CN111189910A - Delay line type based surface acoustic wave sensing circuit system design method - Google Patents

Delay line type based surface acoustic wave sensing circuit system design method Download PDF

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CN111189910A
CN111189910A CN202010027282.XA CN202010027282A CN111189910A CN 111189910 A CN111189910 A CN 111189910A CN 202010027282 A CN202010027282 A CN 202010027282A CN 111189910 A CN111189910 A CN 111189910A
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resistor
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CN111189910B (en
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张涛
朱寒
苏晓敏
姜峰
师晓云
曹晓闯
柯贤桐
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Xian University of Science and Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/02—Analysing fluids
    • G01N29/022—Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
    • H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
    • H03H3/08—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of resonators or networks using surface acoustic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/021—Gases
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    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/028—Material parameters
    • G01N2291/02809—Concentration of a compound, e.g. measured by a surface mass change
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/04—Wave modes and trajectories
    • G01N2291/042—Wave modes
    • G01N2291/0423—Surface waves, e.g. Rayleigh waves, Love waves

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Abstract

The invention discloses a delay line type surface acoustic wave sensing circuit system design method, which comprises the following steps: firstly, manufacturing a delay line type surface acoustic wave device which does not comprise a sensitive film; secondly, manufacturing a delay line type SAW gas sensor containing a sensitive film; thirdly, selecting proper parameters for forming the reference oscillation generating circuit; selecting proper parameters for forming the oscillation generating circuit; fifthly, selecting proper parameters forming the oscillation signal mixing processing circuit; selecting proper parameters for forming the low-frequency signal conditioning circuit; and seventhly, connecting the reference oscillation generating circuit, the oscillation signal mixing processing circuit and the low-frequency signal conditioning circuit. The invention has reasonable design, and the designed delay line type-based surface acoustic wave sensing circuit system has low power consumption and generates high-stability sensing signals.

Description

Delay line type based surface acoustic wave sensing circuit system design method
Technical Field
The invention belongs to the technical field of sensor information acquisition, and particularly relates to a delay line type surface acoustic wave sensing circuit system design method.
Background
In recent years, the emerging information industries such as artificial intelligence and the internet of things are rapidly developed, and particularly, the technology is brought forward by leading-edge core technologies such as 5G high-frequency-band mobile communication, internet +, big data calculation and internet of things perception. The development of a plurality of emerging information industries cannot be supported by the sensor information acquisition technology. Surface acoustic wave sensing, i.e., the SAW sensor, has the advantages of high sensitivity, easy integration, no wireless and the like, accords with the future development trend of the sensor, and is more and more emphasized and favored by engineers in the field of sensors.
The sensing system based on the SAW technology at present puts forward more severe requirements on a matching circuit of the sensing system along with the improvement of the sensitivity of the SAW sensor, however, the problems of low system stability, high power consumption and the like commonly existing in the sensing system based on the SAW technology at present easily cause the faults of false alarm, failure and the like of the sensing system, and cause great loss to national economy and national property. Therefore, a design method based on a delay line type surface acoustic wave sensing circuit system is absent at present, the design is reasonable, the designed delay line type surface acoustic wave sensing circuit system based on the delay line type surface acoustic wave sensing circuit system is low in power consumption, and high-stability sensing signals are generated.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a method for designing a delay line type based surface acoustic wave sensing circuit system, which is simple in steps and reasonable in design, and the designed delay line type based surface acoustic wave sensing circuit system has low power consumption and generates a high-stability sensing signal.
In order to solve the technical problems, the invention adopts the technical scheme that: a design method based on delay line type surface acoustic wave sensing circuit system is characterized by comprising the following steps:
step one, manufacturing a delay line type surface acoustic wave device which does not comprise a sensitive film:
step 101, selecting a piezoelectric film layer, and arranging an input interdigital transducer and an output interdigital transducer on the piezoelectric film layer, wherein the input interdigital transducer and the output interdigital transducer have the same structure, the input interdigital transducer and the output interdigital transducer are symmetrically arranged around the center of the piezoelectric film layer, and sound absorption glue is coated at two ends of the piezoelectric film layer;
102, packaging the delay line type surface acoustic wave device obtained in the step 101 by adopting lead bonding equipment to obtain a delay line type surface acoustic wave device which does not contain a sensitive film; the 1 st pin of the delay line type surface acoustic wave device which does not contain the sensitive film is a pin of the input interdigital transducer, the 2 nd pin of the delay line type surface acoustic wave device which does not contain the sensitive film is a grounding pin of the input interdigital transducer, the 4 th pin of the delay line type surface acoustic wave device which does not contain the sensitive film is an output pin of the output interdigital transducer, and the 3 rd pin of the delay line type surface acoustic wave device which does not contain the sensitive film is a grounding pin of the output interdigital transducer;
step two, manufacturing a delay line type SAW gas sensor containing a sensitive film:
step 201, according to the method in step 101, a sensitive film layer is arranged between an input interdigital transducer and an output interdigital transducer, and the bottom surface of the sensitive film layer is attached to the surface of a piezoelectric film layer;
step 202, packaging the delay line type surface acoustic wave device obtained in the step 201 by adopting lead bonding equipment to obtain a delay line type surface acoustic wave device containing a sensitive film; the first pin 1 of the delay line type surface acoustic wave device containing the sensitive film is a pin of the input interdigital transducer, the second pin 2 of the delay line type surface acoustic wave device containing the sensitive film is a grounding pin of the input interdigital transducer, the fourth pin 4 of the delay line type surface acoustic wave device containing the sensitive film is an output pin of the output interdigital transducer, and the third pin 3 of the delay line type surface acoustic wave device containing the sensitive film is a grounding pin of the output interdigital transducer;
selecting proper parameters for forming the reference oscillation generating circuit:
step 301, selecting the integrated operational amplifier INA1-1, the integrated operational amplifier INA2-1 and the integrated operational amplifier INA3-1 to be operational amplifiers INA-02186;
step 302, selecting a low-pass filter LFCN-1-1 and a low-pass filter LFCN-2-1 as low-pass filters LFCN-255;
step 303, selecting the resistance values of a resistor R1-1, a resistor R2-1, a resistor R3-1, a resistor R4-1, a resistor R5-1 and a resistor R6-1 to be 100 omega-110 omega, selecting the resistance value of a resistor R7-1 to be 270 omega-300 omega, selecting the resistance value of a resistor R8-1 to be 430 omega, and selecting the resistance values of a resistor R9-1 and a resistor R10-1 to be 62 omega;
step 304, selecting capacitors C1-1, C2-1 and C3-1 to have capacitance values of 1 muF-3 muF, selecting capacitors C4-1, C5-1 and C6-1 to have capacitance values of 300 pF-330 pF, selecting capacitors C7-1, C8-1, C9-1, C10-1, C11-1 and C12-1 to have capacitance values of 300 pF-330 pF;
305, selecting the inductance values of the inductor L1-1, the inductor L2-1 and the inductor L3-1 to be 120 nH-124 nH, and selecting the inductance values of the inductor L4-1, the inductor L5-1 and the inductor L6-1 to be 8.2 nH;
step 306, connecting the 1 st pin of the delay line type surface acoustic wave device not including the sensitive film in the step 102 with one end of an inductor L4-1, connecting the other end of the inductor L4-1 with one end of a capacitor C7-1, connecting the other end of the capacitor C7-1 to an input pin of an integrated amplifier INA1-1, connecting the 2 nd pin and the 4 th pin of the integrated amplifier INA1-1 to ground, connecting the 3 rd pin of the integrated amplifier INA1-1 with one end of the inductor L1-1 and one end of the capacitor C8-1, connecting the other end of the inductor L1-1 with one end of the capacitor C4-1, one end of a resistor R1-1 and one end of a resistor R2-1, connecting the other end of the resistor R1-1, the other end of the resistor R2-1 and one end of the capacitor C1-1 to a +9V dc power supply, the other end of the capacitor C4-1 and the other end of the capacitor C1-1 are both grounded; the other end of the capacitor C8-1 is connected with the 1 st pin of the low-pass filter LFCN-1-1, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-1-1 are grounded, the 3 rd pin of the low-pass filter LFCN-1-1 is connected with one end of the capacitor C9-1, one end of the capacitor C9-1 is connected with the 1 st pin of the integrated amplifier INA2-1, the 2 nd pin and the 4 th pin of the integrated amplifier INA2-1 are grounded, the 3 rd pin of the integrated amplifier INA2-1 is connected with one end of an inductor L2-1 and one end of a capacitor C10-1, the other end of the inductor L2-1 is connected with one end of a capacitor C5-1, one end of a resistor R3-1 and one end of a resistor R4-1, the other end of the resistor R3-1 is connected with the other end of the low-, The other end of the resistor R4-1 and one end of the capacitor C2-1 are both connected with a +9V direct-current power supply, and the other end of the capacitor C5-1 and the other end of the capacitor C2-1 are both grounded; the other end of the capacitor C10-1 is connected with one end of a resistor R7-1 and one end of an inductor L6-1, one end of the inductor L6-1 is connected with one end of an inductor L5-1, the other end of the inductor L5-1 is connected with the 4 th pin of a delay line type surface acoustic wave device which does not contain a sensitive film, the other end of the resistor R7-1 is connected with one end of a resistor R8-1 and one end of a resistor R9-1, the other end of the resistor R8-1 is connected with one end of a resistor R10-1 and one end of a capacitor C11-1, the other end of the resistor R9-1 and the other end of the resistor R10-1 are both grounded, the other end of the capacitor C11-1 is connected with the 1 st pin of an integrated amplifier INA3-1, the 2 nd pin and the 4 th pin of the integrated amplifier INA3-1 are both grounded, the 3 rd pin of the integrated amplifier INA3-1 is connected to one end of a capacitor C12-1 and one end of an inductor L3-1, the other end of the capacitor C12-1 is connected to pin 1 of the low pass filter LFCN-2-1, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-2-1 are grounded, the 3 rd pin of the low-pass filter LFCN-2-1 is the output end of the reference oscillation generating circuit, the other end of one end of the inductor L3-1 is connected with one end of the capacitor C6-1, one end of the resistor R5-1 and one end of the resistor R6-1, the other end of the resistor R5-1, the other end of the resistor R6-1 and one end of the capacitor C3-1 are all connected with a +9V direct-current power supply, the other end of the capacitor C3-1 and the other end of the capacitor C6-1 are both grounded;
