RU2454717C1 - Object identification system - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: object identification system comprises: a generator, two high-frequency signal dividers, high-frequency signal divider with 90° phase shift, a high-frequency amplifier, a circulator, a local surface electromagnetic wave former, two mixers, two low frequency amplifiers, two low-pass filters, an analogue-to-digital converter, a digital signal processor, N radio-frequency labels, where N is not less than two, with antennae, a metal cabinet housing the local surface wave former and the objects to be identified, on which radio-frequency labels are attached, having an impedance modulator, a high-frequency current rectifier, an electronic circuit with a random signal generator and an antenna.

EFFECT: reading multiple radio-frequency labels of identified objects in the working volume of a metal cabinet.

3 cl, 5 dwg

Description

The invention relates to telemetric systems for identifying material objects using electromagnetic waves of a microwave frequency range. The primary area of application is the identification of important documents, weapons or material assets stored in metal cabinets or safes and requiring reliable and operational monitoring.

A known system for identifying objects (US patent No. 4739328, CL. G01S 13/78, 1988), which includes: a reader and a passive RFID tag. The reader includes an unmodulated oscillation generator, a transceiver antenna, a transmission line, two directional couplers, two mixers, a 90 ° high frequency phase shifter, two low frequency (LF) amplifiers, a demodulator, and a passive RFID tag. A passive RFID tag contains a transceiver antenna, a modulator, and read only memory (ROM) in series. The ROM provides an identifying sequence of “ones” and “zeros” in the binary code, individual for each object. This code modulates the reflection from the antenna of the RFID tag.

Directional couplers are included in the transmission line towards each other, and their outputs, with a phase shift between them by 90 °, are connected to the inputs of the mixers. The outputs of the mixers through the bass amplifiers are connected to the demodulator.

A reader with unmodulated RF radiation requests a passive RFID tag.

For a reader of this system, the RFID reader zone is determined by the width of the main lobe of the radiation pattern of the transceiver antenna and the effective output signal power of the reader. The presence of metal walls in the reading zone causes the direct RF signal of the reader to interfere with the signals reflected by these walls, which leads to the appearance of standing waves with maxima and minima of the amplitude of the electromagnetic field (EMF). RFID tags that are at the minimums of the amplitude of the EMF intensity cannot be read, and therefore identified. As a result, it does not seem possible to identify the complete set of RFID tags located in a metal cabinet, which is a disadvantage of this method and device.

Signs of the claimed invention that coincide with the characteristics of an analogue are: an unmodulated oscillation generator, two directional couplers, a 90 ° phase shifter at a high frequency, two mixers, two low-frequency amplifiers and a passive RFID tag.

A known method of reading information at a distance from a code sensor (RF Patent No. 2068183, CL. G01S 13/00, 1993). A device operating in accordance with this method, which is adopted as a prototype of the invention, comprises: a microwave generator, a directional coupler, a modulator, a microwave power amplifier, a circulator, a mixer, a transceiver antenna of a reader, a low-pass filter, a coupler, a decoder, a pulse generator control unit, a generator pulses and a code sensor - a radio tag with a transceiver antenna.

In this system, RFID tags are read in the field of electromagnetic waves that are emitted by the transceiver antenna of the reader in the direction of RFID tags.

If identifiable objects with RFID tags are located inside a metal cabinet whose dimensions in one of the coordinates exceed the wavelength of the radio signal, then the cabinet is a multimode resonator [Y.D.Shirman. Radio waveguides and volume resonators. - M .: Svyazizdat, 1959, p. 227]. Moreover, due to a weak decrease in the amplitude of the field strength of the radiated electromagnetic wave (EMW) according to the law 1 / R, where R is the distance from the transceiver antenna to the wall [G.T. Markov, D.M.Sazonov. Antennas - M .: Energia, 1975, p.21], high-frequency (HF) currents are excited on the walls of a metal cabinet, exciting a secondary electromagnetic field inside the cabinet with a voltage amplitude comparable to the amplitude of the primary electromagnetic field strength that is emitted by the antenna. As a result of the interference of the primary and secondary electromagnetic fields, standing waves arise with maxima and minima of the amplitude of the electromagnetic field. Among the many items with RFID tags in the cabinet there may be those whose location is at the minimums of the amplitude of the EMF intensity, where the amplitude of the field strength is insufficient to read passive RFID tags. As a result, the reading of RFID tags that are at the minima is not possible, and therefore, the reading of the complete set of RFID tags of identifiable objects is not provided. This is a disadvantage of the prototype of the invention.

