RU2616342C1 - Passive anti-collision radio frequency identification label on surface acoustic waves with frequency-time code difference - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: passive anticollision radiofrequency identification label surface acoustic wave with a frequency-time code difference, characterized in that it comprises a topology comprising a reflective structure, the reflection coefficient which is determined by the corresponding frequency N-th pulse of the interrogation signal, which makes possible the separation and identification zone reader identification codes of several labels for the two information signs - the timing and frequency, thereby solving the conflict that has arisen between passive SAW tags.

EFFECT: separation of signals from multiple tags in the frequency domain, if in the time domain when reading transceiver antenna reader response signals from several pulses marks coincide, thereby solves the problem of collisions.

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Description

The invention relates to the field of radio engineering and can be used to identify moving and stationary objects, for example, in rail and road transport.

Known radio-frequency devices for identifying objects on surface acoustic waves (A.S. USSR No. 1,773.191, 1.832.318; RF patents No. 2.095.825, 2.126.165, 2.158.936, 2.176.092, 2.276.406, 2.276 .796, 2.333.512, 2.334.440; US patents Nos. 4,068.232, 4.392.102, 4.620.191, 4.724.427, 4.857.893, 6.061.614; UK patent No. 2.289.602; WO patents No. 93 / 13.495, 96 / 33.423, 98 / 41.829; patent EP No. 0.585.132; Morgan D. Signal Processing Devices on Surface Acoustic Waves, Translated from English - Moscow: Radio and Communications, 1990, p. 12, Fig. . 1, 2, “Identification tag working with surface acoustic waves” (RF patent No. 2.158.936, G01S 13/02, 199 5), electronic passport of the product of the Russian Federation No. 2468386, RU 125535 U1; B61L 25/00 Device for radio-frequency identification and positioning of railway vehicles, anti-collision radio-frequency identification system (No. 2333512), radio-frequency identification device for surface acoustic waves (No. 2344440).

The closest analogue to the claimed technical solution is a SAW tag identification device having an interdigital transducer making code discrimination possible, and methods for its use and manufacture (EA 007777 B1, H01L 41/08 (2006.01)). In the known device, an identification tag on surface acoustic waves (SAW) is proposed having an encoded transducer, as well as methods for using and manufacturing such a tag. The known label contains: a piezoelectric substrate having a number of reflectors distributed over a group of slots located on this substrate in accordance with the pulse and phase characteristics, for encoding a number in accordance with the pulse and phase characteristics; as well as a SAW converter located on this substrate to generate an encoded polling pulse.

A disadvantage of the known SAW tag is the limited ability to code distinguish several tags only in the time domain. The phenomenon of overlapping responses from several passive RFID tags in the time domain is called a collision.

The main task, the invention of which is directed to the invention of a passive anti-collision radio frequency identification tag on surface acoustic waves (SAWs) with a function, is to separate the responses from M passive tags on SAWs in the time and frequency domain. The problem of collision is the most acute in the industry, in rail and road transport, where radio frequency identification tags are used for accounting, identification, positioning control, and to optimize logistics and traffic.

The technical result consists in the separation of signals from several tags in the frequency domain, if in the reading area of the transmitter-receiver antenna of the reader, the response pulses of the signals from several tags coincided in the time domain. Thus, the problem of collision of several labels is solved. The result is achieved thanks to a certain topology of passive tags, which should contain a unidirectional interdigital transducer (IDT) with an antenna and reflective structures sequentially located in the slots, one in each and matched with its specific frequency. So, the response of the passive label should be pulses delayed at certain time intervals τ _i , each of which has its own frequency f _0i from all the frequency values of the signal arriving at the label.

The technical result is achieved by the fact that the first slot is a reference one, and in each of the N slots the reflecting structures have a maximum reflection coefficient consistent with the frequency f _{i of the} i-th pulse of the interrogation signal, the distance between the reflecting structures is proportional to R + X * (n _i -k _i ) + X * (n _i + 1-k _i +1), where R is the distance between the slots, n _i is the number of possible positions in the i-th slot, X is the length of one position in the slot, k _i is the position serial number the i-th slot in which the i-th reflecting structure is located.