step four, selecting proper parameters for forming the oscillation generating circuit:
step 401, selecting the integrated operational amplifier INA1-2, the integrated operational amplifier INA2-2 and the integrated operational amplifier INA3-2 to be operational amplifiers INA-02186;
step 402, selecting both the low-pass filter LFCN-1-2 and the low-pass filter LFCN-2-2 as the low-pass filter LFCN-255;
step 403, selecting the resistance values of the resistor R1-2, the resistor R2-2, the resistor R3-2, the resistor R4-2, the resistor R5-2 and the resistor R6-2 to be 100 omega-110 omega, selecting the resistance value of the resistor R7-2 to be 270 omega-300 omega, selecting the resistance value of the resistor R8-2 to be 430 omega, and selecting the resistance values of the resistor R9-2 and the resistor R10-2 to be 62 omega;
step 404, capacitance values of a selected capacitor C1-2, a selected capacitor C2-2 and a selected capacitor C3-2 are all 1 muF-3 muF, capacitance values of the selected capacitor C4-2, the selected capacitor C5-2 and the selected capacitor C6-2 are all 300 pF-330 pF, and capacitance values of the selected capacitor C7-2, the selected capacitor C8-2, the selected capacitor C9-2, the selected capacitor C10-2, the selected capacitor C11-2 and the selected capacitor C12-2 are all 300 pF-330 pF;
step 405, selecting the inductance values of the inductor L1-2, the inductor L2-2 and the inductor L3-2 to be 120 nH-124 nH, and selecting the inductance values of the inductor L4-2, the inductor L5-2 and the inductor L6-2 to be 8.2 nH;
step 406, connecting the 1 st pin of the delay line type surface acoustic wave device containing the sensitive film in the step 202 with one end of an inductor L4-2, connecting the other end of the inductor L4-2 with one end of a capacitor C7-2, connecting the other end of the capacitor C7-2 to an input pin of an integrated amplifier INA1-2, connecting the 2 nd pin and the 4 th pin of the integrated amplifier INA1-2 to ground, connecting the 3 rd pin of the integrated amplifier INA1-2 with one end of the inductor L1-2 and one end of the capacitor C8-2, connecting the other end of the inductor L1-2 with one end of the capacitor C4-2, one end of a resistor R1-2 and one end of a resistor R2-2, connecting the other end of the resistor R1-2, the other end of the resistor R2-2 and one end of the capacitor C1-2 to a +9V direct current power supply, the other end of the capacitor C4-2 and the other end of the capacitor C1-2 are both grounded; the other end of the capacitor C8-2 is connected with the 1 st pin of the low-pass filter LFCN-1-2, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-1-2 are grounded, the 3 rd pin of the low-pass filter LFCN-1-2 is connected with one end of the capacitor C9-2, one end of the capacitor C9-2 is connected with the 1 st pin of the integrated amplifier INA2-2, the 2 nd pin and the 4 th pin of the integrated amplifier INA2-2 are grounded, the 3 rd pin of the integrated amplifier INA2-2 is connected with one end of an inductor L2-2 and one end of a capacitor C10-2, the other end of the inductor L2-2 is connected with one end of a capacitor C5-2, one end of a resistor R3-2 and one end of a resistor R4-2, the other end of the resistor R3-2, the other end of the low-pass filter, The other end of the resistor R4-2 and one end of the capacitor C2-2 are both connected with a +9V direct-current power supply, and the other end of the capacitor C5-2 and the other end of the capacitor C2-2 are both grounded; the other end of the capacitor C10-2 is connected with one end of a resistor R7-2 and one end of an inductor L6-2, one end of the inductor L6-2 is connected with one end of an inductor L5-2, the other end of the inductor L5-2 is connected with a pin 4 of a delay line type surface acoustic wave device comprising a sensitive film, the other end of the resistor R7-2 is connected with one end of a resistor R8-2 and one end of a resistor R9-2, the other end of the resistor R8-2 is connected with one end of a resistor R10-2 and one end of a capacitor C11-2, the other end of the resistor R9-2 and the other end of the resistor R10-2 are both grounded, the other end of the capacitor C11-2 is connected with a pin 1 of an integrated amplifier INA3-2, a pin 2 of the integrated amplifier INA3-2 is both grounded with a pin 4, the 3 rd pin of the integrated amplifier INA3-2 is connected to one end of a capacitor C12-2 and one end of an inductor L3-2, the other end of the capacitor C12-2 is connected to pin 1 of the low pass filter LFCN-2-2, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-2-2 are grounded, the 3 rd pin of the low-pass filter LFCN-2-2 is the output end of the oscillation generating circuit, the other end of one end of the inductor L3-2 is connected with one end of the capacitor C6-2, one end of the resistor R5-2 and one end of the resistor R6-2, the other end of the resistor R5-2, the other end of the resistor R6-2 and one end of the capacitor C3-2 are all connected with a +9V direct-current power supply, the other end of the capacitor C3-2 and the other end of the capacitor C6-2 are both grounded;
step five, selecting proper parameters forming the oscillation signal mixing processing circuit:
step 501, selecting an integrated mixer as a mixer AD 831;
step 502, selecting the capacitance value of the capacitor C25 to be 1 muF, and selecting the capacitance values of the capacitor C34, the capacitor C37, the capacitor C38, the capacitor C39, the capacitor C40, the capacitor C41, the capacitor C44, the capacitor C45, the capacitor C46, the capacitor C47, the capacitor C48 and the capacitor C49 to be 0.1 muF-1 muF;
step 503, according to
Figure BDA0002362926380000061
Obtaining capacitance values of the capacitor C35 and the capacitor C36; wherein f is3dBIs represented by 3dB bandwidth, and f3dB＝1MHz，RERepresents the internal impedance of the mixer AD831, and RE＝14Ω；
Step 504, selecting the inductance value of the inductor L17 as 10 mH;
step 505, selecting the resistance values of the resistor R26 and the resistor R27 to be 5k Ω -5.7 k Ω, the resistance values of the resistor R33 and the resistor R16 to be 51.1 Ω, the resistance value of the resistor R32 to be 1.33k Ω, the resistance value of the resistor R30 to be 51.1 Ω,
step 506, according to
Figure BDA0002362926380000062
Obtaining the resistance value of the resistor R28 and the resistance value of the resistor R29;
step 507, connecting the 1 st pin of the mixer AD831 with one end of a +5V dc power supply and a capacitor C34, connecting the connection of the 2 nd pin and the 3 rd pin of the mixer AD831 with one end of a capacitor C35, connecting the other end of a capacitor C35 with a +5V dc power supply, connecting the 4 th pin of the mixer AD831 with ground, connecting the 5 th pin of the mixer AD831 with one end of a capacitor C38 and the +5V dc power supply, connecting the 6 th pin of the mixer AD831 with one end of a capacitor C40, connecting the other end of a capacitor C40 with one end of a capacitor C39 and one end of an inductor L17, connecting the other end of a capacitor C39 with one end of a resistor R16, connecting the other end of a capacitor C39 and one end of a resistor R16 as one input end of the oscillation signal mixing processing circuit, connecting the 7 th pin of the mixer AD831 with one end of a capacitor C41, connecting the 8 th pin of the mixer AD831 with a-5V dc power supply and one end of a capacitor C45, connecting the first pin of the mixer AD 49 and one end of a capacitor C9, the 10 th pin of the mixer AD831 is connected with one end of a capacitor C46, the 11 th pin of the mixer AD831 is connected with one end of a resistor R33, the connecting end of the other end of a capacitor C46 and the other end of a resistor R33 is used as the other input end of the oscillation signal mixing processing circuit, the 12 th pin of the mixer AD831 is connected with a +5V direct current power supply and one end of a capacitor C48, the 13 th pin of the mixer AD831 is grounded, the 14 th pin of the mixer AD831 is connected with one end of a resistor R32, the other end of a resistor R32 is connected with one end of a +5V direct current power supply and a capacitor C47, the 15 th pin of the mixer AD831 is connected with one end of a-5V direct current power supply and a capacitor C44, the 16 th pin of the mixer AD831 is connected with one end of a resistor R30 and one end of a resistor R29, the other end of a resistor R30 is connected with one end of a capacitor C25, the other end of a capacitor C25 is used as the output end of the oscillation signal processing circuit, and the other end of the mixer AD831, a pin 18 of the mixer AD831 is connected with the other end of the resistor R28, one end of the resistor R27, one end of the resistor R26 and one end of the capacitor C27, the connection end of a pin 19 and a pin 20 of the mixer AD831 is connected with one end of the capacitor C36, the other end of the capacitor C36 is connected with a +5V direct-current power supply, the other end of the capacitor C38, the other end of the inductor L17, the other end of the resistor R16, the other end of the capacitor C41, the other end of the capacitor C45, the other end of the capacitor C49, the other end of the capacitor C48, the other end of the capacitor C47, the other end of the capacitor C44, the other end of the resistor R27, the other end of the capacitor C37 and the other end;
step six, selecting proper parameters for forming the low-frequency signal conditioning circuit:
