查询词典 communication channel

Firstly, oscilloscope control system based on GPIB technique is presented with friendly operation environment to the HIFU system, and it uses multithreading technique in programming to realize real-time recording and display of the signal; Secondly, temperature collection and data recording system is designed, which also could get real-time recording and display of the 16 channel temperature signal, and it's believed to be of great use for further experiments of the HIFU system; Thirdly, multiple ultrasonic phased array's phase shifter is designed,which could provide 8-bit phase control in a range of frequency where the centrical frequency is 1MHZ. Fourthly, the module of serial communication is realized to insure the communication between devices and computer, including both synchronous and asynchronous communication, which enables the system to transfer data reliably and stably; Finally, the module of digital quantity control is accomplished, which provide for upper application the consistent solution to the control of exterior devices via digital interface. It can get or set the devices state using interrupt mode to receive input signal or send output signal.

主要有以下几个方面：设计了基于GPIB的示波器控制系统，给课题的研究工作提供了一个良好的环境，它采用了多线程编程的方法，能够较好的实时显示当前波形并记录数据；设计了温度采集和数据记录系统，能够对16路温度信号进行并行同步的实时采集，用于HIFU剂量学研究中温度场检测和医疗评价；设计了相控阵相位延时电路并且通过调试，满足了课题的相位控制的要求，在中心频率为1MHZ左右的频率范围内都能够达到8-bit相位控制；实现了串口通讯模块，为各项设备与计算机之间的通讯提供保证，它提供同步和异步的通讯能力，使系统能够可靠稳定的传输数据；建立了数字量控制模块，为上层应用程序提供一致的方法使用数字接口控制外部仪器，它使用中断的方式来接收输入或输出设定的开关量信号，从而得到或设定各种仪器的状态。

A general communication system, channel coding theorem and source-channel coding theorem.

通信系统的一般模型，信道编码定理和信源信道编码定理。

Topics include: mathematical definition and properties of information; source coding theorem, lossless compression of data, optimal lossless coding; noisy communication channels, channel coding theorem, the source-channel separation theorem, multiple access channels, broadcast channels, Gaussian noise, and time-varying channels.

课程主题包括：针对「资讯」的明确数学定义及性质描述；信源编码理论、无失真资料压缩技术、最佳化无错误编码；杂讯干扰的通讯频道解析、频道编码理论、资讯来源-通道编码分离理论、多重存取频道解析，广播型态频道解析、高斯杂讯及多变量时间频道解析。

This paper researches thoroughly channel of optical wireless communication and establishes Gauss channel model.

论文对激光无线信道进行了详细的研究，建立了高斯信道模型。

So it holds a ideal ability to anti-interference and has 2 scalar level resolution in location and measuring velocity than traditional radio induction technology. And the channel composed of the new radio induction system for communication is different from the parameter-constant channel and the traditional parameter-changing channel, its parameter is decided by the mutual induction between its antenna and induction-cable, by the location of its antenna, by the signal frequency passing through, its parameter has nothing to do with the time parameter.

而且，由新型无线感应系统组成的信道既不是恒参信道，也不是一般目前所知的变参信道，其信道传递函数的幅值只与信号的频率有关，与系统中天线和感应电缆之间的互感和天线的位置有关，而与时间无关，其信道传递函数的相位只与天线的位置有关，而与时间无关，由新型无线感应系统组成的信道是一种不随时间变化的新型变参信道。

This paper presents a theoretical analysis of time-hopping pule position modulation ultra-wideband communication system under time-varying channel condition. The effect of scatters movement is analyzed under indoor channel condition with different channel parameters by simulation.

分析了时变信道环境条件下TH-PPM-UWB系统的性能，并通过计算机仿真研究了室内信道环境中，散射体移动对不同参数条件下系统性能的影响。

The wireless channel is the transmission media for mobile communication, all the information are transmitted in this channel.

无线信道是移动通信的传输媒体，所有的信息都在这个信道中传输。

This dissertation comprehensibly researches the performance of hybrid DS/FH spread spectrum communication systems, operating in a combined additive white gaussian noise , multiple access interference, and channel fading, particularly operating in hostile interference (partial band interference and multitone jamming). At the same time, the dissertation investigates performance of forward error correction coding and diversity technology against channel noise.

