Nonlinear dynamical systems such as biological systems require substantial resources for digital circuit implementation due to their nonlinearity. This study approximates these systems by converting to the quantized-state system (QSS) solved using the forward Euler method and efficiently implements them on a field-programmable gate array (FPGA). Focusing on coupled nonlinear oscillators that mimic neural circuits, we evaluate the benefits and limitations of the QSS in terms of hardware resource usage and accuracy compared to the original system solved using the forward Euler method. The results provide valuable insights for the miniaturization and energy efficiency of neuromorphic hardware.

This letter presents an integer-N quadrature oversampling phase-locked loop (QOPLL) operating at 5.76-6.48 GHz with low RMS jitter. The QOPLL features a calibration-free gain-boosting quadrature oversampling mechanism. The proposed gain-boosting quadrature oversampling mechanism addresses the incompatibility issues in conventional oversampling mechanisms and gain-boosting techniques. It enhances in-band phase noise performance while eliminating the need for phase detector gain calibration. An isolated reference sampling phase detector (IRSPD) has been developed to ensure quadrature phase accuracy and improve phase detector gain. The QOPLL is fabricated in a 40-nm CMOS process. Measurement results demonstrate an RMS jitter of 103 fs, integrated from 10 kHz to 100 MHz. The reference spur is -71.26 dBc. The power consumption is 15 mW.

With the increasing demand for health monitoring and biometric identification technologies, radar-based heartbeat signal extraction techniques have been widely applied and deeply researched. This article proposes a time-domain method for heartbeat signal extraction, employing a cubic spline-based heartbeat enhancement algorithm combined with an adaptive bandpass filter. The proposed method offers significant advantages, including a simplified computational process and reduced time delay compared to conventional signal decomposition techniques, making it highly suitable for real-time applications. Additionally, it provides higher confidence and better interpretability than signal extraction methods based on neural networks. To achieve this, the method enhances the heartbeat signal of the continuous-wave (CW) radar output signal using cubic spline curve interpolation. The heartbeat signal is subsequently extracted by dynamically adjusting the frequency range of a bandpass filter. The method is implemented on a 2.4 GHz CW radar system based on a phase discriminator, which features a simpler structure and higher accuracy compared to traditional quadrature receivers. Experimental results in multiple subjects validate the effectiveness of the proposed approach, demonstrating an average heartbeat count accuracy of up to 98.06% in the time domain compared to the reference signal collected by the wearable sensor. Furthermore, the method achieves a computational complexity of O(N), highlighting its efficiency and potential for practical deployment.

IGBT module requires accurately intermediate layer temperatures (ILT) monitoring to ensure system safety and reliability. Considering critical failure factor of solder layer voids, this paper implements real-time monitoring to IGBT module ILT using DT. By deriving the nonlinear relationship between thermal resistance of solder layer and junction temperature, a mathematical model is refined to more precisely reflect the actual thermal behavior of IGBT. A nonlinear intermediate layer temperatures observer is designed to further improve the accuracy. Experimental validation demonstrates that, the proposed observer significantly enhances the precision with an error of only 0.1% compared to traditional methods.

A novel parameter extraction method for the Schottky diode’s equivalent-circuit model is proposed, and used to design high-efficiency microwave rectifier circuits. This method only use the Vector Network Analyzer (VNA) to extract the nonlinear intrinsic parameters and linear parasitic parameters in the equivalent circuit through the S-parameters of Schottky diode ports measured under different bias voltages. Taking the Schottky diode HSMS270B as an example, the parameters are extracted and modeled by this method, and it is verified that the simulation results are strongly correlated with the measured results in a microwave rectifier circuit with the operating frequency of 2.45 GHz, particularly in terms of the relationship between the output voltage of the rectifier circuit and the input power.