601, selecting the resistance values of the resistor R4 and the resistor R10 to be 1k omega-1.2 k omega, the resistance value of the resistor R9 to be 200 omega-220 omega, and the resistance value of the resistor R12 to be 50 omega-51 omega;
step 602, according to
Figure BDA0002362926380000071
And
Figure BDA0002362926380000072
obtaining resistance values of a resistor R13 and a resistor R15; wherein, VrRepresenting the input voltage, V, of the attenuator circuitoutRepresents the output voltage of the attenuator circuit, and N represents the input-to-output voltage ratio of the attenuator circuit;
step 603, according to the formula
Figure BDA0002362926380000081
Obtaining the resistance value of the resistor R14;
step 604, selecting the resistance value of the resistor R5 to be 10 omega-20 omega, the resistance value of the resistor R6 to be 175 omega-200 omega, and the resistance values of the resistor R7 and the resistor R8 to be 402 omega-417 omega;
step 605, selecting the capacitance value of the capacitor C1 as 100pF, the capacitance values of the capacitor C2, the capacitor C3 and the capacitor C6 as 0.1 muF-1 muF, and the capacitance values of the capacitor C4 and the capacitor C5 as 6.8 muF-7.3 muF;
step 606, connecting one end of a resistor R12 with one end of a resistor R14 and one end of a resistor R13, connecting the other end of the resistor R14 with one end of a resistor R15, connecting the other end of a resistor R13 with the other end of a resistor R15, wherein the other end of the resistor R12 is an input end of an attenuator circuit, and the connecting end of the other end of the resistor R14 with one end of a resistor R15 is an output end of the attenuator circuit;
step 607, selecting the operational amplifier OPA354aid bv as the voltage follower U1;
step 608, select op amp OPA690ID as op amp U2;
step 609, selecting the NPN type transistor as an NPN type transistor 2N3904, and selecting the Schmitt trigger as a 74LS14D Schmitt trigger;
step 6010, connecting the output terminal of the attenuator circuit with the positive input terminal of the voltage follower U1, connecting the output terminal of the voltage follower U1 with the negative input terminal of the voltage follower U1, connecting the output terminal of the voltage follower U1 with one terminal of the resistor R5, connecting the other terminal of the resistor R5 with one terminal of the capacitor C1, one terminal of the resistor R4 and one terminal of the resistor R6, connecting the other terminal of the resistor R6 with the positive input terminal of the operational amplifier U2, connecting the negative input terminal of the operational amplifier U2 with one terminal of the resistor R7 and one terminal of the resistor R8, connecting the output terminal of the operational amplifier U2 with one terminal of the capacitor C3, the other terminal of the resistor R8 and one terminal of the resistor R9, connecting the other terminal of the resistor R9 with the base of the NPN transistor 2N3904, connecting the emitter of the NPN transistor 2N3904 to ground, connecting the collector of the NPN transistor 2N3904 with one terminal of the resistor R10 and the input terminal of the LS14D, the other end of the resistor R10, the connection end of the positive power supply end of the voltage follower U1 and the positive power supply end of the operational amplifier U2 are connected with a +5V direct-current power supply, one end of the capacitor C2 and one end of the capacitor C4, the other end of the capacitor C3, the connection end of the negative power supply end of the voltage follower U1 and the negative power supply end of the operational amplifier U2 are connected with a-5V direct-current power supply, one end of the capacitor C5 and one end of the capacitor C6, the other end of the capacitor C2, the other end of the capacitor C4, the other end of the capacitor C5 and the other end of the capacitor C6 are grounded, and the output end of the 74LS14D Schmidt trigger
Step seven, connecting the reference oscillation generating circuit, the oscillation signal mixing processing circuit and the low-frequency signal conditioning circuit:
and connecting the output end of the reference oscillation generating circuit in the step 306 with one input end of the oscillation signal mixing processing circuit, connecting the output end of the oscillation generating circuit in the step 406 with the other input end of the oscillation signal mixing processing circuit, and connecting the output end of the oscillation signal mixing processing circuit with the input end of the attenuator circuit to complete the design of the delay line type based surface acoustic wave sensing circuit system.
The design method of the delay line type based surface acoustic wave sensing circuit system is characterized in that: the input interdigital transducer and the output interdigital transducer are made of Al, Pt, Au or Mo, the thicknesses of the input interdigital transducer and the output interdigital transducer are both 0.01 lambda, the widths of interdigital electrodes in the input interdigital transducer and the output interdigital transducer are 0.25 lambda, and the acoustic propagation distance between the input interdigital transducer and the output interdigital transducer is 300 lambda; wherein, lambda represents the wavelength of the surface acoustic wave, and the value range of the wavelength lambda of the surface acoustic wave is 4nm to 4000 nm.
The design method of the delay line type based surface acoustic wave sensing circuit system is characterized in that: in the step 101, the sound absorption glue is epoxy resin glue, the thickness of the sound absorption glue is 0.1-0.8 mm, and the thickness of the piezoelectric film layer is 0.5-0.8 μm; in step 201, the sensitive thin film layer is a tin dioxide thin film layer, the thickness of the sensitive thin film layer is 100 nm-12 nm, gaps are formed between the distance between the two sides of the sensitive thin film layer and the distance between the input interdigital transducer and the output interdigital transducer, and the piezoelectric thin film layer is quartz.
Compared with the prior art, the invention has the following advantages:
1. the method has simple steps and reasonable design, and the designed delay line type-based surface acoustic wave sensing circuit system has low power consumption.
2. The invention adopts the delay line type surface acoustic wave delay line type device, and the delay line type surface acoustic wave device usually has longer acoustic transmission distance, so that the analysis of SAW propagation characteristics is convenient during sensing detection, and the SAW propagation characteristics can be fully sensed to a substance to be detected, therefore, the delay line type surface acoustic wave delay line type device has higher sensitivity and wide frequency modulation range, and the high accuracy and high sensitivity of information sensing are ensured.
3. The invention adopts the delay line type surface acoustic wave device without the sensitive film and the delay line type surface acoustic wave device with the sensitive film for comparison, and takes the delay line type surface acoustic wave device without the sensitive film as the reference, thereby filtering the interference and improving the test accuracy of the delay line type surface acoustic wave device with the sensitive film.
4. The reference oscillation generating circuit and the three-stage amplifying structure in the oscillation generating circuit ensure that the gain of the amplifier is enough to compensate the loss of the frequency selection loop of the SAW broadband surface acoustic wave delay line type device by the front-stage amplifying loop and the third-stage amplifying structure is used for isolating output, thereby reducing the influence of load traction on the loop output.
5. The attenuator circuit is arranged in the low-frequency signal conditioning circuit, and the amplitude of the output signal of the low-frequency signal conditioning circuit can be dynamically adjusted through the resistor R7, the resistor R8, the resistor R9 and the resistor R10, so that the problem of supersaturation of the input of a third-stage amplifier is solved, and the stability and reliability of system signal transmission are improved.
6. The low-frequency signal conditioning circuit is added with the voltage following circuit, so that the isolation of the front stage and the rear stage of the system circuit is increased, and the load capacity of the low-frequency signal conditioning circuit is further improved.
7. The reference oscillation generating circuit, the oscillation signal mixing processing circuit and the low-frequency signal conditioning circuit are powered by a positive direct-current power supply and a negative direct-current power supply, and unnecessary use of peripheral matching components is reduced by each module, so that the overall power consumption of the system is reduced.
8. The design method based on the delay line type surface acoustic wave sensing circuit system is simple and convenient to operate and good in using effect, firstly, a delay line type surface acoustic wave device which does not comprise a sensitive film is manufactured, then, a delay line type SAW gas sensor comprising the sensitive film is manufactured, and then, proper parameters forming a reference oscillation generating circuit are selected and proper parameters forming the oscillation generating circuit are selected; secondly, selecting proper parameters for forming the oscillating signal mixing processing circuit; and then selecting proper parameters for forming the low-frequency signal conditioning circuit, and finally connecting the reference oscillation generating circuit, the oscillation signal mixing processing circuit and the low-frequency signal conditioning circuit to complete the design of the delay line type based surface acoustic wave sensing circuit system.
In conclusion, the method has simple steps and reasonable design, and the designed delay line type-based surface acoustic wave sensing circuit system has low power consumption and generates high-stability sensing signals.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
Fig. 1 is a schematic structural view of a delay line type surface acoustic wave device of the present invention which does not include a sensitive film.
Fig. 2 is a schematic structural view of a delay line type surface acoustic wave device including a sensitive film according to the present invention.
Fig. 3 is a schematic circuit diagram of the reference oscillation generating circuit of the present invention.
Fig. 4 is a schematic circuit diagram of the oscillation generating circuit of the present invention.
Fig. 5 is a schematic circuit diagram of an oscillation signal mixing processing circuit according to the present invention.
Fig. 6 is a schematic circuit diagram of a low frequency signal conditioning circuit according to the present invention.
FIG. 7 is a block flow diagram of a method of the present invention.
Description of reference numerals:
1-a piezoelectric thin film layer; 2-an input interdigital transducer; 3-an output interdigital transducer;
4-a sensitive film layer; and 5, sound absorption glue.
