Sensing system based on surface acoustic wave oscillator

Abstract

The invention relates to a sensing system based on a surface acoustic wave oscillator. The sensing system comprises two resonators, two oscillating circuits, a temperature controller, a fluid pipeline, a frequency mixer, an amplification function comparator and a frequency divider, the temperature controller, the resonators and the oscillating circuits are arranged on the fluid pipeline, the two resonators are located on the upper side and the lower side of the temperature controller respectively, and the two oscillating circuits are located on the upper side and the lower side of the two resonators respectively; the temperature controller transmits heat to the resonators on the upper side and the lower side through the fluid pipeline, the resonators adjust resonant frequencies according to temperature changes and output different frequencies to the adjacent oscillating circuits, and the two oscillating circuits are connected with the frequency mixer. The mixer outputs a difference frequency signal to the amplification function comparator, and the amplification function comparator outputs a square wave signal to the frequency divider.

Description

Technical Field

[0001] The invention relates to a sensing technology based on an oscillator, and in particular to a sensing system based on a surface acoustic wave oscillator. Background Art

[0002] Surface acoustic wave (SAW) is an elastic wave that propagates along the surface of a solid. Through the interdigital transducer structure, the surface acoustic wave can be excited and detected on the surface of a piezoelectric material. The working principle of the surface acoustic wave: the input transducer of the substrate converts the input electrical signal into an acoustic signal through the inverse piezoelectric effect. This acoustic signal propagates along the surface of the substrate, and is finally converted into an electrical signal for output by the output transducer of the substrate. The function of the entire surface acoustic device is completed by performing various processing on the acoustic signal propagating on the piezoelectric substrate and utilizing the characteristics of the acoustic-electric transducer.

[0003] Usually for high-performance SAW temperature sensors, the core structure is an oscillator with high-frequency stability. The two-port SAW resonator structure composed of an interdigital transducer and two adjacent reflectors has the characteristics of simple design, low loss and high Q value, which is conducive to obtaining ideal frequency stability performance. Compared with other types of sensors, the SAW resonator can directly output characteristic frequency signals without analog-to-digital conversion, which is convenient for information processing. It also has the advantages of passive, easy to oscillate, easy to integrate, and mass production.

[0004] The change of SAW wave velocity induced by the external environment can be reflected as the change of the sensor output frequency signal. To obtain the change of frequency information, a matching signal acquisition system is required. By directly connecting the SAW sensor to the vector network analyzer and analyzing the S parameters of the SAW, it is easy to achieve the detection purpose. However, due to the high power consumption and non-portability of the instrument, this method is limited to laboratory use. In addition, some SAW resonators have a wider resonant cavity, which makes the resonator frequency response have multi-mode characteristics, and the loss between each mode is close, which will result in multiple frequency points meeting the oscillation conditions, thereby affecting the frequency stability of the oscillator. In addition, most resonators use aluminum electrodes or electrode structures composed of multiple metals. These electrodes and the core structure of the resonator are in direct contact with the environment to be tested. If the environment to be tested is toxic or corrosive, problems such as affecting the stability and service life of the oscillator may occur. Summary of the invention

[0005] In view of the problems in the prior art, the present invention relates to a sensing system based on a surface acoustic wave oscillator, which can improve the frequency stability and life of the oscillator.

[0006] In order to solve the above technical problems, the present invention relates to the following technical solutions:

[0007] In a first aspect, the present invention relates to a sensing system based on a surface acoustic wave oscillator, the sensing system based on a surface acoustic wave oscillator comprising:

[0008] Two resonators, two oscillation circuits, a temperature controller, a fluid pipeline, a mixer, an amplifying comparator and a frequency divider;

[0009] The temperature controller, the resonator and the oscillation circuit are arranged on the fluid pipeline, the two resonators are respectively located on the upper and lower sides of the temperature controller, and the two oscillation circuits are respectively located on the upper and lower sides of the two resonators;

[0010] The temperature controller transfers heat to the resonators on the upper and lower sides through the fluid pipeline. The resonators adjust the resonant frequency according to the temperature change and output different frequencies to adjacent oscillation circuits. The two oscillation circuits are connected to the mixers respectively. The mixers output difference frequency signals to the amplifying function comparator. The amplifying function comparator outputs square wave signals to the divider.

