高速数字接收机中位同步与滤波联合实现方法

针对高速数字接收机中的位同步问题,提出了一种位同步与滤波联合实现结构.该结构利用一次快速傅里叶变换(FFT)运算将信号变换至频域,从中提取定时信息并实现定时恢复,同时完成滤波处理,极大地降低了系统的运算量,节约了硬件资源,并且能够先于载波同步稳定工作.理论分析与仿真结果表明,该结构算法复杂度低,比常用时域方法减少了约60%的运算量,能够在中等信噪比条件下(15 dB以上)准确实现位同步,适用于高速调制解调系统.     

基于PCF的BOC信号无模糊算法分析

针对BOC (Binary Offset Carrier) 信号的自相关函数存在多峰性,从而造成同步过程中模糊性的问题,提出了一种基于PCF (Pseudo Correlation Function) 算法的同步算法。该算法首先将本地伪码和本地副载波调制到本地产生的辅助信号,再将本地调制后的信号与处理后的接收信号进行相关处理,最后将相关结果进行一定形式的运算得到只有一个单峰的相关函数。并且对提出算法进行了性能分析和仿真比较,结果表明该算法能完全消除同步过程中BOC信号自相关函数的模糊性,并且可以通过改变参数的值来提高捕获精度和捕获性能。     

基于模糊自适应算法的无线视频多路径同步传输方法

多路径无线视频传输幅值控制效果不稳定,导致多路径单视点传输比特率较低.因此,基于模糊自适应算法的无线视频多路径同步传输方法,采用模糊自适应算法设计无线视频多路径同步传输方法,控制无线视频多路径信号传输幅值,根据幅值控制结果配置无线视频多路径传输接口.利用传输接口和模糊自适应算法,采集无线视频传输数据,通过解压处理,完成...     

一种基于FFT算法M-APSK信号载波参数联合检测

随着卫星通信业务的发展,高阶调制技术逐渐应用于卫星通信中,但载波频率和相位偏差对诸如M-APSK等高阶调制信号的影响很大。在回顾载波同步算法理论的基础上,分析了载波频率和相位偏差对APSK信号系统的影响,采用了一种基于最大似然(ML)准则的数据辅助(DA)载波同步算法,并使用FFT快速运算和三线插值法,对频率偏差和相位偏差进行了联合检测。研究表明,该算法在同步性能和实现复杂度上的性能都比较优越。该算法对卫星通信高阶调制M-APSK信号的同步技术提供了一定的参考价值。     

一种QAM符号定时算法

针对目前从频域实现的锁相环提取同步信息的算法结构复杂的状态,提出一种在时域实现的正交幅度调制(QAM)符号定时方案:基于最大平均功率算法实现符号定时同步.通过对该算法的仿真研究,得到符号定时同步的FPGA实现方法,最后用Verilog HDL语言参数化设计方法实现符号定时同步模块的设计.对于QAM系统,利用该算法不需专门设计同步头即可为正确解调提供稳定可靠的符号定时同步信息.经实际验证,该算法稳定性很好,并且只在时域处理,省去了FFT变换,方便FPGA实现.     

PSK信号的图形解调算法——一种新的数字通信解调算法

把图形处理技术和数字通讯理论相结合,提出图形解调算法,并以差分去均值图形调相为例,说明该算法具有较高的解调增益,以及不需频率跟踪,相位跟踪和自提取位同步等特点。     

QPSK数传调制解调器的设计

本文主要介绍4DPSK信号的调制与解调.4DPSK调制方式具有较高的频带利用率和较好的性能,此处将讨论用8031单片机实现4DPSK调制,通过实际的仿真操作证明,该调制器的参数改变灵活,容易实现;此外,还讨论了4DPSK解调器的工作原理,对位同步提取做了简要介绍.     

NLMS算法在轨道电路信号解调中的应用

针对目前轨道电路FSK信号解调中传统解调方法解调精度不足的问题,在对自适应滤波理论研究的基础上,提出采用基于NLMS算法的自适应滤波模块,利用传统频谱分析法得出轨道电路FSK信号的载频信息作为自适应滤波模块的期望信号,通过提取其中一个载频分量从而还原调制方波,经过计算后得出调制频率,实现信号的解调。仿真结果证明NLMS算法不仅实现了轨道电路FSK信号高精度的解调,并且解决了传统LMS算法在轨道电路FSK信号解调中收敛速度慢的缺陷,具有良好的抗噪性能。     

BOC卫星导航信号直接解调的方法及实现

为了分析未知信号结构的二进制偏移载波(BOC)调制卫星导航信号,提出并实现了一种对BOC导航信号进行直接解调的新方法。该方法首先采用二进制相移键控(BPSK)信号解调的算法实现扩频码的同步和载波的剥离,在此基础上剥离BOC调制的亚载波。利用现场可编程门阵列(FPGA)实现了该方法,并进行了解调实验。实验结果表明:该方法能够稳定地进行BOC信号的解调,在信噪比(Eb/N0)大于11 dB时,解调误码率优于1×10-5。     

一种光纤通信系统中位同步电路的设计

描述了一种光纤通信系统中基于FPGA实现的全数字通信系统位同步电路的原理,在MAX PLUSI环境下结合原理图和进行了综合、仿真和配置,该电路实现了位同步电路的全数字化.测试结果表明,该设计方法能比较准确地恢复位同步信号.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

正~~