Efficient Excitation Signals for the Fast Impedance Spectroscopy
AbstractThis paper deals with finding the highly efficient multifrequency excitation waveforms for fast bioimpedance spectroscopy. However, the solutions described here could be useful also in other fields of impedance spectroscopy. Theoretically, the useful excitation power of optimized binary multifrequency signals (BMS) exceeds the power of comparable multisine waveforms. However, part of power of the BMS waveforms is spread between higher harmonics of the wanted frequency components. In practical use of voltage excitation, the higher harmonics complicate the signal processing and produce current spikes passing through the capacitive elements of the impedance to be measured. In the paper, we show that the excitation power of well-optimized multisine with decaying amplitudes comes close to the power of comparable binary waveform while reducing the problems caused by unwanted frequency components. This allows simpler signal processing. Besides, we also show that the overall efficiency of using of the multisine excitation in impedance measurement becomes even higher efficient than the BMS in practice, despite the fact that the power of binary waveforms is the highest.
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