Signs of the claimed invention that coincide with the features of the prototype (figure 1) are: an RF generator (1), an RF amplifier (4), an RF signal divider (2), a circulator (5), a mixer (8), a low-pass filter (10 ), a radio tag (13) with a transceiver antenna (22). In addition, the output of the generator (1) is connected to the input of the divider (2), and the output of the RF amplifier (4) is connected to the input of the circulator (5).

The technical result of the invention is reliable reading by a reader of an object identification system of a complete set of RFID tags of identifiable objects located in the working volume of a metal cabinet. The technical result is achieved due to the shaper of the local traveling surface wave in the working volume of the metal cabinet, and the separate reading of the set of RFID tags is provided due to the random delay of the repeated response code signals of each RFID tag (Figure 5).

The invention is illustrated by drawings.

Figure 1 presents the structural diagram of a telemetry reader of the inventive system of identification of objects (SIO).

Figure 2 presents the design of the shaper of the local traveling surface electromagnetic wave (PDF).

Figure 3 presents the design of the metal cabinet and the location of the FPV in it.

Figure 4 presents the structural diagram of the RFID tag.

Figure 5 presents the diagrams of the envelopes of the code signals of three RFID tags with collisions (black rectangles) and without them (white rectangles - label 1, hatched - label 2 and gray - label 3).

The following notation is introduced in the figures: 1 - generator (G); 2 - RF signal divider (D); 3 - RF signal divider with a phase shift of 90 ° RF signals at its outputs (DF); 4 - amplifier RF signals (UHF); 5 - circulator (C); 6 - shaper local surface EMF (FPV); 7 - coordinated load (CH); 8 - mixer (cm); 9 - low frequency amplifier (VLF); 10 - low-pass filter (low-pass filter); 11 - analog-to-digital Converter (ADC); 12 - digital signal processor (DSP); 13 - radio tag (M); 14 - RF connector, 15 - metal rod; 16 - a rack; 17 - a metal screen; 18 - a line segment of a surface wave; 19 - a metal cabinet; 20 - the working volume of the cabinet 19; 21 - working surface FPV 6; 22 - antenna tag; 23 - a chip of a radio tag; 24 - modulator (MD) impedance; 25 - rectifier (V) RF signal; 26 is an electronic circuit (C) of the chip 23.

The technical result of the invention is achieved due to the fact that the object identification system (SIO) contains: a telemetric reader of RFID codes (Figure 1) and a metal cabinet (Figure 3).

The metal cabinet 19 is intended for placement in it FPV 6 and storage of identifiable items with RFID tags 13 (Figure 3). Cabinet 19 has the dimensions:

- length b, which should be greater than λ, where λ is the operating wavelength of the SIO reader;

- transverse dimension a, which should be larger than ¼λ;

- height c, which should be greater than ¼λ.

The working volume 20 of the local surface EMW (indicated by dashed lines in FIG. 3) of the cabinet 19 has the dimensions:

- the length of e;

- transverse dimension d;

- height f.

The inequalities of the cabinet dimensions and its working volume must be strictly observed: b> e; a> d; c> f.

, где к_З - коэффициент замедления поверхностной ЭМВ, равный отношению скорости света к фазовой скорости поверхностной волны.The size f and the distance from the edges of the PDF to the cabinet walls are determined by the exponential law of decreasing the amplitude of the field strength of the surface EMF in the direction of the cabinet walls. The amplitude of the field strength of the surface wave on the inner walls of the chamber 19 should decrease by at least 10 times, which corresponds to approximate equality

where k ₃ is the deceleration coefficient of the surface electromagnetic wave equal to the ratio of the speed of light to the phase velocity of the surface wave.