[0011] Furthermore, the temperature controller comprises:

[0012] A thermostat, disposed on the fluid pipeline, transfers heat to the resonators on the upper and lower sides respectively through the fluid pipeline;

[0013] A temperature heating module, connected to the thermostat, and used to provide power output to the thermostat;

[0014] The temperature feedback module is connected to the thermostat and adjusts the thermostat according to the temperature of the thermostat so that the thermostat is maintained at a preset temperature.

[0015] Furthermore, the sensing system based on the surface acoustic wave oscillator also includes: a closed cavity, in which the temperature stabilizer and the resonator are arranged.

[0016] Furthermore, the resonator includes: a first short-circuit grating reflector, a second short-circuit grating reflector, and an interdigital transducer arranged between the first short-circuit grating reflector and the second short-circuit grating reflector.

[0017] Further, the distance between the first short-circuit grating reflector and the second short-circuit grating reflector and the interdigital transducer is 1 / 4λ, where λ is the wavelength of the sound wave.

[0018] Furthermore, the oscillation circuit includes: a first DC power supply, a second DC power supply, a high-frequency transistor and a first capacitor;

[0019] The resonator is connected in parallel between the base and collector of the high-frequency transistor, one end of the first capacitor is connected to the output end of the resonator, and the other end of the first capacitor is connected to the input end of the mixer; the positive electrode of the first DC power supply is connected to the base of the high-frequency transistor, the positive electrode of the second DC power supply is connected to the collector of the high-frequency transistor, and the negative electrode of the first DC power supply and the negative electrode of the second DC power supply are grounded.

[0020] Furthermore, the oscillation circuit includes: a first inductor, a second inductor, a third inductor, a resistor, a first capacitor, a second capacitor, a third capacitor, a first DC power supply, a second DC power supply and a high-frequency transistor;

[0021] The resonator is connected in parallel between the base and collector of the high-frequency triode; the second capacitor is connected in parallel between the base and emitter of the high-frequency triode; the output end of the resonator is connected to the second inductor and the positive electrode of the second DC power supply in sequence, and the negative electrode of the second DC power supply is grounded; the output end of the resonator is connected to one end of the third capacitor, and the other end of the third capacitor is grounded; the output end of the resonator is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the input end of the mixer; the emitter of the high-frequency triode is connected in series with the third inductor, and the other end of the third inductor is grounded; the input end of the resonator is connected to the first inductor, the resistor and the positive electrode of the first DC power supply in sequence, and the negative electrode of the first DC power supply is grounded.

[0022] Furthermore, the thermostat includes: a heating wire and a temperature sensor, the temperature sensor reads the temperature of the heating wire and feeds back the read temperature to the temperature feedback module, and the temperature feedback module adjusts the current and voltage of the heating wire according to the temperature to keep the thermostat at a preset temperature.

[0023] Furthermore, the sensing system based on the surface acoustic wave oscillator further includes: a carrier plate with a hollow middle, wherein the carrier plate is provided with a first groove, a second groove, a first step and a second step;

[0024] The first groove and the second groove are coaxially arranged, and the fluid pipeline is accommodated in the first groove and the second groove; the first step is opened along the axial direction of the first groove, and the second step is opened along the axial direction of the second groove, and the depth of the first step and the second step is greater than the depth of the first groove and the second groove.

[0025] The advantages of the present invention are that two groups of resonators are respectively placed on the outer wall of the fluid pipeline, the fluid flows through the fluid pipeline, and the resonator does not directly contact the toxic or corrosive environment, which greatly enhances the service life of the resonator; the resonator adopts a thick aluminum structure and a GAN substrate, and a single resonance mode and a high Q value of the resonator are obtained by adjusting the edge spacing between the interdigital transducer and the short-circuit grid reflector, so that the SAW resonator works in a single mode state, which greatly improves the frequency stability of the oscillator; the PCB carrier is provided with corresponding grooves and steps, which not only play a role in fixing the fluid pipeline, but also reduce the influence of the PCB carrier on the thermal field source, thereby improving the fluid flow monitoring performance.

[0026] The resonator is divided into two groups, an upstream and downstream group, and the two groups of resonators use double-layer electrodes of aluminum / titanium alloy and have a single resonance mode and a high-Q resonator.

