CN107576345A - The wireless measuring system and measuring method of multinode resonator type surface acoustic wave sensor - Google Patents

Abstract

The invention discloses a wireless measurement system and a measurement method of a multi-node resonant surface acoustic wave sensor. Its main feature is that it corresponds to the frequency band of each resonant surface acoustic wave sensor. To transmit excitation signals of multiple frequency points at the same time to measure the resonant frequency of multiple sensors at the same time. Moreover, the receiving circuit of the reader directly performs bandpass sampling on the amplified and filtered radio frequency echo signal, and then performs frequency domain interpolation on the echo spectrum information after Fourier transform. Compared with the traditional reader which adopts a single local oscillator source and measures the resonant frequency of each sensor by polling, the present invention greatly improves the real-time performance of measurement, and improves the measurement accuracy through the frequency domain interpolation method. In addition, since the receiving circuit of the reader adopts the method of direct band-pass sampling of the radio frequency signal, the down-conversion circuit is omitted, which not only has a simple structure and low cost, but also improves the signal-to-noise ratio.

Description

Wireless measurement system and measurement method of multi-node resonant surface acoustic wave sensor

Technical field:

The invention relates to a wireless measuring system and a measuring method of a multi-node resonant surface acoustic wave sensor, belonging to the field of wireless sensing.

Background technique:

Surface acoustic wave devices can be used as sensors, which can be divided into two types: resonant type and delay type, as shown in Figure 1 and Figure 2 respectively. The resonant surface acoustic wave device is composed of a piezoelectric substrate, an interdigital transducer, and a reflective grating. The reflective gratings at both ends of the interdigital transducer are arranged in a dense array to form an acoustic resonant cavity. The delayed surface acoustic wave device is composed of a piezoelectric substrate, an input interdigital transducer, and an output interdigital transducer. When the surface acoustic wave device is used as a sensor, the surface acoustic wave propagation velocity and piezoelectric material parameters change according to the object to be measured, and further cause the resonant frequency of the resonant surface acoustic wave device to change or the time delay of the delay type surface acoustic wave device, Phase change to realize the sensing function.

With the cooperation of the reader and the antenna, the surface acoustic wave sensor does not need a power source while performing wireless sensing. Most notably, SAW sensors are gaining a lot of attention due to their wireless capabilities and passive nature. Compared with the delay type SAW sensor, the Q value (quality factor) of the resonant SAW sensor is higher, the wireless measurement distance is longer under the same conditions, and the electrical-acoustic and acoustic-electric conversion passes through the same finger Transducer, it is easier to realize the sensor's reception of excitation signal and transmission of echo signal through the same antenna, so it is more widely used in the field of wireless sensing.

In the practical application of wireless sensing, usually there is not only a single sensor, but multiple sensors exist simultaneously in the form of multiple nodes. For example, for the temperature detection of the high-voltage switchgear of the smart grid, it is necessary to measure the node temperature at different positions in the cabinet in real time online; for the torque detection of the engine shaft, it is necessary to measure the node torque at different positions on the shaft in real time. Resonant surface acoustic wave sensors usually use frequency division multiple access to achieve anti-collision measurement of multiple nodes, that is, the frequency bands of each sensor are different. In multi-node wireless measurements, many nodes also appear in pairs with a differential structure. For example, in the temperature detection of high-voltage switchgear, the differential structure is used to eliminate the influence of other environmental factors such as antenna impedance changes on the temperature measurement results; in the torque detection of the rotating shaft, the differential structure is used to eliminate environmental factors such as temperature. Influence on torque measurements. For the above-mentioned differential nodes, the frequency division multiple access method is also used to realize the measurement of the differential frequency.

For the wireless measurement of multi-node resonant surface acoustic wave sensors, the following problems currently exist:

(1) There is usually only a single local oscillator source in the traditional reader transmission chain, and only a single frequency point excitation signal is transmitted each time, and the resonance frequency of each sensor is measured in a polling manner. When the number of nodes is large, the polling time becomes longer, which affects the real-time performance of the measurement.

(2) For the differential node, due to the time difference between the polling method and the measurement of the two differential sensors, in the case of rapid changes in the object to be measured, not only will the measurement result have a large error, but also cannot accurately monitor the The dynamic change process of the measured object.