SIO telemetry reader (Figure 1) contains: generator (G) 1, first and second RF signal dividers (D) 2, RF signal divider with phase shift (DF) 3, high-frequency amplifier (UHF) 4, circulator (C) 5; shaper of locally surface EMF (FPV) 6, matched load (SN) 7, first and second mixers (Cm) 8, first and second low-frequency amplifiers (VLF) 9, first and second low-pass filters (LPF) 10, analog-to-digital converter (ADC) 11, digital signal processor (DSP) 12 and RFID tags (M) 13, input and output RF connectors 14; metal rods 15; mounting racks 16; metal screen 17; a line segment of the surface wave 18, antenna 22 RFID tags 13; chips 23 RFID tags 13, which include modulators (MD) 24 impedances, rectifiers (V) 25 RF current and electronic circuits (C) 26.

Generator (G) 1 RF signal has an unmodulated RF signal output with a frequency of 860-960 MHz and a power of at least 10 mW. The generator G 1 can be performed, for example, on the chip HMC821LP6C (Hittite).

The RF signal divider (D) 2 is designed to divide the power of the input RF signal by two and can be performed, for example, on the chip ВР2С (Mini-Circuits), has an input and two outputs of the RF signal.

The divider (DF) 3 is designed to divide the input RF signal into two with a phase shift between them by 90 ° at its outputs and can be performed, for example, on the QCN-12 microcircuit (Mini-Circuits). DF 3 has an input, the first and second outputs of the phase shifted RF signals.

The RF signal amplifier (UHF) 4 can be performed, for example, on a chip HMC453ST89 (Hittite); it works in the frequency range from 860 MHz to 960 MHz, has a gain of at least 20 dB, has an input and output of an RF signal.

Circulator (C) 5 provides the supply of an unmodulated RF signal to the input-output of a surface wave former (FPV) 6, as well as the transmission of the RF signal reflected by the antenna 22 of the RF tag modulated by the label code to the input of the second divider D 2. As a circulator, e.g. MAFRIN0494 (M / A-COM Technology Solutions). C 5 has an input of an unmodulated RF signal, an output-input of an RF signal and an output of an RF signal reflected by antenna 22 of the M 13 tag.

Shaper surface EMF (FPV) 6 (Figure 2) is designed to create in a metal cabinet 19 a local field of a traveling surface EMF necessary for reading RFID tags M 13. The FPM is made in the form of a line segment of a surface wave. The length of the segment of this line should be less than the length of the cabinet b, the width should be less than its transverse dimension a. The thickness of the PDF is determined by the given wave impedance of the line and it is significantly less (10 times or more) of the size f of the working volume of the chamber 19.

A line segment of the surface wave can be made in the form of a metal comb or layered metal-dielectric structure (Figure 2) according to the manufacturing technology of printed circuit boards. FPV 6 has an input-output RF signal and an output RF signal.

The coordinated load (SN) 7 with a wave impedance equal to the wave impedance of a segment of the surface wave line 18, for example, 75 Ohms, is designed to provide traveling waves in the FPV 6 and can be made, for example, of ferrite. CH 7 has an RF signal input, its VSWR in the frequency range of the RF signal should be no more than 1.04.

The mixer (cm) 8 can be performed, for example, on an ADEX-10 microcircuit (Mini-Circuits), has an input of a local oscillator RF signal, a signal input and an output of a low-intermediate frequency signal.

The low frequency amplifier (VLF) 9 can be performed, for example, on a microcircuit of an operational amplifier AD8606ARM (Analog Devices) with a gain of at least 20 dB, has an input and output of a low-frequency signal.

A low-pass filter (LPF) 10 with a passband of up to 1000 kHz, for example, can be made in the form of a L-shaped or U-shaped filter from a set of resistors, capacitors and inductances.

The analog-to-digital converter (ADC) 11 can be performed on the AD9201ARS chip (Analog Devices), has two inputs of orthogonal low-frequency signals and one digital signal output with 2-channel multiplexing (sequential time switching) of the output digital data bus.

