RU2748391C1 - Device for reading information from wireless sensor on surface acoustic waves - Google Patents

Abstract

FIELD: monitoring systems.SUBSTANCE: invention is intended for use in systems for monitoring the state of objects in order to prevent unforeseen situations when monitoring rapidly changing physical quantities. The high-frequency harmonic oscillator 1 generates a sounding continuous radio signal of one frequency with constant amplitude to the transmitting and receiving antenna 7, directed to the transmitting and receiving antenna 8 of the receiving interdigital transducer 10 of the surface acoustic wave sensor 9. The low-frequency signal modulated in accordance with the change in the measured physical quantity at the output of the detector 3 is fed to the input of the ADC 4, which continuously digitizes the signals from the sensor 9, which is connected to the computer 5, which determines the measured physical quantity in real time, and from the output of the low-pass filter the time dependence of the measured physical quantity is removed.EFFECT: invention allows monitoring the measured physical quantity continuously and recording all its changes over time, which eliminates the loss of information.1 cl, 6 dwg

Description

The invention relates to the field of electronics and is intended for reading information from wireless sensors on surface acoustic waves used in systems for monitoring the state of objects in order to prevent unforeseen situations when monitoring rapidly changing physical quantities, namely, the intensity of ultraviolet radiation, the composition of harmful gases, the magnitude of deformations and micro displacements of structures of infrastructure facilities, ambient temperature at various facilities.

An information reader from a wireless surface acoustic wave (SAW) sensor generates interrogating radio signals and emits them through an antenna. A physical quantity sensor (micro displacements, deformation, ultraviolet radiation, gas composition, temperature), falling into the antenna area, in response to the polling signal transmits a response radio signal containing information about the physical quantity, which is determined by the reader and is transmitted to an external data processing device.

It is widely known from the prior art to use a reader to obtain information about physical quantities from wireless SAW sensors (RU2296950, 6MPK G01 D5 / 00 publ. 27.02.2006) [1], RU 2387051, 6MPK, H01L41 / 107, G01D5 / 12, publ. ... 20.04.2010) [2], RU2550697, MPK-2006.01 G01D5 / 00, B82B1 / 00, publ. 05/10/2015 [3], RU2581570, MPK-2006.01 H03H9 / 25, publ. 04/20/2016 [4], RU2585487, MPK-2006.01 G01K 11/24, H01L 41/08, publ. 05/27/2016) [5].

The interrogation radio pulse is received by the transceiving antenna of the sensor on the SAW and the transceiver transceiver transducer (IDT), located on the piezoelectric sound conductor, gets into it, where it is converted into SAW pulses, which, propagating along the acoustic line, are reflected from the reflective IDTs located on the path of SAW propagation, the first of which is a reference, and the latter can be connected to an impedance, the value of which depends on the measured physical quantity. When the impedance changes, the reflection coefficient of the SAW from the reflective IDT changes, which leads to a change in the amplitude and phase of the SAW reflected from it. The SAW pulses reflected from it and from another IDT arrive at the transceiving IDT, where they are converted into an electromagnetic signal representing a sequence of radio pulses, the amplitude and phase of which are proportional to the amplitude of the SAW incident on the transceiving IDT, and enter the reader. In the reader, the amplitudes of the reflected SAWs from the first and last IDTs are compared and the value of the measured physical quantity is determined if the last IDT is loaded with impedance, or the SAW delay between the first and last IDTs is measured if the latter is not loaded. The amplitude and phase (delay) of the reflected SAWs can also change if the SAWs pass under a film located between adjacent reflective IDTs. In this case, under the action of a measurable physical quantity, for example, the intensity of electromagnetic radiation in the visible or ultraviolet region (Wenbo Penga, Yongning Heat, Changbao Wenb, Ke Maa, Surface acoustic wave ultraviolet detector based on zinc oxide nanowire sensing layer // Sensors and Actuators A : Physical Volume 184, September 2012, Pages 34-40 [6], US Patent 6914279, IPC ⁷ H01L 29/82 dated 05.06.2005 [7], US Patent 7989851, IPC-2006.01 H01L 29/82 dated 02.08.2011 [ 8]) in the presence of interference, the signals reflected from the sensors can be at their level, and the signals cannot be detected, since it is not possible to average the received pulses due to the lack of synchronization in the filling frequency of the probing pulses, which is a disadvantage of the known technical solutions ...

