Design of a wideband excitation source for fast bioimpedance spectroscopy

Abstract

Multi-frequency-one-time (MFOT) measurement of bioimpedance spectroscopy (BIS) can greatly reduce measurement time and grasp the transient physiological status of a living body compared with the traditional one-frequency-one-time (OFOT) measurement technology, and a wideband excitation source mixed with multiple frequencies is a crucial part of MFOT measurement of BIS. This communication describes a design of a wideband excitation source. Firstly, a multi-frequency mixed (MFM) signal containing seven primary harmonics is synthesized based on Walsh functions, which is a periodical and rectangular signal and whose 68.9% of the energy is homogeneously distributed on its seven 2nth primary harmonics. Then the MFM signal is generated by a field programmable gate array (FPGA), and a unipolar-to-bipolar convertor (UBC) is designed to convert the unipolar signal into bipolar signal. Finally, the bipolar MFM signal is driven by a voltage-controlled current source (VCCS). A 2R-1C series model is adopted as the load of the VCCS, and the simulated voltage response on the load is obtained based on the theoretical analysis. Experiments show that the practical waveform on the load matches well with the theoretical analysis, which indicates that the VCCS has a good performance on the MFM signal. The design of the wideband excitation source establishes a good foundation for fast measurement of BIS.

Interpulse multifrequency electrical impedance measurements during electroporation of adherent differentiated myotubes

“…However, traditional EIS approaches based on frequency sweeps are not feasible for monitoring the fast dynamical changes in the membrane during pulse application due to the long measuring time needed when compared with the short interpulse period (usually 1 s). Broadband signals such as binary [26], chirp or multisine excitations [27] have previously been proposed to study fast dynamical phenomena with EIS. Other attempts to study fast pore dynamics are based in time domain methods such as time-domain reflectometry [28] or time-domain dielectric spectroscopy [18].…”

Development of a Stair-Step Multifrequency Synchronized Excitation Signal for Fast Bioimpedance Spectroscopy

“…Like the MFM signal, the MFS signals are also synthesized based on the Walsh functions, which already have detailed description in [22]. Similarly, we can synthesize a MFS signal based on simple superposition of the Walsh functions SAL(2 k −1 , t ) in accordance with $\begin{array}{c}f\left(p,t\right)=\sum _{k=\mathrm{normal1}}^p\text{SAL}\left({\mathrm{2}}^{k-\mathrm{1}},t\right),\end{array}$ where p is the order of the MFS signal and also denotes the number of primary harmonics in f ( p , t ).…”

Broadband Bioimpedance Spectroscopy Based on a Multifrequency Mixed Excitation and Nuttall Windowed FFT Algorithm

“…According to the MFM signal synthesis principle introduced by the literature [21], let = 9; then the nine-frequency MFM signal (9, ) is synthesized and the time domain waveform of (9, ) within one period is shown in Figure 1. The harmonic amplitude spectra and power percentage spectra of (9, ) are shown in Figures 2(a) and 2(b), respectively, where the nine expected 2nth harmonics (the red solid points in Figure 1), namely, the 1st, 2nd, 4th, 8th, 16th, 32nd, 64th, 128th, and 256th harmonics (we called them primary harmonics thereafter) are obviously prominent.…”

“…The authors previously proposed a multifrequency mixed (MFM) signal whose majority (65% or more) of energy is concentrated on several expected 2nth primary harmonics [21], which provides a proper broadband excitation for MFS measurement BIS. With the broadband excitation, the complex impedance spectrum then can be just calculated as the ratio of the complex Fourier coefficients of the response voltage to the complex Fourier coefficients of the excitation current signal after FFT operations [15,22].…”

“…It is proved that windows with big side-lobe attenuation and high side-lobe roll-off rate can sufficiently reduce the spectral leakage [28]. This paper synthesizes a nine-frequency MFM signal (9, ) according to the previously proposed method [21] as the broadband excitation, and realizes multifrequency simultaneous (MFS) measurement of BIS based on a Nuttall windowed interpolation FFT Algorithm. The Nuttall window [29], which has excellent characteristics on side-lobe and main-lobe, is adopted to suppress spectral leakage before FFT, and a Nuttall windowed double-spectral-line interpolation FFT algorithm is developed to reduce the error of picket fence effects.…”