垂直腔表面发射激光器的研究

垂直腔表面发射激光器(VCSEL)是一种应用于光纤通信系统的低成本、高性能的特定波长光源,它具有测试简单、易耦舍以及易形成阵列等独特优势,已在光并行互连及高密度光存贮等领域得到大规模应用.文章介绍了VCSEL的结构和当前的制造工艺水平,阐述了各波段VCSEL的发展和应用现状,探讨了VCSEL在不同领域中的应用范围并指出了VCSEL的发展前景.     

Highly Dispersed NiO Clusters Induced Electron Delocalization of Ni?N?C Catalysts for Enhanced CO2 Electroreduction

Oxygen-regulated Ni-based single-atom catalysts (SACs) show great potential in accelerating the kinetics of electrocatalytic CO₂ reduction reaction (CO₂RR). However, it remains a challenge to precisely control the coordination environment of Ni O moieties and achieve high activity at high overpotentials. Herein, a facile carbonization coupled oxidation strategy is developed to mass produce NiO clusters-decorated Ni N C SACs that exhibit a high Faradaic efficiency of CO (maximum of 96.5%) over a wide potential range (−0.9 to −1.3 V versus reversible hydrogen electrode) and a high turnover frequency for CO production of 10 120 h⁻¹ even at the high overpotential of 1.19 V. Density functional theory calculations reveal that the highly dispersed NiO clusters induce electron delocalization of active sites and reduce the energy barriers for *COOH intermediates formation from CO₂, leading to an enhanced reaction kinetics for CO production. This study opens a new universal pathway for the construction of oxygen-regulated metal-based SACs for various catalytic applications.     

Factors Affecting the Morphology of Pb-Based Glass Frit Coated with Ag Material Prepared by Electroless Silver Plating

Pb-based glass frit coated with nanosilver material for Si solar cell applications has been directly prepared by electroless silver plating. Activation of the glass frit was accomplished by using glycol, with the aim of reducing the silver ions to elemental silver on the surface of the glass frit. Electroless silver plating onto the glass frit was successfully realized using two kinds of electroless plating bath. However, the morphology of the composite powder greatly affected the modality, sheet resistance, series resistance, and photoelectric conversion efficiency of the conducting silver films. We found that the activation temperature affected the number and distribution of silver nanoparticles. Meanwhile, the average grain size of the silver particles and the silver content in the Pb-based glass frit coated with Ag material could be controlled by adjusting the pH value and loading capacity, respectively, during plating.     

Anisotropy of composite materials with inclusion with orientation preference

In this paper, the quasicrystalline model and the differential evolution strategy are applied to analyze the effective electromagnetic properties of composite materials with aligned nonspherical inclusions. The relationship between the effective wave number, volume concentration, direction of wave propagation vector, and aspect ratio of the inclusion particle are numerically studied. It is found that composite materials with small inclusion particles behave like uniaxial material. In addition, we observed general effective anisotropy in composite materials with larger inclusion particles.     

A miniaturized silicon-based ground Ring Guarded patch resonator and filter

A new miniaturized ground ring guided microstrip patch filter developed on the silicon wafer using micromachined technology is reported. The ground shunt can be used to lower the operating frequency up to one-third as compared to the traditional patch resonator. The size of the designed band pass filter operating in 5.17 GHz is only 8.7 mm/spl times/2.9 mm.     

Equivalent circuit model of on-wafer CMOS interconnects for RFICs

This paper investigates the properties of the on-wafer interconnects built in a 0.18-/spl mu/m CMOS technology for RF applications. A scalable equivalent circuit model is developed. The model parameters are extracted directly from the on-wafer measurements and formulated into empirical expressions. The expressions are in functions of the length and the width of the interconnects. The proposed model can be easily implemented into commercial RF circuit simulators. It provides a novel solution to include the frequency-variant characteristics into a circuit simulation. The silicon-verified accuracy is proved to be up to 25 GHz with an average error less than 2%. Additionally, equivalent circuit model for longer wires can be obtained by cascading smaller subsections together. The scalability of the propose model is demonstrated.     

SCPC卫星通信系统中计算互调噪声功率谱的一种快速方法

本文利用ＳＣＰＣ的特点，提出和推导了ＳＣＰＣ卫星通信系统中互调噪声功率的一种快速计算方法。对于１３００个载波的ＳＣＰＣ系统，在普通的３８６／３３ＰＣ机上，利用此法计算时间仅需１５ｍｉｎ，因此它对ＳＣＰＣ系统设计具有使用价值。     

一种应用于双通道卫星导航接收机的高效率低噪声电源解决方案

本文提出了一种应用于双通道卫星导航接收机的高效率低噪声电源解决方案,主要包括降压型DC-DC转换器和低压差稳压器。为了获得更好的噪声抑制和抗干扰性能,应用脉冲宽度调制(PWM)作为DC-DC转换器的控制方式。提出了一种改进的低功耗PWM控制电路,通过周期性的关断跨导放大器,将转换器的平均静态功耗降低了一半,并且具有较高的工作频率。针对双通道接收机的特点,对输出级功率管的尺寸进行了优化,使效率最优。另外,提出了一种基于限流原理的新型软启动电路,无须使用片外大电容或数模转换器,降低了设计复杂度。电路使用180nm CMOS工艺流片,测试结果显示,DC-DC转换器在2MHz的工作频率下拥有最高93.1%的转换效率,整个双通道接收机在3.3V电源供电下仅消耗电流20.2mA。     

WiMax近场干扰对UWB系统特性影响的仿真研究

研究了超宽带（UWB）无线通信系统抗WiMax系统的近场电磁干扰能力,为此,首先构建了包括UWB系统和WiMax近场电磁干扰等效的分析模型;其次,基于该分析模型研究了WiMax近场干扰对IEEE 802.15a UWB系统接收灵敏度的影响,得到了在给定场景和WiMax系统参数条件下,UWB系统接收灵敏度的回退量ΔS与其传输速率的关系曲线模型。该关系曲线模型对UWB＋WiMax双模系统共存设计具有重要的理论指导意义。