Phase locking and chaotic synchronization in an array of three lasers

A linear array of three lasers that are coupled mutually in space is investigated. It is shown that the phase of the laser fields is locked with intermediate coupling while the laser intensities are totally chaotic and chaotically synchronized. When the intensities of lasers reenter the regime of chaotic synchronization at smaller coupling constant, the laser fields show low degree of phase locking. The phase differences in the fields between three lasers show rich patterns when the coupling is changed. Received 3 August 2001 and Received in final form 27 September 2001     

战场沙尘环境中三毫米波通信的研究

本文给出了模拟战场沙尘环境中，沙尘对三毫米波通信产生的衰减和通信误码率的测量结果。推导了正态对数分布的沙径分布状态下沙尘产生的裹减理论公式。根据现场测量的沙径的统计参数和通信信道的信嗓比，从理论上计算得到沙尘产生的衰减及通信误码率。     

DMA控制器的设计与仿真

文章介绍了DSP SM9966中的双通道DMA控制器的主要功能和电路结构，给出了主要电路的实现方法，并引入存储器模型，举例说明了对其进行逻辑仿真的基本方法。     

Error correction,interleaving and differential pulse position modulation

This paper discusses the interaction of error, correction, interleaving and modulation format in relation to intersatellite communication by optical technologies, concentrating on the performance and design of pulse position modulation and a variant, differential pulse position modulation with Reed—Solomon codes, helical interleaving and various forecast strategies.     

N版本程序设计的几个问题

本文简要描述了两种主要的容错软件技术－Ｎ版本程序和恢复块。并对Ｎ版本程序设计中的几个有关问题及其解决办法进行了讨论。     

Performance of optical intersatellite links

The performance of optical intersatellite links is described by a model. A significant difference between optical and microwave intersatellite links is the occurrence of so-called burst errors. The statistics of bit error rate for an optical link are derived from simulations taking into account beam mispointing resulting from satellite motions and tracking channel noise. The effect of coding on the bit error rate is also shown. The mutual tracking system between two optical terminals located on different satellites can become unstable if the noise of the tracking loop exceeds a critical value. The results of tracking simulations are presented.     

Magnetization reversal processes of single nanomagnets and their energy barrier

Micromagnetic simulations were performed to investigate the influence of geometry and magnetic anisotropy constant on energy barrier and magnetization reversal mechanism of individual bits important for the bit patterned media concept in magnetic data storage. It is shown that dependency of the energy barrier on magnetic and geometric properties of bits can be described by an analytical approach in the case of quasi-coherent magnetization rotation process. However, when the bit size exceeds a critical size, for which an incoherent magnetization reversal is preferred, the analytical approach becomes invalid and no self-consistent theory is available. By systematically investigating the influence of bit size on the magnetization reversal mode, it was found that the transition from quasi-coherent to incoherent magnetization reversal mode can still be described analytically if an activation volume is considered instead of the bit volume. In this case, the nucleation volume is an important parameter determining thermal stability of the bit. If the volume of the bit is larger than twice the activation volume, the energy barrier stays nearly constant; with further increase in bit size, no gain in thermal stability can be achieved.     

Synchronization of two coupled exciters in a vibrating system of spatial motion

The paper proposes an analytical approach to investigate the synchronization of the two coupled exciters in a vibrating system of spatial motion. Introducing the distur- bance parameters for average angular velocity of two excit- ers, we deduce the non-dimensional coupling equations of angular velocities of two exciters, in which the inertia cou- pling matrix is symmetric and the stiffness coupling matrix is antisymmetric in a non-resonant vibrating system. The analysis of the coupling dynamic characteristic shows that the coupled cosine effect of the phase angles will cause the torque acting on two motors to limit the increase of phase difference between two exciters as well as sustain its sym- metry of two exciters during the running process. It physi- cally explains the peculiarity of self-synchronization of two exciters. The cosine effect of phase angles of the vibrations excited by each exciter will decrease its moment of inertia. The residual moment of inertia of each exciter represents its relative moment of inertia. The stability condition of synchro- nization of two exciters is that the relative non-dimensional moments of inertia of two exciters are all greater than zero and four times their product is greater than the square of their coefficient of coupled cosine effect of phase angles, which is equivalent to that the inertia coupling matrix is positive definite and all its elements are positive. The numeric results show that the structure of the vibrating system can ensure the stability condition of synchronous operation.     

A NEW SYNCHRONIZATION SCHEME USING PERFECT PUNCTURED BINARY SEQUENCE PAIRS IN DS-UWB SYSTEM

Ultra WideBand （UWB） radio is a new wireless technology that transmits extremely short duration radio impulses. In this paper, a new synchronization scheme is proposed in Direct Sequence （DS） UWB system using Perfect Punctured Binary Sequence Pairs （PPBSP） as the preamble. It can acquire both Pseudo- Noise （PN） sequence and frame synchronization at the same time. The properties and the combinatorial admissibility conditions of PPBSP are presented. The simulation results show that PPBSP is good for synchronization by their good cross-correlation properties both under Additive White Gaussian Noise （AWGN） channel and modified Saleh-Valenzuela channel.     

μCos-II在嵌入式通信信号源中的应用

嵌入式通信信号源采用MCU控制DDS芯片的结构,产生FSK、LFM(线性调频)和MSK等多种信号模式。运行实时操作系统μCos-II,将应用程序按功能划分为几个核心任务,由实时内核进行调度,实现了多任务的并行执行,提高了嵌入式系统开发的效率、实时性和可靠性。通过以实时嵌入式操作系统μCos-II为软件平台的嵌入式通信信号源的系统设计,介绍了μCos-II的系统开销、移植和配置、多任务编程以及任务间同步、通信的实现方法。