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FinFETs have a bright future for advanced analog/RF and digital circuit design in 5G/6G technology. As the integration density increases, the self-heating effect (SHE) becomes more severe, and the hot carrier injection (HCI) reliability of FinFETs further deteriorates since it is highly dependent on temperature. In this article, an artificial neural network (ANN) model for HCI prediction is proposed for 14-nm FinFET with consideration of SHE under various voltage stresses and environment temperature. The HCI numerical simulation can be mainly divided into two parts: 1) the temperature responses for the device under different stresses are obtained by numerically solving time-dependent thermal conduction equation with heat generation in the nanoscale FinFET and 2) based on the transient temperature response to different stress voltages, HCI-induced threshold voltage shift (TVS) as a function of time is captured numerically. Our HCI-induced TVS simulation results agree well with others’ experiment results, which verifies the simulation methods. An ANN model is then developed to predict the TVS induced by HCI with the training data obtained from numerical simulations. The ANN model has good accuracy with an average relative error of 0.36% in predicting TVS and greatly reduces simulation cost once the ANN model is built for the HCI prediction of FinFETs, which has great potential for reliability design in circuits and systems. [ABSTRACT FROM AUTHOR]

An axial mode solid dielectric helical antenna (DHA) has been proposed, which is fabricated by using the 3-D printing technique. Fed manners of this antenna have been studied, including conformal coaxial probe and conformal metal strip line. The operating mode of dielectric helix has been analyzed in detail. Circular polarization is achieved by choosing appropriate sizes of the dielectric helix. Furthermore, a miniaturized axial mode DHA with deployable property is implemented. Measured results indicate that the proposed antenna has good radiation performance, such as circular polarization, high gain, and high radiation efficiency. Specially, the radiation patterns of the DHA have good symmetry in the 2 dB axial ratio range. The significant advantage of miniaturized DHA is light in weight, which is only 2.7% of the weight of a metal helical antenna with similar radiation characteristics. The antenna is a good candidate in wireless communication system. [ABSTRACT FROM AUTHOR]

An improved locally 1-D (LOD) finite-difference time-domain (FDTD) method with a one-step leapfrog scheme has been developed, and its numerical dispersion has been further optimized due to the introduction of controlling parameters. On the premise of unconditional stability, we further simplified the implementation through auxiliary field variables. Moreover, the internal relationship between numerical dispersion and important parameters, such as propagation angle, the Courant–Friedrich–Levy number, and frequency, was analyzed in detail. Numerical examples verified the performance of the proposed method in terms of memory, efficiency, and accuracy. [ABSTRACT FROM AUTHOR]

To keep safety of the antenna in wireless capsule endoscopy (WCE) to human body and its use range in different groups of people, seven human abdomen models are established where age, tissue thickness, and organ shape have been considered. On the basis of plane wave propagating theory in lossy multilayered media, each model is composed of simulated skin, subcutaneous fat, muscle, visceral fat, and gastrointestinal organ. Different dielectric constants for the biological tissue component are used. A bendable dual-band antenna is designed for the WCE system, conformed to the capsule shell. An L-shaped branch is used to get better impendence matching. Both the ISM band adopted for data transmission and the WMTS band for midfield wireless power transmission are studied. Fresh pork abdominal tissue samples are used as experiment materials, and it is properly kept consistent with the real human abdominal as far as possible. The experimental results show the performance of antenna stable in the ISM (433 MHz) band. The specific absorption ratio value is checked in different models. The results indicate that dielectric parameters varying with age cannot be ignored, and the antenna must be aimed at middle-aged and elderly population with high incidence of gastrointestinal diseases. [ABSTRACT FROM AUTHOR]

