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

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.

This paper presents the design of a four-port antenna with a double integrated loop-shaped decoupling structure, achieving wide bandwidth and high isolation. The antenna is designed with an inverted-L-shaped monopole strip on a partial ground plane, which facilitates wide-band operating frequencies. A double integrated loop-shaped decoupling structure effectively suppresses surface current coupling among the four antenna elements, improving isolation to a range of 4.2–8 dB without a complex structure. A compact four-port multiple-input multiple-output (MIMO) antenna radiates from 3.6 to 6.4 GHz with an absolute bandwidth of 2.8 GHz, whereas the fractional bandwidth of the antenna is 56%. The MIMO parameters such as correlation coefficient (< 0.35), diversity gain (9.999), channel capacity loss (< 0.4 bit/s/Hz), and total active reflection coefficient validate the eminent performance of the antenna for 5G and biomedical applications, where the low profile of the antenna facilitates easy integration into electronic equipment.

This research paper introduces an innovative voltage-mode instrumentation amplifier circuit employing a single voltage differencing current conveyor (VDCC) in conjunction with four grounded resistors. The designed circuit provides two output signals with opposing phases. This work includes comprehensive analyses encompassing both ideal and non-ideal circuit behaviors. To validate the theoretical findings, we conducted SPICE simulations utilizing 0.18 μm CMOS process parameters. The proposed circuit exhibits a substantial differential-mode gain of 32 dB and a notable bandwidth of 21.93 MHz. Furthermore, it demonstrates a remarkable common-mode rejection ratio (CMRR) of 91.1 dB, with a CMRR bandwidth of 405.3 kHz. Operating within a ±0.9 V range, the circuit's power consumption remains notably low, measuring at a mere 0.6 mW. The circuit's robustness was rigorously tested through extensive simulations, and its performance under process–voltage–temperature variations was thoroughly assessed. To validate its practical viability, we conducted experimental tests using commercially available AD844 and LM13700 ICs.

Capacitance multipliers are essential in applications requiring large capacitance but constrained by size, cost, or integration feasibility. Their ability to simulate high-value capacitors using active components makes them crucial in modern ICs, power electronics, biomedical devices, wireless communication, and sensor interfaces. This paper presents a novel approach for designing resistorless grounded capacitance multiplier (GCM) circuits. The proposed design employs the voltage differencing inverting buffered amplifier (VDIBA) as the active block, leading to the introduction of 18 new GCM circuits. These circuits utilize two VDIBAs and a single capacitor, enabling both positive and negative capacitance multiplication factors (MFs). The MF of all the presented circuits can be electronically tuned using bias voltages and also have independent control. The design eliminates stringent matching constraints, enhancing practical feasibility. Furthermore, the impact of nonideal VDIBA parasitics on circuit performance is thoroughly analyzed and compared with ideal values. To validate the proposed approach, the circuits are applied in the design of a first-order low-pass filter (LPF). Their functionality is further confirmed through a CMOS-based VDIBA implementation using 0.18 μm TSMC technology parameters in PSPICE simulations. Comprehensive analyses, including frequency and transient response, Monte Carlo analysis, process corner evaluation, and temperature variation, demonstrate the robustness of the circuits. The proposed GCM circuits operate over a wide frequency range from 1 mHz to 0.1 GHz, making them suitable for applications such as signal processing, impedance matching, and noise filtering. The capacitance can be enhanced up to 20 times its original value, while the circuit consumes approximately 1.5 mW of power. Experimental frequency response of an application example of a LPF using a VDIBA, implemented with commercially available ICs CA3080 and AD830, is also provided.

The field of portable electronics and smart devices has seen a significant shift toward multi-valued logic (MVL), especially ternary logic, due to its potential to reduce circuit complexity and power consumption. This paper shows how Carbon Nanotubes FETs (CNTFETs) can be used in the design of ternary logic gates, which is a promising alternative to the conventional binary logic design. In particular, we propose a procedure to design CNTFET-based NOR/NAND gates and a Decoder, all in ternary logic, and the proposed method allows us to evaluate the propagation delay. Comparing the proposed design with the existing design, the delay times are reduced by approximately 80%. Moreover, the main novelty is that in this paper all simulations are performed in Verilog-A, thus avoiding the problems presented in SPICE. The obtained results are encouraging and demonstrate that CNTFET-based ternary logic gates can be a viable approach for the design of low-power, high-speed circuits.

