高精度微弱电容检测系统的设计

Design of High Precision Measuring System for Weak Capacitance

针对微弱电容信号的检测问题,提出了一种基于FPGA和数字解调的高精度微弱电容检测系统;通过硬件设计和软件设计,实现了由电源电路、C/V转换电路、FPGA电路、A/D转换电路等组成的高精度电容检测系统;阐述了利用载波调制进行微弱电容检测的原理和系统硬件电路的实现方案,并给出了基于cordic算法的载波生成、数字解调和AD采样控制在FPGA中的具体实现;实际运行表明,该检测系统的电容检测分辨率可达到5fF,具有精度高及抗干扰能力强等优点。

For the measurement of weak signal in capacitance measuring system, a micro capacitance measuring system based on FPGA and digital demodulation was proposed. Through hardware and software design, a kind of high precision capacitance measuring system composed of power circuit, capacitance/voltage converting circuit, FPGA and A/D converting circuit was presented. The theory of weak capacitance measurement based on carrier modulation and the hardware design were analyzed. The implementation of a sinusoidal carrier signal based on the CORDIC algorithm, digital demodulation and the controlment of the AD were also discussed. The practice shows that the capacitance measurement resolution is 5fF and the system has the high precision and reliability.