In this article, a compact magnetic dipole (MD) composite right-/left-handed transmission line (CRLH-TL) leaky-wave antenna (LWA) is proposed, which is periodically loaded with rectangular gaps and short stubs. Then, in light of the dielectric resonator with a high dielectric constant, low loss tangent, and good radiation performance, we further add an alumina ceramic block (ACB) to stack on the gap in each CRLH-TL LWA unit cell for forming the MD, and thus, wide beam-scanning range and compactness are achieved. To validate this design, a traditional uniform CRLH-TL LWA is investigated in detail. The results of S-parameters, electrical field distribution, and radiation properties illuminate the effects of introducing the ACB, such as impendence matching improvement and high radiation efficiency. Furthermore, to verify the flexible control of the balanced condition and the attenuation constant by changing the microstrip gap width and the ACB thickness predicted in the circuit model analysis, a nonuniform CRLH-TL LWA with quasi-constant amplitude is fabricated. Experimental results demonstrate a higher antenna gain and the stability of wide beam-scanning range under the condition of a compact design. [ABSTRACT FROM AUTHOR]

Due to their high optical absorption and atomic thickness, light detectors based on tin disulfide (SnS2) have been investigated extensively. In this letter, a light detector based on a SnS2 monolayer with an Al/SnS2/Au structure for visible light detection is demonstrated. Benefiting from the Au/SnS2 Schottky structure, photoexcited electron-hole pairs are separated, and a remarkable photoresponse is achieved. At $11 ~\mu \text{W}/$ mm2, the peak responsivity and detectivity are 586.18 $\text{A}/\text{W}$ and $1.22\,\,\times10$ 14 Jones, which indicate that these detectors are superior both to most detectors based on two dimensional materials and to commercial Si detectors. The light detector also exhibits a fast response speed with the response time at the microsecond level. Moreover, a low dark current of 2.18 nA is achieved in this structure. [ABSTRACT FROM AUTHOR]

An optimized three-dimensional one-step leapfrog finite-difference time-domain (FDTD) method has been investigated, which is with a weakly conditional stability (WCS) to reduce numerical dispersion further. By introducing the artificial anisotropy parameters in a cross-correspondence manner, the phase velocity error is effectively limited without additional computational time and memory cost. An auxiliary field variable is adopted to simplify the iterative formulae with few additional processes, and the same stability has been validated between methods of conventional leapfrog WCS-FDTD and ourselves. Moreover, much lower numerical dispersion is shown to withstand larger Courant–Friedrich–Levy number under the same error condition. To verify our method efficiently, a newly designed hollow dielectric resonator antenna (DRA), instead of a solid one, is conducted effective calculation. Furthermore, two forms of four-element arrays have been developed with the DRA element above, and a T-shaped power divider is designed as a fed network and subjected to calculations and experimental analyses. Reflection coefficients and radiation patterns are shown the effectiveness of both DRA and arrays. The most noteworthy aspect is that our low-dispersion WCS-FDTD scheme can be effectively simulated the hollow DRA and arrays, and with excellent performance in terms of memory occupation, calculation accuracy, and efficiency. [ABSTRACT FROM AUTHOR]

A compact implantable antenna is proposed for wireless health monitor microsystem, which is operated in frequency of the Industrial, Scientific, and Medical (ISM) band. A circular radiator is cut four L-shaped slots and loading a shortpin between the radiator and ground plane to implement the circular polarization. Two crossed rectangle slots are etched on the ground plane so that the impedance and axial ratio (AR) bandwidths have been expanded at the same time. In addition, to further verify the performance of the antenna for biomedical application, we simulate a microsystem that monitors human health; and establish the simulation environment of the human heart and head. Then, we evaluated the performance of the microsystem in the human tissue simulation environment. The maximum specific absorption rate value satisfies the IEEE standard safety guidelines. The experiment results indicate that the impedance and AR bandwidths of proposed antenna are 2.25–2.78 GHz and 2.32–2.63 GHz, respectively. The total dimensions of π × 42 × 1.27 mm3 are obtained, which is equivalent to π × 0.032λ02 × 0.0102λ0 (λ0 is the free-space wavelength at 2.4 GHz). This compact size is very suitable for the application in health monitoring microsystem. [ABSTRACT FROM AUTHOR]

