Accurate detection of capacitance change is an essential requirement for capacitive sensors development. This paper presents a closed-loop circuit of weakly-coupled RLC resonators for high-resolution capacitive readout. Mode localization effect in the weakly-coupled RLC resonators is studied and the comparison shows superiority in linearity by a closed-loop method. The experimental results validate a capacitive readout resolution of 37.5fF and a 216 times improvement of sensitivity as compared with the frequency shift method. This work indicates that the proposed closed-loop configuration has a better performance than the open loop method, and is less expensive, more compact and much easier for practical application to detect capacitance variance based on mode localization effect in coupled RLC resonators, which makes it a promising method for developing ultra-sensitive capacitive sensors.

准确检测电容变化是电容传感器开发的基本要求。本文提出了一种用于高分辨率电容读数的弱耦合RLC谐振器的闭环电路。研究了弱耦合RLC谐振器中的模式定位效应，并通过闭环方法进行了比较，显示出线性方面的优越性。实验结果证明，与频移方法相比，电容式读数分辨率为37.5fF，灵敏度提高了216倍。这项工作表明，所提出的闭环配置比开环方法具有更好的性能，并且更便宜，更紧凑，并且更易于实际应用，以基于耦合RLC谐振器中的模式定位效应来检测电容变化，