RU2336539C2 - Method of detection and identification of sought-for transponders out of multiple passive transponders and system for method implementation - Google Patents

Abstract

FIELD: physics, radio.

SUBSTANCE: technical solution is related to radio location equipment, in particular, to system of radio identification of movable and stationary objects. Method of detection and identification of transponders includes transmission of coded polling signal, reception and estimation of response radio signals of passive transponders, making decision about detection. Identification code of every transponder differs from codes of other transponders in at least four signs and has autocorrelation function of button type. Polling signal is modulated with signal inverse to code of sought-for transponder. Response signals are compared with threshold level. After decision-making command is sent for performance of the following detection cycle. System for detection and identification of transponders contains multiple passive transponders (l₁-l_n), antenna device (2), coding device (3), which contains unit of transponders identification codes base (7) and unit of codes transformation (8), transmitting device (4), receiving device (5), unit of assessment (6), which contains threshold module (9) and module of registration (10).

EFFECT: higher reliability and validity of detection and identification of one out of multiple passive transponders, every of which has its own identification code.

2 cl, 7 dwg

Description

The proposed technical solution relates to radar technology, in particular to radio-frequency identification systems for moving and stationary objects (RFID systems).

Currently, along with bar coding, radio frequency identification is gaining ground.

A typical RFID system consists of a radio frequency tag (RFID tag) or a passive transponder based on surface acoustic waves (SAW), a reader (reader) with a device for processing information (computer). The transponder and the reader are interconnected by a radio frequency channel. The reader also contains a transmitter, a receiver and an antenna, through which electromagnetic waves of a certain frequency are emitted. The transponders that fall into the range of the reader’s field “respond” with their own signal containing useful information (for example, product code) at the same or different frequency. The signal is captured by the reader antenna, useful information is decoded and transmitted to the computer for processing.

Key Benefits of RFID Technology

Lack of physical contact with the RFID tag (transponder).

High reliability and speed of determining the RFID tag code (transponder).

The RFID system can be used even in hostile environments, and RFID tags (transponders) can be read through dirt, paint, steam, water, plastic, wood.

RFID tags (transponders) have a long life.

RFID tags (transponders) carry a large amount of information.

RFID tags (transponders) are almost impossible to fake.

RFID tags (transponders) can be used to record information.

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.

Typical Applications:

- 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.

In many cases, several radio frequency tags (transponders) fall simultaneously into the reader’s field of action. The reader must not only detect radio frequency tags, but also clearly identify them. Such technologies exist, but their implementation leads to a significant increase in read time or a significant complication of equipment.

In well-known systems for interrogating a passive transponder of the company X, CYTE Inc (see patent US 4725841, publication date 02.16.1988, patent US 4620191, publication date 10.28.1986, patent US 4703327, publication date 10.27.1987) for For more reliable identification of the interrogated passive transponders, a signal mixer (mixer) is installed on the SAW, which receives the request radio signal and the radio signal reflected from the transponder. The mixer produces a resultant signal that contains the sum or difference frequencies of these two signals.

The closest in technical essence to the proposed technical solution is the method and system described in RF patent No. 2196344, publication date 01/10/2003, selected as a prototype.

A known system for detecting and identifying one of a plurality of passive transponders, each of which has its own identification code, consists of passive transponders, an antenna device, an encoding device, a transmitting device, a receiving device, and an evaluation unit.

The known system operates as follows.

In the reader, the encoder generates and, using the transmitting device, transmits through the antenna the radio signal encoded in phase with a binary digital code. When the emitted encoded signal coincides with the entered code in the structure on the SAW transponder, the code symbols are coherently summed and a response uncoded total amplitude signal is received, received by the reader antenna, and the information processing device decides on the presence of the requested object.

The disadvantages of the known system are:

1) the complexity of the transponder design due to the introduction of a code-forming field into it, consisting of reflective elements made in the form of interdigital transducers with output contacts to which an external load is connected, with which the phase of the reflected signal changes. Thus, an additional coded reflective structure is introduced on the surfactant, in addition to the main identification structure, which leads to a significant increase in the cost of the transponder, and, as a consequence, the entire RFID system;

2) insufficient reliability of the identification of the transponders being surveyed, since in the additional reflecting SAW structure corresponding to the encoded signal emitted by the reader, coherent addition will actually occur, however, the same signal addition will occur for the transponder, in which the position of the reflectors corresponding to units in the encoding of the additional reflecting structure , will be the same as in the desired transponder.

