Abstract
This 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. DOI: http://dx.doi.org/10.5755/j01.eee.20.5.7115
Highlights
Electrical bioimpedance spectra are widely used to characterize the structure of tissues and cell cultures [1]
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
In bioimpedance measurements the signal-to-noise ratio (SNR) cannot be improved by increasing the overall amplitude of the excitation signal since it is limited to much lower values [2] than the signal ranges and power supply voltages of non-biologic measurement devices
Summary
Electrical bioimpedance spectra are widely used to characterize the structure of tissues and cell cultures [1]. The energy of the excitation signal must be spread between multiple frequencies during this timeframe Such an important criterion of the efficiency of measurements – the signal-to-noise ratio (SNR) of measured response signal – is proportional to the square of root-mean-square (RMS) values of frequency components of the excitation signal. In bioimpedance measurements the SNR cannot be improved by increasing the overall amplitude of the excitation signal since it is limited to much lower values [2] than the signal ranges and power supply voltages of non-biologic measurement devices. The smallest crest factor (CF = 1) have the waveforms of binary multifrequency signals (BMS).Comparison of RMS values of the frequency components of different wideband excitation signals is given in [4]. It is obvious that the spectral components with sparse frequencies attain higher RMS values in the composite signals with limited amplitudes.
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