[0027] In addition, the sensing system design based on the surface acoustic wave oscillator of the present invention has a small structure, is light, uses few components, has a simple circuit, low power consumption, is stable, and is portable, and can easily achieve the purpose of fluid flow detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 A schematic diagram of the structure of a sensing system based on a surface acoustic wave oscillator according to an embodiment of the present invention;

[0030] Figure 2 It is a schematic structural diagram of a resonator according to an embodiment of the present invention;

[0031] Figure 3 It is a structural schematic diagram of an oscillation circuit 2 according to an embodiment of the present invention;

[0032] Figure 4 It is a structural schematic diagram of an oscillation circuit 2 according to an embodiment of the present invention;

[0033] Figure 5 This is a schematic structural diagram of a thermostat 3 according to an embodiment of the present invention;

[0034] Figure 6 It is a structural schematic diagram of a carrier board 7 according to an embodiment of the present invention;

[0035] Figure 7 It is a schematic diagram of the response of upstream and downstream frequency and temperature difference to changes in fluid flow rate according to an embodiment of the present invention;

[0036] Figure 8 It is a schematic diagram showing the response of the difference frequency signal output after upstream and downstream mixing as the fluid flow rate changes according to an embodiment of the present invention.

[0037] Reference numerals:

[0038] 1: Resonator;

[0039] 2: Oscillation circuit;

[0040] 3: Thermostats;

[0041] 4: Temperature heating module;

[0042] 5: Temperature feedback module;

[0043] 6: Fluid pipeline;

[0044] 7: Carrier board;

[0045] 8: Sealed cavity;

[0046] 9: mixer;

[0047] 10: Amplification function comparator;

[0048] 11: frequency divider;

[0049] 1-1: interdigital transducer;

[0050] 1-2: short-circuit grid reflector;

[0051] 1-3: short-circuit grid reflector;

[0052] 1-4: GaN on silicon substrate;

[0053] l1: edge spacing between short-circuit grid reflector 1-2 and interdigital transducer;

[0054] l2: edge spacing between short-circuit grid reflectors 1-3 and the interdigital transducers;

[0055] 2-1: Inductor;

[0056] 2-2: Inductor;

[0057] 2-3: Inductor;

[0058] 2-4: resistance;

[0059] 2-5: Capacitor;

[0060] 2-6: Capacitor;

[0061] 2-7: Capacitor;

[0062] 2-8: high frequency transistor;

[0063] 2-9: DC power supply;

[0064] 2-10: DC power supply;

[0065] 3-1: Heating wire;

[0066] 3-2: Temperature sensor;

[0067] 7: The carrier board with a hollow middle;

[0068] 7-1: Groove;

[0069] 7-2: Groove;

[0070] 7-3: stairs;

[0071] 7-4: stairs;

[0072] 7-5: Hollow part. DETAILED DESCRIPTION

[0073] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0074] The present invention relates to a sensing system based on a surface acoustic wave oscillator, such as Figure 1 As shown, the sensing system based on the surface acoustic wave oscillator includes: two resonators 1, two oscillation circuits 2, a temperature controller, a fluid pipeline 6, a mixer 9, an amplifying comparator 10 and a frequency divider 11.

[0075] The temperature controller, the resonator 1 and the oscillation circuit 2 are arranged on the fluid pipeline 6, wherein the two resonators 1 are respectively located on the upper and lower sides of the temperature controller, and the two oscillation circuits 2 are respectively located on the upper and lower sides of the resonator 1. On the fluid pipeline 6, the oscillation circuit 2, the resonator 1, the temperature controller, the resonator 1 and the oscillation circuit 2 are arranged from top to bottom.

[0076] By placing the resonator 1 on the fluid pipe 6, according to the temperature characteristics of the resonator 1 itself, when the fluid flows through the fluid pipe 6, the temperature values ​​on the upstream and downstream resonators 1 are different. In a unit time, as the flow rate of the fluid flowing through the fluid pipe 6 is different, the output frequency difference of the upstream and downstream oscillation circuits 2 is also different, so that the upstream and downstream oscillation circuits 2 have different oscillation frequencies.

[0077] The resonator 1 can be arranged on the fluid pipeline 6 by chip adhesive bonding, but the present invention is not limited thereto. The fluid pipeline 6 can be a fluid corrosion resistant pipeline.

[0078] The temperature controller may be an integrated device for realizing temperature control, and may include components such as a heating module, a heating device (such as a resistance wire), a temperature sensor, and a temperature feedback module, but the present invention is not limited thereto.

