基于振荡检测法的延迟线型声表面波气体传感器特性

Characteristics of delay line type surface acoustic wave gas sensor based on oscillation

研究延迟线型声表面波(SAW)气体传感器的信号传输损耗和相位变化,考察了振荡检测法中相移电路和滤波电路对传感器性能的影响。基于延迟线型SAW气体传感器简化数学模型和频率特性测试,探讨叉指电极(IDTs)对传感器性能和传输过程中信号相位幅值变化量的影响。利用不同阶低通滤波器的性质和相移电路频率特性曲线研究振荡电路对延迟线型SAW传感器振荡频率、灵敏度和稳定性的影响机制。结果表明:延迟线型SAW传感器插入损耗和信号带宽反比叉指对数;传输过程中信号相位变化受振荡频率、波速和中心距共同影响;滤波器幅频特性随滤波电路阶次降低而变好,同时传感器灵敏度提高。

The insertion loss and the variation phase of wave propagating in delay line type surface acoustic wave CSAW） gas sensors .were investigated. The influence of phase-shift circuit and low-pass filter circuit on the performance of SAW gas sensor based on oscillation was considered. The simplified mathematical model and testing frequency characteristics of delay line type SAW gas sensors were used to study the influence of： metal inter-digital transducers （IDTs） on the characteristics of gas sensor, the variation of wave phase and amplitude in propagation process. The influence mechanism of oscillation circuit on oscillation frequency, sensitivity and stability of SAW gas sensors was discussed, based on properties of low-pass filter and frequency characteristics of phase shift circuit. The insertion loss and the signal bandwidth were decreased with increasing the number of IDTs. The phase change was influenced by the oscillation frequency, the acoustic velocity and the distance between two centers of IDTs. The phasefrequency characteristics of low-pass filter were improved with decreasing the order of filters, and the sensitivity of delay SAW was increased with decreasing the order of filters.