This drawback is eliminated in the method (RU 2629892, 6MPK N03N 31/00, publ. 04.09.2017) [9], in which, according to the dependent claim 2 of the claims, the reader contains a complex transmission coefficient meter (IKKP) "Obzor-103" connected to the computer. A standard complex transfer ratio meter consists of a generator unit, a control unit, an ADC, a measuring unit that measures complex transfer coefficients S11, S21, VSWR, GVZ. The control unit sets the parameters of the linear - frequency modulation (chirp) of the pulse, the ADC digitizes the data. The output (input) of the IKKP is connected to the transmitting and receiving antenna. A probing electromagnetic pulse is periodically fed to the transceiver IDT of the SAW sensor from the reader antenna, in which the frequency discretely changes according to a linear law. This pulse is reflected from the transmitting-receiving antenna of the sensor and again falls on the receiving-transmitting antenna of the reader, where the frequency dependence of the complex reflection coefficient S _{11 of} this antenna is measured and the Fourier transform of the obtained frequency dependence is performed, according to which the amplitude and delay of the pulses reflected from the sensor are determined. moreover, the duration of the probing electromagnetic pulse is selected in such a way that measurements at each frequency are carried out for some time, during which the SAW travels a distance greater than twice the distance between IDTs. The filling frequency of the electromagnetic pulse is generated using a digital frequency synthesizer. In this case, the determination of the value of the parameter S ₁₁ at each frequency point is made for some time, during which the SAW travels a distance greater than twice the distance between IDTs, this leads to an increase in the measurement accuracy due to the fact that the amplitudes of the reflected signal are measured at a certain frequency more than once , and also due to the fact that the phases of the interference signals are random and mutually attenuated during the measurement. In addition, due to the periodicity of sending frequency-modulated pulses, the measurement at each frequency point is made several times and these measurements can also be summed (averaged), which also leads to a decrease in the influence of interference on the measurement results, and, consequently, to an increase in the measurement accuracy.

To increase noise immunity, a surface acoustic wave sensor for wireless passive displacement measurement (RU 2486646, IPC: H01Q 23/00 (2006.01), G01S 13/75 (2006.01) publ. 06/27/2013) [10] contains a reader and a SAW device , while the reader consists of a transceiver and an antenna, and the SAW device contains an antenna and SAW resonators, each of which contains an interdigital converter, which is electrically connected to the antenna of the SAW device, and two reflective structures. The sensor is polled by the reader as follows. On command from the computer, the reader generates N interrogation radio pulses, where N is equal, for example, 5, with fixed, equally spaced carrier frequencies f ₀₁ ... f _N (for example, f ₀₁ = 433 and f _0N = 434 MHz). The duration of each interrogation pulse depends on the Q-factor of the resonators and with a loaded Q-factor, for example, ~ 8000, it can be, for example, ~ 10 μs. Interrogation pulses are emitted through the antenna in the direction of the SAW device in the housing. The response signals of the SAW device in the housing for each polling radio pulse through the antenna are fed to the reader. The reader performs amplification, filtering and digitization of the received signals. The digitized signals are transmitted to a computer, where they are processed in accordance with the specified algorithms. As a result of processing in the computer, the resonant frequencies of the resonators f _R1 and f _R2 are determined, according to the values of which the magnitude of the displacement ΔX is determined.

However, if the measured physical quantity changes in a time less than the time between pulses, this will lead to the loss of information from the measured physical quantity and, consequently, to a decrease in the measurement accuracy. In addition, the measured physical quantity can change in the time interval between the sending of the readout pulses, which also reduces the measurement accuracy.