[0079] It should be noted that some components of the temperature controller may be fixed on the fluid pipeline 6, but the present invention is not limited thereto.

[0080] The temperature controller transfers heat to the resonators 1 on the upper and lower sides through the fluid pipe 6. The two resonators 1 adjust the resonant frequency according to the temperature change and output different frequencies to the adjacent oscillation circuits 2. The two oscillation circuits 2 are connected to the mixer 9 respectively. The mixer 9 outputs the difference frequency signal to the amplifying function comparator 10. The amplifying function comparator 10 outputs the square wave signal to the divider 11.

[0081] The mixer 9 can select a suitable mixer frequency band so that it can be directly connected to the amplification function comparator 10 without subsequent filtering processing.

[0082] In one embodiment, if Figure 1 As shown, the temperature controller includes: a thermostat 3, a temperature heating module 4 and a temperature feedback module 5. The thermostat 3, the temperature heating module 4 and the temperature feedback module 5 cooperate to finally stabilize the thermostat 3 at a preset temperature and maintain a constant temperature.

[0083] Specifically, the thermostat 3 is disposed on the fluid pipeline 6, and heat is transferred to the resonators 1 on the upper and lower sides respectively through the fluid pipeline 6;

[0084] The temperature heating module 4 is connected to the thermostat 3 to provide power output to the thermostat 3 .

[0085] The temperature feedback module 5 is connected to the thermostat 3 , and adjusts the thermostat according to the temperature of the thermostat 3 so that it is maintained at a preset temperature and maintains a constant temperature.

[0086] The temperature feedback module 5 can be implemented by a relay or the like, and the present invention will not elaborate on it here.

[0087] In order to ensure that the heat is not disturbed by the outside world, in one embodiment, a sealed cavity 8 may be provided outside the thermostat 3 .

[0088] In one embodiment, the resonator 1 is a SAW resonator, such as Figure 2 As shown, the resonator 1 includes: a short-circuit grating reflector 1-2, a short-circuit grating reflector 1-3 and an interdigital transducer 1-1 arranged between the short-circuit grating reflector 1-2 and the short-circuit grating reflector 1-3.

[0089] In one embodiment, the short-circuit grid reflector 1-2, the short-circuit grid reflector 1-3 and the interdigital transducer 1-1 all adopt a double-layer electrode structure of thick aluminum and thin titanium, but the present invention is not limited thereto.

[0090] In one embodiment, the thickness of aluminum is 0.05λ, the thickness of titanium is 5nm, and λ is the wavelength of the sound wave, but the present invention is not limited thereto.

[0091] The distances between the short-circuit grid reflector 1-2 and the short-circuit grid reflector 1-3 and the interdigital transducer 1-1 can be set according to specific working conditions. In one embodiment, the edge spacing l1 between the short-circuit grid reflector 1-2 and the interdigital transducer 1-1 is 1 / 4λ, and the edge spacing l2 between the short-circuit grid reflector 1-3 and the interdigital transducer 1-1 is 1 / 4λ.

[0092] In one embodiment, the IDT 1-1 may adopt a bidirectional transducer structure with a 1 / 4λ electrode width. The number of interdigital pairs in the short-circuit grating reflector 1-2 and the short-circuit grating reflector 1-3 may be set to 20 pairs respectively, and the number of interdigital pairs in the IDT 1-1 is 250 pairs. Figure 2 As shown, the resonator 1 can be manufactured on a silicon-based GaN substrate 1-4, and a single resonance mode and a high Q value can be obtained by adjusting the edge spacing l1 and the edge spacing l2, so that the operating frequency of the resonator 1 is more stable.

[0093] In one embodiment, if Figure 3 As shown, the oscillation circuit 2 includes: a DC power supply 2-9, a DC power supply 2-10, a high-frequency transistor 2-8 and a capacitor 2-5.

[0094] Among them, the resonator 1 is connected in parallel between the base and collector of the high-frequency transistor 2-8, the output end of the resonator 1 is connected to the collector of the high-frequency transistor, and the input end of the resonator 1 is connected to the base of the high-frequency transistor; one end of the capacitor 2-5 is connected to the output end of the resonator 1, and the other end is connected to the input end of the mixer (the direction of the arrow RFout in the figure); the positive pole of the DC power supply 2-9 is connected to the base of the high-frequency transistor 2-8, the positive pole of the DC power supply 2-10 is connected to the collector of the high-frequency transistor, and the negative pole of the DC power supply 2-9, the negative pole of the DC power supply 2-10 and the emitter of the high-frequency transistor 2-8 are grounded.

