自由空间量子通信动态偏振补偿研究(英文)

In polarization-encoded free-space quantum communications, a transmitter on a satellite and a receiver in a ground station each have a respective polarization zero direction, by which they encode and decode every polarization quantum bit required for a quantum communication protocol. In order to complete the protocol, the ground-based receiver needs to track and compensate for the polarization zero direction of the satellite-based transmitter. Expressions satisfied by amplitudes of the s-polarization component and the p-polarization component are derived based on a two-mirror model, and a condition satisfied by the reflection coefficients of the two mirrors is given. A polarization tracking principle is analyzed for satellite-to-ground quantum communications, and quantum key encoding and decoding principles based on polarization tracking are given. A half-wave-plate-based dynamic polarization-basis compensation scheme is proposed in this paper, and this scheme is proved to be suitable for satellite-to-ground and intersatellite quantum communications.     

Rain Attenuation and Doppler Shift Compensation for Satellite Communications

In high‐speed multimedia satellite communication systems, it is essential to provide high‐quality, economical services by using efficient transmission schemes which can overcome channel impairments appearing in the satellite link. This paper introduces techniques to compensate for rain attenuation and the Doppler shift in the satellite communication link. An adaptive transmission technique with a control algorithm to adaptively allocate transmission schemes is used as a countermeasure to rain attenuation. We introduce a new rain attenuation modeling technique for estimating system performance and propose a novel Doppler shift compensation algorithm with reduced hardware complexity. Extensive simulation results show that the proposed algorithm can provide greatly enhanced performance compared to conventional algorithms. Simulation software and hardware which incorporate the proposed techniques are also demonstrated.     

A Modified Barrett-Lampard Expansion and Its Application to Bandpass Nonlinearities with Both AM-AM and AM-PM Conversion

A two-dimensional Barrett-Lampard expansion is developed to handle two-dimensional nonlinear systems with random Gaussian inputs. The theory is applied to the problem of evaluating the mean signal and the inphase and quadrature noise correlation functions at the output of a TWT nonlinearity exhibiting arbitrary AM-AM and AM-PM characteristics, when the input consists of a narrow-band signal and Gaussian noise. As a specialized application, the classical problem of determining the coherent and incoherent noise correlation functions at the output of a power-law bandpass nonlinearity is also considered. The results are of interest in assessing the performance of coherent satellite communication channels. The theory developed is accompanied by numerical examples of practical interest.     

A Direct-Coupled Lambda/4-Coaxial Resonator Bandpass Filter for Land Mobile Communications

A bandpass filter operating at 870 MHz was constructed using lambda/4-coaxial resonators. The resonators were made of metallized high- Q dielectric ceramic (Q>=10 000, epsilon/sub r/ = 37), and were directly coupled to each other through apertures which were formed on the outer side surface of the resonators. In order to couple the input and output resonators to the external circuit, a rectangular metal film was deposited on the open-circuit end. The resonant frequency of each resonator, coupling coefficients between adjacent resonators, and external Q's at both ends were adjusted before assembly. The resonators were then assembled in a housing with no further adjustment. The measured response was in excellent agreement with the theory.     

带通滤波器谐振功率特性分析与研究

通过多个不同拓扑结构带通滤波器并联等效电路,系统地分析了影响滤波器谐振功率特性的主要因素:无载Qu值、相对带宽和主耦合系数以及交叉耦合.同时结合群时延理论解释了相对带宽和主耦合系数对谐振功率特性的影响,针对交叉耦合对滤波器内部三腔、四腔交叉耦合结构中关键谐振腔谐振功率特性的影响,利用相位方法进行了定性的分析.最后,对一款包含三腔交叉耦合结构的TM模式介质滤波器的谐振腔功率进行了耦合测试,得到的测试曲线与电路分析的结果相吻合.     

