Delay Line Type Saw Gas Sensors

SAW gas sensor has the potential of sensing various physical, chemical and biochemical measurement, has the advantages of high sensitivity, low power consumption, lightness and can work in wireless. As compatible with the integrated circuit flat, it is low cost when produced in large volume.Gas senor is one important sensor, but its stability, getting reversible, repetitiveness and respondence time are dissatisfactory, its development lags behind relatively. SAW sensor belongs to the moicro sensor, can improve above mentioned performance. Process with SAW gas sensor to study the SAW sensor is a feasible method. The paper has carried on research from the relation theory of surface acoustic wave. First studies the model of device, the principle and property of surface acoustic wave, on this foundation has designed a dual-path delay resonance gas sensor. In order to obtain the frequency has designed the corresponding signal processing electrocircuit.The thesis is divided into six chapters. In chapter one, we have summarized sensors and the SAW gas sensor development situation; In chapter two , we have first introduced surface acoustic wave and the property of surface acoustic wave in piezoelectricity medium. By discussing the temperature coefficient of materials, the Electromechanical couple coefficient, spread exhaust and beam deviation etc. factor, we have selected the proper base sheet material, slice and spread direction of surface acoustic wave sensor; By studying the transducer model of IDT in chapter three, we have introduced the network of the surface acoustic wave device from the Electromechanical analogy, established general equivalent circuit and the mathematics model of IDT. Based on these, have carried out model analysis and some specific performance calculations about the activation and reflection IDT; In chapter four, we have carried out realization and the design of the SAW gas sense system, include systematic structural frame, number of input and output IDT and device size etc. At last, we have design a 124 MHz dual delay saw gas sensor based on LiNbO₃; In chapter five,considering for raising detection sensitivity, we have adopted frequency adjustment technology and signal gain to realize the measurement of frequency signal; Puting forward some specific needs from systematic feasibility, practicality and such aspect in chapter six, we have carried out theoretical analysis for the sensitive film of detection H2S. At last received theoretical calculation result, reached expected goal. Based on these foundations, in chapter seven, we have summarized and looked ahead for SAW gas sensor system.We can grasp the analysis, design and realization methods by researching. The thesis is very good reference to the SAW gas sensor study further and the industrialization, and it has theoretical meaning and market application prospect.