High frequency stability oscillator for surface acoustic wave-based gas sensor
High frequency stability oscillator for surface acoustic wave-based gas sensor
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DOI：
10.1088/0964-1726/15/6/003
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发表时间：
2006-12-01
影响因子：
4.1
通讯作者：
Pan, Yong
中科院分区：
文献类型：
--
作者：
Wang, Wen;He, Shitang;Pan, Yong
本文提出了一种用于气体传感器的158兆赫表面声波振荡器。作为振荡器元件，在ST-X石英衬底上开发了具有低插入损耗（< 8 dB）和单模选择能力的SAW延迟线。通过电极宽度控制单相单向换能器（EWC/SPUDT）结构实现了低插入损耗。单模选择简单地由梳状换能器完成，梳状换能器是结合两个数字间换能器（idt）的频率选择性的一种手段。在制造前进行模式耦合（COM）仿真以预测器件性能。实测频率响应S-12与模拟结果吻合较好。详细观察了振荡电路系统温度变化对频率稳定性的影响。实验结果表明，在温度控制的实验室环境中，基线噪声通常高达0.7 x 10（-7）。该振荡器成功地应用于一种气体传感器涂层自组装复合单层材料，作为二甲基-甲基膦酸盐（DMMP）的传感器材料。对低浓度DMMP检测的灵敏度评价近似于25 Hz mg(-1) m(-3)，阈值检测限高达0.5 mg m（-3）。
This paper presents a 158 MHz surface acoustic wave ( SAW) oscillator used for a gas sensor. As the oscillator element, a SAW delay line on ST-X quartz substrate with low insertion loss (< 8 dB) and single mode selection capability was developed. Low insertion loss was achieved by an electrode width control single phase unidirectional transducer (EWC/SPUDT) configuration. Single mode selection was simply accomplished by a comb transducer which is a means of combining the frequency selectivity of two interdigital transducers (IDTs). Coupling of modes (COM) simulation was performed to predict device performance prior to fabrication. The measured frequency response S-12 showed a good agreement with simulated results. The effect of the oscillator circuit system temperature shift upon frequency stability was observed in detail. The experimental results showed that the baseline noise was typically up to similar to 0.7 x 10(-7) in a laboratory environment with temperature control. The oscillator was successfully applied to a gas sensor coated self-assembled composite monolayer as a sensor material for dimethyl-methyl-phosphonate ( DMMP). The sensitivity for low DMMP concentration detection was evaluated as similar to 25 Hz mg(-1) m(-3), and the threshold detection limit was up to 0.5 mg m(-3).