Wide-Bandwidth Biological Impedance Spectroscopy System Based on the Digital Lock-In Technique

The spectra of biological impedance can reveal physiological conditions and biological events of biological samples. This paper presents the development of a novel biological impedance spectroscopy system using an improved digital lock-in technique. The hardware of the system mainly consists of a current source, a voltage detector, a clock generator, and a field-programmable gate array (FPGA) device. Digital phase-sensitive detection algorithms including direct digital synthesis, digital multipliers, and digital filters were implemented in the FPGA. Test results show that the proposed spectroscopy has good performance from low frequency to 5MHz with 1% accuracy. It will be suitable for high-accuracy biological impedance spectra analysis in either in vitro or in vivo conditions.