(3) The traditional reader receiving link usually adopts a down-conversion structure, which not only has a complex circuit structure and high cost, but also has problems such as increased noise and reduced signal-to-noise ratio.

(4) The measurement accuracy of the resonant SAW sensor depends on the estimation accuracy of the resonant frequency. For the method of Fourier transform spectrum measurement, due to the limitation of spectrum resolution, the estimation accuracy of resonance frequency is low; if the resonance frequency estimation method of frequency sweep measurement intensity is used, it is necessary to improve the estimation accuracy by subdividing the step frequency. Then the polling time of multiple nodes will become longer dramatically, and the real-time performance of measurement will be further affected.

Invention content:

The present invention provides a wireless measurement system and measurement method of a multi-node resonant surface acoustic wave sensor in order to solve the problems existing in the above-mentioned prior art, and its purpose is for the practical application of surface acoustic wave wireless sensing. When multiple resonant surface acoustic wave sensors are used, corresponding solutions are provided for the existing related problems.

The present invention adopts the following technical scheme: a wireless measurement system of a multi-node resonant surface acoustic wave sensor, which is composed of a reader and several resonant surface acoustic wave sensor nodes; wherein: several resonant surface acoustic wave sensor nodes are divided into There are two types, one is a common node, that is, the node has only one resonant SAW sensor, and the other is a differential node, that is, the node includes two resonant SAW sensors; each resonant SAW sensor The wave sensor has frequency bands that are adjacent but not overlapping with each other; corresponding to the frequency band of each resonant surface acoustic wave sensor, the reader simultaneously transmits excitation signals of multiple frequency points to simultaneously measure the frequency bands of all resonant surface acoustic wave sensors. Resonant frequency.

Further, the reader is composed of a transmitting module, a transceiver isolation module, an antenna module, a receiving module and a signal processing module.

Further, the transmitting module is composed of a multi-local oscillator module, a bandpass filter module and a radio frequency power amplifier module.

Further, the multi-local oscillator source module is composed of a plurality of phase-locked loop modules and combiner modules with identical structures; wherein, the number of phase-locked loop modules and the number of input ports of the combiner module are the same as those of the resonant surface acoustic surface The number of wave sensors is the same, and the output ends of each phase-locked loop module are respectively connected to each input port of the combiner module.

Further, the phase-locked loop module adopts a program-controlled phase-locked loop chip, and each phase-locked loop module has the same reference frequency, and generates different frequencies corresponding to the resonance frequencies of each resonant surface acoustic wave sensor through the difference in frequency multiplication coefficients. point of the stimulus signal.

Further, the frequency band of the antenna module of the reader covers the frequency bands of all resonant surface acoustic wave sensors.

Further, the receiving module of the reader includes a low-noise radio frequency amplifier module, a bandpass filter module and a radio frequency signal bandpass sampling module; wherein, the radio frequency signal bandpass sampling module directly amplifies and filters the radio frequency echo signal Bandpass sampling.

Further, the signal processing module of the reader performs Fourier transform on the received echo signals including all resonant surface acoustic wave sensors to obtain complete echo spectrum information, and then searches for the resonant surface acoustic wave Multiple spectral maxima corresponding to the number of sensors, and then perform frequency domain interpolation around each spectral maxima to obtain the resonant frequency of each resonant surface acoustic wave sensor.

The present invention also adopts the following technical scheme: a measurement method for a wireless measurement system of a multi-node resonant surface acoustic wave sensor, the working steps are as follows:

Step A, the transmitting module of the reader first generates an excitation signal containing multiple frequency points through the multi-local oscillator module, then performs band-pass filtering and power amplification, and then transmits it through the antenna module through the transceiver isolation module;

Step B, each resonant surface acoustic wave sensor receives the excitation signal containing multiple frequency points emitted by the reader through the sensor antenna, selects the frequency through the interdigital transducer and generates the surface acoustic wave of the corresponding frequency through the inverse piezoelectric effect. The surface of the piezoelectric substrate propagates to both sides, and is coherently reflected and superimposed by the reflective grating multiple times, forming a standing wave in the resonant cavity, and then converted into electromagnetic waves by the positive piezoelectric effect through the interdigital transducer, and each sensor is transmitted by the sensor antenna. The echo of the sensor is transmitted back to the reader. When the excitation signal of the reader is modulated into an intermittent signal by the transceiver isolation module, the echo signal of each sensor is a double-sided band signal whose amplitude decays exponentially with time. The resonant frequency of the sensor with the change of the measured object is the same;

