Simultaneous multi-frequency bio-impedance measurement applying synchronised uniform or non-uniform sampling

Abstract

The paper presents some possibilities to perform multi-frequency bio-impedance measurement simultaneously for K tissue-channels (MIMO measurement). The multi-sine excitation currents of all the channels have frequency-sets which 1) consist of L frequencies and 2) are different enough for separating the responses of all the L · K frequencies and close enough for comparing the frequency responses of the tissue-channels in (neighbourhoods of) L points. The approach is based on use of such excitation frequencies and the sampling frequency (or sampling frequencies, simultaneous applying of which leads to non-uniform sampling), which all are properly chosen integer multiples of the basis frequency fE ≥ 1/T0, where T0 is the desired measurement interval. Assuming that the responses to sinusoidal excitations are also sinusoidal (the non-linear distortions are negligible), every response and corresponding value of the complex bioimpedance can be estimated applying numerical synchronous detection. In this process the real and imaginary parts of a bioimpedance can be found simply and simultaneously for all the tissue-channels and frequencies. © Springer-Verlag 2007.