RU2497147C2 - Method for detection and identification of desired transponders from plurality of passive transponders and system for implementing said method - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: system which implements the disclosed method includes passive transponders situated in the scanned zone, and a reader having a transceiving antenna, an encoding device, a transmitting device, first and second receiving devices, an estimation unit, a transponder code base unit, a code conversion unit, a threshold unit, a recording unit, a duplexer, first and second correlators, first and second controlled delay units, first and second multipliers, first and second low-pass filters, first and second optimal controllers, a switch, a range indicator, a receiving antenna and an azimuth indicator.

EFFECT: broader functional capabilities of existing engineering solutions through automatic location of desired transponders.

2 cl, 1 dwg

Description

The proposed method and system relates to radio-frequency identification systems of moving and stationary objects (RFID systems).

Known methods and systems for the detection and identification of wanted transponders (ed. Certificate of the USSR No. 1.054.887, 1.228.722, 1.627.832, 1.769.216, 1.773.191; RF patents No. 02.057.334, 2.176.092, 2.336 .539, 2.344.437, 2.350.982, 2.388.157, 2.410.716; US patents Nos. 4.051.057, 4.605.208, 5.691.698, 6.061.614; Great Britain patent No. 2.165.424; German patent No. 4.336 .898; French patent No. 2.630.236; Burlakov V. Radio-frequency identification. Electronic components. 2005, No. 5, pp. 55-60 and others).

Of the known methods and devices closest to the proposed are the "Method for the detection and identification of wanted transponders from a variety of passive transponders and a system for implementing the method" (RF patent No. 2,336.539, G01S 13/75, 2006), which are selected as the base objects .

Known technical solutions provide increased reliability and reliability of detection and identification of one of the many passive transponders, each of which has its own identification code. A method for detecting and identifying transponders includes transmitting an encoded polling radio signal, receiving and evaluating response radio signals of passive transponders, and making a decision on detection. The identification code of each transponder differs from the codes of other transponders in at least four characters and has a button-type autocorrelation function. The polling radio signal is modulated by a signal inverse to the code of the wanted transponder. Response signals are compared with a threshold level. When making a decision, a command is issued to carry out the next detection cycle.

A system for detecting and identifying transponders comprises a plurality of passive transponders 1.1-1.n, an antenna device 2, an encoding device 3, comprising a transponder identification code base unit 7 and a code conversion unit 8, a transmitting device 4, a receiving device 5, an evaluation unit 6, comprising threshold module 9 and module 10 registration.

However, well-known technical solutions do not fully realize their potential capabilities. They provide only the detection and identification of the wanted transponders, but do not allow to determine their location. Using the remarkable property of the button-type autocorrelation function R (τ), which has a main pronounced lobe and a relatively low level of side lobes, we can automatically measure the azimuth and range to each wanted transponder, i.e. determine its location.

An object of the invention is to expand the functionality of known technical solutions by automatically determining the location of the wanted transponders.

The problem is solved in that a method for detecting and identifying wanted transponders from a plurality of passive transponders, each of which has its own identification code, including, in accordance with the closest analogue, transmitting an encoded polling signal sent to a plurality of passive transponders in the polling area, receiving and evaluating the response of the radio signals generated by the passive transponders and deciding on the presence of the wanted transponder in the plurality of passive transponders onders, in this case, the identification code of each passive transponder of the set is selected different from the identification codes of other passive transponders in at least four characters and having a button-type autocorrelation function, the encoded polling signal is modulated by a time-inverse signal with the code of the wanted transponder, the response signals are evaluated by comparison with threshold level exceeding the maximum values of cross-correlation functions of passive transponder identification codes in with the possibility of highlighting the peak of the button-type autocorrelation function, the decision on the presence of the wanted transponder is made by the selected peak of the button-type autocorrelation function, when making a decision, the team is sent to perform the next detection and identification cycle for the next passive transponder, differs from the closest analogue in that when the threshold is exceeded level enable multiplication of the response radio signal with the encoded polling signal, previously passed through the first block being adjusted delay emit low-frequency voltage proportional to the first autocorrelation function R ₁ (τ), where τ - current time delay, the change of the current time delay τ provide maximum value of the first autocorrelation function supports it at a maximum, which corresponds to the time delay τ, equal to τ _h1 , determine and fix the range R to the wanted transponder

,

,

where c is the propagation velocity of radio waves,

simultaneously multiply the response radio signals received by two antennas spaced in the azimuthal plane by a distance d, having previously passed one of them through the second block of adjustable delay, a low-frequency voltage is proportional to the second autocorrelation function R ₂ (τ), by changing the current time delay τ provide the maximum value the second autocorrelation function, support it at the maximum level, which corresponds to a time delay τ equal to τ _s2 , determine and fix the azimuth β n and the wanted transponder

