基于电光调制的毫米波辐射计研究

研究了一种通过电光调制将毫米波信号加载到光载波上进行处理的毫米波辐射计。天线接收的毫米波信号由电光调制器（EOM）调制加载到光载波的边带上,并通过光纤传输该信号;利用光纤布拉格光栅（FBG）滤波器滤掉载波分量,滤波后保留的边带分量信号由光电探测器（PD）探测。为提高探测灵敏度,使用锁相放大器对PD输出的信号进行检测。分...     

一种多波段矢量毫米波信号概率整形性能分析

光子辅助方法易于产生和调制宽带矢量毫米波或太赫兹信号.基于强度调制器与同相/正交(I/Q)调制器级联的相干光路结构,结合概率整形技术,在VPI和MATLAB环境下对其多波段矢量毫米波信号的产生和传输性能进行了联合仿真分析.在载波频率分别为70 GHz和130 GHz的两个波段上,针对净比特速率为32 Gbit/s的均匀16阶正交幅度调制(16QAM)格式与概率整形16QAM格式的单边带矢量毫米波信号,分析对比了两者的产生与传输性能.研究结果表明:概率整形16QAM毫米波信号的光纤传输性能均优于均匀16QAM毫米波信号,且发现在考虑光纤非线性效应时其概率整形的矢量信号具有更大的传输优势.     

采用半导体光放大器进行直接调制的全双工光纤无线通信系统实验研究

提出并实验研究了一种将光源和光调制器集中于中心站,而基站中使用直接调制半导体光放大器的新型光纤无线通信系统,在中心站采用相位调制器和光交错复用器产生光毫米波,并同时将未调制信号的光载波与光毫米波一起发送到基站;在基站中将下行链路的光载波分离出来作为上行链路的光载波,并利用半导体光放大器将上行链路的信号调制到光载波上,同时对上行链路的信号进行放大.实验结果显示可以将下行链路中2.5Gbit/s的数据和上行链路中250Mbit/s的数据在单模光纤中传输40km.     

光载毫米波在光纤中传输色散性能研究

提出了并理论分析了一种采用单电极Mach–Zehnder调制器(SD-MZM)产生光载毫米波的方案。采用电混频器将射频信号与基带数字信号混频后再利用单电极调制器产生双边带调制信号并发送至光纤,在基站使用一个交叉复用器(IL)将双边带信号的中心载波与一阶边带信号进行分离,中心载波可用于上行链路的光载波,而一阶边带产生光载毫米波;理论分析了该毫米波的色散特性并在仿真平台上验证了其正确性,研究发现由于光纤色散引起两个一阶边带的延时不同, 从而导致毫米波能量的损失和解调信号的码间干扰,限制了毫米波的最大传输距离。     

1.5GHz高线性BPSK调制器

本文介绍了适用于小型化数字微波发信机的分谐波ＢＰＳＫ调制器，具有低失真，低载波泄漏，矢量调制误差小的特点，在１４２７￣１５２５ＭＨｚ频段内载波泄漏抑制大于３５ｄＢｃ，三阶交调抑制大于４０ｄＢｃ，分谐波混频直接调相技术在小型化微波、毫米波数字无线通信系统中具有广阔的应用前景。     

正交调制器的校准设计

在当前许多复杂调制射频信号源中,随着数字基带信号越来越多的加入．需要正交凋制器将其调制到需要的载波信号上。正交调制器原理简单：将生成好的I/Q两路基带信号调制到两路正交的载波上,合路后输出。但是在实现时,想获得好的指标就需要考虑载波相位误差,I/Q基带信号幅度不平衡以及载波泄漏等问题。文章给出了一种正交调制器的校准方案,可以减少和模拟以上三种现象造成的调制误差,并给出自动校准和手动校准两种方法。     

采用单个相位调制器产生毫米波

实验研究了采用单个相位调制器(PM)产生毫米波的方案。该方案采用电混频器将射频(RF)信号与基带信号混频后再利用相位调制器产生双边带调制(DSB)信号,经光纤传输到基站后用一个光交叉复用器(IL)分离一阶边带和中心载波,一阶边带经过光电(O/E)检测器拍频产生两倍频于射频频率的毫米波,而中心载波可以作为上行链路载波重新利用。理论分析了该毫米波的传输性能,研究发现由于色散导致两个一阶边带时延不同,码元的占空比会随着传输距离的增加而减小,将限制毫米波的最大传输距离;实验中采用频率为20 GHz射频信号产生频率为40 GHz的毫米波,速率为2.5 Gbit/s的非归零(NRZ)码作为下行链路数据,经过20 km色散光纤传输后下行链路的功率代价为0.2 dBm。     

基于双平行MZM调制器的矢量毫米波信号传输性能分析北大核心CSCD

提出了一种基于双平行马赫-曾德尔调制器(dual parallel Mach-Zehnder modulators,DP-MZM)的单边带矢量毫米波信号产生和传输方案,在MATLAB和VPI联合仿真环境下分析了90 GHz波段不同调制格式信号的产生和传输性能。仿真中,DP-MZM工作在光载波抑制(optical carrier suppression,OCS)模式时,小信号驱动的两个子调制器输出的单边带信号相互叠加后,无需使用滤波器,可以实现完全抑制中心载波的效果。结果表明:经过该系统传输后,各调制信号的误码率(bit error rate,BER)均可达到硬判决前向纠错(hard judgment forward error currection,HD-FEC)阈值。概率整形后正交幅度调制信号的误码性能明显优于均匀正交幅度调制信号,其中,7 bit/symbol概率整形256阶正交幅度调制(probability shaping 256 quadrature amlitude modulation,PS-256QAM)信号经过系统传输后功率增益最为明显,经过50 km光纤传输后,提升了2.94 dB的功率增益。与目前存在的载波抑制毫米波产生方案相比,该系统结构相对简单,可调节度高,信号传输增益明显,因此具有一定的应用价值。     

分谐波混频在数字微波直接变频调制／解制器中的应用

在微波／毫米波频段，高电平载波泄漏是制约数字直接变频调制器（如ＱＰＳＫ）性能、产生调制矢量误差的一个重要因素。在直接变频接收方式中，二阶交调失真（ＩＭ２）及本振噪声是制约动态范围的关键因素之一。偶次分皮混频可有铲地抑制载波泄漏、二次混频失真及本振噪声、是提高调制器精确度及直接解调器动态范围的有效技术。     

基于级联双平行MZM的16倍频光生毫米波技术

为解决毫米波信号生成中存在的困难,提出了一 种基于级联双平行马赫-曾德尔调制器(DPMZM)的16倍频光生毫米波 系统。首先通过控制第1个DPMZM的直流偏压、驱动信号相位差和调制指数,完全抑制光载波 和±2阶边带,获得±4阶光边带;然后将该光波输入到另一个完全一样的DPMZM,获得±8阶光边 带和光载波输出;最后利用光滤波器(OF)滤除光载波,用光电探测器(PD)拍频得到 16倍频的毫米波输出。详细分析 了系统的工作原理,并通过仿真验证了方案的可行性。当输入射频(RF)驱动信号频率为2.5GHz时,可 得到40GHz毫米波输出,并且调制器的调制带宽仅需要 2.5GHz。本文方案具有倍频次数高、频谱纯度好等优点。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.