[0095] In one embodiment, the high-frequency transistor 2 - 8 may be a high-frequency transistor KT9041.

[0096] Figure 3 In the oscillation circuit 2 shown, the operating frequency of the oscillation circuit is changed by adjusting the voltages of the DC power supply 2-9 and the DC power supply 2-10, so that the operating frequency of the SAW resonator is adjustable within a certain range.

[0097] In one embodiment, if Figure 4As shown, the oscillation circuit 2 includes: an inductor 2-1, an inductor 2-2, an inductor 2-3, a resistor 2-4, a capacitor 2-5, a capacitor 2-6, a capacitor 2-7, a high-frequency transistor 2-8, a DC power supply 2-9 and a DC power supply 2-10.

[0098] Among them, the resonator 1 is connected in parallel between the base and collector of the high-frequency transistor 2-8, the output end of the resonator 1 is connected to the collector of the high-frequency transistor, and the input end of the resonator 1 is connected to the base of the high-frequency transistor; the capacitor 2-6 is connected in parallel between the base and emitter of the high-frequency transistor 2-8; the output end of the resonator 1 is connected to the inductor 2-2 and the positive electrode of the DC power supply 2-10 in sequence, and the negative electrode of the DC power supply 2-10 is grounded; the output end of the resonator 1 is connected to one end of the capacitor 2-7, and the other end of the capacitor 2-7 is grounded; the output end of the resonator 1 is connected to one end of the capacitor 2-5, and the other end of the capacitor 2-5 is connected to the input end of the mixer (the arrow direction RFout in the figure); the emitter of the high-frequency transistor 2-8 is connected in series with the inductor 2-3, and the other end of the inductor 2-3 is grounded; the input end of the resonator 1 and the base of the high-frequency transistor 2-8 are connected to the inductor 2-1, the resistor 2-4 and the positive electrode of the DC power supply 2-9 in sequence, and the negative electrode of the DC power supply 2-9 is grounded.

[0099] Figure 4 In the oscillation circuit 2 shown, capacitors 2-6 and 2-7 are parasitic capacitors. The operating frequency of the oscillation circuit can be adjusted by adjusting the distance between them and the ground line. In addition, the operating frequency of the oscillation circuit can also be changed by adjusting the voltage of DC power supply 2-9 and DC power supply 2-10, so that the operating frequency of the SAW resonator can be adjusted within a certain range.

[0100] In one embodiment, if Figure 5 As shown, the thermostat 3 includes: a heating wire 3-1 and a temperature sensor 3-2. The temperature sensor 3-2 is connected to the heating wire 3-1, reads the temperature of the heating wire, and feeds the read temperature back to the temperature feedback module 5. The temperature feedback module 5 adjusts the current and voltage of the heating wire according to the temperature to keep the thermostat 3 at a preset temperature. Figure 5 As shown, in this embodiment, the temperature sensor 3-2 is wrapped around the periphery of the heating wire 3-1, and can better detect the temperature of the heating wire 3-1, but the present invention is not limited to this.

[0101] In one embodiment, Figure 5The working process of the thermostat 3 shown is as follows: the temperature heating module 4 (heating device) outputs stable power to the heating wire 3-1, the temperature sensor 3-2 reads the temperature value of the heating wire 3-1 and feeds it back to the temperature feedback module 5, and the temperature of the thermostat 3 is finally stabilized at the set value through continuous alternation between the heating device and the temperature feedback module 5, and the temperature error is required to be around ±0.1°C. After the temperature of the thermostat 3 is stabilized, the heat is transferred to the SAW resonator 1 through the heating fluid pipeline 6.

[0102] In one embodiment, the size of the thermostat 3 can be 2×2 mm, the resistance of the heating wire 3 - 1 is 80-130Ω, and the temperature sensor 3 - 2 has a temperature resistance of more than 300°C.

[0103] In one embodiment, the fluid conduit 6 has an outer diameter of 0.5 mm, an inner diameter of 0.2 mm, and a length greater than 50 mm. The center distance between the SAW resonator 1 and the thermostat 3 is 7.5 mm.

[0104] In one embodiment, the heating wire 3 - 1 is a nickel-chromium heating wire, and the temperature sensor 3 - 2 is a PT100 temperature sensor.

