一种多波束阵列重构导航抗干扰算法

多波束抗干扰技术根据期望信号与干扰信号来向自适应形成主瓣和零陷，从而达到抑制导航干扰并增强期望信号的目的。多波束抗干扰技术的性能与阵列规模有着直接关系，更大规模阵列的抗干扰性能更好，但在工程应用中会受到算法收敛速度、硬件资源消耗与抗干扰处理实时性等方面限制，而小尺寸阵列抗干扰性能明显降低。针对这一问题，提出了一种多波束阵列重构导航抗干扰方法，针对不同期望信号与干扰信号来向分别进行优化，通过在全阵列中优化选取部分阵元组成最优子阵列，使用不同子阵列结构对不同来向期望信号进行波束形成。     

PI算法在GPS抗干扰圆形天线阵中的应用

随着GPS的广泛应用,出现了各种各样的干扰措施,为了能使GPS接收机正常工作,提出了许多抗干扰方法,其中自适应天线抗干扰尤为有效,功率反演(PI)算法能够使天线阵产生指向干扰方向的波束零陷,从而达到抗干扰的目的。推导了圆形天线阵中的信号向量表示方式,并且将功率反演算法应用于圆阵之中。仿真结果表明,应用功率反演算法的自适应天线阵不适为一种有效的GPS抗干扰方法。     

一种子阵级波束形成抗干扰方法

自适应波束形成技术是相控阵雷达抗干扰的一种重要手段,目前提出的许多有效方法都是基于阵元级线阵自适应波束形成方法,而实际的相控阵雷达系统多采用阵面结构.结合线性约束最小方差(LCMV)算法,研究了一种子阵级波束合成抗干扰方法.在目标方位接收功率不变的条件下,最大限度抑制干扰方向信号接收.     

基于二次组阵的低旁瓣波束形成方法

为了有效地降低阵列天线在数字波束形成过程中旁瓣水平,提出了一种通过二次组阵实现的低旁瓣自适应波束形成方法。在阵列相互重叠的子阵划分基础上,通过子阵对期望信号及干扰信号进行自适应波束形成,实现对期望信号的增益接收以及对干扰信号的深度抑制。在子阵数字波束形成的基础上,对各个子阵的输出运用二次组阵的方法,对二次组阵的方向图在约束条件下进行波束合成实现对子阵方向图中旁瓣的对消补偿,从而达到降低旁瓣的目的。通过理论分析和实验仿真表明,与常规LCMV方法相比,基于二次组阵的波束形成方法在保证了对干扰信号深度抑制的同时,有效地降低了方向图中的旁瓣水平,提高了系统的抗干扰性能。     

ADC量化位数对阵列天线GNSS接收机的影响

在处理全球卫星导航系统（Global Navigation Satellite System,GNSS）卫星信号时,针对模数转换器（Analog-to-Digital Converter,ADC）量化位数不同导致输出的信号信噪比下降的问题,推导了阵列天线波束形成后输出信号的信噪比理论计算模型,分析了ADC量化位数对阵列天线抗干扰GNSS接收机的性能影响。在7阵元天线且ADC量化位数为10的条件下,理论模型分析和数据仿真结果表明最大抗干扰能力约为85 dB。通过确定ADC量化位数与抗干扰GNSS接收机抗干扰能力之间的关系,其结论为工程应用中抗干扰GNSS接收机的ADC选型和设计提供了理论依据。     

一种应用于GPS抗干扰的改进LCMV算法

研究了一种基于LCMV算法的自适应波束形成算法。结合GPS卫星信号的特点将该算法应用于GPS接收机的抗干扰系统中。文中对该自适应算法进行了推导和Matlab仿真,并使之与LCMV算法的仿真效果作比较,结果表明,该算法能更好地抑制干扰、保留期望信号。     

基于卫星导航定位系统自适应抗干扰控制

在全球卫星导航系统抗干扰问题的研究中,自适应波束形成技术很好地解决了与信号不同来向的干扰的抑制问题。但对与信号同向的窄带干扰抑制程度不够,同时会滤除部分导航信号。针对以上问题,提出了一种改进的自适应波束干扰抑制算法。首先,通过级联IIR格型陷波器预测并抑制与信号同向的窄带干扰,然后,利用基于直接数据域自适应波束形成技术抑制剩余的宽带干扰。该改进算法能够有效的滤除窄带和宽带干扰,提升卫星导航系统的抗干扰性能,并在实际卫星通信应用中更具处理的实时性。最后,通过仿真实验证明了该算法的可行性。     

数字波束形成雷达研究

对采用T/R组件的数字波束形成(DBF)雷达进行了研究。实现数字波束形成有三种很重要的技术,即相位检波技术,多波束形成技术和自适应波束形成技术。为验证这些关键技术我们研制了一DBF阵列测试设备,文中就这几种技术及测试设备的数据进行了介绍。 要实现高的数字波束形成性能,必须以很高的精度将天线单元信号变换为数字信号。为解决这一问题,我们将中频直接采样相位检波同特制大规模集成电路结合使用。 多波束形成技术应用于雷达需采用超高速电路,我们具体采用的是Systolic阵方法。在Systolic阵中,通过控制各个波束的复数加权值就可形成任意和独立控制的多波束。 数字波束形成中易于应用自适应技术,具体使用的是采用了G-S变换方法的Systolic阵,该自适应电路已研制且在室外场地进行了测试。施放干扰信号,然后测量自适应处理前后的天线方向图,文中也给出了所测数据。     

自适应多波束三维阵天线的研究

由于多波束天线系统在近代通信中占有愈来愈重要的地位,本文从阵辐射空间基本性质出发,将最小均方自适应技术扩展应用于多波束天线系统,从而提出自适应多波束三维阵天线课题。它包括:自适应三维阵系统辐射图型表达式;瞬态阵辐射图型生成过程;阵系统输出信/噪比表达式;自适应多波束网络的构成。     

智能天线在移动通信系统中的应用

1 智能天线定义和技术特点智能天线原名自适应天线阵列(AAA,Adaptive An-tenna Array)。最初的智能天线技术主要用于雷达、声纳、抗干扰通信、定位、军事方面等,用来完成空间滤波和定位。智能天线是利用数字技术在基带形成天线波束,以此代替模拟电路形成天线波束,从而提高了天线系统的可靠性与灵活程度,智能天线技术因此在移动通信中得到应用。智能天线分为两大类:多波束智能天线与自适应阵智能天线,简称多波束天线和自适应阵天线。多波束天线利用多个并行波束覆盖整个用户区,每个波束的指向是固定的,波束宽度也随阵元数目的确定而确定…     

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.     

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.     

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.     

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.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

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.