Development of a Stair-Step Multifrequency Synchronized Excitation Signal for Fast Bioimpedance Spectroscopy

Abstract EN

Wideband excitation signal with finite prominent harmonic components is desirable for fast bioimpedance spectroscopy (BIS) measurements.

This work introduces a simple method to synthesize and realize a type of periodical stair-step multifrequency synchronized (MFS) signal.

The Fourier series analysis shows that the p-order MFS signal f(p,t) has constant 81.06% energy distributed equally on its p 2nth primary harmonics.

The synthesis principle is described firstly and then two examples of the 4-order and 5-order MFS signals, f(4,t) and f(5,t), are synthesized.

The method to implement the MFS waveform based on a field-programmable gate array (FPGA) and a digital to analog converter (DAC) is also presented.

Both the number and the frequencies of the expected primary harmonics can be adjusted as needed.

An impedance measurement experiment on a RC three-element equivalent model is performed, and results show acceptable precision, which validates the feasibility of the MFS excitation.