军事通信抗干扰新技术发展研究

本文阐述了军事通信抗干扰技术的发展方向，重点研究了短波高速跳频技术、直扩中OFDM技术和自适应调零天线与跳频相结合的卫星通信综合抗干扰技术，并对此提出了相应的发展建议。     

短波自适应跳频通信抗干扰技术研究

针对军事无线通信抗干扰和保密性需求，给出了自适应跳频通信系统模型。采用双态信道模型，深入分析了自适应跳频系统的抗干扰性能。分别在部分频带噪声干扰和多音干扰下，对常规跳频系统和自适应跳频系统性能进行了仿真，结果表明自适应跳频系统对上述两种干扰有较好的抗干扰性能。     

跳频卫星信号传输波形设计研究

跳频通信是对抗各种恶意干扰的一种基本手段,已经被广泛地应用于卫星通信系统。针对宽带高速跳频卫星通信的传输需求,提出了一种跳频卫星通信系统抗干扰增效策略,在跳频通信的基础上进一步提高系统的综合抗干扰性能。通过建立完整的宽带高速跳频卫星通信系统仿真模型,结合高效LDPC码、π/4-DQPSK调制和交织等多种技术进行传输波形的优化仿真设计。理论分析和仿真结果表明,采用该波形且E_b/N_0不低于6.2 d B时,系统抗阻塞干扰能力不低于22 d B。     

短波全数字自适应跳频通信

自适应跳频方式和短波通信的结合是现代短波通信系统的特点。由于采用了数字信号处理技术、自适应跳频技术和直接数字式频率合成技术,所以短波自适应跳频通信系统具有良好的抗干扰性能,被广泛应用于军事通信中。 一、短波全数字自适应跳频通信系统 在短波单边带通信系统数字化的基础上,增加自适应跳频控制器和跳频调制解调器的数字化电路部分,就形成了短波全数字自适应跳频通信系统。 短波全数字自适应跳频通信系统主要由声码器、编码／解码器、自适应跳频控制器、调制解调器和单边带收／发信机等组成。其中,自适应跳频控制器确定系统…     

自适应跳频在卫星通信抗干扰中的应用

在我国现阶段的卫星通信系统中,多频时分多址技术是一种比较流行的技术,其具备相对完善的跳频能力,也能够以此为基础,实现较好的抗干扰效果。文章主要以多频时分多址技术为研究基点,分析当前的自适应跳频技术,并研究在卫星通信过程中,对相关干扰的检测,最后论述自适应跳频对干扰的躲避应用。     

自适应跳频通信系统抗干扰性能分析

部分频带噪声干扰和多音干扰对常规跳频通信系统危害较大,自适应跳频系统能够改善跳频通信系统的抗干扰性能。基于自适应理论,对两个系统的抗干扰性能进行了仿真和比较,结果表明,自适应跳频通信系统对抗这两种干扰性能较强,适用于军事通信和其它易受人为干扰的通信领域。     

跳频卫星通信系统的设计及关键技术

本文在建立跳频卫星通信系统抗干扰模型的基础上，提出了跳频卫星通信系统的设计思想，重点讨论了跳频卫星通信中必须解决的若干关键技术 。     

跳频通信中的抗干扰同步算法研究

跳频通信体制以其较好的抗干扰和低截获性能,在军事通信中有着广泛的应用,其中跳频同步是该体制的关键技术之一。为提高跳频通信系统抗干扰性能,提出了一种具有自适应抗干扰能力的跳频同步方案,并给出了系统框图及关键算法分析及性能讨论。最后仿真结果表明,该同步方案具有抗干扰能力强,捕获概率高,虚警概率低的特点,而且在保证同步时间要求的前提下,具有根据信道特性,自适应地调整抗干扰门限的能力。     

跳频卫星通信同步技术研究

跳频同步是跳频通信技术的关键.考虑到抗干扰的需要,将跳频体制引入到卫星通信中.比较常规跳频同步实现方法的优缺点,根据设备低复杂度以及同步捕获时间短的要求,将同步头+ TOD的同步方法引入到跳频卫星通信系统中,研究了同步序列格式,同步头的结构,同步频率的算法,设计了初始同步的方案.     

混合DS／SFH CDMA扩频通信系统中的自适应跳频

文章基于进一步提高跳扩频通信系统的抗干扰性能，提出了在混合直接序列扩频（DS／SFHCDMA）通信系统中实现自适应跳频（AFH）方式，给出了基于优化考虑的自适应跳频地址编码方法，在给出信道仿真参数的前提下，对自适应跳频系统的误码性能进行了分析。结果表明自适应方式优于传统方式。     

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.     

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.     

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.     

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.