The problem is solved in that a system for detecting and identifying wanted transponders from a plurality of passive transponders, each of which has its own identification code containing, in accordance with the closest analogue, a transceiver antenna, a coding device and a transmitting device connected to a first receiving device in series and an evaluation unit configured to decide on the presence of the wanted transponder in the plurality of passive transponders Moreover, the identification code of each passive transponder of the set differs from the identification codes of other passive transponders by at least four characters and has a push-button autocorrelation function, the encoding device contains sequentially connected block of the base of identification codes of passive transponders and a code conversion unit for generating an encoded polling signal time-inverse signal with the identification code of the wanted transponder, the output of which is connected n with the input of the transmitting device, the evaluation unit contains a threshold module sequentially connected to the output of the first receiving device for extracting the peak of the button-type autocorrelation function from the wanted transponder and the registration module configured to give the command to perform the next search cycle for the next passive transponder differs from the nearest analogue the fact that it is equipped with a duplexer, a receiving antenna, a second receiving device, a key, two adjustable delay units, two I have multipliers, two low-pass filters, two extreme controllers, a range indicator and an azimuth indicator, and the output of the transmitting device through a duplexer, the input-output of which is connected to the transceiving antenna, is connected to the input of the first receiving device, the first block of the adjustable is connected in series to the output of the transmitting device delays, the first multiplier, the second input of which is connected via key to the outputs of the first receiving device and the threshold module, the first low-pass filter, the extremal regulator, the first adjustable delay unit and the range indicator, the output of which is connected to the second input of the registration module, the second receiving device, the second multiplier, the second input of which is connected to the key output through the second adjustable delay unit, the second lower filter frequencies, the second extreme controller, the second adjustable delay unit and the azimuth indicator, the output of which is connected to the third input of the registration module, transceiver and reception Single antennas are separated in the azimuth plane by a distance d.

The structural diagram of the system for detecting and identifying one of the many passive transponders on surface acoustic waves (SAWs) that implements the proposed method is presented in the drawing.

The system contains 1.i (i = 1,2, ..., n) passive transponders located in the polling zone, and a reader (reader) containing sequentially connected block 7 of the transponder code base, block 8 of code conversion, transmitting device 4, duplexer 11 the input-output of which is connected to the transceiver antenna 2, the first receiving device 5, the threshold module 9 and the registration module 10, connected in series to the output of the transmitting device 4, the first adjustable delay unit 13, the first multiplier 14, the second input of which is connected via the key 17 to the output the first receiving device 5 and the threshold module 9, the first low-pass filter 15, the first extremal regulator 16, the first adjustable delay unit 13 and the range indicator 18, the output of which is connected to the second input of the registration module 10, the receiving antenna 19 connected in series, the second receiving device 20 , the second multiplier 23, the second input of which is connected through the second block 22 of the adjustable delay to the output of the key 17, the second low-pass filter 24, the second extreme regulator 25, the second block 22 of the adjustable delay and indication Op bearing 26, whose output is connected to the third input register unit 10. In this case, the transponder code base unit 7 and the code conversion unit 8 form an encoding device 3. The threshold module 9 and the registration module 10 form an evaluation unit 6. The first adjustable delay unit 13, the first multiplier 14, the first low-pass filter 15 and the first extreme controller 16 form the first correlator 12. The second adjustable delay unit 22, the second multiplier 23, the second low-pass filter 24 and the second extreme controller 25 form the second correlator 21. The transceiver antenna 2 and the receiving antenna 19 are spaced in the azimuthal (horizontal) plane by a distance d (measuring base).

A system that implements the proposed method works as follows.

A signal from one of the transponders 1.i (i = 1,2, ..., n) is issued from block 7 of the transponder base, which is required to be determined from the set of those in the polling area. Under its influence, block 8 generates a time-inverse signal M ₁ (t), which enters the transmitting device 4, where the harmonic oscillation is manipulated in phase

u _c (t) = U _c cos (w _c t + ψ _s ), 0≤t≤T _s .

At the output of the transmitting device 4, a complex signal with phase shift keying (PSK) is formed

u ₁ (t) = U _c · cos [w _c t + φ _к1 (t) + φ _s ], 0≤t≤T _s ,

where φ _к1 (t) = {0, π} is the manipulated phase component that displays the phase manipulation law in accordance with the modulating code M ₁ (t),

which through the duplexer 11 enters the transceiver antenna 2, is radiated by it into space and irradiates transponders 1.i (i = 1,2, ..., n).

In each transponder, the electromagnetic signal u ₁ (t) is converted by an interdigital transducer (IDT) into an acoustic wave that propagates along the surface of the sound duct, reflected from a set of reflectors, and again converted into a complex FMN signal whose internal structure is determined by the IDT structure. The structure of the IDT of the wanted transponder is similar to the structure of the modulating code M ₁ (t) and differs from the structure of the IDT of other passive transponders by at least four characters.