本文以此为背景，较为详细地研究了在信道中出现各种噪声干扰（高斯白噪声、多址干扰和信道衰落），特别是敌方的人为干扰（部分带宽噪声干扰和部分带宽多频干扰）时，混合DS/FH扩频通信系统的性能，以及前向纠错信道编码和分集技术对混合扩频通信系统信道出现噪声干扰时系统性能的改进情况。

By time-varying filtering, we realize the signal selectivity and interference suppression, especially for the signals with time-varying power spectrum. It is shown herein that conventional eigenstructure based methods are lower dimensional special case of the time-frequency subspace fitting method. The closed-form array response estimation algorithms for blind source separation in wireless communication is also developed in the dissertation by exploiting the data structure of second-order statistics of the array output in the presence of multipath. The proposed method achieves array response estimation with little constraint on signal property and propagation environment such as scatters or angular spread. Moreover, the array utilized here can be of arbitrary geometry and even uncalibrated. Since the closed-form solution is obtained, no misconvergency may occur and large amount of computation can be saved. The equivalent feed model and corresponding optimization designation are proposed to realize the downlink multi-user selective transmission. By coherent and non-coherent superposition of the electromagnetical field, multiple beams can be formed using a single array, so that each co-channel user signal is transmitted in each beam and will not interfered with each other. The proposed system scheme implements the digital beamforming and the channel allocation in the base band, therefore is suitable for the utilization of the radio software technology. The feasibility and effectiveness of the proposed model are proved by the RF experiment.

在窄带条件下，GSC－SSF方法还可以提高阵列的虚拟孔径，从而提高估计的性能；可以证明，Cyclic DOA 和SC-SSF方法可看作该方法的特例或近似； 3、提出了二维GSC－SSF方法和宽带谱相关DOA矩阵方法，利用信号的循环平稳特性解决了宽带条件下二维 DOA 估计问题，并具有阵元数少、计算量较小的特点； 4、提出了时频子空间拟合和宽带时频DOA估计算法，将联合时频分析的理论和方法引入到阵列信号的空间谱估计研究中，利用时变滤波实现信号选择性测向和干扰抑制，特别适合于谱时变信号；可以证明传统特征结构法可看作是时频子空间拟合方法的特例； 5、提出了多用户环境下阵列响应的估计方法——CARE方法，该方法对信号结构和传播参数（主要是散射源分布与角度散布）的约束较少，适用于各种几何结构的阵列甚至未校准的阵列，能够直接得到阵列响应的闭式解，因此计算量小、稳健性好，不存在收敛问题； 6、提出了针对多用户下行选择性发送的阵列等效激励模型、优化设计方法及其系统实现方案，通过空间场的相干叠加与非相干叠加使得单一阵列能够形成多个波束，并保证各波束内的用户信号各不相同且相互干扰最小；其系统方案具有在基带实现数字波束成形、信道分配并便于软件无线电实现的特点，其有效性已得到外场实测数据的证实。

Network advertisement than other media the largest dominant position is interactive sex, easily enterprise and consumer establish one-to-one sale relationship, the association between person of no less than and person carries each other communication and channel an versatile person only can promotional each other concern is same, interactive means makes advertisement is mixed by the conduct propaganda that sets out from company point of view so homiletic the communication that turns into to set out from consumer angle and communication, increased a target to suffer greatly numerous pair of advertising welcome degree and accept rate.

网络广告较之其它媒体最大的优势便是互动性，易于企业与消费者建立一对一的营销关系，正如人与人之间的交往只有通过相互的交流与沟通才能增进彼此的关系一样，互动方式使广告由原来从企业角度出发的宣传和说教变为从消费者角度出发的沟通与交流，大大增加了目标受众对广告的欢迎程度和接受程度。

Cynanchum Lingtai apricot production in the average weight 65 grams, the brightly-colored fruit, juicy rich, sweet-sour taste, sweet from the nucleolus, when the late Qing Dynasty famous Shaanxi, Gansu provinces, the Qing imperial court Tongzhi tribute for years.

灵台生产的牛心杏平均单果重65克，果实色泽鲜艳，汁多味浓，甜酸适口，离核仁甜，清末时就驰名陕、甘两省，清同治年间曾为朝廷贡品。

Chenopodium album,Solanum nigrum, and Amaranthus retroflexus were very susceptible to the herbicides. Polygonum persicaria and Abutilon theophrasti were relatively less susceptible to the herbicides, and Lycopersicon esculentum was not susceptible to it. The relationship between reduction rates of weed biomass and PPM values of weed leaves 2,4, and 6 days after treatment was established.

供试的6种杂草对该混剂的敏感性存在显著差异：红心藜Chenopodium album、龙葵Solanum nigrum和反枝苋Amaranthus retroflexus对该混剂最敏感，ED90值分别为47.65、71.67和29.17g/hm2；春蓼Polygonum persicaria和苘麻Abutilon theophrasti敏感，ED90值分别为96.91、114.20g/hm2；而番茄不敏感。