[0105] In one embodiment, if Figure 1 As shown, the sensing system based on the surface acoustic wave oscillator of the present invention further includes: a carrier plate 7 with a hollow middle. Figure 6 As shown, the carrier plate is provided with a groove 7-1, a groove 7-2, a step 7-3, a step 7-4 and a hollow portion 7-5.

[0106] Groove 7-1 and groove 7-2 are coaxially arranged so that the fluid pipe 6 can be accommodated in groove 7-1 and groove 7-2 at the same time; step 7-3 is opened along the axial direction of groove 7-1, and step 7-4 is opened along the axial direction of groove 7-2. The depth of steps 7-3 and 7-4 is greater than the depth of groove 7-1 and groove 7-2.

[0107] In one embodiment, the depth and width of the grooves 7-1 and 7-2 are greater than the outer diameter of the fluid pipe 6. The widths of the steps 7-3 and 7-4 are greater than the widths of the grooves 7-1 and 7-2.

[0108] In one embodiment, the length of the groove is about 3 mm. The thickness of the plate at the step 7-3 and the step 7-4 is about 0.6 mm, the step length is greater than 9 mm, and the step width is about 4 mm.

[0109] By providing the steps 7 - 3 and 7 - 4 , the thermal influence of the carrier plate on the heating source can be avoided, so as to increase the temperature difference between the upstream and downstream of the fluid pipeline 6 .

[0110] In one embodiment, the middle hollow portion 7-5 is longer than 20 mm and has a width of about 17 mm.

[0111] In one embodiment, the carrier board 7 may be a PCB carrier board. The structural design of the carrier board 7 can not only fix the fluid pipeline 6, the oscillation circuit 2, the temperature heating module 4 and the temperature feedback module 5, but also prevent them from becoming a heat load.

[0112] Figure 7 Schematic diagram of the response of the upstream and downstream frequency and temperature difference to the change of fluid flow rate in an embodiment of the present invention. Figure 7 It can be observed that the upstream and downstream frequencies and temperature differences vary with the fluid flow rate. When different fluid flow rates flow through the fluid pipeline 6, the upstream and downstream frequencies are different, and the upstream and downstream differences are different. According to the temperature characteristics of the SAW resonator, the upstream and downstream temperature differences are obtained.

[0113] Figure 8 Schematic diagram of the response of the difference frequency signal output after upstream and downstream mixing according to the change of fluid flow rate in an embodiment of the present invention. Figure 8 It can be observed that the intermediate frequency signal output after the upstream and downstream mixing changes with the fluid flow rate. In order to avoid using filters in the future, it is necessary to adjust the bias voltage of the upstream and downstream oscillator circuits so that the starting point of the intermediate frequency is 1Mhz-5Mhz. When different fluid flows flow through the fluid pipeline 6, the intermediate frequency after mixing will also change accordingly.

[0114] The advantages of the present invention are that two groups of resonators are respectively placed on the outer wall of the fluid pipeline, and the fluid flows through the fluid pipeline. The resonators do not directly contact the toxic or corrosive environment, which greatly enhances the service life of the oscillator; the resonator adopts a thick aluminum structure and a GAN substrate to obtain a single resonance mode and a high Q value of the resonator by adjusting the edge spacing between the interdigital transducer and the short-circuit grid reflector, so that the SAW resonator works in a single mode state, which greatly improves the frequency stability of the oscillator; the PCB carrier is provided with corresponding grooves and steps, which not only play a role in fixing the fluid pipeline, but also reduce the influence of the PCB carrier on the thermal field source, thereby improving the fluid flow monitoring performance.

[0115] The resonator is divided into two groups, an upstream and downstream group, and the two groups use double-layer electrodes of aluminum / titanium alloy, and have a single resonance mode and a high-Q resonator.

[0116] In addition, the sensing system based on the surface acoustic wave oscillator of the present invention is small in structure, light in weight, uses few components, has a simple circuit, low power consumption, is stable, and is portable, and can easily achieve the purpose of fluid flow detection.

[0117] In the present specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradicting each other. The above is only an embodiment of the embodiment of the present specification and is not intended to limit the embodiment of the present specification. For those skilled in the art, the embodiment of the present specification may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiment of the present specification shall be included in the scope of the claims of the embodiment of the present specification.