Digital signal processor (DSP) 12 is a digital computing device that performs quadrature processing of orthogonal signals, ensuring independence of the amplitude of the demodulated low-frequency signal from the phase of the reflected RF signal of the RF tag, and also selects a temporary mismatch, i.e. the absence of collision, RFID signals (Figure 5) and transmits to the user of the identification system (SIO) the codes of each selected RFID tag M 13 from the entire complete set of RFID tags that are in the working volume 20 of the cabinet 19.

DSP 12 can be performed on the ADSP BF56115 BB600 chip (Analog Devices); it has one input intended for digital input of the ADC 11, and one output for outputting information from the SIO.

The object identification system contains N passive RFID tags M 13, where N is a number of at least two. RFID 13 (Figure 4) is intended for storage in non-volatile memory of its identification code and its reproduction. Each RFID tag 13 contains: an antenna 22, an impedance modulator 24, an RF current rectifier 25, and an electronic circuit 26 with a random signal generator providing a random repetition period of the RFID code being read. Antenna 22, modulator 24 and rectifier 25 are connected in parallel. The output of the rectifier 25 is connected to the input of the electronic circuit 26, and its control output is connected to the control input of the modulator 24. All N RF tags M 13 with their antennas 22 are connected to the FPV 6 shaper by means of a surface electromagnetic field.

As the input and output RF connectors 14 can be applied to the connector type SMA-BJ1.

The metal rods 15 are intended for the electrical connection of the central conductors of the RF connectors 14 with the input and output of the surface wave line section 18. They can be made, for example, of brass or copper with a diameter of at least 0.8 mm.

Racks 16 are designed for mounting the printed circuit board at a predetermined distance above the metal screen 17. Rack 16 is made in the form of a rod made of a dielectric with low dielectric losses (the loss tangent is less than 0.01), for example, from polystyrene.

The metal screen 17 may be made, for example, of brass or copper sheet.

A segment of the surface wave line 18 is made in the form of a printed circuit on a board — a dielectric substrate made of a material with low dielectric losses (the loss tangent is less than 0.001).

The antenna 22 of the RF tag M 13 can be made in the form of a symmetrical half-wave vibrator.

The microcircuit 23 of the RFID tag M 13 (Figure 4) consists of an impedance modulator (MD) 24, a rectifier (V) 25 RF current and an electronic circuit (C) 26 generating a RFID code with a random repetition period. The microcircuit 23 contains all the mentioned electronic components of the RF tag, necessary for its functioning. For example, an EM4123 chip (EM Microelectronic-Marin SA) can be used.

The impedance modulator (MD) 24 of the microcircuit 23 is a variable resistor, the resistance of which changes in step with the value of the control code signal of the electronic circuit C 26. The MD 24 is connected in parallel with the input of the microcircuit 23, so a change in its resistance leads to a change in the impedance of the microcircuit and, therefore, a change in the reflection coefficient of the electromagnetic wave from the antenna 22 per cycle with the voltage of the code identification signal of the RFID tag M 13. MD 24 has a control signal input from the output of the electronic circuit C 26. As MD 24, t used FET insulated gate.

A rectifier (V) 25 RF signal is designed to power the electronic circuit C 26 and has an RF signal input and a DC signal output. It can be performed, for example, based on semiconductor diodes with a Schottky barrier.

The electronic circuit (C) 26 of the M 13 RFID tag includes a signal generator for reading the RFID code with a random repetition period, which implements the anti-collision protocol, i.e. Collisions resolved - superposition of signals from different RFID tags. According to the ALOHA method [K. Finkenzeller. RFID technology. Reference manual / trans. with him. - M .: Dodeka-XXI, 2010, p.238], the random delay of repeated messages - response signals of each RFID tag, ensures the correct reading of its code identification signals (Figure 5). The electronic circuit C 26 can be performed on the basis of a microcontroller and non-volatile memory.

