Capacitive electrocardiogram (cECG) systems are increasingly used for the monitoring of cardiac activity. They can operate within the presence of a small layer of air, hair or cloth and do not require a qualified technician. They can be integrated into wearables, clothing or objects of daily life, such as beds or chairs. While they offer many advantages over conventional electrocardiogram systems (ECG) that rely on wet electrodes, they are more prone to be affected by motion artifacts (MAs). These effects, which are due to the relative movement of the electrode in relation to the skin, are several orders of magnitude higher than ECG signal amplitudes, they occur in frequencies that might overlap with the ECG signal, and they may saturate the electronics in the most severe cases. In this paper, we provide a detailed description of MA mechanisms that translate into capacitance variations due to electrode-skin geometric changes or into triboelectric effects due to electrostatic charge redistribution. A state-of-the-art overview of the different approaches based on materials and construction, analog circuits and digital signal processing is provided as well as the trade-offs to be made using these techniques, to mitigate MAs efficiently.

This brief presents a novel level-shifter circuit for high-frequency high-voltage (HV) gate-drives. The proposed level shifter (LS) is designed based on a capacitive-coupler/current mirror/ latch structure which helps to extend operation voltage of a floating supply into the negative range, achieves sub-ns and constant delay, and consumes very low power from the floating supply. Additionally, common-mode noise cancellers based on a cross-current mirror and transmission gates are also presented to enhance the dV/dt immunity of the LS against slewing of the floating ground. Implemented in 0.18 μm HV BCD-on-SOI (bipolar-CMOS-DMOS on silicon-on-isolator) process, the post-layout simulation of the proposed design shows a delay of 680 ps, 200 V/ns of dV _SSF /dt slew rate immunity, It dissipates no static power and only 8.1 pJ/transition from the floating supply, improving FoM ¹ and FoM ² of the proposed LS by 3 times and 11.7 times compared to respective state-of-the-art works.

Traditional capacitive electrocardiogram (cECG) electrodes suffer from limited patient comfort, difficulty of disinfection and low signal-to-noise ratio in addition to the challenge of integrating them in wearables. A novel hybrid flexible cECG electrode was developed that offers high versatility in the integration method, is well suited for large-scale manufacturing, is easy to disinfect in clinical settings and exhibits better performance over a comparable rigid contactless electrode. The novel flexible electrode meets the frequency requirement for clinically important QRS complex detection (0.67–5 Hz) and its performance is improved over rigid contactless electrode across all measured metrics as it maintains lower cut-off frequency, higher source capacitance and higher pass-band gain when characterized over a wide spectrum of patient morphologies. The results presented in this article suggest that the novel flexible electrode could be used in a medical device for cECG acquisition and medical diagnosis. The novel design proves also to be less sensitive to motion than a reference rigid electrode. We therefore anticipate it can represent an important step towards improving the repeatability of cECG methods while requiring less post-processing. This would help making cECG a viable method for remote cardiac health monitoring.

Optical receiver front ends that are intentionally designed to have a bandwidth low enough that significant inter-symbol interference (ISI) is introduced are becoming commonplace. Although the resultant ISI must be removed using an equalizer, the lower bandwidth allows for higher gain in the front-end's first stage, lower input-referred noise, and fewer gain stages. With fewer main-amplifier stages, power dissipation is reduced. The noise analysis of these front ends presents several challenges. This paper derives integrated input-referred noise for inverter-based shunt-feedback transimpedance amplifiers from first principles and highlights the importance of correctly estimating the gain and noise bandwidth of the receiver. The notion of the effective gain of the receiver is introduced, which is lower than the midband gain typically used in noise calculations. The analysis of the inverter-based TIA is used to discuss the important design tradeoffs depending on the type of equalizer used. Integrated input-referred noise is derived and compared for front ends using decision-feedback equalizers (DFEs), continuous-time linear equalizers, and feed-forward equalizers. The simulation results show that a DFE-based receiver achieves the lowest input-referred noise.

This paper presents a microring resonator-based weight function for neuromorphic photonic applications achieving a record-high precision of 11.3 bits and accuracy of 9.3 bits for 2 Gbps input optical signals. The system employs an all-analog self-referenced proportional-integral-derivative (PID) controller to perform real-time temperature stabilization within a range of up to 60 $^{\circ }$C. A self-calibrated weight function is demonstrated for a range of 6 $^{\circ }$C with a single initial calibration and minimal accuracy and precision degradation. By monitoring the through and drop ports of the microring with variable gain transimpedance amplifiers, accurate and precise weight adjustment is achieved, ensuring optimal performance and reliability. These findings underscore the system's robustness to dynamic thermal environments, highlighting the potential for high-speed reconfigurable analog photonic networks.

The integration of optical receivers in nanoscale CMOS technologies is challenging due to less intrinsic gain and more noise compared to SiGe BiCMOS technologies. Recent research revealed that low-noise, high-gain, and low-power CMOS optical receivers can be designed by limiting the bandwidth of the front-end followed by equalization techniques that benefit from good switching characteristics offered by CMOS technologies. In this tutorial brief, the operation of decision-feedback equalization, feed-forward equalization, and continuous-time linear equalization is reviewed in the context of high baud-rate 2-PAM and 4-PAM modulation. Recent advances and techniques in 4-PAM optical receivers are reviewed and compared in terms of speed, sensitivity, bandwidth, and efficiency.