A Method of Synchronous Sampling in Multifrequency Bioimpedance Measurements

Uniform sampling of a known carrier or of multiple carriers is a preferred method for measuring of biomodulation of a tissue impedance. Still, due to limits to parameters of analog-to-digital converters (ADC) and limited availability of signal processing power and/or energy resources, the implementation of algorithms based on conventional discrete Fourier transform is not effective. A new method for multichannel and multifrequency synchronous sampling with summing up the obtained samples is proposed instead of application of the Fourier transform. In addition, a 6 to 7 bit enhancement of digitizing resolution is achieved by compensation of a constant part of the response voltage. As a result, the 0.01% biomodulation can be demodulated and processed when using up to 1 MHz excitation