Detailed Description
A method for designing a delay line type based surface acoustic wave sensing circuit system as shown in fig. 1 to 7 includes the following steps:
step one, manufacturing a delay line type surface acoustic wave device which does not comprise a sensitive film:
101, selecting a piezoelectric thin film layer 1, and arranging an input interdigital transducer 2 and an output interdigital transducer 3 on the piezoelectric thin film layer 1, wherein the input interdigital transducer 2 and the output interdigital transducer 3 have the same structure, the input interdigital transducer 2 and the output interdigital transducer 3 are symmetrically arranged relative to the center of the piezoelectric thin film layer 1, and sound absorption glue 5 is coated on two ends of the piezoelectric thin film layer 1;
102, packaging the delay line type surface acoustic wave device obtained in the step 101 by adopting lead bonding equipment to obtain a delay line type surface acoustic wave device which does not contain a sensitive film; the 1 st pin of the delay line type surface acoustic wave device which does not contain the sensitive film is a pin of the input interdigital transducer 2, the 2 nd pin of the delay line type surface acoustic wave device which does not contain the sensitive film is a grounding pin of the input interdigital transducer 2, the 4 th pin of the delay line type surface acoustic wave device which does not contain the sensitive film is an output pin of the output interdigital transducer 3, and the 3 rd pin of the delay line type surface acoustic wave device which does not contain the sensitive film is a grounding pin of the output interdigital transducer 3;
step two, manufacturing a delay line type SAW gas sensor containing a sensitive film:
step 201, according to the method in step 101, a sensitive thin film layer 4 is arranged between an input interdigital transducer 2 and an output interdigital transducer 3, and the bottom surface of the sensitive thin film layer 4 is attached to the surface of a piezoelectric thin film layer 1;
step 202, packaging the delay line type surface acoustic wave device obtained in the step 201 by adopting lead bonding equipment to obtain a delay line type surface acoustic wave device containing a sensitive film; the 1 st pin of the delay line type surface acoustic wave device containing the sensitive film is a pin of the input interdigital transducer 2, the 2 nd pin of the delay line type surface acoustic wave device containing the sensitive film is a grounding pin of the input interdigital transducer 2, the 4 th pin of the delay line type surface acoustic wave device containing the sensitive film is an output pin of the output interdigital transducer 3, and the 3 rd pin of the delay line type surface acoustic wave device containing the sensitive film is a grounding pin of the output interdigital transducer 3;
selecting proper parameters for forming the reference oscillation generating circuit:
step 301, selecting the integrated operational amplifier INA1-1, the integrated operational amplifier INA2-1 and the integrated operational amplifier INA3-1 to be operational amplifiers INA-02186;
step 302, selecting a low-pass filter LFCN-1-1 and a low-pass filter LFCN-2-1 as low-pass filters LFCN-255;
step 303, selecting the resistance values of a resistor R1-1, a resistor R2-1, a resistor R3-1, a resistor R4-1, a resistor R5-1 and a resistor R6-1 to be 100 omega-110 omega, selecting the resistance value of a resistor R7-1 to be 270 omega-300 omega, selecting the resistance value of a resistor R8-1 to be 430 omega, and selecting the resistance values of a resistor R9-1 and a resistor R10-1 to be 62 omega;
in this embodiment, it is further preferable that the resistance values of the resistor R1-1, the resistor R2-1, the resistor R3-1, the resistor R4-1, the resistor R5-1 and the resistor R6-1 are 100 Ω, and the resistance value of the resistor R7-1 is 270 Ω.
Step 304, selecting capacitors C1-1, C2-1 and C3-1 to have capacitance values of 1 muF-3 muF, selecting capacitors C4-1, C5-1 and C6-1 to have capacitance values of 300 pF-330 pF, selecting capacitors C7-1, C8-1, C9-1, C10-1, C11-1 and C12-1 to have capacitance values of 300 pF-330 pF;
in the embodiment, it is further preferable that the capacitance values of the capacitor C1-1, the capacitor C2-1 and the capacitor C3-1 are 1 μ F, the capacitance values of the capacitor C4-1, the capacitor C5-1 and the capacitor C6-1 are 300pF, and the capacitance values of the capacitor C7-1, the capacitor C8-1, the capacitor C9-1, the capacitor C10-1, the capacitor C11-1 and the capacitor C12-1 are all 300 pF.
305, selecting the inductance values of the inductor L1-1, the inductor L2-1 and the inductor L3-1 to be 120 nH-124 nH, and selecting the inductance values of the inductor L4-1, the inductor L5-1 and the inductor L6-1 to be 8.2 nH;
in this embodiment, it is further preferable that the inductance values of the inductor L1-1, the inductor L2-1, and the inductor L3-1 be 120 nH.
Step 306, connecting the 1 st pin of the delay line type surface acoustic wave device not including the sensitive film in the step 102 with one end of an inductor L4-1, connecting the other end of the inductor L4-1 with one end of a capacitor C7-1, connecting the other end of the capacitor C7-1 to an input pin of an integrated amplifier INA1-1, connecting the 2 nd pin and the 4 th pin of the integrated amplifier INA1-1 to ground, connecting the 3 rd pin of the integrated amplifier INA1-1 with one end of the inductor L1-1 and one end of the capacitor C8-1, connecting the other end of the inductor L1-1 with one end of the capacitor C4-1, one end of a resistor R1-1 and one end of a resistor R2-1, connecting the other end of the resistor R1-1, the other end of the resistor R2-1 and one end of the capacitor C1-1 to a +9V dc power supply, the other end of the capacitor C4-1 and the other end of the capacitor C1-1 are both grounded; the other end of the capacitor C8-1 is connected with the 1 st pin of the low-pass filter LFCN-1-1, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-1-1 are grounded, the 3 rd pin of the low-pass filter LFCN-1-1 is connected with one end of the capacitor C9-1, one end of the capacitor C9-1 is connected with the 1 st pin of the integrated amplifier INA2-1, the 2 nd pin and the 4 th pin of the integrated amplifier INA2-1 are grounded, the 3 rd pin of the integrated amplifier INA2-1 is connected with one end of an inductor L2-1 and one end of a capacitor C10-1, the other end of the inductor L2-1 is connected with one end of a capacitor C5-1, one end of a resistor R3-1 and one end of a resistor R4-1, the other end of the resistor R3-1 is connected with the other end of the low-, The other end of the resistor R4-1 and one end of the capacitor C2-1 are both connected with a +9V direct-current power supply, and the other end of the capacitor C5-1 and the other end of the capacitor C2-1 are both grounded; the other end of the capacitor C10-1 is connected with one end of a resistor R7-1 and one end of an inductor L6-1, one end of the inductor L6-1 is connected with one end of an inductor L5-1, the other end of the inductor L5-1 is connected with the 4 th pin of a delay line type surface acoustic wave device which does not contain a sensitive film, the other end of the resistor R7-1 is connected with one end of a resistor R8-1 and one end of a resistor R9-1, the other end of the resistor R8-1 is connected with one end of a resistor R10-1 and one end of a capacitor C11-1, the other end of the resistor R9-1 and the other end of the resistor R10-1 are both grounded, the other end of the capacitor C11-1 is connected with the 1 st pin of an integrated amplifier INA3-1, the 2 nd pin and the 4 th pin of the integrated amplifier INA3-1 are both grounded, the 3 rd pin of the integrated amplifier INA3-1 is connected to one end of a capacitor C12-1 and one end of an inductor L3-1, the other end of the capacitor C12-1 is connected to pin 1 of the low pass filter LFCN-2-1, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-2-1 are grounded, the 3 rd pin of the low-pass filter LFCN-2-1 is the output end of the reference oscillation generating circuit, the other end of one end of the inductor L3-1 is connected with one end of the capacitor C6-1, one end of the resistor R5-1 and one end of the resistor R6-1, the other end of the resistor R5-1, the other end of the resistor R6-1 and one end of the capacitor C3-1 are all connected with a +9V direct-current power supply, the other end of the capacitor C3-1 and the other end of the capacitor C6-1 are both grounded;
step four, selecting proper parameters for forming the oscillation generating circuit:
step 401, selecting the integrated operational amplifier INA1-2, the integrated operational amplifier INA2-2 and the integrated operational amplifier INA3-2 to be operational amplifiers INA-02186;
step 402, selecting both the low-pass filter LFCN-1-2 and the low-pass filter LFCN-2-2 as the low-pass filter LFCN-255;
step 403, selecting the resistance values of the resistor R1-2, the resistor R2-2, the resistor R3-2, the resistor R4-2, the resistor R5-2 and the resistor R6-2 to be 100 omega-110 omega, selecting the resistance value of the resistor R7-2 to be 270 omega-300 omega, selecting the resistance value of the resistor R8-2 to be 430 omega, and selecting the resistance values of the resistor R9-2 and the resistor R10-2 to be 62 omega;
in this embodiment, it is further preferable that the resistance values of the resistor R1-2, the resistor R2-2, the resistor R3-2, the resistor R4-2, the resistor R5-2 and the resistor R6-2 are 100 Ω, and the resistance value of the resistor R7-2 is 270 Ω.