The object of the present invention is the ability to read signals from a SAW sensor when the measured physical quantity changes rapidly during the measurement. This is achieved due to the fact that information from the sensor is read continuously, and not by a sequence of readout pulses, during which and between which the measured physical quantity could change.

The proposed device for reading information from a wireless sensor on surface acoustic waves contains a high-frequency harmonic oscillator, which sends a probing radio signal of one frequency with a constant amplitude through a resistor to the transceiver antenna of the reader, directed to the transceiver antenna of the receiving interdigital transducer of the sensor on surface acoustic waves, the output of the resistor connected to the input of the detector, the output of which is connected to the input of the ADC, the output of which is connected to the input of the calculator, which determines the measured physical quantity from the equation f (x _i ) - F (x _i ) = 0 in real time and whose output is connected to the input of the low-pass filter , from the output of which the time dependence of the measured physical quantity x (t) is taken, where f (x _i ) is the signal at the ADC output, F (x _i ) is the known dependence of the amplitude of the signal reflected from the sensor on the measured physical quantity. in this case, the transceiver antenna is connected at one end to the body of the harmonic oscillator, and at the other end to a resistor at the point of its connection with the detector input.

In a preferred embodiment, a detector head is used as the detector.

The essence of the invention lies in the fact that the proposed device for reading information allows you to monitor the measured physical quantity continuously and record all its changes in time, which eliminates the loss of information inherent in known readers based on the measurement of complex coefficients of chirp pulses,

The device for reading information from a wireless sensor on surface acoustic waves (SAW) is illustrated by the figures of the drawings, where:

Fig. 1 is a functional diagram of a device for reading information from a wireless sensor on a SAW, where it is indicated:

1- high-frequency generator of harmonic oscillations;

2- resistor;

3- detector;

4- ADC;

5- calculator f (x _i ) - F (x _i ) = 0;

6- LPF;

7- transceiver antenna of the reader;

8 -transmitter antenna of the SAW sensor;

9 - surfactant sensor;

10- transceiving IDT;

11- reflective IDT.

FIG. 2 is a graph of the change in the frequency dependence of the parameter S11 of the antenna during physical impact on the sensor on the SAW.

FIG. 3 - oscillogram at the output of the detector head under physical impact with a frequency of 500 kHz on a SAW sensor.

FIG. 4 - oscillogram at the output of the detector head under physical impact with a frequency of 50 kHz on a SAW sensor.

FIG. 5 - oscillogram at the output of the detector head under physical impact with a frequency of 5 kHz on a SAW sensor.

FIG. 6 - oscillogram at the output of the detector head under physical impact with a frequency of 500 Hz on a SAW sensor.

The device for reading information from a wireless sensor on surface acoustic waves contains a high-frequency harmonic oscillator 1, which sends a probing radio signal of one frequency with a constant amplitude through a resistor 2 to the transceiver antenna 7 of the reader, directed to the transceiver antenna 8 of the receiving interdigital transducer 10 of the sensor on surface acoustic waves waves 9, the output of resistor 2 is connected to the input of the detector 3, the output of which is connected to the input of the ADC 4, the output of which is connected to the input of the calculator 5, which determines the measured physical quantity from the equation f (x _i ) - F (x _i ) = 0 in real time scale and the output of which is connected to the input of the low-pass filter 6, from the output of which the time dependence of the measured physical quantity x (t) is taken, where f (x _i ) is the signal at the ADC output, F (x _i ) is the known dependence of the amplitude of the signal reflected from the sensor 9 from the measured physical quantity, while the transceiver antenna read One end of the probe is connected to the body of the harmonic oscillator, and the other end is connected to resistor 2 at the point of its connection with the input of the detector 3.

The calculator 5 is a computer in the memory of which the values of F (x _i ) are entered. Also, the values f (x _i ) are entered into it and the equation f (x _i ) - F (x _i ) = 0 is solved by one of the many well-known methods (for example, the method of half division).