Thus, the same collisions arise when identifying a particular transponder. The method is unreliable and unreliable.

The technical result achieved by the proposed method and system is to increase the reliability and reliability of the detection and identification of one of the many passive transponders, each of which has its own identification code. This technical result is achieved without complicating the design of the transponders.

The specified technical result is achieved by the fact that a method for detecting and identifying wanted transponders from a plurality of passive transponders, each of which has its own identification code, which includes transmitting at least one encoded polling radio signal sent to a plurality of passive transponders located in the polling area, receiving response radio signals generated by passive transponders, an assessment of the response radio signals and the conclusion about the presence or absence of the wanted transponder, Gaeta supplemented by the following operations:

- to encode transponders to form an array of identification codes having button-type autocorrelation functions, for which the peak of the autocorrelation function exceeds the maximum values of the cross-correlation functions of the array codes,

- modulate the polling radio signal with a time inverse signal to the signal with the wanted transponder code,

- levels of the response radio signals generated by passive transponders, compare with a pre-selected threshold level that exceeds the maximum level of signals from transponders whose codes do not correspond to the code of the wanted transponder,

- when detecting a response signal exceeding the selected threshold level, make a conclusion about the presence of the wanted transponder in many passive transponders.

Button-type autocorrelation functions are described in the following literature:

1. Theoretical Foundations of Radar, ed. Dulevich V.E., M .: Soviet Radio, 1964, p. 315;

2. Handbook of Radar, ed. Sokolnik M., vol. 1 "Fundamentals of radar", M., "Soviet Radio", 1976, p.122.

The selection of codes for transponders is as follows.

First, a plurality of codes with button-type autocorrelation functions are selected. Depending on the required number of codes, M-sequences, pseudo M-sequences, Gould codes, Cassami codes, etc. are used.

Then, from this set of codes, codes are selected that differ as much as possible from each other. For example, from the set of 64-digit codes, the required number of codes is selected - Q, differing from each other by at least 4 characters. After that, the autocorrelation functions of all the selected Q codes and cross-correlation functions are calculated. Estimate the level of excess of the peak of autocorrelation functions over the maximum level of cross-correlation functions. The codes for transponders are finally selected, or the next iteration is performed, that is, a new number of Q codes are selected. A new calculation of their autocorrelation functions and cross-correlation functions is performed.

To implement this method, a system for detecting and identifying a wanted transponder from a plurality of passive transponders, each of which has its own identification code containing passive transponders, an antenna device, an encoding device, a transmitting device, a receiving device and an evaluation unit, is implemented as follows:

- each passive transponder must contain an identification code with a button-type autocorrelation function, the peak of the autocorrelation function of which exceeds the maximum values of the cross-correlation functions,

- the encoding device should contain a transponder code base unit and a code conversion unit for generating a time-inverse signal with a wanted transponder code,

- the evaluation unit must contain a threshold module for generating a threshold level exceeding the maximum level of signals from transponders whose codes do not correspond to the code of the wanted transponder, and a registration module,

- moreover, the output of the transponder code base block should be connected to the input of the code conversion block,

- the output of the code conversion unit must be connected to the input of the transmitting device, the output of which is connected to the input of the antenna device,

- the output of the antenna device must be connected to the input of the receiving device,

- the output of the receiving device must be connected to the input of the threshold module,

- the output of the threshold module must be connected to the input of the registration module.

The proposed method for the detection and identification of wanted transponders and a system for its implementation can significantly increase the reliability of identification of a wanted transponder, as well as simplify the design of transponders compared to the prototype and increase the reliability of the system.

The essence of the proposed technical solution is illustrated by the following drawings.

Figure 1 - Structural diagram of a system for detecting and identifying one of the many passive transponders on surface acoustic waves (SAW),

where 1a-1n are passive transponders located in the polling area,

2 - antenna device,

3 - encoding device,

4 - transmitting device,

5 - receiving device,

6 - evaluation unit,

7 - block base transponder codes,

8 - block conversion codes

9 - threshold module,

10 - registration module.