In this work, two approximation techniques are presented for solving nonlinear Volterra integro-differential equations with boundary conditions, arising in the modeling of inelastic cables subjected to external loads. The foundation of the required numerical computation is established through the operational matrices of interpolating basis functions and the Gegenbauer wavelet technique, which transform the original problem into a system of algebraic equations. To construct the interpolation basis functions, orthonormal Lagrangian basis functions are employed. Subsequently, the resulting algebraic system is solved using Newton–Cotes nodes to obtain the desired numerical solution. The use of operational matrices simplifies the problem and significantly reduces the computational complexity of solving integro-differential equations. Moreover, error bounds are established, and a comprehensive convergence analysis of the proposed methods is carried out. Finally, numerical experiments supported by graphical illustrations clearly demonstrate the reliability and computational efficiency of the developed techniques.

This article evaluates the effectiveness of polycrystalline diamond (PCD) thermal vias in mitigating self-heating issues in the two-dimensional electron gas (2DEG) layer of GaN high-electron mobility transistors (HEMTs). Thermal simulations conducted using Silvaco Victory Device identified and characterized hotspots within the 2DEG layer, which were further analyzed using Ansys Icepak. For GaN-on-sapphire HEMTs, the integration of PCD thermal vias resulted in a significant reduction of up to 23.5% in hotspot temperatures, with optimal performance observed when the thermal via protruded into the GaN layer. Even when the thermal via terminated at the GaN/sapphire interface, it still demonstrated substantial thermal management benefits. In contrast, for GaN-on-Si and GaN-on-SiC HEMTs, the effectiveness of PCD thermal vias was notably diminished. This is attributed to the higher thermal conductivities of Si (148 Wm⁻¹ K⁻¹) and SiC (490 Wm⁻¹ K⁻¹) compared to sapphire (23 Wm⁻¹ K⁻¹), limiting the potential for hotspot temperature reduction despite using high-quality PCD (1000 Wm⁻¹ K⁻¹). These results significantly extend existing thermal management studies by uniquely addressing the thermal challenges posed by GaN-on-sapphire substrates through the introduction of PCD thermal vias, a substrate-material combination that has not been comprehensively explored in prior research. The findings highlight that while PCD thermal vias offer substantial improvements in thermal management for GaN-on-sapphire HEMTs, their impact is less pronounced for GaN-on-Si and GaN-on-SiC HEMTs. A preliminary cost–benefit analysis suggests that while PCD thermal vias have a higher initial cost, their long-term reliability and reduction in thermal-induced failures make them a cost-effective solution. Future work will focus on experimental validation and exploring alternative thermal management strategies such as microchannel cooling and advanced thermal interface materials.

As in many medical device systems development, the design of radiofrequency breast tumor detection systems undergoes a test phase based on the use of liquid phantoms. It is well known the difficulty in obtaining phantoms that precisely model each tissue for each frequency of interest while keeping such properties for a long time. Despite the many available studies using such phantoms, limited information is available on a systematic analysis of the effect that the use of an imprecise phantom may have on the characterization of radiofrequency systems. This work presents the design and fabrication of ultra-wideband liquid breast and tumor phantoms. The main issue with this approach is that incorrect phantom properties, as well as an incorrect frequency response, lead to assessment errors. The current research focus is mainly focused on the model of the phantom, rather than its electromagnetic properties. Typically, the EM properties of breast phantoms are accurate only in a small frequency range, and these properties are frequency dependent. To address this issue, we validated a homogeneous breast phantom with good results in terms of dielectric permittivity (1.613% < error < 3.22%) and loss tangent (error < 33%) in the wide frequency range of [1–6] GHz. The proposed phantom retains its properties for a significant period of time, degrading only 6.78% in 2 h after fabrication while exposed to the environment. When it is stored in a container, only a small variation of ±1.7% was registered after 9 months.

Wireless identified Surface acoustic waves (SAWs) sensors operating in the real-time offer a wide range of applications. The novelty of this paper is the use of two-dimensional (2D) COMSOL FEM modelling of two types of one-port reflective SAW delay lines (DL): a simple reflective one designed with conventional Bragg reflectors and a coded reflective one that employs a specific spatial distribution of Bragg mirrors to encode the SAW electrical response for radio frequency identification (RFID). The SAW structures are made of Al/AlN/Si stratified layers, forming respectively the IDT electrodes, the piezoelectric layer, and the substrate. The geometry and materials are selected to achieve a SAW device operating frequency around 441.2 MHz. The reflection scattering parameters of all the studied structures are calculated in the frequency domain S₁₁(f) and transformed to the time domain S₁₁(t) by performing an inverse Fourier transform (IFFT). In the coded reflective delay line structure, eight Bragg systems containing eight reflectors each are employed to generate the 10010110 code. This structure is tested as a temperature sensor; its normalized sensitivity in the temperature range of −25°C to 200°C is evaluated at −25.39 ppm/°C. The tag sensor's identification procedure is performed by using the cross-correlation technique on two RFID temperature sensors interrogated simultaneously: namely, one coded 10010110 and another one coded 11010111.