The signals re-emitted from the transponders are received by the antennas 2 and 19 and fed to the receiving devices 5 and 20 directly through the duplexer 11. The received signals are proportional to the envelopes of the autocorrelation and cross-correlation functions of the transponders. In the case where the considered set contains a transponder whose code matches the code M ₁ (t) selected from the database, then this transponder re-emits a signal proportional to its autocorrelation function, and the remaining transponders re-emit signals proportional to the cross-correlation functions. Since the signal from the wanted transponder is many times higher than the signals from the remaining transponders, it can be distinguished in the threshold module 9 with high reliability.

If the considered set contains a transponder whose code matches the code M ₁ (t) selected from the database, then the indicated transponder re-emits a complex PSK signal, which is received by transceiver 2 and receiver 19 antennas:

u ₂ (t) = U ₂ · cos [w _c (t-τ _з1 ) + φ _к1 (t-τ _З1 ) + φ _с ],

u ₃ (t) = U ₃ · cos [w _c (t-τ _З2 ) + φ _к1 (t-τ _З2 ) + φ _с ], 0≤t≤T _s ,

- время запаздывания ретранслированного сигнала от разыскиваемого транспондера относительно опросного сигнала;Where

- the delay time of the relay signal from the wanted transponder relative to the interrogation signal;

R is the range from the reader (reader) to the wanted transponder;

c is the propagation velocity of electromagnetic waves;

;

;

t ₁ , t ₂ - travel time of the relayed signal from the wanted transponder to transceiver 2 and receive 19 antennas, respectively;

d is the distance in the azimuthal (horizontal) plane between the transceiver 2 and the receiving 19 antennas;

β is the azimuth to the wanted transponder.

Complex QPSK signal u ₂ (t) from the output of the transceiver antenna 2 through the duplexer 11 and the first receiving device is fed to the input of the threshold module 9, where the threshold level U _then exceeds the threshold module 9, a constant voltage is generated, which is supplied to the first input of the registration module 10 , which indicates the detection of the wanted transponder, and to the control input of the key 17, opening it. In the initial state, the key 17 is always closed.

In this case, the QPSK signal u ₂ (t) from the output of the first receiving device 5 through the public key 17 is fed to the first input of the multiplier 14, the second input of which through the block 13 adjustable delay serves complex QPSK signal u ₁ (t) from the output of the transmitting device . The voltage obtained at the output of the multiplier 14 is passed through a low-pass filter 15, at the output of which the first autocorrelation function R ₁ (τ) is formed, where τ is the current time delay. The extreme controller 16, designed to maintain the maximum value of the autocorrelation function R ₁ (τ) and connected to the output of the low-pass filter 14, acts on the control input of the adjustable delay unit 13 and maintains the delay τ introduced by it equal to τ _s1 (τ = τ _s1 ), which corresponds to the maximum value of the autocorrelation function R ₁ (τ). The range indicator 18 associated with the scale of the adjustable delay unit 13 allows you to directly read the measured distance R between the reader and the wanted transponder

,

,

which is fed to the second input of the registration module 10.

The voltage u ₃ (t) from the output of the receiving antenna 19 through the receiving device 20 is supplied to the first input of the multiplier 23, the second input of which is supplied via the adjustable delay unit 22 to the voltage u ₂ (t) from the output of the receiving device 5 through the public key 17. Received on the output of the multiplier 23, the voltage is passed through a low-pass filter 24, at the output of which an autocorrelation function R ₂ (τ) is formed. The extreme controller 25, designed to maintain the maximum value of the autocorrelation function R ₂ (τ) and connected to the output of the low-pass filter 24, acts on the control input of the adjustable delay unit 22 and maintains the delay τ introduced by it equal to τ _s2 (τ = τ ₃₂ ), which corresponds to the maximum value of the autocorrelation function R ₂ (τ). The scale of the adjustable delay unit 22 (azimuth indicator 26) is calibrated directly in the value of the angular coordinate β of the wanted transponder

,

,

where β is the azimuth of the wanted transponder.

Therefore, the task of measuring the angular coordinate (azimuth β) of the wanted (detected) transponder is reduced to measuring the relative time delay τ _s2 between the relayed signals received by antennas 2 and 19.

