AD8302-based polar demodulator interface for impedance spectroscopy oriented to biomedical applications

This paper proposes a polar demodulator circuit architecture for electrical impedance spectroscopy. The proposed system implements a dynamic gain inverting amplifier and a signal network conditioning technique to effectively utilize the AD8302 RF/IF gain and phase detector across a wide frequency range. The implemented feedback gain control allows the integrated circuit to expand the measurable impedance range while maintaining high linearity of response from 100 Hz to over 10 MHz exhibiting the maximum modulus and phase errors of 14.42% and 5.73°, respectively. This performance represents an advancement over existing impedance measurement systems that implements commercial ICs, particularly in applications where wide-range, high-accuracy measurements are critical. The architecture enable a multifrequency electrical bioimpedance spectroscopy across a broad frequency spectrum where low and high-frequency information provide valuable analytical insights.