The electronic circuit C 26, the modulator MD 24 impedance and the rectifier V 25 RF signal are implemented as part of the microcircuit 23, for example, type EM4123 (EM Microelectronic-Marin SA).

The technical result of the invention is ensured by the fact that inside the metal cabinet, in its working volume, where identifiable items with RFID tags 13 are placed, a local running surface EMF is formed, and the RFID tags 13 are read separately due to the random delay of the repeated response signals of each RFID tag, which is ensured schematic diagram and algorithm of operation of the DSP 12 (Figure 1).

With the appropriate choice of the ratio of the dimensions of the cabinet, its working volume, deceleration coefficient and amplitude of the field strength of the surface electromagnetic wave at the cabinet walls, they achieve the absence of standing waves in the working volume of the cabinet, which makes it possible to read all RFID tags 13 in this volume. Separate reading of RFID tags is provided due to the random delay of the repetitive response signals of each RFID tag (Figure 5).

Electrical connections

The output of G 1 is connected to the input of the first D 2, one output of which is connected to the input of the UHF 4, and the second output is connected to the input of the DF 3.

The output of the UHF 4 is connected to the input of Ts 5, the output-input of which is connected to the input-output of the surface shaper EMF FPV 6, and the output is connected to the input of the second D 2. The output of the shaper FPV 6 is connected to the input of CH 7.

One output of the DF 3 is connected to the heterodyne input of the first mixer, see 8, and the second to the heterodyne input of the second mixer, see 8.

One output of the second divider D 2 is connected to the signal input of the first mixer cm 8, and the second to the signal input of the second mixer cm 8. The outputs of the first and second cm 8, through series-connected VLF 9 and low-pass filter 10, are connected to the quadrature inputs I and Q of the ADC 11 The output of the ADC 11 is connected to the input of the DSP 12, the output of which is the output of the SIO.

Antennas 22 of RFID tags 13 are connected to the FPV 6 driver by a local surface wave.

The device operates as follows.

, где к₃ - коэффициент замедления поверхностной ЭМВ, равный отношению скорости света к фазовой скорости этой поверхностной волны. При таком размещении ФПВ 6 амплитуда напряженности поля поверхностной ЭМВ на внутренних стенках шкафа 19 снижается не менее чем в 10 раз. Соответственно, в рабочем объеме 20 шкафа амплитуда напряженности вторично возбужденного поля ЭМВ более чем в 10 раз меньше амплитуды напряженности первичного поля поверхностной ЭМВ; следовательно, стоячие волны с минимумами амплитуды напряженности поля в этом рабочем объеме пренебрежимо малы.The shaper of the surface EMF FPV 6 is placed with its screen on the cabinet wall 19 of a larger length (Fig.), So that the distances from the edges of the FPV 6 to the adjacent walls of the cabinet are greater than 0.1λ, and from the working surface 21 of the shaper FPV 6 to the opposite cabinet wall - no less

where k ₃ is the deceleration coefficient of the surface electromagnetic wave equal to the ratio of the speed of light to the phase velocity of this surface wave. With this arrangement of FPV 6, the amplitude of the field strength of the surface EMF on the inner walls of the cabinet 19 is reduced by at least 10 times. Accordingly, in the working volume of the cabinet 20, the amplitude of the intensity of the secondary excited field of the electromagnetic field is more than 10 times less than the amplitude of the primary field of the surface electromagnetic field; therefore, standing waves with minima of the amplitude of the field strength in this working volume are negligible.

Items with attached RFID tags M 13 are placed inside the metal cabinet 19 in the working volume 20 of the surface EMF driver 6. The generator G 1, UHF 4, ULF 9, ADC 11 and DSP 12 are supplied with power. The generator G 1 begins to generate an unmodulated RF signal. Using the first divider D 2, the generator signal is divided in half, one half of the signal is fed to the input of the UHF amplifier 4, and the other to the input of the DF divider 3. At the outputs of the DF 3, the phases of the RF signals are shifted 90 ° relative to each other, i.e. are in quadrature (orthogonal), are used as heterodyne signals, are fed to the corresponding heterodyne inputs of the cm 8 mixers.

