一种矢量阻抗测量电路的原理与设计

针对常用频带和阻抗范围、低功耗场合的矢量阻抗测量应用,该文提出基于矢量伏安法和同步检波技术的自由轴法数字化矢量阻抗测量方法,采用直接数字频率合成芯片产生激励信号和用于检波的参考信号,通过测量被测对象上的电压与电流,以计算阻抗的实部和虚部,并给出了基于两端对网络模型的测量校准与软件补偿算法.介绍了该测量系统的结构方案,及以嵌入式CPU、DDS芯片、混频器、椭圆滤波器等为主的电路实现.该测量系统已获实际应用.

The Principle and Design of a Vector Impedance Measurement Circuit

Focused on the general low-power application of vector impedance measurement for the common frequency band and impedance range,this paper proposes a digital vector impedance measurement scheme using free-axis method,which combines vector I-V measurement concept and synchronous detection technology.It utilizes direct digital synthesizers（DDS） to generate the driving signal and the reference detection signal,and calculates the real and imaginary parts for the impedance of the device under test by measuring the voltage on it,and the current through it.The system calibration based on an unknown two-terminal pair network model and its software compensation algorithms are introduced.The paper also presents the structure and the key circuits of the vector impedance measuring system with an embedded 32bit ARM CPU,two DDS chips,a mixer,and 9th order elliptic filters,etc.The measuring circuit has been applied in real measurement systems.