A high-frequency harmonic oscillator 1 (HF generator) provides a sounding continuous radio signal of one frequency with a constant amplitude to the transmitting and receiving antenna 7 (shown in Fig. 1 as a sinusoid, arrow down), directed to the transmitting and receiving antenna 8 of the receiving interdigital converter 10 surface acoustic wave sensors 9.

In this case, the voltage U at the transmit-receive antenna 7 with impedance Z is determined by the formula:

, (1)

, (one)

where: U _g - voltage amplitude at the HF generator;

R _g - internal resistance of the RF generator;

R - resistor resistance

Z is the impedance of the transceiver antenna of the reader.

The radio signal from the transmitting-receiving antenna 8 of the sensor 9 is converted by the receiving interdigital transducer 10 into a surface acoustic wave, which propagates towards the reflective IDT 11. When the physical quantity changes, the speed or attenuation and velocity of the SAW, or the SAW reflection coefficient from the reflective IDT 11 under the influence of changes in the impedance Z1, the value of which depends on the measured physical quantity, which will lead to a change in the impedance of the IDT 11, and, consequently, to a change in the amplitude of the SAW reflected from it. Next, the reflected SAW fall on the transmitting-receiving IDT 10, which leads to a change in its impedance, as well as the signal reflected from the antenna 8 connected to the IDT 10 of the sensor 9. The signal reflected from the sensor (shown in Fig. 1 in the form of a sinusoid and an upward arrow ) hits the transceiver antenna 7 of the reader and changes (modulates) its impedance Z, which can be determined knowing the parameter S11 of the antenna [11]:

, (2)

, (2)

where R ₀ is the resistance of the measuring device.

Fig. 2. the frequency dependence of the parameter S11 is shown, when the reflection coefficient of the SAW from the reflective IDT is different. It can be seen that at a frequency of 439.45 MHz, the S11 parameter changes especially strongly. Then the impedance Z of the antenna will also change more at this frequency than at other frequencies. Choosing this frequency equal to the frequency of the generator 1, we obtain the maximum change in the voltage at the input of the detector head 4 with a change in the SAW reflection coefficient from the reflective IDT.

Thus, in accordance with formula (1), the voltage at the input of the detector head 3 will be modulated in accordance with the change in the measured physical quantity (if Z << R _r + R ), and at the output of detector 3, which is used as a detector head (for example, from the X1-42 device), there will be an envelope of the modulated RF signal. Then the low-frequency signal is fed to the input of the ADC 4, which continuously digitizes the signal from the sensor to the SAW 9. In this case, the sampling frequency of the ADC is selected in such a way that a change in the physical quantity between samples is unlikely. This makes it possible to detect any changes in the measured physical quantity in a time interval that will be much less than the oscillation period of the HF signal, which at frequencies of the HF signal in the range of 433-2500 MHz can be 4-20 μs. The resulting data array from ADC 4 is fed to the calculator 5, where discrete values of the measured physical quantity are determinedx _i due to the solution of the equationf (x _i ) - F (x _i ) =0, wheref (x _i ) -signal at the output of ADC 4,F (x _i ) - the known dependence of the amplitude of the signal reflected from the sensor on the measured physical quantity (calibration curve). Thus, a calculator is a computer program installed on a PC that solves the equationf(x _i ) - F (x _i ) =0 in real time. Further discrete signalx _i goes to low-pass filter 6 (LPF), where it is converted into a continuous signalx (t)... Thus, at the output of the reader, a continuous dependence of the measured physical quantity on time is obtained, which makes it possible to track any changes in it.

An example of execution.

The SAW sensor 9 is a delay line containing one transceiver 10 and one reflective 11 narrowband IDT.

Narrowband IDTs each contain 20 single-wave sections, the distance between which is equal to 17 SAW lengths at the central frequency in the transmit-receive IDT and 260 SAW lengths in the reflective IDT. The distance between the IDTs is 1 cm. The distance between the antennas is 2 m.

