无线扩频通信机研究

扩频是源于军事保密而发展起来的一种数字编码技术，随着技术与器件的发展，扩频技术正从军用通信领域进入到民用通信领域。本文介绍了一种利用扩频通信技术实现的工作在２．４￣２．４８３５ＧＨｚ工业，科学，医学（ＩＳＭ）频段的点对点数字微波电台，阐述了扩频通信技术的有关理论，并介绍了实现该系统的硬件和控制软件。     

扩频通信技术原理及其应用

文中阐述了扩频通信技术的理论依据和基本概念,并结合扩频通信技术的分类及原理,重点分析了直接序列扩频和跳频扩频两种通信模式的技术特点,最后介绍了扩频通信在三个领域中的应用,可为从事无线电通信和电磁频谱管理等相关行业的技术人员提供参考。     

扩频通信

扩频通信即扩展频谱通信。它是一种新型的通信体制，是扩频技术在通信领域中的应用，是未来通信领域的一个重要发展方向。由于扩频通信系统具有抗干扰能力强、信号被截获率低、码分多址、通信安全保密、易于组同等一系列特点，引起了世界各国的关注和极大兴趣，使扩频通信技术的研究取得了飞速的发展。预计扩频通信今后的发展将会更快。     

扩频技术在航天通信中的应用

介绍了扩频技术在航天通信中的应用;讨论了扩频通信系统的抗干扰特性;最后,展望扩频通信在实际工程及航天领域的发展前景。     

直扩技术分析及其应用

扩频通信技术由于具有抗干扰能力强，信号隐蔽性好，容易实现多址传输等优点而在卫星通信、数据传输、移动通信、无线数据通信等领域的应用日益广泛。其中直扩通信技术是目前使用的最典型扩频工作方式，弄清楚扩频和解扩处理过程的机制，是理解直接扩频通信技术本质的关键所在。首先介绍了直扩通信系统的基本工作原理，其次结合构建的系统模型，对其扩频和解扩的机制进行了详尽分析，提出了采用直扩技术通信的优势。最后给出了直扩技术在国内外的应用现状。     

扩频通信技术在经纬仪对外通信中的应用

经纬仪作为靶场主要的高精度外弹道测量设备,在使用过程中,经常与测控中心互传数据,在经纬仪对外通信中采用扩频通信技术,实现了远程通讯.本文主要介绍了扩频通信技术在经纬仪对外通信中的应用.介绍了扩频通信的原理及典型的工作方式,描述了几种典型工作方式的具体实现方法;重点介绍了扩频微波通信技术的特点、系统组成、使用方案及系统连...     

软扩频通信系统的研究

文章介绍了软扩频通信系统的基本原理、编码和实现框图,分析了软扩频通信系统接收机的性能,并比较了软扩频系统同步接收的几种方案。结果表明,滑动相关捕获是一种有效的伪码捕获方法,软扩频通信系统能够进行可靠的通信。     

无线保密通信系统的核心技术分析

本文以实现无线保密通信为需求,引出了扩频保密通信技术.文章首先阐述了扩频保密通信的实现原理,给出了两种扩频通信的具体实现和组网方法,然后分别从抗干扰容限、信道容量与带宽关系、信息传输差错概率、频谱分布四个方面对扩频保密通信的可靠性进行了分析,说明扩频技术在保密通信方面的应用是完全可行的.文章最后对无线扩频保密通信的应用进行了展望.     

扩展频谱通信技术的应用及其发展研究

本文对常见的几种扩展频谱技术，即直接序列扩频通信技术、跳频通信技术、跳时通信技术以及混合扩频技术在军事通信中的应用情况分别进行了讨论，重点介绍了上述各种扩频通信技术当前的研究进展情况，并对未来的发展趋势进行了展望。     

扩频技术在CDMA中的应用

扩频技术最大的特点是利用宽频带来传输信号。由于扩频系统具有许多优点，如抗干扰能力强、截获概率低和保密性强以及良好的码分多址通信能力，所以扩频技术已被广泛应用。ＣＤＭＡ就是利用扩频技术发展起来的一种扩频通信方式，它具有容量大，通信质量好，节约发射功率等优点。文章试就一些扩频通信的原理及ＣＤＭＡ中采用的扩频技术作些讨论。     

自编码直接序列扩频通信原理样机的实现及测试

自编码直接序列扩频通信由于提高了通信信号的隐蔽性,且保持了直接序列扩频通信技术原有的抗干扰性能,对改善军事抗干扰通信具有积极意义。根据自编码直接序列扩频通信的特点,设计出了原理样机,并提出和实现了一种基于帧变化并发送同步头的初始同步方案,效果良好。经过测试,所有性能指标均已达到预期目标,并且与单用户下的理论分析结论相吻合。     

自编码扩频通信技术研究

扩展频谱通信是军事保密通信的基本方式，它是采用信息的频谱展宽进行传输的，从而达到抗干扰和信息保密的目的。而目前采用的PN序列具有周期性，为了寻找一种具有真正的随机性扩频码，并具有较强的抗干扰和信息保密能力的扩频通信技术，人们提出了自编码扩频的概念，文中介绍了自编码扩频原理，分析了系统的性能，并且进行了仿真。     