Step C, the reader receives the echo signals superimposed by all sensors through the antenna module, enters the receiving module through the transceiver isolation module, and enters the radio frequency signal bandpass sampling module after low noise amplification and bandpass filtering to obtain the echo digital signal;

Step D, the echo digital signal enters the signal processing module, obtains the spectrum information including the resonant frequency of all resonant surface acoustic wave sensors through Fourier transform, and then searches for multiple spectral maxima corresponding to the number of resonant surface acoustic wave sensors value, and then perform frequency-domain interpolation around each spectrum maximum value to obtain the resonant frequency of each resonant SAW sensor more accurately;

Step E, for a common node, measure the value of the object to be measured at the node according to the resonance frequency of the corresponding resonant surface acoustic wave sensor; for a differential node, measure the value of the object to be measured at the node according to the resonance frequency The difference in frequency measures the value of the measurand at the node.

The present invention has following beneficial effect:

(1) The reader simultaneously transmits excitation signals of multiple frequency points through multiple local oscillator sources to measure the resonance frequency of multiple sensors at the same time, compared with the traditional reader using a single local oscillator source and measuring by polling , the real-time performance of its measurement has been greatly improved;

(2) For differential nodes, when the object to be measured changes rapidly, the polling method avoids the problem of time difference in the measurement of two differential sensors, which not only greatly reduces the measurement error, but also can More accurately monitor the dynamic change process of the object to be measured;

(3) The receiving circuit of the reader adopts the direct band-pass sampling method of the radio frequency signal, which saves the down-conversion circuit of the traditional reader, not only has a simple structure and low cost, but also improves the signal-to-noise ratio;

(4) The reader performs frequency-domain interpolation on the echo spectrum information after Fourier transform, which improves the estimation accuracy of the resonant frequency, thereby obtaining more accurate values of the object to be measured.

Description of drawings:

Figure 1 shows a resonant surface acoustic wave device.

Figure 2 is a delayed surface acoustic wave device.

Figure 3 shows the structure of the wireless measurement system of the multi-node resonant surface acoustic wave sensor.

Fig. 4 is the reader structure of the system.

Figure 5 shows the structure of the launch module of the system.

Figure 6 shows the multi-local oscillator module structure of the system.

Figure 7 shows the structure of the receiving module of the system.

Figure 8 is the function of the signal processing module of the system.

detailed description:

Below in conjunction with accompanying drawing, technical scheme of the present invention is described in further detail:

Please refer to shown in Fig. 3, the wireless measuring system of multi-node resonant surface acoustic wave sensor of the present invention is made of reader and several resonant surface acoustic wave sensor nodes; Wherein: several resonant type surface acoustic wave sensor nodes are divided into two There are two types, one is common node, that is, the node has only one resonant SAW sensor, and the other is differential node, that is, the node includes two resonant SAW sensors; each resonant SAW sensor The sensors have adjacent but non-overlapping frequency bands; corresponding to the frequency band of each resonant surface acoustic wave sensor, the reader simultaneously transmits excitation signals of multiple frequency points to simultaneously measure the resonance of all resonant surface acoustic wave sensors frequency.

Please refer to Figure 4, the reader is composed of a transmitting module, a transceiver isolation module, an antenna module, a receiving module and a signal processing module.

Please refer to FIG. 5 , the transmitting module is composed of multiple local oscillator modules, a bandpass filter module and a radio frequency power amplifier module.

Please refer to Figure 6, the multi-LO source module is composed of multiple phase-locked loop modules and combiner modules with the same structure; among them, the number of phase-locked loop modules and the number of input ports of the combiner module are the same as those of the resonant type The number of surface acoustic wave sensors is the same, and the output ends of each phase-locked loop module are respectively connected to each input port of the combiner module.

The phase-locked loop module adopts a program-controlled phase-locked loop chip, and each phase-locked loop module has the same reference frequency, and generates excitation signals of different frequency points corresponding to the resonance frequency of each resonant surface acoustic wave sensor through different frequency multiplication coefficients.