Step 404, capacitance values of a selected capacitor C1-2, a selected capacitor C2-2 and a selected capacitor C3-2 are all 1 muF-3 muF, capacitance values of the selected capacitor C4-2, the selected capacitor C5-2 and the selected capacitor C6-2 are all 300 pF-330 pF, and capacitance values of the selected capacitor C7-2, the selected capacitor C8-2, the selected capacitor C9-2, the selected capacitor C10-2, the selected capacitor C11-2 and the selected capacitor C12-2 are all 300 pF-330 pF;
in the embodiment, it is further preferable that the capacitance values of the capacitor C1-2, the capacitor C2-2 and the capacitor C3-2 are 1 μ F, the capacitance values of the capacitor C4-2, the capacitor C5-2 and the capacitor C6-2 are 300pF, and the capacitance values of the capacitor C7-2, the capacitor C8-2, the capacitor C9-2, the capacitor C10-2, the capacitor C11-2 and the capacitor C12-2 are all 300 pF.
Step 405, selecting the inductance values of the inductor L1-2, the inductor L2-2 and the inductor L3-2 to be 120 nH-124 nH, and selecting the inductance values of the inductor L4-2, the inductor L5-2 and the inductor L6-2 to be 8.2 nH;
in this embodiment, it is further preferable that the inductance values of the inductor L1-2, the inductor L2-2, and the inductor L3-2 be 120 nH.
Step 406, connecting the 1 st pin of the delay line type surface acoustic wave device containing the sensitive film in the step 202 with one end of an inductor L4-2, connecting the other end of the inductor L4-2 with one end of a capacitor C7-2, connecting the other end of the capacitor C7-2 to an input pin of an integrated amplifier INA1-2, connecting the 2 nd pin and the 4 th pin of the integrated amplifier INA1-2 to ground, connecting the 3 rd pin of the integrated amplifier INA1-2 with one end of the inductor L1-2 and one end of the capacitor C8-2, connecting the other end of the inductor L1-2 with one end of the capacitor C4-2, one end of a resistor R1-2 and one end of a resistor R2-2, connecting the other end of the resistor R1-2, the other end of the resistor R2-2 and one end of the capacitor C1-2 to a +9V direct current power supply, the other end of the capacitor C4-2 and the other end of the capacitor C1-2 are both grounded; the other end of the capacitor C8-2 is connected with the 1 st pin of the low-pass filter LFCN-1-2, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-1-2 are grounded, the 3 rd pin of the low-pass filter LFCN-1-2 is connected with one end of the capacitor C9-2, one end of the capacitor C9-2 is connected with the 1 st pin of the integrated amplifier INA2-2, the 2 nd pin and the 4 th pin of the integrated amplifier INA2-2 are grounded, the 3 rd pin of the integrated amplifier INA2-2 is connected with one end of an inductor L2-2 and one end of a capacitor C10-2, the other end of the inductor L2-2 is connected with one end of a capacitor C5-2, one end of a resistor R3-2 and one end of a resistor R4-2, the other end of the resistor R3-2, the other end of the low-pass filter, The other end of the resistor R4-2 and one end of the capacitor C2-2 are both connected with a +9V direct-current power supply, and the other end of the capacitor C5-2 and the other end of the capacitor C2-2 are both grounded; the other end of the capacitor C10-2 is connected with one end of a resistor R7-2 and one end of an inductor L6-2, one end of the inductor L6-2 is connected with one end of an inductor L5-2, the other end of the inductor L5-2 is connected with a pin 4 of a delay line type surface acoustic wave device comprising a sensitive film, the other end of the resistor R7-2 is connected with one end of a resistor R8-2 and one end of a resistor R9-2, the other end of the resistor R8-2 is connected with one end of a resistor R10-2 and one end of a capacitor C11-2, the other end of the resistor R9-2 and the other end of the resistor R10-2 are both grounded, the other end of the capacitor C11-2 is connected with a pin 1 of an integrated amplifier INA3-2, a pin 2 of the integrated amplifier INA3-2 is both grounded with a pin 4, the 3 rd pin of the integrated amplifier INA3-2 is connected to one end of a capacitor C12-2 and one end of an inductor L3-2, the other end of the capacitor C12-2 is connected to pin 1 of the low pass filter LFCN-2-2, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-2-2 are grounded, the 3 rd pin of the low-pass filter LFCN-2-2 is the output end of the oscillation generating circuit, the other end of one end of the inductor L3-2 is connected with one end of the capacitor C6-2, one end of the resistor R5-2 and one end of the resistor R6-2, the other end of the resistor R5-2, the other end of the resistor R6-2 and one end of the capacitor C3-2 are all connected with a +9V direct-current power supply, the other end of the capacitor C3-2 and the other end of the capacitor C6-2 are both grounded;
step five, selecting proper parameters forming the oscillation signal mixing processing circuit:
step 501, selecting an integrated mixer as a mixer AD 831;
step 502, selecting the capacitance value of the capacitor C25 to be 1 muF, and selecting the capacitance values of the capacitor C34, the capacitor C37, the capacitor C38, the capacitor C39, the capacitor C40, the capacitor C41, the capacitor C44, the capacitor C45, the capacitor C46, the capacitor C47, the capacitor C48 and the capacitor C49 to be 0.1 muF-1 muF;
in this embodiment, the capacitance values of the capacitor C34, the capacitor C37, the capacitor C38, the capacitor C39, the capacitor C40, the capacitor C41, the capacitor C44, the capacitor C45, the capacitor C46, the capacitor C47, the capacitor C48, and the capacitor C49 are 0.1 μ F.
Step 503, according to
Figure BDA0002362926380000161
Obtaining capacitance values of the capacitor C35 and the capacitor C36; wherein f is3dBRepresents a 3dB bandwidth, and f3dB＝1MHz，RERepresents the internal impedance of the mixer AD831, and RE＝14Ω；
In this embodiment, the capacitance values of the capacitor C35 and the capacitor C36 are 11.37nF according to the formula, so in order to purchase the resistor conveniently, the capacitance values of the capacitor C35 and the capacitor C36 are selected to be 10 nF.
Step 504, selecting the inductance value of the inductor L17 as 10 mH;
step 505, selecting the resistance values of the resistor R26 and the resistor R27 to be 5k Ω -5.7 k Ω, the resistance values of the resistor R33 and the resistor R16 to be 51.1 Ω, the resistance value of the resistor R32 to be 1.33k Ω, the resistance value of the resistor R30 to be 51.1 Ω,
in this embodiment, the resistance values of the resistor R26 and the resistor R27 are 5k Ω.
Step 506, according to
Figure BDA0002362926380000171
Obtaining the resistance value of the resistor R28 and the resistance value of the resistor R29;
in this embodiment, the resistance of the resistor R28 and the resistance of the resistor R29 are further obtained according to a formula, so that in order to purchase the resistor conveniently, the resistance of the resistor R28 is 51.1 Ω and the resistance of the resistor R29 is 110 Ω.
Step 507, connecting the 1 st pin of the mixer AD831 with one end of a +5V dc power supply and a capacitor C34, connecting the connection of the 2 nd pin and the 3 rd pin of the mixer AD831 with one end of a capacitor C35, connecting the other end of a capacitor C35 with a +5V dc power supply, connecting the 4 th pin of the mixer AD831 with ground, connecting the 5 th pin of the mixer AD831 with one end of a capacitor C38 and the +5V dc power supply, connecting the 6 th pin of the mixer AD831 with one end of a capacitor C40, connecting the other end of a capacitor C40 with one end of a capacitor C39 and one end of an inductor L17, connecting the other end of a capacitor C39 with one end of a resistor R16, connecting the other end of a capacitor C39 and one end of a resistor R16 as one input end of the oscillation signal mixing processing circuit, connecting the 7 th pin of the mixer AD831 with one end of a capacitor C41, connecting the 8 th pin of the mixer AD831 with a-5V dc power supply and one end of a capacitor C45, connecting the first pin of the mixer AD 49 and one end of a capacitor C9, the 10 th pin of the mixer AD831 is connected with one end of a capacitor C46, the 11 th pin of the mixer AD831 is connected with one end of a resistor R33, the connecting end of the other end of the capacitor C46 and the other end of a resistor R33 is used as the other input end of the oscillation signal mixing processing circuit, the 12 th pin +5V direct current power supply of the mixer AD831 is connected with one end of a capacitor C48, the 13 th pin of the mixer AD831 is grounded, the 14 th pin of the mixer AD831 is connected with one end of a resistor R32, the other end of the resistor R32 is connected with one end of a +5V direct current power supply and a capacitor C47, the 15 th pin of the mixer AD831 is connected with one end of a-5V direct current power supply and a capacitor C44, the 16 th pin of the mixer AD831 is connected with one end of a resistor R30 and one end of a resistor R29, the other end of the resistor R30 is connected with one end of a capacitor C25, the other end of a capacitor C25 is used as the output end of the oscillation signal mixing processing circuit, and the other end of the resistor AD, a pin 18 of the mixer AD831 is connected with the other end of the resistor R28, one end of the resistor R27, one end of the resistor R26 and one end of the capacitor C27, the connection end of a pin 19 and a pin 20 of the mixer AD831 is connected with one end of the capacitor C36, the other end of the capacitor C36 is connected with a +5V direct-current power supply, the other end of the capacitor C38, the other end of the inductor L17, the other end of the resistor R16, the other end of the capacitor C41, the other end of the capacitor C45, the other end of the capacitor C49, the other end of the capacitor C48, the other end of the capacitor C47, the other end of the capacitor C44, the other end of the resistor R27, the other end of the capacitor C37 and the other end;
step six, selecting proper parameters for forming the low-frequency signal conditioning circuit:
601, selecting the resistance values of the resistor R4 and the resistor R10 to be 1k omega-1.2 k omega, the resistance value of the resistor R9 to be 200 omega-220 omega, and the resistance value of the resistor R12 to be 50 omega-51 omega;
step 602, according to
Figure BDA0002362926380000181
And
Figure BDA0002362926380000182
obtaining resistance values of a resistor R13 and a resistor R15; wherein, VrRepresenting the input voltage, V, of the attenuator circuitoutRepresents the output voltage of the attenuator circuit, and N represents the input-to-output voltage ratio of the attenuator circuit;
in this embodiment, the resistance values of R4 and R10 are 1k Ω, R9 is 200 Ω, and R12 is 50 Ω.
