SDH微波交叉极化传输系统的几个问题

本文以ＳＤＨ微波交叉极化传输系统在实际应用中的问题，诸如系统的性能指标预测、系统内的干扰、ＸＰＤ恶化等进行了分析。     

XPD与CPA统计分布的计算机模拟研究

在考虑天线调养高差和层结高度的基础上，研究了ＸＰＤ与ＰＣＡ的统计分布和ＸＰＤ和ＣＰＡ等概率值的线性关系，并与实验结果吻合较好。，分析了天线交叉极化方向图对ＸＰＤ与ＣＰＡ统计分布的影响，指出峰值型交叉极化方向图天线有利于克服去极化。     

TI DSP的软件设计方法

查询号：１３１数字信号处理器（ＤＳＰ）是一种可编程的高性能处理器,近年来发展很快,它不仅适用于数字信号处理,而且在图像处理、语音处理、通信等领域都得到了广泛的应用。德州仪器公司（ＴＩ）是当今世界ＤＳＰ（ＤＳＰ）芯片的主要供应商之一,其ＤＳＰ芯片可分为两类：一类是定点ＤＳＰ,包括Ｃ１Ｘ,Ｃ２Ｘ,Ｃ２ＸＸ,Ｃ５Ｘ,Ｃ５４Ｘ,Ｃ６２Ｘ等;另一类是浮点ＤＳＰ,包括Ｃ３Ｘ,Ｃ４Ｘ,Ｃ６７Ｘ等。ＴＭＳ３２０Ｃ３０是ＴＩ公司的一种浮点ＤＳＰ,我们用它进行了图像压缩软件的开发。基于我们的工作经验,在本文中评价了…     

广义多径信道MDPSK相位比较解调性能

本文提出了一种适合于广义多径信道多进制差分相移键控信号相位比较解调的性能分析方法，推导出符合平均错误率积分表达式。该表达式考虑了信号幅度衰落，时间选择性衰落和高斯白噪声对体制性能的影响。并针对几种形式的衰落功率谱分别对二进制，四进制和八进制的符号平均错误率进行了数值计算，讨论了衰落功率谱的形式对ＭＤＰＳＫ信号性能的影响，并给出了ＭＤＰＳＫ信号的“不可克服符号错误率”与衰落功率谱归一化带宽的关系曲线     

数字微波接力系统中的交叉极化鉴别率

本文论述了在数字微波接力系统中交叉极化鉴别率（ＸＰＤ）性能劣化的机理和传播模型,提供了在多径传播条件下ＸＰＤ性能的计算机模拟计算结果和实际测得的典型天线的ＸＰＤ的统计分布。     

应用MSP430微控制器时需注意的问题

ＴＩ的ＭＳＰ４３０微控制器包含４３０Ｘ１Ｘ、４３０Ｘ３１Ｘ、４３０Ｘ３２Ｘ、４３０Ｘ３３Ｘ等型号,使用者可根据不同应用目标作有针对性的选择。ＭＳＰ４３０系列微控制器在性能上有一定特色,如低功耗、高抗干扰、高集成度等。其中的４３０Ｘ３２Ｘ有片内１４位Ａ／Ｄ。并可提供内部的参考 电压。本文将介绍应用ＭＳＰ４３０Ｘ３２Ｘ片 内Ａ／Ｄ转换器原理及需注意的问题。 ＭＳＰ４３０Ｘ３２Ｘ的 １４位 Ａ／Ｄ ４３０Ｘ３２Ｘ片内Ａ／Ｄ有８通道（Ａ０～７）,但目前的型号（３２３、３２５、３２５Ａ）引脚上只有Ａ０～５。其中…     

创新推出8倍速DVD-ROM套件

创新公司的ＤＶＤ－ＲＯＭ套件又将升级,配备８倍速ＤＶＤ－ＲＯＭ的ＰＣ－ＤＶＤＥｎｃｏｒｅ８Ｘ即将上市。ＰＣ－ＤＶＤＥｎｃｏｒｅ８Ｘ套件包括一个８ＸＤＶＤ－ＲＯＭ和一块采用Ｄｘｒ３技术的ＭＰＥＧ２解压缩卡,能提供效果上佳的硬件ＭＰＥＧ２解压缩的影音播放效果。创新的ＤＸＲ３（ＤｙｎａｍｉｃＸｔｅｎｄｅｄＲｅｓｏｌｕｔｉｏｎ３）技术,除了能完成硬件ＭＰＥＧ２解压缩外,还可将ＤＶＤ影片普遍使用的ＡＣ－３５．１声道数码音效输出,再通过ＡＣ－３解码器由５．１声道音箱输出相当于影院的效果,该卡还配有Ｓ／ＰＤＩ…     