From the output of the high-frequency amplifier UHF 4, the signal is fed to the input of the circulator C 5, and from its output-input to the input-output of the surface driver EMF FPV 6. The surface wave generated above the working surface 21 FPV 6 is received by transceiver antennas 22 of all N RF tags M 13, placed in a metal cabinet 19 on identifiable items. Electronic circuits With 26 RFID tags 13 receive DC power from their rectifiers B 25 and simultaneously start to generate signals - each its own identification code with a random delay in the repetition period. The code signals are fed to the control inputs of their modulators MD 24. The modulators, in time with the identifying code signals, change the impedance of their microcircuits 23, which are the loads of the antennas 22; the signals reflected from the transmitting and receiving antennas 22 of the RFID tags 13 are modulated by code identification signals and fed through the FPV 6 shaper to the output-input of the circulator C 5, and from its output to the input of the second divider D 2. From the outputs of the second divider D 2 in-phase high-frequency signals arrive to the corresponding signal inputs of the first and second mixers, see 8. In the mixers, see 8, the spectra of the HF signals reflected by M 13 radio tags are converted to the orthogonal spectra of the LF signals, i.e. into the quadrature components of the low-frequency signals I and Q, which, after amplification in the amplifiers of the VLF 9 and filtering in the filters of the low-pass filters 10, are fed to the input of the ADC 11, where they are digitized. After digitization, the signals arrive at the DSP 12, in which their quadrature processing and collision selection are completed - coincidences in time of the code signals of RFID tags located in the working volume 20 of cabinet 19.

устраняется зависимость амплитуды сигнала u_м от фазы отраженного радиометкой ВЧ кодового сигнала.The digital signal processor DSP 12 performs the finishing operation of processing the quadrature components of the low-frequency signals I and Q: s _I = (u _m · sinφ) and s _Q = (u _m · cosφ), where u _m is the envelope of the signal corresponding to the identification code of the RF tag 13, and φ is the phase difference between the reflected RF tag RF signal and heterodyne signals at the input of the mixers, see 8. As a result of the digital operation

the dependence of the signal amplitude u _m on the phase of the RF code signal reflected by the RF tag is eliminated.

In addition, the DSP 12 selects the signals of the RFID tags M 13, which do not have collisions with the signals of other RFID tags located in the cabinet 19. As a result of the collision, the duration changes and the internal structure of the code signal is violated. Using these features, the DSP 12 digitally filters out the tag code signals superimposed on each other and transmits the codes of the read RF tags, the parameters of which are not violated by collisions (Figure 5).

From the output of the DSP 12, identification information is sent to the user of the SIO object identification system to ascertain the presence of all M 13 RFID tags placed in the cabinet, i.e. to determine the result of an inventory or monitoring of identifiable items.

The RF tag M 13 is a passive device, its power source is a rectified RF current of the antenna 22, which is powered by the energies of the surface EMF.

For the functioning of the RFID tag, it is necessary to have an EMF with an amplitude of intensity exceeding the threshold value, called the sensitivity of the passive RFID tag. The principle of operation of the RF tag M 13 consists in modulating the EME reflected by its antenna 22. The module of the reflection coefficient and, therefore, the depth of the amplitude modulation of the field strength of the reflected EMV depends on the load impedance of this antenna.

The RF energy received by the antenna 22 is supplied to a chip 23, which includes a rectifier B 25, which is necessary to provide power to the electronic circuit C 26 of the RF tag 23, which contains a signal generator with a random repetition rate for reading the code from a non-volatile memory in which the identification code is stored RFID tags. The code signal of the RF tag 13 is fed to the impedance modulator Md 24 of the microcircuit 23, which is the load of the antenna 22, thereby causing modulation of the electromagnetic radiation reflected by the antenna.

