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Application circuit of surface acoustic wave transducer

A surface acoustic wave device and surface acoustic wave technology, applied in the field of sensors, can solve problems such as the unsatisfactory output waveform of the surface acoustic wave oscillator, the inability to measure the physical quantity to be measured, and the submersion of the measured signal, so as to achieve small impedance, easy measurement, The effect of high-precision measurement

Inactive Publication Date: 2014-06-18
CHANGAN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

At present, most surface acoustic wave oscillators use simple LC parallel resonance as the frequency selection network. However, the output waveform of this kind of surface acoustic wave oscillator is not ideal and the stability is poor. When it is used in the design of surface acoustic wave sensors, it cannot Take high-precision measurements
At the same time, because surface acoustic wave devices are susceptible to interference from external environments such as humidity, temperature, electromagnetic and other measurement conditions, these interferences will not only bring measurement errors, but even cause the measured signal to be completely submerged in interference and noise signals

Method used

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  • Application circuit of surface acoustic wave transducer

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0051] Surface acoustic wave devices SAW1 and SAW2 both use surface acoustic wave devices with multiple couplers with a center frequency of 50.882MHz, capacitor C13=C23=C14=C24=27pF; high-frequency low-power tubes BJT1 and BJT2 have a cut-off frequency of 6.5GHz NPN type C3355 silicon transistor. When winding the inductance coil, for the sake of simple calculation, the diameter D of the coil is taken as 1Cm, and the length L of the coil is N Take 1Cm, then determine L and the number of turns N of the coil according to formulas (1), (2), and (3), and calculate L12=L22=725nH, N=10.

[0052] During the production process of the first surface acoustic wave oscillator and the second surface acoustic wave oscillator, due to the difference in the distribution of the devices and the difference in the parameters of the same device, the first surface acoustic wave oscillator and the second surface acoustic wave oscillator output different frequencies signal of. Pass the test of the ap...

Embodiment 2

[0054] The surface acoustic wave devices SAW1 and SAW2 use multiple couplers with a center frequency of 101.764MHz, and the capacitance value is C13=C23=C14=C24=27pF; the high-frequency low-power tubes BJT1 and BJT2 are NPN with a cut-off frequency of 7GHz Type C3358 silicon triode; inductance coil diameter D=1Cm, length L N =1Cm, calculated according to formula (1), (2), (3) to get L12=L22=188nH, N=5. Observe the signal waveforms of the waveform output port of the first SAW oscillator, the waveform output port of the second SAW oscillator and the difference frequency signal output port of the two oscillators respectively through the Agilent oscilloscope, and the output waveforms are as follows: Figure 6 , Figure 7 , Figure 8 shown. in, Figure 6 The waveform frequency is 101.224MHz, Figure 7 The waveform frequency is 100.712MHz, Figure 8 The waveform frequency is 434.23KHz. The data shows that the application circuit of the surface acoustic wave sensor can output th...

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Abstract

The invention discloses an application circuit of a surface acoustic wave transducer. The application circuit comprises a first surface acoustic wave oscillator circuit, a second surface acoustic wave oscillator circuit, a mixer circuit and an LC passive low-pass filter circuit, wherein the output end of the first surface acoustic wave oscillator circuit and the output end of the second surface acoustic wave oscillator circuit are connected with the input end of the mixer circuit respectively, and the output end of the mixer circuit is connected with the input end of the LC passive low-pass filter circuit. According to the application circuit, a three-point capacitive negative feedback element is adopted as a frequency selection and feedback network, the feedback voltage of the capacitive negative feedback element is tapped from the two ends of a capacitor, higher harmonics can be effectively filtered out with small impedance, and stable waveform output is achieved; a high-frequency low-power tube amplifying circuit is a bias-emitter common-collector amplifying circuit, persistent oscillation is achieved, and therefore oscillation signals are more stable; two surface acoustic wave oscillators form a two-channel structure, interference caused by the external environment is avoided, and high-precision measurement of physical quantities to be measured is achieved.

Description

technical field [0001] The invention belongs to the field of sensors, and in particular relates to an application circuit of a surface acoustic wave sensor. Background technique [0002] Due to the advantages of small size, light weight, good stability, high sensitivity, and convenient wireless and passive working mode, the surface acoustic wave sensor is often used for the measurement of various physical quantities to be measured in complex and harsh environments. A common surface acoustic wave sensor consists of a surface acoustic wave device, a sensitive film and related detection circuits. When the external physical quantity to be measured, such as gas concentration, acts on the sensitive film on the surface acoustic wave device, the resonant frequency of the surface acoustic wave device changes accordingly. Then the corresponding relationship between gas concentration and frequency change is obtained, and the measurement of the physical quantity to be measured is realiz...

Claims

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Application Information

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IPC IPC(8): H03H9/25H03H9/145
Inventor 文常保方吉善李演明巨永锋许宏科全思
Owner CHANGAN UNIV
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