Journal of Electronic Science and Technology最新文献

Commonly, the classical formulas for designing TE₂₁-mode coupler are suitable for the operating frequency under Ka-band by virtue of ignoring wall thickness. However, in real application of TE₂₁-mode coupler design beyond Ka-band, the new formulas need to consider the effect of wall thickness. Herein, we demonstrate a design measure of a TE₂₁-mode coupler beyond Ka-band via computer simulation, giving attention to wall thickness. The experimental results show that a measure of linear second weighted sum for coupling hole size could improve coupler performance. Amazingly, such coupler shows 10% bandwidth with less than 0.5 ​dB coupling loss and more than 40 ​dB isolation is possible.

A terahertz dual-mode extended interaction oscillator (EIO) driven by a pseudospark-sourced sheet electron beam (SEB) was presented. The major advantages of the newly developed circuit include 1) high-density SEB interacting with the TM₁₁ and TM₃₁ modes, respectively, and 2) high output power of over 1 ​kW ​at the sub-terahertz frequency range. Two different types of 2π modes and their output characteristics were studied, and the circuit was optimized to ensure efficient outputs of two standing-wave modes. The three-dimensional (3D) particle-in-cell (PIC) simulation predicts the maximum output power of 1.3 ​kW with a 3-dB bandwidth of ~0.5 ​GHz ​at 303 ​GHz when operating at the TM₁₁ mode, and 3.18 ​kW, 3-dB bandwidth of ~0.85 ​GHz ​at 364 ​GHz when operating at the TM₃₁ mode.

Chiral metamaterial absorbers (CMMAs), a particular class of chiral metamaterials that refuse the transmission of incident radiation and exhibit different optical responses upon interactions with left and right circularly polarized (LCP, RCP) light, have gained research traction in recent years. CMMAs demonstrate numerous exotic and specialized applications owing to their achievable compatibility with various physical, chemical, and biomolecular systems. Aside from their well-evolved fabrication modalities for a broad range of frequencies, CMMAs exhibit strong chiroptical effects, making them central to various detection, imaging, and energy harvesting applications. Consequently, within the past decade, studies encompassing the design, optimization, and fabrication, as well as demonstrating the diverse applications of CMMAs have emerged. In this review, the theory, design, and fabrication of CMMAs are discussed, highlighting their top-down fabrication techniques as well as recent algorithmic and machine-learning (ML)-based approaches to their design and optimization. Some of their broad-spectrum applications are also discussed, spanning their roles in enantioselective photodetection, chiral imaging, generation of hot electrons, selective temperature sensing, and active chiral plasmonics.

Recently the diagnoses of dental caries and other dental issues are in a queue as only X-ray-based techniques are available in most hospitals around the world. Terahertz (THz) parametric imaging (TPI) is the latest technology that can be applied for medical applications, especially dental caries. This technology is harmless and thus suitable for biological samples owing to the low energy of THz emission. In this paper, a developed TPI system is used to investigate the two-dimensional (2D) and three-dimensional (3D) images of different samples from human teeth. After analyzing the measured images of the human tooth, the results suggest that the novel THz parametric technology is capable of investigating the inner side structure of the teeth. The technique can be useful in detecting the defects in all types of human and animal teeth. The measurement and analytical calculations have been performed by using the TPI system and MATLAB, respectively, and both are in good agreement. The characteristics of THz waves and their interactions with the tooth samples are summarized. And the available THz-based technologies, such as TPI, and their potential applications of diagnoses are also presented.

The quantitative optical measurement of deep sub-wavelength features with sub-nanometer sensitivity addresses the measurement challenge in the semiconductor fabrication process. Optical scatterings from the sidewalls of patterned devices reveal abundant structural and material information. We demonstrated a parametric indirect microscopic imaging (PIMI) technique that enables recovery of the profile of wavelength-scale objects with deep sub-wavelength resolution, based on measuring and filtering the variations of far-field scattering intensities when the illumination was modulated. The finite-difference time-domain (FDTD) numerical simulation was performed, and the experimental results were compared with atomic force microscopic (AFM) images to verify the resolution improvement achieved with PIMI. This work may provide a new approach to exploring the detailed structure and material properties of sidewalls and edges in semiconductor-patterned devices with enhanced contrast and resolution, compared with using the conventional optical microscopy, while retaining its advantage of a wide field of view and relatively low cost.

To fill the continuous needs for faster processing elements with less power consumption causes large pressure on the complementary metal oxide semiconductor (CMOS) technology developers. The scaling scenario is not an option nowadays and other technologies need to be investigated. The quantum-dot cellular automata (QCA) technology is one of the important emerging nanotechnologies that have attracted much researchers’ attention in recent years. This technology has many interesting features, such as high speed, low power consumption, and small size. These features make it an appropriate alternative to the CMOS technique. This paper suggests three novel structures of XNOR gates in the QCA technology. The presented structures do not follow the conventional approaches to the logic gates design but depend on the inherent capabilities of the new technology. The proposed structures are used as the main building blocks for a single-bit comparator. The resulted circuits are simulated for the verification purpose and then compared with existing counterparts in the literature. The comparison results are encouraging to append the proposed structures to the library of QCA gates.

Photovoltaic grid-connected inverter is an important interface between the photovoltaic power generation system and power grid. Its high-quality operation is directly related to the output power quality of the power grid. In order to further optimize the control effect of the quasi-Z source grid-connected photovoltaic inverter, a fuzzy proportional complex integral control (PCI) method was proposed for the current internal loop control. This method can eliminate the steady-state error, and has the characteristic of zero steady-state error adjustment for the AC disturbance signal of a specific frequency. The LCL filter is adopted in the grid-connected circuit, and the feedback capacitive current is taken as the control variable of the inner loop to form the active damping control method, which can not only effectively suppress the resonance of the LCL circuit, but also significantly inhibit the high-order harmonics in the grid-connected current. Finally, a system simulation model is built in MATLAB/Simulink to verify the superiority and effectiveness of the proposed method.

This study presents an overview of the current status of hydrogen production in relation to the global requirement for energy and resources. Subsequently, it symmetrically outlines the advantages and disadvantages of various production routes including fossil fuel/biomass conversion, water electrolysis, microbial fermentation, and photocatalysis (PC), in terms of their technologies, economy, energy consumption, and costs. Considering the characteristics of hydrogen energy and the current infrastructure issues, it highlights that onsite production is indispensable and convenient for some special occasions. Finally, it briefly summarizes the current industrialization situation and presents future development and research directions, such as theoretical research strengthening, renewable raw material development, process coupling, and sustainable energy use.

In this paper, the problems of robust consensus tracking control for the second-order multi-agent system with uncertain model parameters and nonlinear disturbances are considered. An adaptive control strategy is proposed to smooth the agent’s trajectory, and the neural network is constructed to estimate the system’s unknown components. The consensus conditions are demonstrated for tracking a leader with nonlinear dynamics under an adaptive control algorithm in the absence of model uncertainties. Then, the results are extended to the system with unknown time-varying disturbances by applying the neural network estimation to compensating for the uncertain parts of the agents’ models. Update laws are designed based on the Lyapunov function terms to ensure the effectiveness of robust control. Finally, the theoretical results are verified by numerical simulations, and a comparative experiment is conducted, showing that the trajectories generated by the proposed method exhibit less oscillation and converge faster.