Claims

1. A sensing system based on a surface acoustic wave oscillator, characterized in that: include: Two resonators, two oscillation circuits, a temperature controller, a fluid pipeline, a mixer, an amplifying comparator and a frequency divider; The temperature controller, the resonator and the oscillation circuit are arranged on the fluid pipeline, the two resonators are respectively located on the upper and lower sides of the temperature controller, and the two oscillation circuits are respectively located on the upper and lower sides of the two resonators; The temperature controller transfers heat to the resonators on the upper and lower sides through the fluid pipeline. The resonators adjust the resonant frequency according to the temperature change and output different frequencies to adjacent oscillation circuits. The two oscillation circuits are connected to the mixers respectively. The mixers output difference frequency signals to the amplifying function comparator. The amplifying function comparator outputs square wave signals to the divider.

2. The sensing system based on surface acoustic wave oscillator according to claim 1, characterized in that: The temperature controller comprises: A thermostat, disposed on the fluid pipeline, transfers heat to the resonators on the upper and lower sides respectively through the fluid pipeline; A temperature heating module, connected to the thermostat, and used to provide power output to the thermostat; The temperature feedback module is connected to the thermostat and adjusts the thermostat according to the temperature of the thermostat so that the thermostat is maintained at a preset temperature.

3. The sensing system based on surface acoustic wave oscillator according to claim 2, characterized in that: Also includes: A sealed cavity, wherein the temperature stabilizer and the resonator are arranged in the sealed cavity.

4. The sensing system based on surface acoustic wave oscillator according to claim 1, characterized in that: The resonator includes: a first short-circuit grating reflector, a second short-circuit grating reflector, and an interdigital transducer arranged between the first short-circuit grating reflector and the second short-circuit grating reflector.

5. The sensing system based on surface acoustic wave oscillator according to claim 4, characterized in that: The distance between the first short-circuit grating reflector and the second short-circuit grating reflector and the interdigital transducer is 1 / 4λ, where λ is the wavelength of the sound wave.

6. The sensing system based on surface acoustic wave oscillator according to claim 1, characterized in that: The oscillation circuit comprises: a first DC power supply, a second DC power supply, a high-frequency triode and a first capacitor; The resonator is connected in parallel between the base and collector of the high-frequency transistor, one end of the first capacitor is connected to the output end of the resonator, and the other end of the first capacitor is connected to the input end of the mixer; the positive electrode of the first DC power supply is connected to the base of the high-frequency transistor, the positive electrode of the second DC power supply is connected to the collector of the high-frequency transistor, and the negative electrode of the first DC power supply and the negative electrode of the second DC power supply are grounded.

7. The sensing system based on surface acoustic wave oscillator according to claim 1, characterized in that: The oscillation circuit comprises: a first inductor, a second inductor, a third inductor, a resistor, a first capacitor, a second capacitor, a third capacitor, a first DC power supply, a second DC power supply and a high-frequency triode; The resonator is connected in parallel between the base and collector of the high-frequency triode; the second capacitor is connected in parallel between the base and emitter of the high-frequency triode; the output end of the resonator is connected to the second inductor and the positive electrode of the second DC power supply in sequence, and the negative electrode of the second DC power supply is grounded; the output end of the resonator is connected to one end of the third capacitor, and the other end of the third capacitor is grounded; the output end of the resonator is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the input end of the mixer; the emitter of the high-frequency triode is connected in series with the third inductor, and the other end of the third inductor is grounded; the input end of the resonator is connected to the first inductor, the resistor and the positive electrode of the first DC power supply in sequence, and the negative electrode of the first DC power supply is grounded.

8. The sensing system based on surface acoustic wave oscillator according to claim 2, characterized in that: The thermostat includes: a heating wire and a temperature sensor. The temperature sensor reads the temperature of the heating wire and feeds back the read temperature to the temperature feedback module. The temperature feedback module adjusts the current and voltage of the heating wire according to the temperature to keep the thermostat at a preset temperature.

9. The sensing system based on surface acoustic wave oscillator according to claim 1, characterized in that: Also includes: A carrier plate with a hollow center, wherein a first groove, a second groove, a first step and a second step are provided on the carrier plate; The first groove and the second groove are coaxially arranged, and the fluid pipeline is accommodated in the first groove and the second groove; The first step is opened along the axial direction of the first groove, the second step is opened along the axial direction of the second groove, and the depths of the first step and the second step are greater than the depths of the first groove and the second groove.

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