声表面波气体传感器振荡电路设计

基于反馈振荡器的工作原理,采用对振荡电路的开环增益和相位进行检测和调节的方法,设计制作了用于声表面波(SAW)气体传感器的振荡电路。根据开环测量的结果,通过改变匹配电感值来使得0°相位在增益峰值附近,以获得稳定的振荡和提高振荡器可承受的最大传感器插损。在印制电路板(PCB)版图设计中,采用50Ω特性阻抗和保证最短RF回流电流路径等措施以实现稳定的振荡。基于上述方法,分别制作了频率为315,433.92 MHz的振荡电路。后者的噪声幅度在20 Hz以内,标准方差约为3.92。该实验结果表明:此设计方法具有快速、便捷、可靠的优点,设计的振荡电路具有较高的稳定性,可广泛用于SAW传感器设计。

Oscillating circuit design for SAW gas sensors

According to the working principle of feedback oscillator,surface acoustic wave(SAW)gas sensor oscillating circuit are established by measuring phase and gain characteristics of their open-loop.By changing the value of matching inductors,the loop phase must be adjusted near the peak magnitude of the gain curve,so that a robust and stable oscillation will occur with the maximum range of sensor loss.In the aspect of PCB layout design,a characteristic impedance of 50 Ω and minimizing the RF current return path are requisite for achieving stable oscillation.Based on this process,the oscillating circuit for 315 MHz and 433.92 MHz two-port resonators are designed respectively.For the latter,the noise magnitude is less than 20 Hz and the standard deviation is about 3.92.The experimental results show that this process is fast,convenient,reliable,oscillating circuit designed in this way have a high stability and can be widely used in surface acoustic wave sensor.