Bioelectrical impedance analysis and bioelectrical impedance spectroscopy (BIA/BIS) of tissues reveal important information on molecular composition and physical structure that is useful in diagnostics and prognostics. The heterogeneity in structural elements of cells, tissues, organs, and the whole human body, the variability in molecular composition arising from the dynamics of biochemical reactions, and the contributions of inherently electroresponsive components, such as ions, proteins, and polarized membranes, have rendered bioimpedance challenging to interpret but also a powerful evaluation and monitoring technique in biomedicine. BIA/BIS has thus become the basis for a wide range of diagnostic and monitoring systems such as plethysmography and tomography. The use of BIA/BIS arises from (i) being a noninvasive and safe measurement modality, (ii) its ease of miniaturization, and (iii) multiple technological formats for its biomedical implementation. Considering the dependency of the absolute and relative values of impedance on frequency, and the uniqueness of the origins of the α-, β-, δ-, and γ-dispersions, this targeted review discusses biological events and underlying principles that are employed to analyze the impedance data based on the frequency range. The emergence of BIA/BIS in wearable devices and its relevance to the Internet of Medical Things (IoMT) are introduced and discussed.

Testing is an important part of the design flow in the semiconductor industry. Unfortunately, it also consumes up to half of the production cost. On-silicon stimulus generators and response analyzers can be integrated with the Device-Under-Test (DUT) to reduce production costs with a minimum increment in power and area consumption. This practice is known as the Built-In Self-Test (BIST). This work presents a single-tone generator for BIST applications that is based on the Harmonic-Canceling (HC) technique. The main idea is to cancel or filter out the harmonics of a square-wave signal in order to obtain a highly pure sine wave. The design challenges of this technique are the precise implementation of irrational coefficients in silicon and the strong dependence of the output’s linearity on the coefficients’ precision. In order to reduce this dependence, this work introduces an irrational coefficient generator that is based on the recursive use of special matrices called skew-circulant matrices (SCMs). A complete study of the SCM-based HC synthesizer, its properties, and the proposed implementation in 180 nm CMOS technology are presented. The measured results show that the proposed HC synthesizer is able to filter out up to the 47th harmonic of a given square wave and to generate signals from 0.8 to 100 MHz with a maximum Spurious-Free Dynamic Range (SFDR) of 66 dB.

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