ADSP—2106X在高速并行信号处理系统中的应用

ＡＤＳＰ－２１０６Ｘ是当前性能最高的浮点ＤＳＰ处理器这一,利用它可方便地构成多处理器并行数据信号处理器,统一的地址空间允许处理器间直接存取每片ＡＤＳＰ－２１０６Ｘ的片内ＳＲＡＭ,片内分布总线总裁逻辑允许直接把六片ＡＤＳＰ－２１０６Ｘ和一个主机组成一个多机并行系统。本文讨论了基于ＡＤＳＰ－２１０６Ｘ的数字信号处理器的设计方法并给出了它在“移位付立叶变换”算法中的应用。     

PSD3XX的16位单片机系统设计

ＷＳＩ公司的ＰＳＤ３ＸＸ系列强上围器件可调微控制器系统资源,在系统设计中灵活性强,集成高度,功耗小。本文介绍了如何利用ＰＳＤ３ＸＸ的实现与１６位微控制器的接口。     

基于TTCN的分组装／拆设备的一致性测试组织

ＣＣＩＴＴＸ．２８、Ｘ．２９、Ｘ．３建议定义了公用数据网中分组装／拆设备（ＰＡＤ）与分组式ＤＴＥ和起止式ＤＴＥ之间的规程。由于三Ｘ（Ｘ．３、Ｘ．２８、Ｘ．２９）协议的复杂性，其一致性测试在国际、国内研究成果很少，而且尚未形成国际标准。本文在分析ＰＡＤ测试关键技术的基础上，提出了一种基于树形结构及表格组合表述法（ＴＴＣＮ）的ＰＡＤ一致性测试组织。     

Small-scale variations of cross-polar discrimination in ricean fading channels

Cross-polarised antenna systems are an attractive way to reduce equipment size while maintaining low inter-antenna correlation. The cross-polar discrimination (XPD) is an important parameter of crosspolarised systems. Starting from the definition of Ricean fading channels, it is shown that the small-scale variations of the XPD have a doubly non-central F-distribution. The simulated XPD distribution obtained as a function of the Ricean parameters is successfully compared with measurement results for validation.     

Binary and Quaternary PSK Radio Systems in a Multiple-Interference Environment

The planning of a digital radio network requires an evaluation of the effect of quite a large number of interfering sources. These in turn are dependent upon many parameters, such as the network structure, channel arrangement, antenna patterns, and so on. This paper presents a performance analysis of a digital radio-relay system during fading periods. The possibility of attaining a required fading margin is analyzed when many co-channel and interchannel interferences are simultaneously present, both for long-haul and shorthaul radio relay systems. A comparison is presented between two possible techniques for the reusing of the same frequency band in each hop, by taking advantage of the cross-polarization discrimination (XPD). The reduction of the XPD expected during fading periods is also taken into account. Binary and quaternary coherent PSK modulations are considered, with realizable filters (of the Butterworth type), both at the transmitter and at the receiver. The error probability calculations were performed with a combined analytical and computer simulation approach. The results seem to indicate the feasibility of the frequency reuse technique.     

A First-Order Model for Depolarization of Propagating Signals by Narrowband Ricean Fading Channels

We show by simulation that when the fading signals observed on orthogonally polarized diversity branches follow Ricean statistics, the distribution of polarization states on the Poincar′e sphere is well-approximated by a Fisher distribution. Further, we show that the Fisher concentration parameter is: (1) completely determined by the corresponding Ricean Kfactors and the cross-correlation coefficient between the diversity branches, both of which can be estimated from simple measurements of received power vs. time, and (2) a good indicator of the level of cross-polar discrimination (XPD) on the channel. The insights gained are potentially useful to those engaged in the development and validation of schemes that use either polarization re-use or polarized MIMO.     

