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For measuring of the spectra of complex electrical impedance, the chirp excitation signals can be used. The analysis of the response signal of an object, often dynamical, in time, or circuit under test can be performed by short-time Fourier transform in the sliding time-domain window. Computationally more efficient and accurate could be the usage of the simple correlation (multiplication-and accumulation...
Developed testing platform is intended for creating dynamic time dependent impedance in order to evaluate the performance of impedance measurement devices. The device is targeted mostly for biomedical impedance devices and other applications where evaluation by using time invariant objects does not give enough information about the adequacy of impedance measurement device for the current application.
The impedance analyzers are widely used to measure, test and validate the properties of the materials, tissues, electrical and electronics networks etc. To make simple power-and cost-efficient device for real-time dynamical measurements in the wide frequency range, special binary waveforms excitation signals can be used, covering the desired spectrum points. Drawback of the using of the binary measurement...
This paper presents our work in the search for a realistic thorax impedance model that is suitable for the simulation of an impedance cardiography (ICG) signal model. The developed ICG signal model would be useful to evaluate the performance of e.g. algorithms for the separation of cardiac and respiratory signals. Five different impedance models of the thorax were studied to evaluate their suitability...
This paper presents a comparative study of multifrequency excitation signals that are suitable for fast bioimpedance spectroscopy. If properties of an object are changing fast or if the objects are moving fast, e.g. cells flowing within microfluidic channels, the excitation signal should cover the frequency range of interest in short timeframes. However, since shorter signals carry less energy this...
This paper reports on a novel system architecture for measuring impedance spectra of a biological tissue close to the tip of a hollow needle. The measurement is performed online using fast broadband chirp signals. The time domain measurement raw data are transformed into the transfer function of the tissue in frequency domain. Correlation technique is used to analyze the characteristic shape of the...
In this paper, using of short-time chirp excitation for the bio-impedance measurement is discussed. The short-time chirp waveforms have at least two advantages. First, flat and wideband amplitude spectrum together with shortness of signal enable fast and adequate estimation of the object under study. Second, low power consumption with more than 90% concentration of the generated excitation energy...
Using of Minimal Length Chirps (MLC) as excitation signals for the bioimpedance measurement is discussed in this paper. It is shown that reducing the length of chirps and thereby minimizing the required signal energy still allows for a fast and wideband estimation of the bioimpedance. This is very important in the field of implantable and wearable devices, where low power consumption is mandatory...
The paper discusses the usability of multi-frequency binary waveforms for broadband excitation in fast measurements of impedance spectrum of biological objects. It is shown that up to 70% of the energy of the amplitude spectrum of such two-level binary signals can be concentrated into the selected separate frequencies. The levels of selected frequency components are controllable in tens and hundreds...
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