Showing papers by "Wen-Yan Yin published in 2022"
TL;DR: In this paper , a new stabilized 3D control volume finite element method (FEM) was proposed for massively parallel simulation of drift-diffusion transport in semiconductor devices, which employs unstructured hexahedral elements, thus leading to a very efficient scheme; both Poisson and current continuity equations are discretized with control volume FEM, and thus, the accuracy and stability are improved.
Abstract: We present a new stabilized 3-D control volume finite element method (FEM) for massively parallel simulation of drift-diffusion transport in semiconductor devices. This new solver employs unstructured hexahedral elements, thus leading to a very efficient scheme; both Poisson and current continuity equations are discretized with control volume FEM, and thus, the accuracy and stability are improved. Furthermore, a fully coupled Newton’s method is applied to solve these nonlinear equations, thus remarkably increasing the numerical stability. Then, we apply this new solver to simulate diode, MOSFET, and multifinger MOSFET devices. Numerical results indicate that the hexahedron-based method requires fewer iterative numbers, and its computing speed is 3.44–4.61 times faster than the tetrahedron-based counterpart. Moreover, our fully coupled Newton’s method permits constant iterative numbers, showing strong numerical stability even when the drain voltage is 160 V.
4 citations
TL;DR: In this paper , the authors used an in-house finite element method (FEM)-based parallel computing simulator to model multiphysics processes of resistive random access memories (RRAMs).
Abstract: In this article, we use an in-house finite element method (FEM)-based parallel computing simulator to model multiphysics processes of resistive random access memories (RRAMs). These RRAMs are based on six different metal oxides, including TiOx, NiOx, HfOx, WOx, ZrOx, and TaOx. In a single RRAM cell, the resistance ratio, reset voltage, reset current, reset power, and temperature are numerically compared. In the RRAM array, the resistance ratio, the minimum feature size (FS) to avoid bit loss, temperature, and oxygen vacancy density are obtained and discussed. The advantages of the six metal oxides-based RRAMs are analyzed based on their physical parameters, including diffusivity, electrical conductivity, and thermal conductivity. Numerical results reveal that thermal crosstalk effects are more severe when the FSs decrease, even the inactive cell can be transferred from a low-resistance state (LRS) into a high-resistance state (HRS). A crossbar array with a diamond heat sink is proposed to suppress the thermal crosstalk effect.
3 citations
DOI•
01 Oct 2022
TL;DR: In this paper , the authors derived the analytical expressions of the transfer impedance and admittance of a shielded structure with non-uniform current distribution around the shield surfaces and generalized the formulations to be applicable for shielded twisted-wire pair (TWP) and twinax cables with line apertures and a braided structure with a nonuniform shield current.
Abstract: In this article, the transmission line model of multibraided shielded cables is improved by including the proximity effect in the shield model. This is performed by deriving the analytical expressions of the transfer impedance and admittance of a shielded structure with nonuniform current distribution around the shield surfaces. After that, the formulations are generalized to be applicable for shielded twisted-wire pair (TWP) and twinax cables with line apertures and braided structure with nonuniform shield current. It is found that the nonuniform distribution of the currents in the outer and inner shield surfaces have high effects on the inner induced common-mode and differential-mode currents of braided shielded cables. In addition, the crosstalk between multishielded TWP and twinax cables is investigated in detail, indicating that the proximity effects between the shields have a critical impact on generating the crosstalk between the shielded cables. The proposed model is validated with the commercial software FEKO and excellent agreements are achieved.
2 citations
DOI•
TL;DR: In this paper , the authors proposed the concept of localized loss engineering in electromagnetic (EM) metasurfaces, showing that an ordinary symmetric retroreflector can be switched to an extraordinary asymmetric one by introducing absorptive defects in local regions.
Abstract: Metasurfaces based on subwavelength resonators enable novel ways to manipulate the flow of light at optical interfaces. In pursuit of multifunctional or reconfigurable metadevices, efficient tuning of macroscopic performance with little structural/material variation remains a challenge. Here, we propose the concept of localized loss engineering in electromagnetic (EM) metasurfaces, showing that an ordinary symmetric retroreflector can be switched to an extraordinary asymmetric one by introducing absorptive defects in local regions. The asymmetric performance begins with zero at the Hermitian state, gradually increases under non-Hermitian localized loss modulation, and reaches the maximum at the exceptional point (EP). The metasurface at the EP exhibits extremely asymmetric performance without the need of deeply discretized subwavelength elements. As a proof of concept, the localized loss-assisted asymmetric reflection is experimentally demonstrated at microwave frequencies via the observation of near-field distributions and far-field scatterings from a planar metasurface. Our methodology opens new opportunities for engineering EM systems with small perturbations and designing reconfigurable or multifunctional metadevices.
