the time of the last code position of the time code zone T _C , the possible limit positions of the response radio code pulse ( dashed line) and its average position corresponding to the distance from the reader R _n (solid fill), in the extended n-th time code position, the middle of which is T _n = (t _n + t _n +1) / 2, where t _n is the moment start of the nth time slot (time code position).

, определяемая из условия:The design of the claimed utility model uses an extended code position

determined from the condition:

(Y)

V _S is the surfactant speed, ΔR is the allowable range of distances from the reader, s is the speed of light, τ is the duration of the polling pulse.

The distance L _n between the transceiver IDT and the reflector of the code in the label with the number n, given the condition of the extended code position (U), is determined by the ratio:

L _n = V _S / 2 (t ₀ + n (τ + 2ΔR / c)),

where t ₀ is the initial delay of the code pulse.

Principle of operation

The RF interrogation pulse generated by the reader 1 is emitted by the reader antenna to the region D of the group k of identifiable tags 2. All RIMs receive an RIO and each respond with its own pulse, the delay time of which does not go beyond its code position if condition (Y) is fulfilled. In this case, the reader simultaneously determines the codes of all k marks located in region D by the presence of response pulses within the extended time code positions.

Concrete example

So, for a label on a lithium niobate substrate with a Y + 128 ° cut, operating in the frequency range 860–960 MHz, with a code number n = 1, the distance between the IDT and a reflector is L ₁ = 2 mm, for a label with a code number n = 2 - L ₂ = 2.08 mm, for a tag with a code number n = 100 - L ₁₀₀ = 10 mm, etc. to number N. The maximum value of N for a given frequency range is 1000 pieces. Such marks work at the maximum size of the object location area ΔR = 5 meters and allow the simultaneous determination of codes of any groups of k marks, including at k = N.

For the frequency range 2400-2483 MHz, the value of N is 200 pieces.

For the frequency range 5650-6425 MHz, the value of N is 50 pieces.

Claims (7)

Anti-collision radio frequency identification tag on surface acoustic waves, designed to be placed within an acceptable range of distances

R from the reader antenna in a group of k similar identifiable tags from a set of N tags, including a transceiver interdigital transducer and a reflector located on a substrate, characterized in that the distance L _n between the transceiver interdigital transducer and a code reflector is selected from the condition

, where V _s is the speed of surface acoustic waves, t ₀ - the initial delay of the code pulse,

- the duration of the radio pulse of the survey reader, c is the speed of light n∈ [1; N] is the label number in the set.

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