Two-dimensional probability distribution of attenuation and depolarisation on Earth-space path

Two-dimensional probability distribution of attenuation and crosspolarisation discrimination (XPD) on Earth-space path at 19.5 GHz (circular polarisation) is derived. Moreover, the distribution is approximated by a mathematical function. The distribution is compared with the theoretical relationship between rain-induced attenuation and XPD, which is based on the deformed raindrop model. It is found that the measured attenuation and XPD values are distributed two-dimensionally in an attenuation-XPD plane, and the results cannot be explained by the theoretical relationship. This fact implies that special attention should be paid when the XPD statistics on the Earth-space path are predicted by the theoretical relationship between attenuation and XPD.     

Centimeter wave propagation experiments using the beacon signals of CS and BSE satellites

The wave propagation experiments using Japanese geostationary satellites CS (20/30 GHz) and BSE (12/14 GHz) satellites have been performed at the Kashima earth station of the Radio Research Laboratories (RRL). Cumulative rain attenuation and cross-polarization discrimination (XPD) statistics are given for the period of three years at 11.7 GHz (vertical polarization) and for the period of four years at 19.5 GHz (circular polarization). It is shown that the yearly rainfall rate and attenuation distributions are well approximated by log-normal distributions, and the XPD distribution is well approximated by a normal distribution. Monthly and time-of-day variation of the attenuation and XPD distributions are presented. Duration statistics of attenuation and XPD are presented and characterized. Other characteristics in the wave propagation, such as effective path length, frequency dependence of attenuation, and joint statistics of attenuation and XPD are derived and discussed. Rainfall events are classified into three rainfall types, "stratus," "cumulus," and "others" using measurements of the radar reflectivity factor along the satellite-to-earth path, and the dependence of XPD characteristics on the rainfall type is also presented and discussed. Some prediction methods of calculating attenuation and XPD statistics are applied to the data obtained in these experiments and the predicted results are compared with the measured ones. It is found that some corrections are needed when the XPD statistics are predicted from the attenuation statistics using the theoretical relation between XPD and attenuation.     

Effect of raindrop shape on crosspolarisation/attenuation relationships

It is found that raindrop eccentricity and water temperature have a pronounced effect on crosspolarisation XPD and attenuation CAP, respectively. This has implications on the use of XPD/CPA relationships for radio link planning.     

Discriminator-MLSE Detection of a GTFM Signal in the Presence of Fast Rayleigh Fading

This paper examines the influence of fast Rayleigh fading and cochannel interference on GTFM with discriminator-MLSE detection using a hardware fading simulator. The degradation in BER performance, due to fading, can be largely recovered by using two-branch selection diversity. The resultant bit error patterns are also presented.     

在卫星移动信道中不同条件下Turbo码的纠错性能研究

研究了采用Turbo码技术的抗衰落性能,首先分析了Turbo码在卫星移动遮蔽Rician衰落信道下的误差纠错性能限,然后通过计算机仿真模拟了三种不同的卫星移动衰落信道下Turbo码的性能,研究了不同衰落信道特性对Turbo码性能的影响情况,同时还讨论了在衰落信道下Turbo码的子码约束长度和交织器长度两个主要参数对性能的影响情况。     

认知车载网的频谱感知性能分析

认知车载网中不同的衰落传播信道会影响频谱感知的性能.为了描述不同信道下的频谱感知性能,分析了加性高斯白噪声信道、瑞利衰落信道和Nakagami-m衰落信道条件下的频谱感知单用户能量检测概率和协作能量检测概率,重点是Nakagami-m衰落信道、检测衰落因子、次用户的数量和信噪比这几个参数对协作频谱感知性能的影响.仿真结果表明,通过对不同信道特性的准确了解能够帮助车辆在不同衰落信道环境下提高频谱的检测概率.     

Fading correlations in wireless MIMO communication systems

We investigate the effects of fading correlations on wireless communication systems employing multiple antennas at both the receiver and the transmitter side of the link, so called multiple-input multiple-output (MIMO) systems. It turns out that the amount of transmitter sided channel knowledge plays an important part when dealing with fading correlations. Furthermore, the possible availability of time diversity in a time-selective channel can have essential influence on performance. To study the influence of time-selectivity, the concept of sample-mean outage is introduced and applied to information theoretic measures, like capacity or cutoff rate. It will be shown, that in some cases correlated fading may offer better performance than uncorrelated fading permits, which is due to exploitable antenna gain, that will also be defined in a general form for MIMO systems.