Figure 2 - The signal code of the passive transponder on surface acoustic waves (SAW).

Figure 3 - The signal with a time-inverse passive transponder code at the output of the code conversion unit.

Figure 4 - Response signals from transponders at the input of the threshold module, with a signal from the wanted transponder exceeding the threshold level.

Figure 5 - The detected signal of the wanted transponder at the output of the threshold module after passing through it the signals presented in figure 4.

6 - Response signals from transponders at the input of the threshold module in the absence of a signal from the wanted transponder.

Fig.7 - The absence of a useful signal at the output of the threshold module after passing through it of the signals presented in Fig.6.

The method is as follows (see figure 1).

From block 7 of the transponder code base, a signal is generated from one of the transponders 1a-1n, which must be determined from the plurality of those located in the polling area. Under its influence, block 8 generates a time-inverse signal, which enters the transmitting device 4. Then this signal is transmitted through the antenna device 2 into space. The signals re-emitted from the transponders are received by the antenna device 2 and fed to the receiving device 5. The received signals are proportional to the envelopes of the autocorrelation and cross-correlation functions of the transponders. In the event that in the considered set there is a transponder whose code matches the code 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 (see Fig. 4) . 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. Registration module 10 makes a conclusion about the result of the operation (whether or not there is a wanted transponder in the group being surveyed) and, if necessary, gives a command to carry out the next search cycle for the next transponder.

All devices, blocks and modules (see figure 1) of the proposed system can be made of known components.

Block 7 base transponder codes can be performed on the basis of the chip M48Z512.

Registration module 10 - based on max 7000 - programmable logic.

Block 8 code conversion - based on max 7000 - programmable logic.

Threshold module 9 is based on the AD 8611 chip.

Antenna device 2 - based on the Hmc284ms8g chip.

The advantages of the proposed method and system for implementing this method are more reliable and reliable detection and identification of one of the many passive transponders without making any changes to the design of the transponder. Since the number of transponders in identification systems can reach several hundred thousand, a significant simplification and cheapening of the system as a whole is achieved.

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, which includes transmitting an encoded polling signal sent to a plurality of passive transponders located in the polling zone, receiving and evaluating response radio signals generated by passive transponders, and transmitting decisions about the presence of the wanted transponder in the set of passive transponders, characterized in that the identification code of each passive t a set of opponders is chosen different from the identification codes of other passive transponders by at least four characters and having a push-button autocorrelation function, the coded interrogation radio signal is modulated by a time-inverse signal with the code of the wanted transponder, the response signals are evaluated by comparison with a threshold level exceeding the maximum values of the reciprocal functions correlation of identification codes of passive transponders with the possibility of highlighting the peak of the autocorrelation function to of the button type, the decision on the presence of the wanted transponder is made by the selected peak of the button-type autocorrelation function, when making the decision, the team is sent to execute the next detection and identification cycle for the next passive transponder. 2. A system for detecting and identifying wanted transponders from a plurality of passive transponders, each of which has its own identification code, comprising an antenna device, an encoding device, a transmitting device, a receiving device for receiving response radio signals from passive transponders and an evaluation unit configured to make a decision about the presence of the wanted transponder in the set of passive transponders, characterized in that the identification code of each passive transponder sets differs from the identification codes of other passive transponders in at least four characters and has a button-type autocorrelation function, the encoding device contains a base unit of identification codes of passive transponders and a code conversion unit for generating a coded polling signal, time-inverse to the signal with the identification code of the wanted transponder, the evaluation unit contains a threshold module for extracting the peak of the button-type autocorrelation function from the wanted about the transponder and the registration module, configured to issue a command to perform the next search cycle for the next passive transponder, wherein the output of the transponder code base block is connected to the input of the code conversion block, the output of the code conversion block is connected to the input of the transmitting device, the output of the transmitting device is connected to the antenna input devices, the output of the antenna device is connected to the input of the receiving device, the output of the receiving device is connected to the input of the threshold module, the output of the threshold the muzzle is connected to the input of the registration module.

Images