MPSK数字解调器同步方案的实现

多进制相移键控MPSK调制信号的解调中,为提高解调性能,得到精确快速的载波同步和时钟同步,需要对载波检测和时钟检测作精心的设计。对MPSK的数字解调方法做了一些探讨,在载波同步中,分析了基于功率检测的频差检测方法及基于相差检测进行相位锁定的方法;详细介绍了时钟同步的波形估计方法的基本原理及幅度和频谱宽度对定时误差的影响。     

激光距离选通成像关键技术

距离选通技术是克服激光后向散射、提高激光距离选通成像系统信噪比的有效方法.阐述了激光距离选通成像原理,详细分析了距离选通关键技术,指出传统的距离选通同步控制系统的缺点,并提出一种改进的距离选通同步控制方案.     

DSP极低码率的远程视频监控系统

笔者以TI的低成本DSP芯片F206为例,介绍了一种基于此芯片的极低码率双绞线视频图像监控系统,包括它的整体方案,及实现时的一些难点解析。实践表明:此系统经济、实用且具有广播能力。     

Capital budgeting and optimal timing of investments in flexible manufacturing systems

This paper investigates the financial-economic decision process for investments in flexible manufacturing systems (FMS). Contrary to popular belief, we show that conventional capital budgeting techniques can be used to make such investment decisions. First, we identify theoverall impact of installing an FMS and present guidelines for a cash flow forecasting model. We then present ways in which to incorporate uncertainty in these cash flows within a risk-adjusted discount rate. These expected cash flows and the discount rate are used in calculating the net present value (NPV). Once the capital budgeting analysis is completed, a critical issue facing the firm is the optimal timing of the installation. We reinterpret the general results on optimal timing of investments within the special context of an FMS project. Finally, we illustrate the above technique via a stylized example.     

The Generalized Delay-Locked Loop

The delay-locked loop (DLL) is a synchronization device that is widely used for PN-code tracking in spread spectrum systems. The error detector characteristic (S-curve) of the DLL has a major impact on the performance. Using more than two correlators will extend the tracking range of the S-curve. The Generalized DLL (GenDLL) theory provides a concept to analyze a large class of DLL configurations including the classical DLL. The focus of the performance criteria is on tracking jitter and the mean time to lose lock (MTLL). It is shown that the MTLL can be considerably improved by using extended S-curves. However, the tracking jitter is increased by additional correlators. The tradeoff between the two criteria is explained. With the GenDLL theory loop configurations can be designed having both low tracking jitter and high loop robustness against loss of lock.     

无线ATM通信网的定时信息恢复技术研究

本文对无线ＡＴＭ通信网ＣＢＲ业务定时信息的恢复技术进行了研究，提出了异步剩余时间标签（ＡＲＴＳ）技术，并通过码速调整改善收端的ＣＢＲ业务时钟性能，给出了实现方案，同时提出采用ＡＲＴＳＦＩＦＯ吸收定时信息的延时抖动，由于无线ＡＴＭ通信网的误码率较大，其信元丢失率较高，本文在分析ＲＴＳ的多重码速调整特性基础上，还提出了利用收到相邻ＡＲＴＳ之间的差值规律来估计丢失的ＡＲＴＳ的新方法，理论计算和模拟结果表     

一种新的混沌调制技术在保密通信中的应用

提出一种混沌脉冲宽度调制(CPWM)新技术，它将数字信息隐藏在脉冲的宽度之中，给出了基于一维、高维混沌动力学系统的实现模型。讨论了系统的同步措施及保密性；并用Matlab仿真，给出了相关的仿真结果。     

Generating the tame and wild kernels by Dennis-Stein symbols

For many number fieldsF, it is proved that the tame kernel, K₂( ), and the wild kernel, W(F), ofF are generated by Dennis-Stein symbols. For some real quadratic number fields, generators for the tame kernel are given.     

A mean-field limit for a class of queueing networks

A model of centralized symmetric message-switched networks is considered, where the messages having a common address must be served in the central node in the order which corresponds to their epochs of arrival to the network. The limitN is discussed, whereN is the branching number of the network graph. This procedure is inspired by an analogy with statistical mechanics (the mean-field approximation). The corresponding limit theorems are established and the limiting probability distribution for the network response time is obtained. Properties of this distribution are discussed in terms of an associated boundary problem.     

A comparative study on the performance of MIMO‐STBC subject to Weibull fading channels

In this paper, we investigate the analytical performance of the multiple‐input multiple‐output system (MIMO) with orthogonal space‐time block codes (STBCs) subject to Weibull fading channels (WFC). Space‐time block code technique provides an efficient pattern for wireless transmission over various fading channels using multiple transmit antennas. Two approximating methods of the sum of independent Weibull random variables are studied. For each approach, we derive accurate approximate expressions for several performance metrics of MIMO‐STBC system operating under independent and nonidentical WFC. The proposed approximations are expressed in terms of 2 generalized hypergeometric functions, namely, Fox's H and Meijer's G functions. All the derived approximate expressions prove high accuracy, while compared with the simulation results established via Monte Carlo method and Kolmogorov‐Smirnov test as well. Although the 2 approaches have approximately the same accuracy, the second method approximate expressions are much less complex than those of the first method.