FPGA Synchronous Phase Detection System for bioimpedance computing applications

This paper describes the design of a phase synchronous detection system as a solution of the digital stage for high frequency bioimpedance computing in a four-electrodes-measuring configuration. The proposed design is implemented on reconfigurable hardware. The phase detection system is proposed as part of a bioimpedance measuring system, where biompedance value is obtained as a complex division of voltage and current in the measuring cell. The use of parallel processing to obtain such complex values allows high frequency bioimpedance measurements. Since this project is focused only on the digital stage design of the bioimpedance measurement system, the phase delay between the biological tissue current and voltage is digitally generated with delay blocks. In this way bioimpedance value result is tested for a given delay, corresponding to a phase difference. According to obtained results, small measurement errors for wideband frequency range are achieved with the proposed system.