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

Abstract

Bioimpedance spectroscopy (BIS) has become an important clinical indicator for monitoring the pathological status of biological tissues, and multifrequency simultaneous measurement of BIS may provide more accurate diagnostic information compared with the traditional frequency-sweep measurement technology. This paper proposes a BIS multifrequency simultaneous measurement method based on multifrequency mixed (MFM) signal excitation and a Nuttall windowed interpolation FFT algorithm. Firstly, the excitation source adopts the nine-frequency MFM signalf(9,t), which has excellent spectral characteristic and is very suitable for BIS measurement. On this basis, a Nuttall window is adopted to truncate sample data, and an interpolation FFT algorithm based on Nuttall window is built to perform spectral analysis, in which the parameter correction formula is provided based on polynomial approximation. A BIS measurement simulation experiment is performed on an RC three-element equivalent circuit, and results on the 9 primary harmonic frequencies ranging from 3.9 kHz to 1 MHz show a high accuracy with the impedance amplitude relative error|Ez|<0.3%, and the phase absolute error|Ep|<0.1°. This paper validates the feasibility of BIS multifrequency simultaneous measurement method and establishes an algorithm foundation for the development of practical broadband BIS measurement system.

Performance Analysis of an MLS-Based Interface for Impulse Response Estimation of Resistive and Capacitive Sensors

“…These systems exhibit a drawback related to the measurement time, which depends on the minimum frequency point used for the excitation. A more convenient choice in order to decrease the measurement time is the adoption of pseudo-random binary signals (PRBS), as excitation signals, in broadband EIS systems [11]- [14]. In particular, a subclass called maximum length sequences (MLS) results interesting for EIS [15].…”