In this embodiment, the attenuation amplitude of the attenuator circuit is designed to be 9.5dB, the input-output voltage ratio of the attenuator circuit is 2.9853, and the resistance values of the resistor R13 and the resistor R15 are 100.4 Ω, so that in order to purchase the resistor, the resistance values of the resistor R13 and the resistor R15 are selected to be 100 Ω in specific implementation.
Step 603, according to the formula
Figure BDA0002362926380000191
Obtaining the resistance value of the resistor R14;
in this embodiment, when the resistance values of the resistor R13 and the resistor R15 are 100.4 Ω, the resistance value of the resistor R14 is 66.3 Ω, and therefore, in order to purchase the resistor, the resistance value of the resistor R14 is 68 Ω.
Step 604, selecting the resistance value of the resistor R5 to be 10 omega-20 omega, the resistance value of the resistor R6 to be 175 omega-200 omega, and the resistance values of the resistor R7 and the resistor R8 to be 402 omega-417 omega;
in this embodiment, it is further preferable that the resistance value of the resistor R5 is 10 Ω, the resistance value of the resistor R6 is 175 Ω, and the resistance values of the resistors R7 and R8 are 402 Ω.
Step 605, selecting the capacitance value of the capacitor C1 as 100pF, the capacitance values of the capacitor C2, the capacitor C3 and the capacitor C6 as 0.1 muF-1 muF, and the capacitance values of the capacitor C4 and the capacitor C5 as 6.8 muF-7.3 muF;
in this embodiment, it is further preferable that the capacitance values of the capacitor C2, the capacitor C3, and the capacitor C6 be 0.1 μ F, and the capacitance values of the capacitor C4 and the capacitor C5 be 6.8 μ F.
Step 606, connecting one end of a resistor R12 with one end of a resistor R14 and one end of a resistor R13, connecting the other end of the resistor R14 with one end of a resistor R15, connecting the other end of a resistor R13 with the other end of a resistor R15, wherein the other end of the resistor R12 is an input end of an attenuator circuit, and the connecting end of the other end of the resistor R14 with one end of a resistor R15 is an output end of the attenuator circuit;
step 607, selecting the operational amplifier OPA354aid bv as the voltage follower U1;
step 608, select op amp OPA690ID as op amp U2;
step 609, selecting the NPN type transistor as an NPN type transistor 2N3904, and selecting the Schmitt trigger as a 74LS14D Schmitt trigger;
step 6010, connecting the output terminal of the attenuator circuit with the positive input terminal of the voltage follower U1, connecting the output terminal of the voltage follower U1 with the negative input terminal of the voltage follower U1, connecting the output terminal of the voltage follower U1 with one terminal of the resistor R5, connecting the other terminal of the resistor R5 with one terminal of the capacitor C1, one terminal of the resistor R4 and one terminal of the resistor R6, connecting the other terminal of the resistor R6 with the positive input terminal of the operational amplifier U2, connecting the negative input terminal of the operational amplifier U2 with one terminal of the resistor R7 and one terminal of the resistor R8, connecting the output terminal of the operational amplifier U2 with one terminal of the capacitor C3, the other terminal of the resistor R8 and one terminal of the resistor R9, connecting the other terminal of the resistor R9 with the base of the NPN transistor 2N3904, connecting the emitter of the NPN transistor 2N3904 to ground, connecting the collector of the NPN transistor 2N3904 with one terminal of the resistor R10 and the input terminal of the LS14D, the other end of the resistor R10, the connection end of the positive power supply end of the voltage follower U1 and the positive power supply end of the operational amplifier U2 are connected with a +5V direct-current power supply, one end of the capacitor C2 and one end of the capacitor C4, the other end of the capacitor C3, the connection end of the negative power supply end of the voltage follower U1 and the negative power supply end of the operational amplifier U2 are connected with a-5V direct-current power supply, one end of the capacitor C5 and one end of the capacitor C6, the other end of the capacitor C2, the other end of the capacitor C4, the other end of the capacitor C5 and the other end of the capacitor C6 are grounded, and the output end of the 74LS14D Schmidt trigger
Step seven, connecting the reference oscillation generating circuit, the oscillation signal mixing processing circuit and the low-frequency signal conditioning circuit:
and 701, connecting the output end of the reference oscillation generating circuit in the step 306 with one input end of an oscillation signal mixing processing circuit, connecting the output end of the oscillation generating circuit in the step 406 with the other input end of the oscillation signal mixing processing circuit, and connecting the output end of the oscillation signal mixing processing circuit with the input end of an attenuator circuit to complete the design of the delay line type-based surface acoustic wave sensing circuit system.
In this embodiment, the input interdigital transducer 2 and the output interdigital transducer 3 are made of Al, Pt, Au or Mo, the thicknesses of the input interdigital transducer 2 and the output interdigital transducer 3 are both 0.01 λ, the widths of interdigital electrodes in the input interdigital transducer 2 and the output interdigital transducer 3 are 0.25 λ, and the acoustic propagation distance between the input interdigital transducer 2 and the output interdigital transducer 3 is 300 λ; wherein, lambda represents the wavelength of the surface acoustic wave, and the value range of the wavelength lambda of the surface acoustic wave is 4nm to 4000 nm.
In the embodiment, in the step 101, the sound absorption glue 5 is an epoxy resin glue, the thickness of the sound absorption glue 5 is 0.1mm to 0.8mm, and the thickness of the piezoelectric film layer 1 is 0.5 μm to 0.8 μm;
in step 201, the sensitive thin film layer 4 is a tin dioxide thin film layer, the thickness of the sensitive thin film layer 4 is 100 nm-12 nm, gaps are formed between the distance between the two sides of the sensitive thin film layer 4 and the distance between the input interdigital transducer 2 and the output interdigital transducer 3, and the piezoelectric thin film layer 1 is quartz.
In this embodiment, the delay line type surface acoustic wave device not including the sensitive film and the reference oscillation generating circuit constitute a reference circuit, the delay line type surface acoustic wave device including the sensitive film and the oscillation generating circuit constitute a gas concentration sensor detecting circuit, and since the delay line type surface acoustic wave device including the sensitive film can sense the gas concentration, the delay line type surface acoustic wave device which does not transmit the sensitive film can not sense the gas concentration, so that the gas electric signal output by the delay line type surface acoustic wave device which comprises the sensitive film has deviation with a reference circuit, therefore, the output signals of the reference circuit and the detection circuit of the gas concentration sensor are compared and analyzed to obtain the change condition of the gas concentration signal, the error signal caused by the gas concentration signal deviation caused by the non-sensing signal is reduced, and the accuracy of gas concentration signal detection is ensured.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims (3)

1. A design method based on delay line type surface acoustic wave sensing circuit system is characterized by comprising the following steps:
step one, manufacturing a delay line type surface acoustic wave device which does not comprise a sensitive film:
101, selecting a piezoelectric thin film layer (1), arranging an input interdigital transducer (2) and an output interdigital transducer (3) on the piezoelectric thin film layer (1), wherein the input interdigital transducer (2) and the output interdigital transducer (3) have the same structure, the input interdigital transducer (2) and the output interdigital transducer (3) are symmetrically arranged relative to the center of the piezoelectric thin film layer (1), and sound absorption glue (5) is coated at two ends of the piezoelectric thin film layer (1);
102, packaging the delay line type surface acoustic wave device obtained in the step 101 by adopting lead bonding equipment to obtain a delay line type surface acoustic wave device which does not contain a sensitive film; the 1 st pin of the delay line type surface acoustic wave device which does not contain the sensitive film is a pin of the input interdigital transducer (2), the 2 nd pin of the delay line type surface acoustic wave device which does not contain the sensitive film is a grounding pin of the input interdigital transducer (2), the 4 th pin of the delay line type surface acoustic wave device which does not contain the sensitive film is an output pin of the output interdigital transducer (3), and the 3 rd pin of the delay line type surface acoustic wave device which does not contain the sensitive film is a grounding pin of the output interdigital transducer (3);
step two, manufacturing a delay line type SAW gas sensor containing a sensitive film:
step 201, according to the method in step 101, a sensitive film layer (4) is arranged between an input interdigital transducer (2) and an output interdigital transducer (3), and the bottom surface of the sensitive film layer (4) is attached to the surface of a piezoelectric film layer (1);
step 202, packaging the delay line type surface acoustic wave device obtained in the step 201 by adopting lead bonding equipment to obtain a delay line type surface acoustic wave device containing a sensitive film; the 1 st pin of the delay line type surface acoustic wave device containing the sensitive film is a pin of the input interdigital transducer (2), the 2 nd pin of the delay line type surface acoustic wave device containing the sensitive film is a grounding pin of the input interdigital transducer (2), the 4 th pin of the delay line type surface acoustic wave device containing the sensitive film is an output pin of the output interdigital transducer (3), and the 3 rd pin of the delay line type surface acoustic wave device containing the sensitive film is a grounding pin of the output interdigital transducer (3);