This article presents a novel toroidal metasurface that is able to support a toroidal response at almost all incident angles for a transverse magnetic (TM) wave at the microwave range. A flat band is observed from the calculated band structure where the radiation power of the toroidal response is highest around 7.51 GHz. A high transmission at a resonant frequency is observed from the simulated and measured transmission coefficients with different incident angles, whereas the transmission is lower at the rest frequency range. The resonance frequency at a high sensitivity of 0.78 GHz/refraction index unit (RIU) is experimentally demonstrated, which is very sensitive to the thickness and the refraction index of the surrounding materials such that the proposed toroidal metasurface could be used for a tunable highly efficient filters. [ABSTRACT FROM AUTHOR]

In this article, a novel miniaturized concept named strong-coupled frequency selective surface (SC-FSS) with excellent angular stability is presented. First, a conceptual design of SC-FSS is introduced, where the resonant frequencies are insensitive to almost all incident angles. A corresponding equivalent circuit model is developed to interpret the operating principle and formulate relevant design equations with an error of 0.2%. Furthermore, an ultraminiaturized and ultrathin band-stop structure with a unit cell size of λ0/35 and thickness of 0.26 mm (λ0/578) is designed and fabricated to verify this concept. Analysis and experiment show that the proposed band-stop SC-FSS structure can work stably at 2 GHz for both TE and TM modes, even when the incident angle varies from 0° to 84°. The measurement results are consistent with those obtained by full-wave simulations and the equivalent circuit model, which fully demonstrates that the concept of SC-FSS can be widely used in designing antenna reflectors, electromagnetic interference shielding, and angle-insensitive absorbers. [ABSTRACT FROM AUTHOR]

To model the object with concave and convex surfaces accurately, an economical conformal subgridding scheme is proposed in this article. Its double conforming procedure with coarse grid (CG) and fine grid (FG) guarantees the modeling accuracy. Fast linear interpolation effectively exchanges electromagnetic fields information on the interface between grids of two sizes. One-step leapfrog alternating direction implicit (ADI) finite-difference time-domain (FDTD) method overcomes the Courant stability condition in FG region; meanwhile, conventional FDTD ensures the efficiency of simulation in CG region. While we concern the unconditionally stable method, there is not any grid omitted in our irregularly profiled fine region and any extra time wasted in solving small-scale tridiagonal matrixes cell by cell. To verify our codes, a 2-D arc component has been simulated first. Then the performance of a probe-fed normal one-eighth spherical dielectric resonator antenna (DRA), a new designed conformal-microstrip-fed one-eighth spherical shell DRA, and a four-element array with the spherical shell DRAs connected by a T-shaped power divider has been calculated by our codes. Satisfactory performance of the antenna has been obtained in return loss and radiation patterns, which are verified by measured results. The shell antenna features smaller size, lighter weight, and more convenience in conforming to the corners of the instrument housing, even with different dimensions. Most particularly, the proposed conformal subgridding scheme and its hybrid FDTD implementation perform outstandingly in simulating the thin shell antenna in terms of computer memory, CPU time, as well as accuracy. [ABSTRACT FROM AUTHOR]

We systematically investigated graphene-based slot and multi-slot waveguides. A tri-slot waveguide which significantly enhances the light-graphene interaction was experimentally demonstrated with low insertion loss. By integrating a dual-layer graphene h-BN heterostructure on the tri-slot waveguide, a high efficiency modulator is designed, which combines the advantages of high modulation efficiency (0.376 dB/μm), low insertion loss (0.01 dB/μm), large modulation bandwidth (∼0.13 THz) and low power consumption (∼0.128 pJ/bit). Our work may promote the development of future high efficient graphene-based optical devices. [ABSTRACT FROM AUTHOR]

In order to adapt to the applications of the wireless capsule endoscope (WCE) system, a wideband implantable antenna is designed. We engrave some slots on both the radiator and the ground plane to miniaturize the size and expand the impedance bandwidth of the antenna. The capacitance loading technique is used to improve the impedance match. The influence of different organs such as the stomach, small intestine, and colon is discussed when the antenna is embedded in the WCE system. Compared to other implantable antennas with similar performance, impedance bandwidth, radiation pattern, and specific absorption rate in one-layer skin phantom model, this design has the best performance. Finally, experiments are carried out on a chicken breast slab to validate our design. Results are shown the proposed antenna available. [ABSTRACT FROM AUTHOR]