Yang Yuxiang, Bian He, Du Fangling, Sun Qiang, Wen He
Department of Precision and Instrumentation Engineering, Xi'an University of Technology, Xi'an 710048, China.
Department of Electronic Engineering, Xi'an University of Technology, Xi'an 710048, China.
Biomed Res Int. 2014;2014:143461. doi: 10.1155/2014/143461. Epub 2014 Feb 19.
Wideband excitation signal with finite prominent harmonic components is desirable for fast bioimpedance spectroscopy (BIS) measurements. This work introduces a simple method to synthesize and realize a type of periodical stair-step multifrequency synchronized (MFS) signal. The Fourier series analysis shows that the p-order MFS signal f(p, t) has constant 81.06% energy distributed equally on its p 2(n)th primary harmonics. The synthesis principle is described firstly and then two examples of the 4-order and 5-order MFS signals, f(4, t) and f(5, t), are synthesized. The method to implement the MFS waveform based on a field-programmable gate array (FPGA) and a digital to analog converter (DAC) is also presented. Both the number and the frequencies of the expected primary harmonics can be adjusted as needed. An impedance measurement experiment on a RC three-element equivalent model is performed, and results show acceptable precision, which validates the feasibility of the MFS excitation.
具有有限显著谐波成分的宽带激励信号对于快速生物阻抗谱（BIS）测量是理想的。本文介绍了一种合成并实现一种周期性阶梯多频同步（MFS）信号的简单方法。傅里叶级数分析表明，p阶MFS信号f(p, t)有81.06%的恒定能量均匀分布在其p/2(n)次基波谐波上。首先描述了合成原理，然后合成了4阶和5阶MFS信号f(4, t)和f(5, t)的两个示例。还提出了基于现场可编程门阵列（FPGA）和数模转换器（DAC）实现MFS波形的方法。预期基波谐波的数量和频率都可以根据需要进行调整。在一个RC三元等效模型上进行了阻抗测量实验，结果显示精度可接受，这验证了MFS激励的可行性。