The main advantages of RFID technology are:

- lack of physical contact with the RFID tag (transponder);

- high reliability and speed of determining the transponder code;

- The RFID system can be used even in hostile environments, and transponders can be read through dirt, paint, steam, water, plastic, wood;

- transponders do not have power sources, they have a long service life;

- transponders carry a large amount of information, it is almost impossible to fake;

- RFID systems are used in a variety of cases when operational and accurate control, tracking and accounting of numerous movements of various objects is required;

- electronic control of access and movement of personnel on the territory of enterprises;

- Automation and management of the production, issuance and movement of goods and tangible assets in commodity and customs warehouses, large stores;

- automatic collection of data on the movement of vehicles and bulky goods on railways and roads, at freight stations and terminals;

- payment for services at paid parking lots and expressways;

- control, planning and traffic management, optimization of traffic schedules and selection of optimal routes;

- management of public transport, fare control, optimization of passenger flows.

Along with the advantages of radio frequency tags (transponders), there are also some disadvantages. These include:

- relatively high cost;

- mutual conflicts;

- susceptibility to interference in the form of electromagnetic fields.

Thus, the proposed technical solutions, in comparison with basic objects and other technical solutions of a similar purpose, provide automatic measurement of the range (distance) and azimuth of the wanted (detected) transponder, i.e. provide location of the detected transponder. Thus, the functionality of the known method and system is expanded.

Claims (2)

1. A method for detecting and identifying wanted transponders from a plurality of passive transponders, each of which has its own identification code, including transmitting an encoded polling signal sent to a plurality of passive transponders in the polling area, receiving and evaluating response radio signals generated by passive transponders, and making decisions about the presence of the wanted transponder in the set of passive transponders, with the identification code of each passive transponder m the knives are selected that are different from the identification codes of other passive transponders by at least four characters and have a push-button autocorrelation function, the encoded polling signal is modulated by a time-inverse signal with the code of the wanted transponder, response signals are evaluated by comparison with a threshold level exceeding the maximum value of the cross-correlation function identification codes of passive transponders with the possibility of highlighting the peak of the autocorrelation function of a push-button type a, the decision on the presence of the wanted transponder is made by the selected peak of the button-type autocorrelation function, when the decision is made, the team is sent to perform the next cycle of detection and identification of the next passive transponder, characterized in that when the threshold level is exceeded, the response radio signal is multiplied with the encoded polling signal, previously passed through the first adjustable delay unit, allocate a low-frequency voltage proportional to the first autocorre of the lambda function R ₁ (τ), where τ is the current time delay, by changing the current time delay τ provide the maximum value of the first autocorrelation function, maintain it at the maximum level, which corresponds to a time delay τ equal to τ _s1 , determine and fix the distance R to the wanted transponder
$$R=\frac{c{\tau }_{s\mathrm{one}}}{2}$$

where c is the propagation velocity of radio waves,
simultaneously multiply the response radio signals received by two antennas spaced in the azimuthal plane by a distance d, having previously passed one of them through the second block of adjustable delay, a low-frequency voltage is proportional to the second autocorrelation function R ₂ (τ), by changing the current time delay τ provide the maximum value the second autocorrelation function, maintain it at the maximum level, which corresponds to a time delay τ equal to τ _s2 , determine and fix the azimuth β n and the wanted transponder
$$\beta =arccos\frac{c\tau {}_{s2}}{d}$$

2. A system for detecting and identifying wanted transponders from a plurality of passive transponders, each of which has its own identification code containing a transceiver antenna, an encoding device, a transmitting device, a first receiving device and an evaluation unit configured to decide on the presence of the wanted transponder in the set passive transponders, while the identification code of each passive transponder is different from the identification codes of other passwords transponders in at least four characters and has a button-type autocorrelation function, the encoder contains sequentially connected passcode transponder identification code base unit and a code conversion unit for generating a polled interrogated radio signal with a time-inverse signal with the identification code of the wanted transponder, the output of which is connected to the input of the transmitting device, the evaluation unit contains a threshold connected in series to the output of the first receiving device a new module for isolating a peak of a button-type autocorrelation function from a wanted transponder and a registration module configured to give a command to execute the next search cycle for the next passive transponder, characterized in that it is equipped with a duplexer, a receiving antenna, a second receiving device, a key, two adjustable blocks delays, two multipliers, two low-pass filters, two extreme controllers, range indicator and azimuth indicator, and the output is transmitted the transmitting device through a duplexer, the input-output of which is connected to the transceiver antenna, is connected to the input of the first receiving device, the first adjustable delay unit, the first multiplier, the second input of which is connected through the key to the outputs of the first receiving device and the threshold module, are sequentially connected to the output of the transmitting device, the first low-pass filter, the first extreme controller, the first adjustable delay unit and the range indicator, the output of which is connected to the second input of the registration module, to you The second receiving device, the second multiplier, the second input of which is connected to the key output through the second adjustable delay unit, the second low-pass filter, the second extreme regulator, the second adjustable delay unit and the azimuth indicator, the output of which is connected to the third input of the registration module, are connected in series to the receiving antenna , the transceiver and receiver antennas are spaced in the azimuthal plane at a distance d.