The electronic circuit C 26 of the microcircuit 23 includes a signal generator with a random repetition rate, with which an anti-collision protocol is implemented, i.e. Collisions are resolved - superposition of signals from multiple RFID tags. Moreover, according to the ALOHA method [K. Finkenzeller. RFID technology. Reference manual / trans. with him. - M .: Dodeka-XXI, 2010, p.238], a random delay is used for repeated messages - response tags of the RF tag, as a result of which the SIO correctly reads the information of each RF tag that does not coincide in time with its code signal with the code signals of other RF tags in the working volume 20 of the cabinet 19 (Figure 5).

The implementation of the invention

The invention is made in accordance with figures 1, 2 and 3.

The metal cabinet 19 is made in the form of a safe in the form of a rectangular parallelepiped, which has the dimensions of the cavity:

- length b = 600 mm,

- transverse dimension a = 250 mm,

- height c = 200 mm.

The working volume 20 of the cabinet 19 has the dimensions:

- length = 450 mm,

- transverse dimension d = 160 mm,

- height f = 150 mm.

The generator (G) of 1 RF unmodulated signal with a frequency of 900 MHz and a power of 10 mW is made on a HMC821LP6C microcircuit (Hittite).

The dividers of the RF signal (D) 2 and DF 3 are made on microchips BP2C (Mini-Circuits) and QCN-12 (Mini-Circuits, respectively).

The RF signal amplifier (UHF) 4 is made on the HMC453ST89 chip (Hittite) and operates at a frequency of 900 MHz, has a gain of 20 dB.

The circulator (C) 5 is made on a device of the type MAFRIN0494 (M / A-COM Technology Solutions).

Shaper surface EMF (FPV) 6 is made in the form of a line segment of the surface wave, which is made of a metal meander using printed circuit board technology and has a wave impedance of 75 Ohms. The substrate of the printed circuit is made of a dielectric type FR-4.

PCB dimensions:

- length 420 mm,

- width 160 mm,

- thickness 0.5 mm.

Agreed load (SN) 7 is made with a wave impedance of 75 Ohms in the form of a cone of ferrite, VSWR = 1.04.

The metal rods 15 are made of brass wire with a length of 10 mm and a diameter of 0.8 mm.

Racks 16 in the form of a rod of polystyrene 15 mm long and 5 mm in diameter.

The metal screen 17 is made of brass sheet with a thickness of 0.5 mm, a length of 500 mm and a width of 160 mm.

The mixer (cm) 8 is made on the ADEX-10 microcircuit (Mini-Circuits).

The low frequency amplifier (VLF) 9 has a gain of 20 dB and is made on the AD8606ARM (Analog Devices) operational amplifier chip.

A low-pass filter (LPF) 10 with a passband of 1000 kHz is made of a set of 2 resistors and 3 capacitors according to the L-shaped filter circuit.

The analog-to-digital converter (ADC) 11 is made on the AD9201ARS (Analog Devices) chip.

Digital signal processor (DSP) 12 on the ADSP BF56115 BB600 chip (Analog Devices).

The number of marks M 13 is three. The RFID tag 13 is made on the EM4123 chip (EM Microelectronic-Marin SA) according to the scheme of Figure 4 and contains: an antenna 22, made in the form of a symmetric vibrator, and a chip 23. The composition of the chip includes: an impedance modulator (MD) 24, made of a field-effect transistor with an insulated gate, a rectifier (B) 25 RF current made of semiconductor diodes with a Schottky barrier, and an electronic circuit (C) 26, including a non-volatile EEPROM memory and a random delay signal generator of repeating RFID tags (Figure 5).

As input and output RF connectors 14, a connector of type SMA-BJ1 is used.

The antenna 22 of the RF tag M 13 is made in the form of a symmetrical half-wave vibrator.

Features of the invention

The second RF signal divider, RF signal divider with a phase shift of 90 ° (3), surface electromagnetic wave shaper (6), matched load (7), second mixer (8); first and second low-frequency amplifiers (9), a second low-pass filter (10), an analog-to-digital converter (11), a digital signal processor (12), a metal cabinet (19) and an N-1 RFID tag, where N is at least two .

