Liu J Z, Li X B, Xiong H
The School of Control Science and Engineering, Tiangong University, Tianjin 300387, People's Republic of China.
Rev Sci Instrum. 2021 Sep 1;92(9):094707. doi: 10.1063/5.0062640.
A high output impedance current source with a wide bandwidth is needed in electrical impedance tomography systems. Limitations appear mainly at higher frequencies and non-simple loads. In order to adjust the output current, the amplitude and phase are made to achieve the expected value automatically. A current source based on the field programmable gate array is designed. In this paper, we proposed a double DAC differential current source structure. By measuring the voltage of the sampling resistor in series with the load and using the proposed dynamic reference point demodulation algorithm, the actual current amplitude and phase on the load can be quickly obtained. Through the adaptive compensation module, the output current is adjusted to the expected value. The experimental results show that the output resistance of the current source can reach 10 MΩ and the output capacitance can be less than 0.8 pF in the frequency range of 10 kHz-1.28 MHz. At the same time, the current amplitude attenuation is less than 0.016%, and the phase error is less than 0.0025° after compensation. Therefore, the proposed current source achieves widebands, biocompatibility, and high precision.
电阻抗断层成像系统需要一个具有宽带宽的高输出阻抗电流源。局限性主要出现在较高频率和非简单负载情况下。为了调节输出电流，需使幅度和相位自动达到预期值。设计了一种基于现场可编程门阵列的电流源。本文提出了一种双数模转换器差分电流源结构。通过测量与负载串联的采样电阻两端的电压，并使用所提出的动态参考点解调算法，可快速获取负载上的实际电流幅度和相位。通过自适应补偿模块，将输出电流调整到预期值。实验结果表明，在10 kHz至1.28 MHz频率范围内，该电流源的输出电阻可达10 MΩ，输出电容可小于0.8 pF。同时，补偿后电流幅度衰减小于0.016%，相位误差小于0.0025°。因此，所提出的电流源实现了宽带、生物相容性和高精度。