selecting proper parameters for forming the reference oscillation generating circuit:
step 301, selecting the integrated operational amplifier INA1-1, the integrated operational amplifier INA2-1 and the integrated operational amplifier INA3-1 to be operational amplifiers INA-02186;
step 302, selecting a low-pass filter LFCN-1-1 and a low-pass filter LFCN-2-1 as low-pass filters LFCN-255;
step 303, selecting the resistance values of a resistor R1-1, a resistor R2-1, a resistor R3-1, a resistor R4-1, a resistor R5-1 and a resistor R6-1 to be 100 omega-110 omega, selecting the resistance value of a resistor R7-1 to be 270 omega-300 omega, selecting the resistance value of a resistor R8-1 to be 430 omega, and selecting the resistance values of a resistor R9-1 and a resistor R10-1 to be 62 omega;
step 304, selecting capacitors C1-1, C2-1 and C3-1 to have capacitance values of 1 muF-3 muF, selecting capacitors C4-1, C5-1 and C6-1 to have capacitance values of 300 pF-330 pF, selecting capacitors C7-1, C8-1, C9-1, C10-1, C11-1 and C12-1 to have capacitance values of 300 pF-330 pF;
305, selecting the inductance values of the inductor L1-1, the inductor L2-1 and the inductor L3-1 to be 120 nH-124 nH, and selecting the inductance values of the inductor L4-1, the inductor L5-1 and the inductor L6-1 to be 8.2 nH;
step 306, connecting the 1 st pin of the delay line type surface acoustic wave device not including the sensitive film in the step 102 with one end of an inductor L4-1, connecting the other end of the inductor L4-1 with one end of a capacitor C7-1, connecting the other end of the capacitor C7-1 to an input pin of an integrated amplifier INA1-1, connecting the 2 nd pin and the 4 th pin of the integrated amplifier INA1-1 to ground, connecting the 3 rd pin of the integrated amplifier INA1-1 with one end of the inductor L1-1 and one end of the capacitor C8-1, connecting the other end of the inductor L1-1 with one end of the capacitor C4-1, one end of a resistor R1-1 and one end of a resistor R2-1, connecting the other end of the resistor R1-1, the other end of the resistor R2-1 and one end of the capacitor C1-1 to a +9V dc power supply, the other end of the capacitor C4-1 and the other end of the capacitor C1-1 are both grounded; the other end of the capacitor C8-1 is connected with the 1 st pin of the low-pass filter LFCN-1-1, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-1-1 are grounded, the 3 rd pin of the low-pass filter LFCN-1-1 is connected with one end of the capacitor C9-1, one end of the capacitor C9-1 is connected with the 1 st pin of the integrated amplifier INA2-1, the 2 nd pin and the 4 th pin of the integrated amplifier INA2-1 are grounded, the 3 rd pin of the integrated amplifier INA2-1 is connected with one end of an inductor L2-1 and one end of a capacitor C10-1, the other end of the inductor L2-1 is connected with one end of a capacitor C5-1, one end of a resistor R3-1 and one end of a resistor R4-1, the other end of the resistor R3-1 is connected with the other end of the low-, The other end of the resistor R4-1 and one end of the capacitor C2-1 are both connected with a +9V direct-current power supply, and the other end of the capacitor C5-1 and the other end of the capacitor C2-1 are both grounded; the other end of the capacitor C10-1 is connected with one end of a resistor R7-1 and one end of an inductor L6-1, one end of the inductor L6-1 is connected with one end of an inductor L5-1, the other end of the inductor L5-1 is connected with the 4 th pin of a delay line type surface acoustic wave device which does not contain a sensitive film, the other end of the resistor R7-1 is connected with one end of a resistor R8-1 and one end of a resistor R9-1, the other end of the resistor R8-1 is connected with one end of a resistor R10-1 and one end of a capacitor C11-1, the other end of the resistor R9-1 and the other end of the resistor R10-1 are both grounded, the other end of the capacitor C11-1 is connected with the 1 st pin of an integrated amplifier INA3-1, the 2 nd pin and the 4 th pin of the integrated amplifier INA3-1 are both grounded, the 3 rd pin of the integrated amplifier INA3-1 is connected to one end of a capacitor C12-1 and one end of an inductor L3-1, the other end of the capacitor C12-1 is connected to pin 1 of the low pass filter LFCN-2-1, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-2-1 are grounded, the 3 rd pin of the low-pass filter LFCN-2-1 is the output end of the reference oscillation generating circuit, the other end of one end of the inductor L3-1 is connected with one end of the capacitor C6-1, one end of the resistor R5-1 and one end of the resistor R6-1, the other end of the resistor R5-1, the other end of the resistor R6-1 and one end of the capacitor C3-1 are all connected with a +9V direct-current power supply, the other end of the capacitor C3-1 and the other end of the capacitor C6-1 are both grounded;
step four, selecting proper parameters for forming the oscillation generating circuit:
step 401, selecting the integrated operational amplifier INA1-2, the integrated operational amplifier INA2-2 and the integrated operational amplifier INA3-2 to be operational amplifiers INA-02186;
step 402, selecting both the low-pass filter LFCN-1-2 and the low-pass filter LFCN-2-2 as the low-pass filter LFCN-255;
step 403, selecting the resistance values of the resistor R1-2, the resistor R2-2, the resistor R3-2, the resistor R4-2, the resistor R5-2 and the resistor R6-2 to be 100 omega-110 omega, selecting the resistance value of the resistor R7-2 to be 270 omega-300 omega, selecting the resistance value of the resistor R8-2 to be 430 omega, and selecting the resistance values of the resistor R9-2 and the resistor R10-2 to be 62 omega;
step 404, capacitance values of a selected capacitor C1-2, a selected capacitor C2-2 and a selected capacitor C3-2 are all 1 muF-3 muF, capacitance values of the selected capacitor C4-2, the selected capacitor C5-2 and the selected capacitor C6-2 are all 300 pF-330 pF, and capacitance values of the selected capacitor C7-2, the selected capacitor C8-2, the selected capacitor C9-2, the selected capacitor C10-2, the selected capacitor C11-2 and the selected capacitor C12-2 are all 300 pF-330 pF;
step 405, selecting the inductance values of the inductor L1-2, the inductor L2-2 and the inductor L3-2 to be 120 nH-124 nH, and selecting the inductance values of the inductor L4-2, the inductor L5-2 and the inductor L6-2 to be 8.2 nH;
step 406, connecting the 1 st pin of the delay line type surface acoustic wave device containing the sensitive film in the step 202 with one end of an inductor L4-2, connecting the other end of the inductor L4-2 with one end of a capacitor C7-2, connecting the other end of the capacitor C7-2 to an input pin of an integrated amplifier INA1-2, connecting the 2 nd pin and the 4 th pin of the integrated amplifier INA1-2 to ground, connecting the 3 rd pin of the integrated amplifier INA1-2 with one end of the inductor L1-2 and one end of the capacitor C8-2, connecting the other end of the inductor L1-2 with one end of the capacitor C4-2, one end of a resistor R1-2 and one end of a resistor R2-2, connecting the other end of the resistor R1-2, the other end of the resistor R2-2 and one end of the capacitor C1-2 to a +9V direct current power supply, the other end of the capacitor C4-2 and the other end of the capacitor C1-2 are both grounded; the other end of the capacitor C8-2 is connected with the 1 st pin of the low-pass filter LFCN-1-2, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-1-2 are grounded, the 3 rd pin of the low-pass filter LFCN-1-2 is connected with one end of the capacitor C9-2, one end of the capacitor C9-2 is connected with the 1 st pin of the integrated amplifier INA2-2, the 2 nd pin and the 4 th pin of the integrated amplifier INA2-2 are grounded, the 3 rd pin of the integrated amplifier INA2-2 is connected with one end of an inductor L2-2 and one end of a capacitor C10-2, the other end of the inductor L2-2 is connected with one end of a capacitor C5-2, one end of a resistor R3-2 and one end of a resistor R4-2, the other end of the resistor R3-2, the other end of the low-pass filter, The other end of the resistor R4-2 and one end of the capacitor C2-2 are both connected with a +9V direct-current power supply, and the other end of the capacitor C5-2 and the other end of the capacitor C2-2 are both grounded; the other end of the capacitor C10-2 is connected with one end of a resistor R7-2 and one end of an inductor L6-2, one end of the inductor L6-2 is connected with one end of an inductor L5-2, the other end of the inductor L5-2 is connected with a pin 4 of a delay line type surface acoustic wave device comprising a sensitive film, the other end of the resistor R7-2 is connected with one end of a resistor R8-2 and one end of a resistor R9-2, the other end of the resistor R8-2 is connected with one end of a resistor R10-2 and one end of a capacitor C11-2, the other end of the resistor R9-2 and the other end of the resistor R10-2 are both grounded, the other end of the capacitor C11-2 is connected with a pin 1 of an integrated amplifier INA3-2, a pin 2 of the integrated amplifier INA3-2 is both grounded with a pin 4, the 3 rd pin of the integrated amplifier INA3-2 is connected to one end of a capacitor C12-2 and one end of an inductor L3-2, the other end of the capacitor C12-2 is connected to pin 1 of the low pass filter LFCN-2-2, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-2-2 are grounded, the 3 rd pin of the low-pass filter LFCN-2-2 is the output end of the oscillation generating circuit, the other end of one end of the inductor L3-2 is connected with one end of the capacitor C6-2, one end of the resistor R5-2 and one end of the resistor R6-2, the other end of the resistor R5-2, the other end of the resistor R6-2 and one end of the capacitor C3-2 are all connected with a +9V direct-current power supply, the other end of the capacitor C3-2 and the other end of the capacitor C6-2 are both grounded;
step five, selecting proper parameters forming the oscillation signal mixing processing circuit:
step 501, selecting an integrated mixer as a mixer AD 831;
