Cole-Cole Bio-Impedance Parameters Estimation From Sinewave Excitation Signal with a Minimum Number of Frequencies

Cole-Cole impedance model is widely used in electrical bioimpedance measurements to characterize biological tissues. Accurate estimation of the Cole-Cole impedance parameters is crucial in bioimpedance measurements to obtain reliable results. Many studies have proposed approaches to estimate the Cole-Cole impedance parameters with high accuracy and minimal error. However, there is still a need to investigate the minimum number and positions of frequencies required to accurately estimate the Cole-Cole impedance parameters and, thus, efficiently reconstruct the impedance spectrum. This paper proposes a novel approach to reconstruct Cole-Cole bioimpedance parameters using a minimum number of frequencies. The study utilizes an IV method-based system implemented on an STM32 platform to perform impedance measurements. The results obtained from this system are compared with those obtained from a commercial impedance analyzer, Agilent 4294A, in the frequency range of 1 kHz to 1 MHz. After applying nonlinear least squares fitting, the results of two and three impedance measurement frequencies showed that selecting certain positions significantly affects the accuracy. Using three frequencies, including the extreme points and an additional point in the high-frequency range, gave better results with 0.56%. The results described here may be useful in other implementations of impedance spectroscopy.