Please refer to Figure 3 and Figure 4, the antenna module of the reader has a wide frequency band, covering the frequency bands of all resonant surface acoustic wave sensors.

Please refer to Figure 7, the receiving module of the reader includes a low-noise radio frequency amplifier module, a bandpass filter module and a radio frequency signal bandpass sampling module; wherein, the radio frequency signal bandpass sampling module directly amplifies and filters the radio frequency echo The signal is sampled in a band pass, which saves the down-conversion link and avoids problems such as increased noise and lower signal-to-noise ratio caused by the down-conversion process.

Please refer to Figure 8. The signal processing module of the reader performs Fourier transform on the received echo signals including all resonant surface acoustic wave sensors to obtain complete echo spectrum information, and then searches for the echo signals that are compatible with the resonant surface acoustic wave sensors. Multiple spectral maxima corresponding to the number of surface wave sensors, and then perform frequency domain interpolation around each spectral maxima to more accurately obtain the resonant frequency of each resonant surface acoustic wave sensor.

Please refer to Fig. 3, the measurement method of the wireless measurement system of the multi-node resonant surface acoustic wave sensor of the present invention, the working steps are as follows:

Step A, the transmitting module of the reader first generates an excitation signal containing multiple frequency points through the multi-local oscillator module, then performs band-pass filtering and power amplification, and then transmits it through the antenna module through the transceiver isolation module;

Step B, each resonant surface acoustic wave sensor receives the excitation signal containing multiple frequency points emitted by the reader through the sensor antenna, selects the frequency through the interdigital transducer and generates the surface acoustic wave of the corresponding frequency through the inverse piezoelectric effect. The surface of the piezoelectric substrate propagates to both sides, and is coherently reflected and superimposed by the reflective grating multiple times, forming a standing wave in the resonant cavity, and then converted into electromagnetic waves by the positive piezoelectric effect through the interdigital transducer, and each sensor is transmitted by the sensor antenna. The echo of the sensor is transmitted back to the reader. When the excitation signal of the reader is modulated into an intermittent signal by the transceiver isolation module, the echo signal of each sensor is a double-sided band signal whose amplitude decays exponentially with time. The resonant frequency of the sensor with the change of the measured object is the same;

Step C, the reader receives the echo signals superimposed by all sensors through the antenna module, enters the receiving module through the transceiver isolation module, and enters the radio frequency signal bandpass sampling module after low noise amplification and bandpass filtering to obtain the echo digital signal;

Step D, the echo digital signal enters the signal processing module, obtains the spectrum information including the resonant frequency of all sensors through Fourier transform, and then searches for a plurality of spectrum maxima corresponding to the number of sensors, and then finds a maximum of each spectrum Frequency-domain interpolation is performed around the value to obtain the resonant frequency of each sensor more accurately;

Step E, for a normal node, measure the value of the object to be measured at the node according to the resonance frequency of the corresponding sensor; for a differential node, measure the value of the object to be measured at the node according to the difference between the resonance frequencies of the two differential sensors measured object value.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, some improvements can also be made without departing from the principle of the present invention, and these improvements should also be regarded as the invention. protected range.

Claims (9)