光纤通信非线性补偿中的非线性光环路镜

介绍了用于光纤通信非线性补偿中的几种非线性光环路镜(NOLM,包括ANOLM、DALM、NALM、DILM、RA-NOLM、NBLM及DANLM)的构成和功能,给出了部分传输补偿实例,指出NOLM的发展趋势是小型化和集成化。     

微带SIR带通滤波电路寄生通带的分析

本文分析微带SIR（阶梯阻抗谐振器）带通滤波电路的寄生通带问题。这种滤波器的特点是其寄生响应时以通过阻抗比K进行控制，因而增进了谐波抑制性能。SIR可以采用等电长度或非等电长度。等电长度SIR滤波电路的第三寄生通带的带宽来零，然而，非等电长度SIR滤波电路却增加了设计的灵活性，分析与探讨微带SIR滤波电路的寄生带通问题，对于合理设计与应用这种滤波电路是有益的。     

网络通信PCB市场分析

2001年全球PCB产品供需严重失衡,美、日等PCB巨头纷纷减产关厂,而2002年上述情况均实现了较明显的恢复。但由于市场竞争日益激烈,全球包括单面板、双面板、多层板及挠性板在内的全线PCB产品价格不断走低。再力上2002年下半年市场需求复苏未达预期,因此全球PCB市场销量虽有上升,总体上结束了下滑的颓势,但销售额与2001年相比基本持平。     

Dissipativity Analysis and Stabilization for Stochastic Systems with Repeated Scalar Nonlinearities and Applications

This paper investigates the problem of exponential dissipativity for stochastic systems with repeated scalar nonlinearities. The nonlinear system is described by a state equation containing a repeated scalar nonlinearity, which typically appears in recurrent neural networks. Attention is focused on the exponential dissipativity analysis of stochastic systems with repeated scalar nonlinearities with respect to quadratic supply rates. Passive and non-expansive property of stochastic systems with repeated scalar nonlinearities is also characterized. Moreover, a controller has been designed to make the stochastic systems with repeated scalar nonlinearities asymptotically stable. A Marketing-Production system and a Chua circuit are given to illustrate the effectiveness of the proposed design method.     

高速光纤通信中的偏振模色散及其补偿技术

偏振模色散已成为当前发展下一代高速长距离光纤传输系统的主要限制因素,介绍了偏振模色散的概念、描述方法以及测试和补偿技术。根据国外的研究情况和我国的具体实情,指出研究振模色散的测试和补偿技术对提高我国高速光纤通信技术的水平具有重大意义。最后在此基础上提出了开展相关研究的建议。     

短波地空通信链路可靠度分析

可靠度是衡量短波地空通信链路性能的重要指标.分析了空间多样性和频率多样性对短波通信链路可靠度的影响,在此基础上将两者联合考虑,得出了飞机航空站与地面固定站进行短波通信时,2个地面站和7个频点情况下可以提供较高的联合可靠度的结论,通过仿真验证该结论为合理的站点数和频率数组合.     

展宽器元件失调及带通分析

通过光线追迹法给设计的反射式单光栅展宽器建立了一个数学计算模型。利用这个数学模型计算和分析了元件失调对反射式单光栅展宽器二阶色散量和输出光束发散角的影响,并考虑了反射式单光栅展宽器中衍射光栅和球形凹面镜的尺寸与展宽器带通的关系。发现当平面反射镜 M1 的纵向偏离角为 0. 2°时,展宽器的二阶色散量最大,偏离角大于或小于0 .2°时,展宽器的二阶色散量随之减小;得到了元件失调会增加输出光束发散角的结论;并发现展宽器中衍射光栅和球形凹面镜尺寸的有限大小对带通有限制作用。提出了利用反射镜 M1 纵向的适当偏离增大展宽器二阶色散量的方法,以及增大衍射光栅和反射镜尺寸来提高展宽器带通的方法,从而进一步减少展宽过程中的光谱剪切。     

对大功率滤波器的设计与分析

为了抑制微波发射机的杂波输出,需要在其后面连接一个大功率带通滤波器.文中介绍了可满足系统要求的微波梳状线带通滤波器的原理、结构和设计方法,分析了介质陶瓷电容片对滤波器脉冲功率容量的影响.采用切比雪夫低通原型设计了6级平行耦合带状线滤波器,用HFSS优化结构尺寸,制作了中心频率为1 085 MHz,相对带宽大于20%,插入损耗小于0.7 dB,宽阻带,脉冲功率容量大于800 W的带通滤波器,滤波器具有结构牢固,性能稳定,重量轻等特点.     

