Department of Electrical and Electronic Engineering, Tokyo Denki University, Tokyo 120-8551, Japan.
School of Allied Health Science, Kitasato University, Kanagawa 252-0373, Japan.
Sensors (Basel). 2021 Oct 20;21(21):6951. doi: 10.3390/s21216951.
Herein, we propose an impedance spectroscopy method using a mode-switching nonsinusoidal oscillator and apply this method for measuring the impedance of biological tissues and continuous impedance measurement. To obtain impedance spectra over a wide frequency range, we fabricated a novel nonsinusoidal oscillator incorporating binary counters and analog switches. This oscillator could periodically switch oscillation frequency through the mode switching of the feedback resistor. From the oscillation waveform at each oscillation frequency of this circuit (oscillator), we determined the impedance spectrum of a measured object using the discrete-time Fourier transform. Subsequently, we obtained the broad impedance spectrum of the measured object by merging odd-order harmonic spectral components up to the 19th order for each oscillation frequency. From the measured spectrum, the resistive and capacitive components of the circuit simulating bioimpedance were estimated with high accuracy. Moreover, the proposed method was used to measure the impedance of porcine myocardium; changes in the impedance spectrum of the myocardial tissue due to coagulation could be measured. Furthermore, rapid variations in the resistance value of a CdS photocell could be continuously measured using the proposed method.
在此，我们提出了一种使用模式切换非正弦振荡器的阻抗谱方法，并将该方法应用于生物组织的阻抗测量和连续阻抗测量。为了在宽频率范围内获得阻抗谱，我们制造了一种新型的非正弦振荡器，该振荡器结合了二进制计数器和模拟开关。通过反馈电阻的模式切换，该振荡器可以周期性地切换振荡频率。从该电路（振荡器）的每个振荡频率的振荡波形中，我们使用离散傅立叶变换确定被测物体的阻抗谱。随后，通过合并每个振荡频率的第 19 阶奇数阶谐波频谱分量，我们获得了被测物体的宽阻抗谱。从测量的光谱中，用电路模拟生物阻抗的电阻和电容分量可以高精度地估计。此外，该方法还用于测量猪心肌的阻抗；可以测量心肌组织的阻抗谱由于凝结而发生的变化。此外，使用所提出的方法可以连续测量 CdS 光电管的电阻值的快速变化。