1 citations
TL;DR: In this article , a CMOS Ku-band phased-array transmitter with eight elements is demonstrated, and a fully symmetrical sampling structure is proposed to improve the testing accuracy of the built-in self-test (BIST) circuit.
Abstract: In this article, a CMOS Ku -band phased-array transmitter with eight elements is demonstrated. To mitigate the measurement time and complexity, a built-in self-test (BIST) circuit is developed in this chip. A fully symmetrical sampling structure is proposed to improve the testing accuracy of the BIST system. To decrease the phase and amplitude errors, two compensation methods based on inductors and capacitors are, respectively, used in the phase shifters and attenuators to minimize severe parasitic effects of transistors in high-frequency bands. In addition, a scalable power divider is developed to save chip area and reduce insertion loss. According to the measurement results, the 5-bit passive phase shifter in each transmitting channel achieves less than 3.6° root-mean-square phase error (RMSPE) and 0.8-dB root-mean-square amplitude error (RMSAE). The transmitter’s attenuators are formed by four bridge- $T/\pi $ -type units and achieve less than 0.94-dB RMSAE and RMSPE of 3.2°. Each channel of the transmitter is capable of delivering about 13-dBm linear power at 16 GHz. The BIST system is also employed to detect the phase and amplitude performances of the eight-element transmitter, and the BIST testing errors are less than 10.3% compared to the microwave equipment measurement.
08 Aug 2022
TL;DR: In this article , a broadband topological slow light was demonstrated in a photonic topological insulator, where the chiral photonic states can wind many times around the Brillouin zone, achieving an ultra-low group velocity in the entire topological bandgap.
Abstract: Slow-light devices are able to significantly enhance light-matter interaction due to the reduced group velocity of light, but a very low group velocity is usually achieved in a narrow bandwidth, accompanied by extreme sensitivity to imperfections that causes increased disorder-induced attenuation. Recent theories have suggested an ideal solution to this problem—unidirectional chiral photonic states, previously discovered in structures known as photonic topological insulators, not only resist backscattering from imperfections but can also be slowed down in the entire topological bandgap with multiple windings in the Brillouin zone. Here, we report on the experimental demonstration of broadband topological slow light in a photonic topological insulator. When coupled with periodic resonators that form flat bands, the chiral photonic states can wind many times around the Brillouin zone, achieving an ultra-low group velocity in the entire topological bandgap. This demonstration extends the scope of topological photonics into slow light engineering, and opens a unique avenue in the dispersion manipulation of chiral photonic states.
DOI•
TL;DR: In this article , a wideband integrated log-periodic antenna (LPA) based on multilayer printed circuit board for 5G Q-band applications is presented, which is fed by the broadband radial slot transition balun.
Abstract: A wideband integrated log-periodic antenna (LPA) based on multilayer printed circuit board for fifth-generation (5G) Q-band applications is presented in this letter. The LPA is fed by the broadband radial slot transition balun. The LPA has four dipoles which are separately placed on different thickness printed circuit board substrates. To enhance the gain and reduce the cross-polarization level, the symmetrical layout and differential feeding are adopted in the 4 × 4 LPA array design. The measured results show that the proposed 4 × 4 LPA array achieves the impedance bandwidth of 32.5% (32.5–45 GHz) and the peak gain of 15.5 dBi. Due to these advantages of low cost, wideband and easy for integration, the 4 × 4 LPA array will be a potential candidate scheme for 5G Q-band applications.
22 Apr 2022
TL;DR: In this paper , a four-element ultra-wideband MIMO antenna is proposed, which is composed of four half-cut monopole sub-elements placed perpendicular to each other, adopting an improved CPW feeding method, and adding a special isolation structure to achieve high isolation.
Abstract: This paper proposes a four-element ultra-wideband MIMO antenna. The antenna is composed of four half-cut monopole sub-elements, which are placed perpendicular to each other, adopting an improved CPW feeding method, and adding a special isolation structure to achieve high isolation. Combined with the new structure of the semi-circumferential ground, the impedance matching in the ultra-wideband range is realized. With many improvements and optimizations, excellent antenna performance has been achieved. Both simulation and test results show that the designed antenna working bandwidth can cover the 2.71-19.70GHz frequency band, the isolation within the entire bandwidth is greater than 18dB, the antenna’s radiation omnidirectionality is good, the radiation efficiency reaches more than 73%, and it has good gain characteristics, Envelope Correlation Coefficient (ECC) shows that the antenna can well meet the polarization diversity characteristics, the antenna has a compact overall size of only 38*38*1.6mm3. The antenna we designed can be used for portable wireless ultra-wideband applications.