阵列天线的切比雪夫方向图综合

阵列天线是指由多个离散的辐射元,按一定规律排列组成的天线系统.其具有高增益,强方向性,主瓣可控等特性.文中研究了利用切比雪夫法对阵列天线输入不同参数:馈源单元数N,馈源间距d,副瓣电平SLL,得出参数改变对阵列天线方向图的综合影响,通过工程示例论证出切比雪夫法用于方向图综合的优缺点.为切比雪夫法用于天线方向图综合比较提供了一种有效的参考方法.     

基于Gilbert丢包机制的TCP吞吐量模型

 丢包机制是推导TCP吞吐量模型的关键,直接影响模型的准确性.本文利用四状态Gilbert丢包机制来描述端到端路径上的丢包行为,对TCP的拥塞控制过程进行建模,在此基础上提出了一种更精确的TCP吞吐量模型.实验表明,改进的模型能较好的与实际值相拟合,可以更精确地预测实际TCP数据流的吞吐量性能.     

MEMS光栅光调制器与CMOS驱动单片集成的研究

为了消除光栅光调制器阵列的交叉效应,提出利用post-CMOS工艺将光栅光调制器与CMOS驱动单片集成.介绍了单片集成器件的工作原理,详细分析了单片集成器件的关键参数.通过分析表明,在满足调制器响应频率条件下,通过改变悬臂梁的各个参数可以减小调制器的弹性系数,从而降低光栅光调制器的工作电压;在满足开关速度的条件下,较大存储电容具有更好的电压保持特性.利用中芯国际提供的0.18μm工艺设计包完成该单片集成器件的物理版图设计和仿真.最后,通过实验测得该器件的上升沿和下降沿时间分别为:36.8ns和36.4ns,且经过16.73ms的保持时间后压降为2.1v.实验结果与仿真结果具有较好的一致性,结果表明:加工的单片集成器件具有较快的开关速度和较好的电压保持特性,能够满足设计要求.     

Low-Dimensional Waveguide Grating Fabrication in GaN with Use of SiCl<Subscript>4</Subscript>/Cl<Subscript>2</Subscript>/Ar-Based Inductively Coupled Plasma Dry Etching

Optimized fabrication of submicron-sized features in gallium nitride (GaN) with the use of inductively coupled plasma (ICP) dry etching, based on SiCl₄/Cl₂/Ar gas mixture, is presented. Dense periodic patterns, i.e., 400-nm-period gratings, were transferred into a gallium nitride waveguide under different etching conditions. ICP power, radiofrequency (RF) power, chamber pressure, and Ar/Cl₂ gas mixing ratio were altered during the experiment. Depths of fabricated grating couplers up to 670 nm were achieved. The most suitable etching conditions are discussed with the assessment based on etching selectivity, scanning electron microscopy (SEM) observation of grating tooth slope, hard-mask erosion process, and etched surface morphology.     

Proposal for a novel and simple WDM NRZ-DPSK system

A novel and simple non-return-to-zero differential phase shift keying (NRZ-DPSK) wavelength division multiplexing (WDM) system, which can simultaneously demultiplex and demodulate multiple wavelengths, is proposed and investigated in this paper.The phase-to-intensity demodulation principle is based on detuned filtering, which is achieved by using a single commercial array waveguide grating (AWG) in our scheme.By properly choosing appropriate AWG channels at the transmitter, the AWG at the receiver can act as both the demultiplexer and the demodulator of the DPSK signals.Simulations at 10, 20, and 40 Gbit/s show good flexibility and performance for the proposed system.     

A discrete convolution involving Fourier sine and cosine series and its applications

ABSTRACT

In this paper, we introduce a discrete convolution involving both the Fourier sine and cosine series. We study Young's type inequality and a discrete transform related to this convolution and solve in closed form a class of discrete Toeplitz plus Hankel equations.     

Development of an Event Stream Processing System for the Vehicle Telematics Environment

In this letter, we present an event stream processing system that can evaluate a pattern query for a data sequence with predicates. We propose a pattern query language and develop a pattern query processing system. In our system, we propose novel techniques for run‐time aggregation and negation processing and apply our system to stream data generated from vehicles to monitor unusual driving patterns.     

Switchable Printed Yagi-Uda Antenna with Pattern Reconfiguration

A switchable Yagi-Uda antenna prototype with radiation pattern reconfiguration is presented in this letter. The proposed reconfigurable antenna is based on the concept of switching between the reflector and director of a Yagi-Uda antenna using a radio frequency PIN diode. As a result, the minimum/maximum radiation can be steered towards desired signals or away from interfering signals in opposite directions. The measured 10 dB impedance bandwidth and gain are 210 MHz (7%) and 8.02 dBi at 3 GHz, respectively. Details of the antenna design and its performance are described and empirically analyzed.     

Repeated Transfer of Colloidal Patterns by Using Reversible Buckling Process

The reversible nature of buckling is employed to repeatedly transfer colloids assembled in buckling patterns to flat surfaces. The cycle of colloidal loading–transfer–buckling is repeatedly carried out to fabricate the same colloidal patterns. The key to success is the reduction in the amplitude of the buckling patterns to a few nanometers as well as the recovery of initial buckling patterns after repeated stretching. The reduced buckling amplitude by poststretching or thermal annealing embosses the colloids assembled in the trenches of the buckling patterns, which enables the transfer regardless of the size, species, or layer thickness of the particles. This report demonstrates various transferred patterns composed of colloidal crystals, fluorescence hydrogel colloids, Au nanoparticles, and iron oxide magnetic particles. Since the process does not require surface modification of the colloids, it can be used to fabricate any colloidal patterns.