Testing the Schedulability of Synchronous Traffic for the Timed Token Medium Access Control Protocol

One of the key issues related to guaranteeing synchronous message deadlines in a timed token network (such as fiber distributed data interface) where the timed token medium access control protocol is used is the schedulability test of synchronous traffic (i.e., testing whether or not all synchronous messages can be transmitted before their deadlines, under a given setting of network parameters). Much work has been done on how to assign network parameters appropriately in order to guarantee timely transmission of synchronous traffic. As a result quite a few synchronous bandwidth allocation schemes and some good guidelines on selection of the target token rotation time have been proposed. In contrast, limited research has been conducted on how to effectively test whether or not given network parameters can guarantee timely transmission of all synchronous messages (of a considered synchronous message set) before their deadlines. The previous testing methods for synchronous message schedulability only provide a sufficient (but not necessary) test and therefore fail to always keep effective for any synchronous message set considered. In this paper, we propose two testing methods for determining the schedulability of a synchronous message set with message deadlines no longer than periods. The proposed tests perform better than any previous test in the sense that they are both sufficient and necessary. Some numerical examples are given to compare different testing methods, all of which have demonstrated the superiority of the proposed tests to other existing testing methods.     

Ridged waveguide structures with improved fundamental mode cutoff wavelength and bandwidth characteristics

A new circular waveguide loaded with two T‐shaped septa and a new triple ridge loaded trough rectangular waveguide are proposed and theoretically analyzed using the Finite Element Method. Numerical results are presented demonstrating that these structures offer a significant increase in both fundamental mode cutoff wavelength and bandwidth when compared to various unloaded and loaded waveguides. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12: 190–197, 2002.     

一种扩展任意波形发生器输出带宽的设计

增加输出带宽和降低输出噪声是关系任意波形发生器发展的两个重要方面.本文在论述任意波形发生器工作特点的基础上,提出了一种多路组合的任意波形发生器设计方案.它能在不降低输出信噪比的条件下,用较低速的波形存储器和数-模转换器实现较高速率的波形输出.论文着重介绍了这种电路结构的设计思想和实现这种设计所要解决的关键技术,并给出了四路组合的任意波形发生器实验系统及测试结果.     

HMPMB：一个拥有优先级多处理机系统带宽分析

本文详细地分析了拥有优先级的层次型部分多总线多处理机系统（以下简称“ＨＭＰＭＢ”）带宽性能，获得的带宽模型基于访存请求均匀分布于各存贮器模块，为了验证该模型，我们还做了仿真实验，结果表明：模型结果值与仿真值吻合得很好．     

塑料管壁厚超声测量的信号处理

为了保证塑料管挤出的质量以及为自动控制挤出生产线提供数据，需要在线测量塑料管的壁厚。本文研究壁厚超声测量的信号处理方法，通过对回波信号时域和频谱的分析，并结合测量精度的要求，提出了处理电路应具有的性能指标及设计方法，并用实验数据进行了验证。     

脉冲测试系统最佳带宽的数值计算

由于受测试系统带宽的限制，脉冲信号在测试过程中其能量将受到不同程度的损失。本文用Romberg数值积分法计算出在一定能量损耗限值要求下的脉冲信号频谱宽度，并用付氏级数对其进行了信号重构验证，据此得出了脉冲信号测试系统带宽的最佳值。     

一种通用的微波六端口反射计研究

在微波阻抗与网络参量测量方面,反射计应用举足轻重;在通过对反射计的S参数进行分析的基础上,介绍了一个六端口反射计的通用设计方案,并确立了设计指标;依据设计指标,利用LSBRM方法、频移法、渐变线分割的方法和数值积分等算法完成了六端口反射计的设计;最后通过实际的反射计测量检验验证其满足设计指标的要求.     

有效带宽测量及在MPEG4流控中的应用

通过测量网络有效带宽,获得网络信息,可进行端到端的流量控制,提高QoS.简要介绍各种常用的有效带宽测量原理和方法.针对MPEG4流的特点提出了一种将有效带宽测量技术应用到MPEG4流量自适应控制机制当中的方法,给出了实现和实验结果.     

GPON系统带宽利用率的研究

文章在深入分析吉比特无源光网络(GPON)上下行帧结构的基础上,找出了影响其上下行带宽利用率的各个因素,并逐一进行了量化分析,给出了计算上下行带宽利用率的表达式,并且计算出了GPON上下行带宽利用率的变化范围.最后,对比了GPON和以太网无源光网络(EPON)的带宽利用率和成本,结果表明GPON具有更高的效能成本比.     

电阻加载偶极天线阻抗带宽及脉冲辐射特性研究

分析了偶极天线电阻加载方面的若干问题，包括不同电阻加载方式阻抗频率特性比较，连续与离散串联集中电阻加载脉冲辐射特性比较，证明其它加载方式具有与Wu-King电阻加载相似的特性，与未加载偶极天线相比，阻抗带宽较宽，辐射脉冲失真较小。