Phase-locked loop based micro-displacement/capacitance measurement and control system and its application to MEMS

Phase-locked loop (PLL), as well known, is a very popular and cheap tool for pulse generation with almost constant frequency. On the other hand, a user-friendly and cheap tool for micro-displacement/capacitance servo control system still lacks in the market, although it is increasing the need in MEMS (micro-electro-mechanical system) industries. In this article, a cheap ( for a micro capacitance/displacement scan movement, without the need of A/D and D/A converters) and stable micro-displacement/capacitance measurement and control system is proposed. Simulations and experimental results show that, if the properties of the electronic components used in the PLL remain close to their nominal values, the proposed system can achieve good capacitance/displacement measurement and/or servo control accuracy with high resolution. Application examples show that it is very useful in the micro-positioning system and MEMS industries.