International Journal of Numerical Modelling-Electronic Networks Devices and Fields最新文献

In this paper, analytical models have been developed for the analysis of flicker and thermal noise in a double-gate junctionless MOSFET with double metal gates (DMDG). We first formulate drain current and bulk charge density models of our proposed device structure. The drain current as well as the noise models are validated with experimental results, and excellent matching has been observed. The effect of temperature on the noise power density spectrum is also studied. The modeling results show that flicker noise reduces with an increase in the length and thickness of the channel. This is due to the reduced influence of traps and fluctuations on carrier mobility. The flicker noise changes inversely with V_gs, as it increases with an increase in V_ds and temperature. The thermal noise decreases when the thickness and doping concentration of the channel, along with the gate-oxide thickness, are increased. This results from more ionized impurity scattering and weaker gate control over the channel. Also, the thermal noise enhances with the increase in V_gs, whereas it varies inversely with V_ds. The proposed model can be helpful to analyze the influence of noise on the DMDG device characteristics, which has potential applications in analog/RF circuits.

This paper presents a data-driven methodology for designing a highly efficient power amplifier (PA) incorporating spoof surface plasmon polariton (SSPP) based matching networks. The PA employs a CG2H40010F GaN HEMT transistor and is optimized to operate across 3.0–4.8 GHz. Log-periodic line (LPL)-based SSPP unit cells are utilized in both the input and output matching networks to achieve enhanced field confinement and circuit miniaturization. A two-stage design approach is adopted: initial optimization is performed through harmonic balance simulations using simplified real frequency technique (SRFT), followed by electromagnetic (EM) co-simulation to capture full-wave effects. A Bayesian Optimization framework is applied to systematically tune the SSPP geometrical parameters and LPL configurations, using output power (P_out), power-added efficiency (PAE), and gain as optimization objectives. The final design demonstrates a peak P_out of 43 dBm, a drain efficiency exceeding 80%, and a gain of 13.6 dB. The proposed approach enables an efficient and compact SSPP-based PA design without requiring hardware measurements, offering a promising direction for future wideband front-end amplifier solutions.

This research addresses instability in GaN HEMT half-bridge circuits caused by high switching speeds and parasitic parameters, which induce oscillations at the gate-source and drain-source terminals. These oscillations increase switching loss, risk false triggering, and can lead to device failure. A small-signal model based on a bootstrap driver is proposed to study this phenomenon. During dead time, reverse conduction and parasitic-induced positive feedback worsen the oscillation. The system is modeled as a second-order underdamped network, and a damping ratio is introduced to evaluate stability. Strategies such as reducing common source inductance and optimizing gate resistance are used to improve damping. Additionally, an RCD circuit is added across the gate-source to absorb resonant energy and suppress negative voltage spikes during turn-off. LTspice simulations and pulse testing using GS66508B devices show a reduction in negative spikes from −3.35 to −1.20 V and in turn-off loss from 8.23 to 7.68 μJ. These results verify the effectiveness of the proposed method in enhancing switching stability.

The recent developments in wireless technology have given rise to the emergence of wearable antennas (Ants.). These Ants. are employed in the context of wireless body area networks (WBANs), which find applications in diverse fields including healthcare, military operations, sports, and identification systems. In this work, an ultra-wideband, compact, low-profile, and low specific absorption rate (SAR), metamaterial (MTM) integrated wearable Ant. featuring a flexible for WBAN applications is presented. The Ant. and MTM structures are designed on a felt substrate with sizes of 50 × 50 × 1 mm³ and 61.60 × 61.60 × 2 mm³, respectively. The proposed MTM Ant. has a physical thickness of only 4.14 mm, offering the thinnest profile among similar MTM-integrated UWB wearable Ants. reported in the literature. The MTM structure is designed to mitigate the SAR effect and enhance the Ant. performance parameters, including impedance matching, radiation pattern, and realized gain. The performance of the proposed MTM Ant. was evaluated through simulations conducted in free space and on a human body model, specifically on the chest, arm, and leg. The SAR values of the MTM Ant. are found to be well below the maximum permissible limits of 0.49 W/kg (1 g) and 0.125 W/kg (10 g) established by the European and US standards. Additionally, the integration of an MTM structure into the Ant. configuration was demonstrated to result in a notable enhancement in the simulated peak gain of the Ant., reaching 6.95 dBi. Furthermore, it was observed that the maximum front-to-back ratio exhibited an increase to 24.78 dB. Also, the bending conditions of the MTM integrated Ant. are evaluated in detail. The designed Ant. and MTM were fabricated and subsequently subjected to measurements. The results of the measurements were found to be in good agreement with the results of the simulations. Simulation and measurement results show that the proposed Ant. with MTM has satisfactory performance characteristics for WBAN applications.

