Application circuit of surface acoustic wave transducer

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...

Images