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In this paper, we present a quadrature-phase oscillator that can provide four output voltages while operating from a single 0.5 V supply. The oscillator is based on two cross-coupled modified differential pair cells and provides signals with a phase difference of ± 180 ° or ± 90 ° depending on the chosen output nodes. A test chip with an active area of 0.175 mm2 was designed and fabricated in a 65-nm CMOS process and its measurement results show a phase noise of −119.5 dBc/Hz at 1 MHz offset from a carrier frequency of 1.967 GHz while consuming 6.15mW. Finally, experimental results show a FoM of 185.5 dB for the core oscillator and a quadrature-phase error of less than ± 0.5 °. [ABSTRACT FROM AUTHOR]

Double-dispersion impedance models are important for the accurate fitting of spectral impedance measurements in Electrical Impedance Spectroscopy (EIS). While the Cole–Cole model is the most widely known, it is possible to define double-dispersion Cole–Davidson and Havriliak–Negami models as well. In this work, we show that more freedom can be exercised when these three models are combined together and that this combination can be done in various forms. Experimental results using a two-stage optimization algorithm applied on the suggested models are provided. [ABSTRACT FROM AUTHOR]

The original version of this article unfortunately contained a mistake. The co-authors’ affiliation details were incorrect in the original publication of this article. [ABSTRACT FROM AUTHOR]

A novel non-uniform Kramers–Kronig Transform algorithm for bioimpedance phase extraction is proposed and tested in this work. The algorithm error is studied and compared with a previously proposed phase extraction technique, also based on the Kramers–Kronig transform. Results using simulated datasets and experimental datasets confirm the excellent performance of the algorithm. [ABSTRACT FROM AUTHOR]

This corrects the article DOI: 10.1038/srep38568 [ABSTRACT FROM AUTHOR]

Presents a corrected version of the article, entitled 'A comparison of three multipliers based on the V[sub gs]² technique for low-voltage applications,' by Brent Maundy and Mona Maini, published in the July 2003 issue of the journal 'IEEE Transactions on Circuits and Systems'.

In this paper we use a least-squares fitting routine to approximate the stopband ripple characteristics of fractional-order inverse Chebyshev lowpass filters which have fractional-order zeros and poles. MATLAB simulations of $$(1+\alpha )$$ -order lowpass filters with fractional steps from $$\alpha =0.1$$ to $$\alpha =0.9$$ are given as examples. SPICE simulations of 1.2-, 1.5-, and 1.8-order lowpass filters and experimental results of a 1.5-order filter using approximated fractional-order capacitors in a Multiple-Input Biquad circuit validate the implementation of these circuits. [ABSTRACT FROM AUTHOR]

In this work, a generic impedance modeling technique is proposed. The technique is able to identify a circuit model that is most suitable for fitting measured impedance magnitude data using a genetic algorithm solver as well as the optimum circuit model parameters. Experimentally measured and simulated data sets with different noise levels are used to validate the technique. [ABSTRACT FROM AUTHOR]

The measurement of bio-impedance spectra at ultra low frequencies (sub-Hz) is known to require a considerably long time with the classical frequency-sweep method or other narrow-band periodic excitation signals. In this work, an impedance measurement technique based on using wide-band chaotic signals is proposed and experimentally validated over the frequency range [Formula: see text]. The technique was tested in both potentiostatic and galvanostatic modes, first using commercial components and then using an enhanced Howland current pump designed and fabricated in a 65nm CMOS technology. The accuracy of the proposed technique was assessed on fruit samples compared to measurements conducted using a research-grade Biologic VSP-300 electro-chemical station., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

In the field of bioimpedance measurements, the Cole impedance model is widely used for characterizing biological tissues and biochemical materials. In this work, a nonlinear least squares fitting is applied to extract the double-dispersion Cole impedance parameters from simulated magnitude response datasets without requiring the direct impedance data or phase information. The technique is applied to extract the impedance parameters from MATLAB simulated noisy magnitude datasets showing less than 1.2 % relative error when 60 dB SNR Gaussian white noise is present. This extraction is verified experimentally using apples as the Cole impedances showing less than 3 % relative error between simulated responses (using the extracted impedance parameters) and the experimental results over the entire dataset.