This study presents a hybrid numerical technique for solving multi-dimensional time-fractional wave equations, combining Laplace transforms and a Chebyshev-node-based Lagrange pseudo-spectral method (LPPSM). The method is designed to overcome the computational burdens of time-stepping schemes for fractional derivatives. By transforming the temporal derivatives into the frequency domain, it enhances numerical stability and avoids time-stepping constraints. The spatial discretization via LPPSM ensures spectral convergence. The time-domain solution is recovered using an optimized Talbot contour inversion. The efficacy of the proposed method is demonstrated on benchmark problems, including the fractional Klein-Gordon equation, achieving exceptional accuracy (errors on the order of $��{10}^{�-�12�}�$). Crucially, to bridge the gap with practical applications, the method is applied to a time-fractional telegraph equation modeling signal propagation in a transmission line with physical parameters $��\left(�R�,�L�,�C�\right)�$. The results confirm the method's high computational efficiency, superior accuracy, and potential for real-time analysis of fractional-order dynamics in high-frequency electronic systems.

This study presents a new three-dimensional chaotic system characterized by a solitary unstable equilibrium point and introduces the direct derivative integration (DDI) approach for attaining accurate control of multistable dynamics. The direct derivative integration (DDI) method expands the 3D seed system into a six-dimensional framework by incorporating its derivatives, maintaining the inherent chaotic behavior, but facilitating ongoing offset enhancement to create a structured lattice of coexisting attractors. A physical implementation of the system was executed using a breadboard prototype to validate the theoretical study, with findings corroborated by circuit simulations. The results indicate that the suggested method successfully produces an unlimited array of coexisting attractors organized in a structured grid, underscoring the practical viability and dependability of the direct derivative integration (DDI) approach for the creation of chaotic systems with manageable multistability.

Artificial neural networks (ANNs) have become integral in the accurate modeling of gallium nitride high electron mobility transistors (GaN HEMTs), but the convergence, robustness, and accuracy of such models are highly sensitive to the tuning of initial values of weights and biases. Optimization algorithms are often utilized for the initialization of parameters to improve the performance of GaN HEMT models. Therefore, this work evaluates and extensively compares hybrid modeling procedures for GaN HEMTs to investigate key aspects such as accuracy, efficiency, and complexity. Specifically, grey wolf optimizer (GWO), black hole optimization (BHO), reptile search algorithm (RSA), and spotted hyena optimizer (SHO) optimization algorithms are utilized with ANN to develop the hybrid approaches. The models are trained and tested across a wide range of operating conditions. A comparative analysis demonstrated that the GWO-based hybrid optimization approach (GWO-ANN) consistently outperformed the BHO-ANN, RSA-ANN, and SHO-ANN hybrid optimization approaches in terms of accuracy, complexity, and convergence, and displayed superior alignment between measured and simulated S-parameters over the full frequency spectrum. The BHO-ANN based models, while slightly less accurate, manifested reduced computation time due to their simpler implementation. In contrast, the SHO-ANN based models exhibited the least favorable performance across all metrics, including accuracy, convergence, complexity, and computational time.

High-power microwaves (HPM) coupled into the RF front-ends through antennas pose a significant threat to the low-noise amplifier (LNA). As the core component of the LNA, the reliability of pHEMT devices faces major challenges. This paper presents a comprehensive study on the performance variations of pHEMT devices with different gate lengths during HPM injection, using TCAD simulation. The study compares the temperature variation, electric field distribution, and current density across devices with varying gate lengths under HPM injection conditions. The findings reveal that, regardless of the gate length, hotspots consistently form in the gate-source access region during HPM injection, with this region being the first to experience thermal failure. Notably, as the gate length increases, the peak temperature in the device under HPM injection exhibits a distinct decreasing trend, highlighting the significant impact of gate length on device performance under high-power microwave conditions. This analysis provides new insights into the thermal management and reliability of HEMT devices in high-power applications, emphasizing the crucial role of gate length in mitigating thermal failure.

On the basis of the canonical section-wise piecewise linear (CSWPL) technique, this work presents the novel modified drain and gate current models for advanced spice model (ASM) that take temperature effects into account. Compared with the classic ASM current model, the proposed approach incorporates an error-correction module based on the CSWPL technique, providing enhanced prediction accuracy. In addition, temperature dependence is explicitly modeled through a polynomial function, enabling reliable performance across a wide temperature range. To experimentally validate the new model, multi-temperature current measurement data obtained from a 0.25 × 440 μm² gallium-nitride (GaN) high-electron-mobility transistor (HEMT) are used. The achieved results demonstrate that the modified model significantly improves current prediction accuracy compared to the classic current model.

A spoof surface plasmon (SSPP) structure is applied to the design of a radio frequency (RF) reconfigurable power amplifier (PA). An input matching network of a reconfigurable PA is designed by a SSPP structure, while an output matching network is formed by a reconfigurable matching structure. An analysis and discussion of the electromagnetic characteristics of the proposed SSPP structure is presented. Gradient algorithms are used in the ADS tool to further optimize the performance of the PA. According to the test results, the reconfigurable PA based on SSPP theory achieves 41.8 dBm output power (Pout) and 65.5% power added efficiency (PAE) at 1.5 GHz and 40.1 dBm Pout and 64.2% PAE at 2.4 GHz. This layout has a total size of 71.5 by 35 mm. Compared to previously published reconfigurable works, the PA designed in this work has a simpler structure and smaller size while maintaining high efficiency and output power. A digital pre-distortion (DPD) is implemented to further verify the linearity of the SSPP-based PA. With the DPD, the linearity of the SSPP PA was significantly improved.