The invention is illustrated by drawings, where:

In FIG. 1 - passive anti-collision label on a surfactant;

In FIG. 2 - response signal - label response;

And the following notation is introduced:

1. Antenna.

2. Interdigital transducer.

3. Reflective structures.

4. Slots.

The present invention operates as follows. A reader (not shown in the drawings) emits a signal of the form:

и

- начальное и конечное время опросного импульса соответственно,Where:

and

- the initial and final time of the interrogation pulse, respectively,

A is the amplitude of the pulse,

f _i is the frequency of the i-th pulse,

ϕ _i is the phase of the i-th pulse,

N is the number of interrogation pulses for the duration of the interrogation signal.

A passive anti-collision radio frequency identification tag on surface acoustic waves with a time-frequency code difference shown in FIG. 1 consists of a unidirectional interdigital transducer (2) with an antenna (1) and reflective structures (3), the reflection coefficient of which is determined by the corresponding pulse frequencies interrogation signal and sequentially located on the surface of the substrate of piezoelectric material in the slots. Slots (4) located at a certain distance R must be divided into n parts. The number of slots on the entire label N. The first slot with a reflective structure should be a reference. All reflective structures matched to a specific frequency can be located in any of the n parts of each slot.

The incoming interrogation signal is converted by IDT into a signal in the form of surface acoustic waves. Acoustic pulses propagate over the surface of a piezoelectric substrate. If the frequency of the i-th pulse coincides with the frequency with which the reflecting structure is matched, this pulse is reflected back into the IDT. The remaining pulses continue to propagate until they reach the corresponding reflective structures. The reflected pulses come back to the IDT, and in this way the response of the identification mark is formed in the form of successive pulses:

и

- начальное и конечное время каждого импульса в отклике метки,Where:

and

- the initial and final time of each pulse in the response label,

A is the amplitude of the reflected i-th amplitude of the pulse,

f _i is the frequency of the i-th pulse,

ϕ _i - phase of the i-th reflected pulse,

N is the number of response pulses from one SAW label.

Reflected pulses are presented in figure 2.

The frequency with which the reference reflective structure (reference frequency) is matched is selected from the frequency spectrum of the signal coming from the reader, i.e. from f ₁ to f _N. The frequency value for subsequent reflective structures is selected by cyclic frequency shift relative to a pre-selected reference frequency. Thus, a signal is emitted from the IDT to the reader device as a sequence of time-delayed pulses, each with its own frequency.

The pulses are delayed relative to each other in time proportional to the distance determined by the label topology: R + X * (n _i -k _i ) + X * (n _{i + 1} -k _{i + 1} ), where R is the distance between the slots, n _i is the number of possible positions in the i-th slot, X is the length of one position in the slot, k _i is the serial number of the position of the i-th slot in which the i-th reflecting structure is located.

Thus, the topology of the described passive tags on the surfactant allows you to get the time and frequency information feature for further time-frequency coding of each tag and its identification in the event of a collision of several tags.

Information sources

1. Morgan D. Signal processing devices on surface acoustic waves. Per. from English - M.: Radio and Communications, 1990. - 416 p.

2. Alien Technology Corporation, http://www.alientechnology.com/rfid/ J. Sanford, "Antenna Polarization Considerations in Wireless; Communications Systems", Cushcraft Corporation, http://www.cushcraft.com; Symbol Technologies Inc., "Two RF inputs makes a better RFID tag", http://www.symbol.com/products/rfid.

Claims (1)

A passive anti-collision radio frequency identification tag on surface acoustic waves with a time-frequency code difference, consisting of sequentially arranged on a piezoelectric substrate antenna, a unidirectional broadband interdigital transducer and sequentially located slots, each of which has one reflective structure in one of n possible positions, the distance between the structures is proportional to the delay time between the reflected pulses, different yuschayasya in that the first slot is a support, and in each of N slots reflecting structures have a maximum reflection coefficient, compatible with the frequency f _{i i-th} pulse of the interrogation signal, the distance between the reflecting structures proportionally _{R + X * (n i -k} i) + X * (n _i + 1-k _i +1), where R is the distance between slots, n _i is the number of possible positions in the i-th slot, X is the length of one position in the slot, k _i is the serial number of the i- ith slot in which the i-th reflecting structure is located.

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