Structured Approach and Impedance Spectroscopy Microsystem for Fractional-Order Electrical Characterization of Vegetable Tissues

Accuracy measurement of the impedance over a spread spectrum is the foundation of impedance spectroscopy (IS) technique, which has been recently proposed as a simple noninvasive technique for impedance spectrum measurement of a biological material (BM). This measurement is used to develop the equivalent electrical model (EEM) and to perform electrical characterization of the BM. In this paper, we propose a suitable approach for high-reliability electrical characterization of vegetable tissues by using a high-accuracy impedance spectrum measurement based on a structured algorithm, a flexible IS microsystem, and fractional-order (FO) models. The designed microsystem uses minimal discrete circuits and a programmable mixed-signal circuit, and it is validated by using EEMs of integer-order (IO), that is, the IS measures were compared with the simulation results. Also, impedance spectrum measures of vegetable tissues are carried out using the microsystem. In this case, five EEMs described by IO and FO differential equations are used to perform the parametric optimization using the Nelder-Mead "simplex" algorithm. Taking into account the obtained simulation results and experimental measures, it is possible to mention that the structured approach is suitable for applications that require to measure the bioimpedance over a spread spectrum, such as electrical IS (EIS) and electrical impedance tomography (EIT).