基于多门限极性判决的QAM载波恢复算法

正交幅度调制(QAM)是现代通信中最为常用的一种调制方法,其载波恢复是决定接收机性能的关键因素之一.从提高收敛速度和减小锁定误差的角度出发,提出了一种用于QAM解调的多门限极性判决载波恢复算法,该算法充分利用QAM星座图中对角线上锁定误差为零的信号点,增加了用于提取相位误差的符号集.分析和仿真表明,与传统的面向判决载波恢复算法相比,该算法不仅保留了极性判决载波恢复算法频偏搜索范围大的优点,且能进一步提高收敛速度.     

DVB系统原理与Systemview仿真实现

数字视频广播DVB（Digital Video Broadcasting）标准是欧洲数字电视的传输标准,它包括数字信源压缩编码、节目数据流的统计复用、信道纠错编码、调制等数字传输链路各相关环节所采用的技术及接口标准。本文在介绍DVB技术原理的基础上,深入探讨了DVB系统的构成及调制、解调原理,并在Systemview下对该系统进行了完整仿真。通过信号观察窗对比信号波形发现,输入输出基本一致,说明该系统在通常信噪比条件下可以满足可靠传输的基本要求,达到了预期目的,证明了系统的可靠性。     

海岛MMDS系统调试及维护

本文介绍了综合利用MMDS和HFC传输技术。实现海岛数字电视信号覆盖,以及在安装调试和日常维护中的一些技巧和注意事项。     

基于分区初等元胞自动机的二维伪随机耦合映像格系统及其动态特性

针对基于耦合映像格的时空混沌系统中,某些控制参数会导致弱混沌的现象,以及系统生成序列频率分布不均的情况,提出了一种基于分区初等元胞自动机的二维伪随机耦合映像格系统.首先,基于初等元胞自动机,设计了高维的分区初等元胞自动机.然后,根据该高维自动机的输出,实现了伪随机的耦合方案,同时将自动机的输出作为扰动添加至时空混沌系统...     

A generalisation of a theorem of Koldunov with an elementary proof

We generalize a Theorem of Koldunov [2] and prove that a disjointness proserving quasi-linear operator between Resz spaces has the Hammerstein property.     

CMMB地方节目传输的探索和实践

CMMB地方节目传输利用广电SDH网,实现了省级信号至各地市的传输。在不增加设备的情况下,解决了同时传送加密卫视、清流全运两套节目的问题。     

浅谈数字正交中频调制器件

以正交幅度调制为代表的正交调制技术在有线电视传输和ADSL(不对称数字用户线)中得到了广泛应用.介绍了两款典型的正交数字调制芯片,对其架构和性能作了对比分析,并预测了调制芯片的发展方向.     

仿射辛群作用下的面轨道生成的格

设ASU(2v,F_q)是F_q上的2v维仿射辛空间,ASp_(2v)(F_q)是F_q上的2v次仿射辛群,设M(m,s)是ASp_(2v)(F_q)作用下的(m,s)面的轨道,用L(m,s)表示M(m,s)中面的交生成的集合.讨论了各轨道生成的集合之间的包含关系,一个面是由给定M(m,s)生成的集合中的一个元素的条件,以及L(m,s)何时做成几何格.     

Ethylene‐vinyl alcohol copolymers partially modified with benzoate groups: Study of their polymorphic behavior

The crystalline structure exhibited by terpolymers obtained through chemical modification with benzoyl chloride from an ethylene‐vinyl alcohol copolymer with a molar fraction in vinyl alcohol of 68%, EVOH68, has been studied by either wide angle X‐ray diffraction or small angle X ray scattering experiments and differential scanning calorimetry. The type of crystal lattice developed has been found to be strongly dependent on modification degree and thermal history. A highly‐disordered crystalline lattice with very small crystallites has been found for the quenched specimen with the highest benzoate content while the rest of fast cooled samples crystallized into an orthorhombic lattice. On the other hand, a monoclinic crystal cell has been observed in the slowly cooled specimens with low benzoate incorporation. At the last given thermal treatment, this monoclinic lattice evolves and seems to be transformed into an orthorhombic‐like crystal for the terpolymer with the highest modification ratio. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1026–1036, 2007     

A characterization of MV-algebras free over finite distributive lattices

Mundici has recently established a characterization of free finitely generated MV-algebras similar in spirit to the representation of the free Boolean algebra with a countably infinite set of free generators as any Boolean algebra that is countable and atomless. No reference to universal properties is made in either theorem. Our main result is an extension of Mundici’s theorem to the whole class of MV-algebras that are free over some finite distributive lattice.