1. A kind of 1. wireless measuring system of multinode resonator type surface acoustic wave sensor, it is characterised in that：By reader and some Individual resonator type surface acoustic wave sensor node is formed；Wherein：Several resonator type surface acoustic wave sensor nodes are divided into two species Type, one kind is plain edition node, i.e. the node only one resonator type surface acoustic wave sensor, and another kind is differential-type node, i.e., The node includes two resonator type surface acoustic wave sensors；Each resonator type surface acoustic wave sensor have it is adjacent but each other it is each not Overlapping frequency band；Corresponding with the frequency band of each resonator type surface acoustic wave sensor, reader launches multiple frequencies simultaneously Pumping signal, to measure the resonant frequency of all resonator type surface acoustic wave sensors simultaneously.
2. 2. the wireless measuring system of multinode resonator type surface acoustic wave sensor as claimed in claim 1, it is characterised in that：Institute Reader is stated to be made up of transmitter module, transceiver insulation module, Anneta module, receiving module and signal processing module.
3. 3. the wireless measuring system of multinode resonator type surface acoustic wave sensor as claimed in claim 2, it is characterised in that：Institute Transmitter module is stated to be made up of more local oscillator source modules, bandpass filter module and radio-frequency power amplifier module.
4. 4. the wireless measuring system of multinode resonator type surface acoustic wave sensor as claimed in claim 3, it is characterised in that：Institute More local oscillator source modules are stated by multiple completely identical in structure phase-locked loop modules and combiner module composition；Wherein, phase-locked loop module Quantity and combiner module input port quantity it is all identical with the quantity of resonator type surface acoustic wave sensor, each lock phase The output end of ring moulds block is connected with each input port of combiner module respectively.
5. 5. the wireless measuring system of multinode resonator type surface acoustic wave sensor as claimed in claim 4, it is characterised in that：Institute State phase-locked loop module and use program control phase-locked loop chip, each phase-locked loop module has identical reference frequency, passes through Clock Multiplier Factor Difference produce the pumping signal of different frequent points corresponding with the resonant frequency of each resonator type surface acoustic wave sensor.
6. 6. the wireless measuring system of multinode resonator type surface acoustic wave sensor as claimed in claim 2, it is characterised in that：Institute The frequency band for stating the Anneta module of reader covers the frequency band of all resonator type surface acoustic wave sensors.
7. 7. the wireless measuring system of multinode resonator type surface acoustic wave sensor as claimed in claim 2, it is characterised in that：Institute Stating the receiving module of reader includes low noise RF amplifier modules, bandpass filter module and the sampling of radiofrequency signal band logical Module；Wherein, radiofrequency signal band logical sampling module directly carries out bandpass sampling to amplification and filtered rf echo signal.
8. 8. the wireless measuring system of multinode resonator type surface acoustic wave sensor as claimed in claim 2, it is characterised in that：Institute The signal processing module for stating reader carries out Fu to the echo-signal including all resonator type surface acoustic wave sensors received In leaf transformation, obtain complete echo spectrum information, then search corresponding with resonator type surface acoustic wave number of sensors more Individual spectrum maximum, frequency domain interpolation is carried out respectively near each spectrum maximum afterwards, to obtain each mode of resonance sound The resonant frequency of surface wave sensor.
9. A kind of 9. measurement side of the wireless measuring system of multinode resonator type surface acoustic wave sensor as claimed in claim 1 Method, it is characterised in that：Job step is as follows：

   Step A, the transmitter module of reader produce the pumping signal for including multiple frequencies by more local oscillator source modules first, then Carry out bandpass filtering and power amplification, after launched through transceiver insulation module by Anneta module；

   Step B, each resonator type surface acoustic wave sensor by sensor antenna receive reader launch include multiple frequencies The pumping signal of point, the surface acoustic wave of corresponding frequencies is produced along piezoelectric substrate by interdigital transducer frequency-selecting and through inverse piezoelectric effect Surface is propagated to both sides, through the multiple coherent reflection of reflecting grating and is superimposed, standing wave is formed in resonator, then pass through interdigital transducer Electromagnetic wave is converted into through direct piezoelectric effect, and the echo of each sensor is transmitted back to reader through sensor antenna, works as reading When the pumping signal of device is modulated to intermittency signal through transceiver insulation module, the echo-signal of each sensor is in the time for amplitude The double-sideband signal of exponential law decay, its carrier frequency are consistent with the sensor resonant frequency with object variation to be measured；

   Step C, reader receive the echo-signal of all the sensors superposition through Anneta module, are entered by transceiver insulation module and connect Module is received, radiofrequency signal bandpass sampling module is entered after low noise amplification, bandpass filtering, obtains echo data signal；

   Step D, echo data signal entering signal processing module, obtained by Fourier transformation and include all mode of resonance sound surfaces The spectrum information of wave sensor resonant frequency, then search multiple frequency spectrums corresponding with resonator type surface acoustic wave number of sensors Maximum, carry out frequency domain interpolation respectively near each spectrum maximum again afterwards, it is humorous more precisely to obtain each The resonant frequency of vibration shape surface acoustic wave sensor；

   Step E, for plain edition node, measured according to the resonant frequency of corresponding resonator type surface acoustic wave sensor at the node Object value to be measured, for differential-type node, surveyed according to the difference of the resonant frequency of two differential-type resonator type surface acoustic wave sensors Obtain the object value to be measured at the node.