As an element that changes the reflection coefficient of the reflective IDT, a KV-102 varicap is used, which is connected to the reflective IDT 9. An alternating voltage in the form of rectangular pulses was applied to the varicap through chokes that have high resistance at frequencies around 439 MHz. The duration of the pulses is equal to the distance between them, and the repetition rate is chosen equal to 500 kHz, 50 kHz, 5 kHz, respectively.

The output of the detector head 4 was connected to one of the inputs of the digital oscilloscope "Rigol", to the other input of which the voltage supplied to the varicaps was applied. The detector head from the X1-42 device was used as a detector head. R _g = R = 50 ohms. Thus, it is possible to visually continuously observe the change in the measured physical quantity.

Figure 3 shows that at a frequency of 500 kHz, the supplied pulses have a different from rectangular shape, but the pulses at the output of the detector head differ significantly from the shape of the pulses supplied to the varicap. It is clearly seen that the change in the voltage amplitude at the output of the detector head follows the changes in the voltage at the varicap. When the frequency decreases, the pulses (Fig. 4-6) supplied to the varicap have a rectangular shape, and the pulses at the detector output differ from the rectangular shape, gradually approaching it as the frequency decreases (Fig. 6).

Thus, it is shown that the inventive reader allows you to remotely measure physical quantities without wires using a passive sensor of physical quantities on surface acoustic waves in a continuous mode, unlike known solutions, where the interrogation of passive sensors was carried out exclusively in a pulsed mode.

Information sources:

1.RU2296950, 6MPK G01 D5 / 00 publ. February 27, 2006.

2. RU 2387051, 6MPK, H01L41 / 107, G01D5 / 12, publ. 20.04.2010).

3. RU2550697, MPK-2006.01 G01D5 / 00, B82B1 / 00, publ. 05/10/2015.

4. RU2581570, MPK-2006.01 H03H9 / 25, publ. 04/20/2016.

5. RU2585487, MPK-2006.01 G01K 11/24, H01L 41/08, publ. 05/27/2016.

6. Wenbo Penga, Yongning Heat, Changbao Wenb, Ke Maa, Surface acoustic wave ultraviolet detector based on zinc oxide nanowire sensing layer // Sensors and Actuators A: Physical Volume 184, September 2012, Pages 34–40.

7. US Patent 6914279, IPC ⁷ H01L 29/82 dated 05.06.2005.

8. US Patent 7989851, IPC-2006.01 H01L 29/82 dated 02.08.2011.

9. RU 2629892, 6MPK N03N 31/00, publ. 04.09.2017).

10. RU 2486646, MPK-2006: H01Q 23/00, G01S 13/75, publ. June 27, 2013.

11. Microwave - electronic devices. Lecture 1. Scattering matrix. Matching devices. https://ppt-online.org/150867.

Claims (2)

1. A device for reading information from a wireless sensor on surface acoustic waves, containing a high-frequency harmonic oscillator, which sends a probing radio signal of one frequency with a constant amplitude through a resistor to the receiving-transmitting antenna of the reader, directed to the receiving-transmitting antenna of the receiving interdigital transducer of the sensor on surface acoustic waves, the output of the resistor is connected to the input of the detector, the output of which is connected to the input of the ADC, the output of which is connected to the input of the calculator, which determines the discrete values of the measured physical quantity x _i from the equation f (x _i ) - F (x _i ) = 0 in real time and the output of which is connected to the input of the low-pass filter, from the output of which the time dependence of the measured physical quantity is taken x (t) ,Where f (x _i ) -signal at the ADC output, F (x _i ) - the known dependence of the amplitude of the signal reflected from the sensor on the measured physical quantity, while the receiving-transmitting antenna of the reader is connected at one end to the body of the harmonic oscillator, and at the other end to a resistor at the point of its connection with the detector input. 2. The device according to claim 1, characterized in that a detector head is used as a detector.

Images