A State-Space Approach to Intermodulation Distortion Estimation in Fully Balanced Bandpass Gm– C Filters With Weak Nonlinearities

A state-space approach to estimating intermodulation distortion in bandpass G_m-C filters with fully balanced, weakly nonlinear transconductors is introduced. It results in compact analytic expressions applicable to G_m-C filters of any order. For verifying the theory, two G_m-C filters with fully balanced weakly nonlinear transconductors have been designed using Cadence. They have been simulated in SpectreS as well as modeled and simulated in Simulink. Theory and simulation results are found in good agreement     

FIR低通和带通滤波器的关系分析与仿真

为了避开直接设计带通滤波器的繁琐设计步骤要求,利用低通滤波器与带通滤波器的关系,间接设计带通滤波器是创新之处,即通过设计简单的低通滤波器从而达到设计带通滤波器的要求。介绍了窗函数法FIR数字低通、带通滤波器的设计,给出了低通滤波器与带通滤波器的频率响应函数,并分析了它们之间的关系,得出了相关结论,结合实例,利用Matlab证实了该结论的正确性,为带通滤波器的设计提供了一种新方法。     

Queueing Models for Computer Communications System Analysis

Modeling and performance prediction are becoming increasingly important issues in the design and operation of computer communications systems. Complexities in their configuration and sophistications in resource sharing found in today's computer communications demand our intensive effort to enhance the modeling capability. The present paper is intended to review the state of affairs of analytic methods, queueing analysis techniques in particular, which are essential to modeling of computer communication systems. First we review basic properties of exponential queueing systems, and then give an overview of recent progress made in the areas of queueing network models and discrete-time queueing systems. A unified treatment of buffer storage overflow problems will be discussed as an application example, in which we call attention to the analogy between buffer behavior and waiting time in theGI/G/1queue. Another application deals with the analysis of various multiplexing techniques and network configuration. An extensive reference list of the subject fields is also provided.     

空间信息传输网络层协议分析

网络层处于空间信息传输协议体系的关键层,其协议选择关系着能否实现未来航天任务提出的动态数据传输、灵活路由选择、与地面网络的互操作性等技术要求。对CCSDS空间分包协议、SCPS-NP协议和IP协议等可用于空间通信的网络层协议进行了总结分析,并从功能、地址空间、协议开销和技术成熟度及产品支持等方面进行了比较。可以看出,IP协议是未来空间任务的合理选择。对于没有空间链路路由选择的任务,可先使用CCSDS空间分包协议解决动态数据传输问题。     

个人通信信令系统性能分析

本文提出一种个人通信信令系统分析的通用模型,用它对GSM和采用IS-41信令系统的负荷进行了性能分析.     

立急通信国际标准组织研究情况分析

应急通信是信息通信网络安全保障的重要机制之一。随着日益增多的大型集会,以及一系列的突发事件如,地震、火灾、疫情的频发,应急通信的作用越来越凸显,也越来越受到各国政府和标准化组织的重视。本文介绍了国际上标准化组织针对应急通信的研究现状,总结并分析了应急通信技术研究重点。     

Models for Analysis of Packet Voice Communications Systems

In a packet voice communication system, packets are fed to a common queue by a number of independent voice sources and are removed from this queue on a first-come-first-serve basis for transmission over a communication link of finite capacity. Each voice source alternates between active periods, during which packets are generated at regular intervals, and inactive periods, during which no packets are generated. In this paper, we discuss three models, a semi-Markov process model, a continuous-time Markov chain model, and a uniform arrival and service model, to assess the queueing behavior of such systems. Numerical results obtained from each of the three models are compared to each other, to results obtained from a discrete event simulation program, and to results obtained from anM/D/1analysis. Parameters of the model are the average duration of active and inactive periods, the packet generation rate, the communication link capacity, and the total number of voice sources. Conclusions are drawn regarding which models appear to be most appropriate in the parameter ranges investigated.