基于均匀相位采样提高阻抗谱测量精度的研究

周期性信号采样中，等效采样利用较低采样频率的A/D转换实现高频周期信号的采集，一定程度上弥补欠采样测量精度低的缺陷。本文提出一种基于等效采样思想的均匀相位采样的阻抗谱测量方法，有效地提高高频测量中阻抗谱测量精度与稳定性。在利用单片机共时钟基准的DAC与ADC模块，在完成激励信号产生、输入输出信号同步采集的基础上，合理设计激励信号频率、采集频率与信号重构方法，实现高频信号单周期内均匀相位分布的等效高频采样，同时为克服常规A/D转换速度条件下难以准确实现高频阻抗谱测量的问题提供了新思路。从误差假设与拟合算法的角度，理论上分析证明了该方法降低误差的原因；并通过两种等效电路模型的阻抗谱测量对比实验，表明该方法在所设计的20k-100kHz高频段上，阻抗测量精度与稳定性得到了显著的提高。

Improving the measuring accuracy of high-frequency Impedance spectroscopy based on Uniform-phase sampling

In periodic signal sampling, equivalent sampling utilizes the A/D conversion with lower sampling frequency to gather high frequency periodic signals, which, to some extent, compensates for the defects of the low accuracy of under sampling measurement. The paper proposes a method to measure the impedance spectrum of uniform phase sampling based on the idea of equivalent sampling, which effectively improves the accuracy and stability of impedance spectrum measurement in high frequency measurements. In DAC and ADC modules based on common clock reference of microcontroller, by generating the excitation signals and synchronously collecting the input and output signals, the method of excitation signal frequency, acquisition frequency and signal reconstruction is reasonably designed to realize the equivalent high frequency sampling of uniform phase distribution in a single cycle of high frequency signal, which provides a new idea to overcome the problem of the difficulty to accurately measure the frequency impedance spectrum under the condition of conventional A/D conversion speed. From the perspective of error assumption and fitting algorithm, the theoretical analysis proves the reasons for the error reduction of the method; the comparison experiments of two equivalent circuit models of the impedance spectrum measurement show that the accuracy and stability of impedance measurement are significantly improved in the high frequency band of 20k -100kHz.