| abstract |
Methods and apparatus for digital demodulation of signals obtained in the measurement of electrical bioimpedance or bioadmittance of an object. One example comprises: generating an excitation signal of known frequency content; applying the excitation signal to the object; sensing a response signal of the object; sampling and digitizing the response signal to acquire a digitized response signal representing the response signal with respect to frequency content, amplitude and phase; correlating, for each frequency f AC of the excitation signal applied, digitized samples of the response signal, with discrete values representing the excitation signal; calculating, using the correlated signals for each frequency f AC of the excitation signal applied, complex values for the bioimpedance Z(f AC ); providing, over time, a set of digital bioimpedance waveforms Z(f AC ,t)); separating the base bioimpedance Z 0 (f AC ), from the waveforms; and separating the changes of bioimpedance ΔZ(f AC ,t), from the waveforms. |