step 502, selecting the capacitance value of the capacitor C25 to be 1 muF, and selecting the capacitance values of the capacitor C34, the capacitor C37, the capacitor C38, the capacitor C39, the capacitor C40, the capacitor C41, the capacitor C44, the capacitor C45, the capacitor C46, the capacitor C47, the capacitor C48 and the capacitor C49 to be 0.1 muF-1 muF;
step 503, according to
Figure FDA0002362926370000051
Obtaining capacitance values of the capacitor C35 and the capacitor C36; wherein f is3dBRepresents a 3dB bandwidth, and f3dB＝1MHz，RERepresents the internal impedance of the mixer AD831, and RE＝14Ω；
Step 504, selecting the inductance value of the inductor L17 as 10 mH;
step 505, selecting the resistance values of the resistor R26 and the resistor R27 to be 5k Ω -5.7 k Ω, the resistance values of the resistor R33 and the resistor R16 to be 51.1 Ω, the resistance value of the resistor R32 to be 1.33k Ω, the resistance value of the resistor R30 to be 51.1 Ω,
step 506, according to
Figure FDA0002362926370000052
Obtaining the resistance value of the resistor R28 and the resistance value of the resistor R29;
step 507, connecting the 1 st pin of the mixer AD831 with one end of a +5V dc power supply and a capacitor C34, connecting the connection of the 2 nd pin and the 3 rd pin of the mixer AD831 with one end of a capacitor C35, connecting the other end of a capacitor C35 with a +5V dc power supply, connecting the 4 th pin of the mixer AD831 with ground, connecting the 5 th pin of the mixer AD831 with one end of a capacitor C38 and the +5V dc power supply, connecting the 6 th pin of the mixer AD831 with one end of a capacitor C40, connecting the other end of a capacitor C40 with one end of a capacitor C39 and one end of an inductor L17, connecting the other end of a capacitor C39 with one end of a resistor R16, connecting the other end of a capacitor C39 and one end of a resistor R16 as one input end of the oscillation signal mixing processing circuit, connecting the 7 th pin of the mixer AD831 with one end of a capacitor C41, connecting the 8 th pin of the mixer AD831 with a-5V dc power supply and one end of a capacitor C45, connecting the first pin of the mixer AD 49 and one end of a capacitor C9, the 10 th pin of the mixer AD831 is connected with one end of a capacitor C46, the 11 th pin of the mixer AD831 is connected with one end of a resistor R33, the connecting end of the other end of a capacitor C46 and the other end of a resistor R33 is used as the other input end of the oscillation signal mixing processing circuit, the 12 th pin of the mixer AD831 is connected with a +5V direct current power supply and one end of a capacitor C48, the 13 th pin of the mixer AD831 is grounded, the 14 th pin of the mixer AD831 is connected with one end of a resistor R32, the other end of a resistor R32 is connected with one end of a +5V direct current power supply and a capacitor C47, the 15 th pin of the mixer AD831 is connected with one end of a-5V direct current power supply and a capacitor C44, the 16 th pin of the mixer AD831 is connected with one end of a resistor R30 and one end of a resistor R29, the other end of a resistor R30 is connected with one end of a capacitor C25, the other end of a capacitor C25 is used as the output end of the oscillation signal processing circuit, and the other end of the mixer AD831, a pin 18 of the mixer AD831 is connected with the other end of the resistor R28, one end of the resistor R27, one end of the resistor R26 and one end of the capacitor C27, the connection end of a pin 19 and a pin 20 of the mixer AD831 is connected with one end of the capacitor C36, the other end of the capacitor C36 is connected with a +5V direct-current power supply, the other end of the capacitor C38, the other end of the inductor L17, the other end of the resistor R16, the other end of the capacitor C41, the other end of the capacitor C45, the other end of the capacitor C49, the other end of the capacitor C48, the other end of the capacitor C47, the other end of the capacitor C44, the other end of the resistor R27, the other end of the capacitor C37 and the other end;
step six, selecting proper parameters for forming the low-frequency signal conditioning circuit:
601, selecting the resistance values of the resistor R4 and the resistor R10 to be 1k omega-1.2 k omega, the resistance value of the resistor R9 to be 200 omega-220 omega, and the resistance value of the resistor R12 to be 50 omega-51 omega;
step 602, according to
Figure FDA0002362926370000071
And
Figure FDA0002362926370000072
obtaining resistance values of a resistor R13 and a resistor R15; wherein, VrRepresenting the input voltage, V, of the attenuator circuitoutRepresents the output voltage of the attenuator circuit, and N represents the input-to-output voltage ratio of the attenuator circuit;
step 603, according to the formula
Figure FDA0002362926370000073
Obtaining the resistance value of the resistor R14;
step 604, selecting the resistance value of the resistor R5 to be 10 omega-20 omega, the resistance value of the resistor R6 to be 175 omega-200 omega, and the resistance values of the resistor R7 and the resistor R8 to be 402 omega-417 omega;
step 605, selecting the capacitance value of the capacitor C1 as 100pF, the capacitance values of the capacitor C2, the capacitor C3 and the capacitor C6 as 0.1 muF-1 muF, and the capacitance values of the capacitor C4 and the capacitor C5 as 6.8 muF-7.3 muF;
step 606, connecting one end of a resistor R12 with one end of a resistor R14 and one end of a resistor R13, connecting the other end of the resistor R14 with one end of a resistor R15, connecting the other end of a resistor R13 with the other end of a resistor R15, wherein the other end of the resistor R12 is an input end of an attenuator circuit, and the connecting end of the other end of the resistor R14 with one end of a resistor R15 is an output end of the attenuator circuit;
step 607, selecting the operational amplifier OPA354aid bv as the voltage follower U1;
step 608, select op amp OPA690ID as op amp U2;
step 609, selecting the NPN type transistor as an NPN type transistor 2N3904, and selecting the Schmitt trigger as a 74LS14D Schmitt trigger;
step 6010, connecting the output terminal of the attenuator circuit with the positive input terminal of the voltage follower U1, connecting the output terminal of the voltage follower U1 with the negative input terminal of the voltage follower U1, connecting the output terminal of the voltage follower U1 with one terminal of the resistor R5, connecting the other terminal of the resistor R5 with one terminal of the capacitor C1, one terminal of the resistor R4 and one terminal of the resistor R6, connecting the other terminal of the resistor R6 with the positive input terminal of the operational amplifier U2, connecting the negative input terminal of the operational amplifier U2 with one terminal of the resistor R7 and one terminal of the resistor R8, connecting the output terminal of the operational amplifier U2 with one terminal of the capacitor C3, the other terminal of the resistor R8 and one terminal of the resistor R9, connecting the other terminal of the resistor R9 with the base of the NPN transistor 2N3904, connecting the emitter of the NPN transistor 2N3904 to ground, connecting the collector of the NPN transistor 2N3904 with one terminal of the resistor R10 and the input terminal of the LS14D, the other end of the resistor R10, the connection end of a positive power supply end of the voltage follower U1 and a positive power supply end of the operational amplifier U2 is connected with a +5V direct-current power supply, one end of the capacitor C2 and one end of the capacitor C4, the other end of the capacitor C3, the connection end of a negative power supply end of the voltage follower U1 and a negative power supply end of the operational amplifier U2 is connected with a-5V direct-current power supply, one end of the capacitor C5 and one end of the capacitor C6, the other end of the capacitor C2, the other end of the capacitor C4, the other end of the capacitor C5 and the other end of the capacitor C6 are grounded, and the output end of the 74LS14D Schmitt trigger is;
step seven, connecting the reference oscillation generating circuit, the oscillation signal mixing processing circuit and the low-frequency signal conditioning circuit:
and connecting the output end of the reference oscillation generating circuit in the step 306 with one input end of the oscillation signal mixing processing circuit, connecting the output end of the oscillation generating circuit in the step 406 with the other input end of the oscillation signal mixing processing circuit, and connecting the output end of the oscillation signal mixing processing circuit with the input end of the attenuator circuit to complete the design of the delay line type based surface acoustic wave sensing circuit system.
2. The design method for a delay line based surface acoustic wave sensing circuit system according to claim 1, wherein: the input interdigital transducer (2) and the output interdigital transducer (3) are made of Al, Pt, Au or Mo, the thicknesses of the input interdigital transducer (2) and the output interdigital transducer (3) are both 0.01 lambda, the widths of interdigital electrodes in the input interdigital transducer (2) and the output interdigital transducer (3) are 0.25 lambda, and the acoustic propagation distance between the input interdigital transducer (2) and the output interdigital transducer (3) is 300 lambda; wherein, lambda represents the wavelength of the surface acoustic wave, and the value range of the wavelength lambda of the surface acoustic wave is 4nm to 4000 nm.
3. The design method for a delay line based surface acoustic wave sensing circuit system according to claim 1, wherein: in the step 101, the sound absorption glue (5) is epoxy resin glue, the thickness of the sound absorption glue (5) is 0.1-0.8 mm, and the thickness of the piezoelectric film layer (1) is 0.5-0.8 μm;
in the step 201, the sensitive thin film layer (4) is a tin dioxide thin film layer, the thickness of the sensitive thin film layer (4) is 100 nm-12 nm, gaps are formed between the two sides of the sensitive thin film layer (4) and the distance between the input interdigital transducer (2) and the output interdigital transducer (3), and the piezoelectric thin film layer (1) is quartz.
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