Aspects of Using Chirp Excitation for Estimation of Bioimpedance Spectrum

Paavle, Toivo; Min, Mart; Parve, Toomas

doi:10.5772/37315

Cited by 10 publications

(7 citation statements)

References 22 publications

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“…It is conceivable that some applications need, for example, more or different signal frequencies than in this work suggested. Additionally, the implementation of multi-frequency excitation currents, such as chirp signals [21], might be useful in the future. Some measurement applications might also need a different current source circuit topology.…”

Section: Discussionmentioning

confidence: 99%

Galvanically Decoupled Current Source Modules for Multi-Channel Bioimpedance Measurement Systems

2017

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Abstract:Bioimpedance measurements have become a useful technique in the past several years in biomedical engineering. Especially, multi-channel measurements facilitate new imaging and patient monitoring techniques. While most instrumentation research has focused on signal acquisition and signal processing, this work proposes the design of an excitation current source module that can be easily implemented in existing or upcoming bioimpedance measurement systems. It is galvanically isolated to enable simultaneous multi-channel bioimpedance measurements with a very low channel-coupling. The system is based on a microcontroller in combination with a voltage-controlled current source circuit. It generates selectable sinusoidal excitation signals between 0.12 and 1.5 mA in a frequency range from 12 to 250 kHz, whereas the voltage compliance range is ±3.2 V. The coupling factor between two current sources, experimentally galvanically connected with each other, is measured to be less than −48 dB over the entire intended frequency range. Finally, suggestions for developments in the future are made.

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Section: Discussionmentioning

confidence: 99%

Galvanically Decoupled Current Source Modules for Multi-Channel Bioimpedance Measurement Systems

2017

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“…Unlike the frequency sweep, where the frequency sweep is stepwise, the frequency function in chirp signals is continuous. This frequency function defines the type of chirp as linear, exponential, logarithmic, etc [16,17]. Among the aforementioned signals, only linear chirp signals keep the amplitude spectrum quasi-flat, and therefore two of its variants are studied: the linear sine chirp and the linear signum chirp.…”

Section: Chirp Signalsmentioning

confidence: 99%

“…The linear signum chirp uses a rectangular pulsewave signal as a signal base, with the same frequency function formula as the linear sine chirp f (t) defined in (2). The term 'signum' comes from a possible interpretation of this signal as a sign of the linear sine chirp [16]. The mathematical equation of this signal can be described as in (3):…”

Section: Linear Sine Chirpmentioning

confidence: 99%

“…This equation cognates with the energy efficiency in [16] and power efficiency in [32], and is used as a metric to evaluate the energy of the waste signal during signal generation, compared to the signal energy to be used in impedance spectroscopy. In table 6, a comparison between the signals based on the energy efficiency for the full spectrum and the energy efficiency within the frequency range of interest (1-100 kHz) is depicted.…”

Section: Useful Spectrum and Energy Efficiencymentioning

confidence: 99%

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Critical implementation issues of excitation signals for embedded wearable bioimpedance spectroscopy systems with limited resources

Kallel

Bouchaala

Kanoun

2021

Meas. Sci. Technol.

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Wideband excitation signals are essential in bioimpedance spectroscopy for measurements in a time ensuring a quasi-stable measurement condition. In particular, for wearable biomedical systems, due to limited system resources, several aspects regarding measurement time, crest factor, slew rate requirements, frequency distribution, amplitude spectrum, and energy efficiency need to be thoroughly investigated. In this paper, we present an investigation of excitation signals, which includes not only the theoretical aspects but also aspects of real implementation on microcontroller-based systems. At a fixed number of samples and sampling rate, we investigate the implementability of signal frequencies and the resulting spectral efficiency. We focus on sources of signal distortion due to timer and amplitude deviations. The results show that for 4096 samples and a sampling frequency of 1 MHz, wideband signals are 2.76 times faster than a stepped frequency sweep. The multisine signal provides a better energy efficiency and has a lower slew rate requirement on hardware (around 0.3 V µs−1), but has a relatively high crest factor, even after optimization. An exemplary investigation of the distortion of the time/frequency and amplitudes following implementation on a standard industrial advanced RISC machines microcontroller has shown that a sampling rate compensation is required to overcome timer inaccuracies. Furthermore, non-return-to-zero binary signals are more sensitive to distortion due to hardware-related issues and have a lower signal-to-distortion-and-noise (SINAD) ratio than 24 dB, which is lower than the multisine signal, having a SINAD of 31 dB.

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“…By using a simple multiplexing algorithm it is possible to realize up to 16 current and 16 voltage channels with four 8-to-1 multiplexers. In addition to the single frequency measurement mode, the system is able to use chirp signal excitation [13] and to determine the magnitude as well as the phase of the impedances. Depending on the multiplexing algorithm, the system allows measurements of up to 3480 impedance spectra per second (ISPS).…”

Section: Introductionmentioning

confidence: 99%

A FPGA-Based Broadband EIT System for Complex Bioimpedance Measurements—Design and Performance Estimation

et al. 2015

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Electrical impedance tomography (EIT) is an imaging method that is able to estimate the electrical conductivity distribution of living tissue. This work presents a field programmable gate array (FPGA)-based multi-frequency EIT system for complex, time-resolved bioimpedance measurements. The system has the capability to work with measurement setups with up to 16 current electrodes and 16 voltage electrodes. The excitation current has a range of about 10 µA to 5 mA, whereas the sinusoidal signal used for excitation can have a frequency of up to 500 kHz. Additionally, the usage of a chirp or rectangular signal excitation is possible. Furthermore, the described system has a sample rate of up to 3480 impedance spectra per second (ISPS). The performance of the EIT system is demonstrated with a resistor-based phantom and tank phantoms. Additionally, first measurements taken from the human thorax during a breathing cycle are presented. OPEN ACCESSElectronics 2015, 4 508

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Aspects of Using Chirp Excitation for Estimation of Bioimpedance Spectrum

Cited by 10 publications

References 22 publications

Galvanically Decoupled Current Source Modules for Multi-Channel Bioimpedance Measurement Systems

Galvanically Decoupled Current Source Modules for Multi-Channel Bioimpedance Measurement Systems

Critical implementation issues of excitation signals for embedded wearable bioimpedance spectroscopy systems with limited resources

A FPGA-Based Broadband EIT System for Complex Bioimpedance Measurements—Design and Performance Estimation

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