Each RFID tag (23) contains an impedance modulator (24), an RF current rectifier (25), and an electronic circuit (26) with a random signal generator providing a random repetition period of the RFID code being read. Antenna 22, modulator (24) and rectifier (25) are connected in parallel. The output of the rectifier (24) is connected to the input of the electronic circuit (26), and its control output is connected to the control input of the modulator (24).

One output of the first RF signal divider (2) is connected to the input of the RF amplifier, and its other output is connected to the input of the RF signal divider with a phase shift of 90 ° (3), the outputs of which are connected to the heterodyne inputs of the first and second mixers. In addition, the output-input of the circulator (5) is connected to the input-output of the surface electromagnetic wave shaper (6), the output of which is connected to the matched load (7).

The output of the circulator (5) is connected to the input of the second RF signal divider (2), the outputs of which are connected to the signal inputs of the first and second mixers (8), respectively, the output of each mixer through a series-connected low-frequency amplifier and a low-pass filter are connected to the corresponding quadrature analog inputs -digital converter (11), the output of which is connected to the input of a digital signal processor (12).

The surface electromagnetic wave former (6) is placed inside the cabinet (19) near one of its walls, and the RF tags (13) are mounted on identifiable objects that are located above the surface electromagnetic wave former (6) in the working volume (20) of the metal cabinet (19) .

The shaper of the surface electromagnetic wave (6) is made in the form of a line segment of the surface wave of a metal comb or layered metal-dielectric structure.

The first, second RF signal dividers (2) and the RF signal divider with a phase shift of 90 ° (3) are made by dividing the input RF signal by two output RF signals of equal amplitude.

Claims (3)

1. An object identification system comprising: an RF generator (1), an RF amplifier (4), an RF signal divider (2), a circulator (5), a mixer (8), a low-pass filter (10), a radio tag (13) with an antenna (22), moreover, the output of the generator (1) is connected to the input of the divider (2), and the output of the RF amplifier (4) is connected to the input of the circulator (5), characterized in that: N-1 RF tags (13) with antennas (22) ), where N is a number of at least two, the second RF signal divider (2), the RF signal divider with a phase shift of 90 ° (3), the surface electromagnetic wave former (6), the matched load (7), the second mesitel (8); first and second low-frequency amplifiers (9), a second low-pass filter (10), an analog-to-digital converter (11), a digital signal processor (12) and a metal cabinet (19), and the RF tags (13) contain an impedance modulator (24) , an RF current rectifier (25) and an electronic circuit (26) with a random signal generator, an antenna (22), in addition, a modulator (24) and a rectifier (25) are connected in parallel, the output of the rectifier (24) is connected to the input of the electronic circuit (26) ), and its control output is connected to the control input of the modulator (24), moreover, one output of the first divider The RF signal (2) is connected to the input of the RF amplifier, and its other output is connected to the input of the RF signal divider with a phase shift of 90 ° (3), the outputs of which are connected to the heterodyne inputs of the first and second mixers, in addition, the output-input of the circulator (5 ) is connected to the input-output of the surface electromagnetic wave shaper (6), the output of which is connected to the matched load (7), and the output of the circulator (5) is connected to the input of the second RF signal divider (2), the outputs of which are connected to the signal inputs of the first and second mixers (8) respectively Actually, the output of each mixer through a series-connected low-frequency amplifier and a low-pass filter is connected to the corresponding quadrature inputs of an analog-to-digital converter (11), the output of which is connected to the input of a digital signal processor (12), in addition, a local surface electromagnetic wave shaper ( 6) is located inside the cabinet (19) near one of its walls, and RFID tags (13) are mounted on identifiable objects that are placed above the surface electromagnetic wave former (6) in bochem screen (20) of the metal enclosure (19). 2. The object identification system according to claim 1, characterized in that the shaper of the local surface electromagnetic wave (6) is made in the form of a segment of the surface wave line of a metal comb or layered metal-dielectric structure. 3. The object identification system according to claim 1, characterized in that the first, second RF signal dividers (2) and the RF signal divider with a phase shift of 90 ° (3) are made by dividing the input RF signal by two output RF signals of equal amplitude.

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