| 摘要 |
A method and apparatus for digital demodulation by means of correlation and further processing of signals obtained in the single and multi-frequency measurement of electrical bioimpedance or bioadmittance in which the amplitude of changes or rate of changes thereof can be determined with a higher amplitude resolution than before. It comprises: signal generation means which apply an excitation signal and a first measuring means (44, 46; 50, 52) for acquiring, sampling and digitizing a response signal to said excitation signal with respect to frequency content, amplitude and phase, whereas said excitation signal is either held at a constant, known amplitude and defined by a digital excitation waveform or measured by a second measuring means for acquiring, sampling and digitizing said excitation signal;
memory means (48, 58) for temporarily storing said digitized response signal and, optionally, said digitized excitation signal;
digital demodulation means (80; 81-86) for correlating for each frequency of the excitation signal applied digitized samples of said digitized response signal with corresponding discrete values of a sinusoidal reference signal to the excitation signal or said excitation signal, respectively;
processing means (60) for calculating for each frequency of the excitation signal applied complex values for the bioimpedance or bioadmittance from the output values of the digital demodulation means,
a first separating means (64) for separation the base bioimpedance or bioadmittance from said waveforms; and either a second separating means (66) for separation the changes in the bioimpedance or bioadmittance from said waveforms, and a differentiating means (67) for obtaining the rate of change of said changes, or a differentiating means (67) means for obtaining the rate of change in the bioimpedance or bioadmittance waveforms; as well as
recording means (110) for either recording the temporal course or recording the rate of change in said waveforms. |