Spreading Codes Generator for Wireless CDMA Networks

The prime characteristic of spread spectrum modulated signals is that their bandwidth is greater than the information rate. In this way a redundancy is introduced that allows the severe levels of inteference inherent in the transmission of digital information over radio and satellite links to be overcome. Current spread spectrum applications are primarily in military communications; nevertheless, there is growing interest in this technique for third generation mobile radio networks (UMTS, FPLTS, etc.) with open discussion regarding the practicality of using a multiple access system based on spread spectrum techniques (CDMA). However, in order to support as many users in the same bandwidth as other multiple access techniques such as TDMA or FDMA, it is important how to generate large families of sequences that present low cross-correlation. The aim of this paper is to describe a spreading codes generator that can produce a large number of PN sequences with good properties of auto- and cross-correlation. Moreover, the codes generated shows high unpredictability and good statistical behaviour. This also allows the implementation of some features that are common on military networks such as message privacy (increasingly important in commercial networks) without additional cost. The structure presented shows itself to be advantageous for high speed generation of codes at a low cost, low power consumption (allowing longer life for batteries), small size and simplicity of implementation, essential ingredients for commercial equipment. Another attractive feature is its structural parallelism, useful in VLSI implementations. All of these features render it potentially suitable for the implementation of channel bandwidth sharing systems in future wireless personal communications networks.     

美军卫星通信系统的发展及其技术研究

随着信息技术的快速发展,美军为满足未来战争需要不断地规划研发新的通信卫星系统。文中主要讨论了美军卫星通信系统的现状和未来发展,归纳了相关的关键技术,最后总结了目前卫星通信的重要性并指出了今后研究的方向。研究美军在这一领域的新发展和成果,目的是为我国构建空间信息网络奠定必要的基础。     

卫星通信系统中的抗干扰技术研究

卫星通信是军事通信的重要组成部分,在复杂电磁环境下,卫星通信的环境又是十分恶劣的,它容易受到敌方的侦收、干扰和攻击等威胁。文中重点对现代卫星通信系统中最常用的抗干扰技术——直接序列扩频技术和跳频技术的基本原理进行了研究分析,给出了简单的仿真结果并总结了这两项技术各自的特点。这两类技术的共同特点是信号的频谱在发送时得到了扩展,在接收方又恢复为原来的宽度。这两项技术是保证战争中己方通信畅通的关键技术,在军事通信中有着极为重要的意义。     

弱湍流下Turbo码编码数字脉冲间隔调制差错性能分析

数字脉冲间隔调制(DPIM)的符号长度变化不固定,因而分析该调制方式在Turbo码编码下的差错性能存在困难.在建立分析模型和推导差错率的基础上,在弱湍流信道条件下仿真分析了Turbo码编码前后的系统差错性能,同时与高斯信道条件下的系统差错性能进行了比较.仿真分析结果表明,弱湍流信道条件下的系统差错性能不如高斯信道条件下的系统差错性能,但在两种信道条件下,引入Turbo码编码技术均可获得3~6 dB的编码增益,能够有效改善系统的差错性能,具有良好的军事应用价值.     

基于时空混沌同步的数字图像保密通信

以单向流耦合映像格子时空混沌系统模型为基础，采用驱动－响应同步方法达到时空混沌同步，利用时空混沌序列具有复杂度高、伪随机性好、宽频谱的特点，实现对数字图像在扩展频谱基础上的保密传输，使加密信号有较强的抗破译能力。计算机仿真结果证实了利用该方法进行数字图像保密通信的有效性。     

2014年美国海军通信装备与技术发展综述

2014年,美国海军在军事通信与数据链领域围绕战场网络系统、先进战术数据链系统、机载通信系统、卫星通信系统以及新型通信技术等热点领域展开了大量研究和装备部署工作。跟踪外军通信装备的发展动态,研究外军通信装备和技术发展趋势对促进我国海军通信和通信电子战能力建设具有重要借鉴意义。概述了2014年美国海军通信装备与技术的发展情况,并分析了海军信息网络、数据链和软件无线电的未来发展趋势。     

数字微波通信电子反对抗研究

介绍了数字微波通信技术的主要特点,并对微波、散射和卫星通信的工作特点和军事应用场合进行了综合比较;分析了对数字微波信号实施电子对抗的策略方法-侦察定位、截获分析和实施干扰。阐述了数字微波通信电子反对抗的策略目的-可被截获的电波信号能量最小化,并说明了各种数字微波通信电子反对抗技术措施的优缺点,视情综合运用效果最佳。     

Performance Analysis of Multiband Complex Wavelet Based MC-CDMA System with Space Diversity Combining in Rayleigh Fading Channel

In this paper, the multiband complex wavelet used as multi-carrier basis function is optimized. On the basis of analyzing the principle of multi-carrier code division multiple access (MC-CDMA), a new multiband complex wavelet based MC-CDMA (MBCW-MC-CDMA) system model is proposed, and space diversity combining (SDC) technique is employed to improve the system performance further. The uplink performance of proposed MBCW-MC-CDMA system with SDC technique is investigated in Rayleigh fading channel, and corresponding bit error rate (BER) analysis is given in detail. Without any cyclic prefix (CP), the system can avoid the decrease of spectrum efficiency and data rate of conventional MC-CDMA with CP. By comparison, our scheme outperforms real wavelet packet based MC-CDMA and slightly outperforms conventional MC-CDMA with CP via utilizing superior properties of the optimized multiband complex wavelet. Theoretical analysis and simulation result show that the application of SDC technique can improve the proposed system ability to combat spatial fading and various interferences effectively. Moreover, the proposed system based on SDC technique has superior BER performance over conventional DFT and SDC based MC-CDMA system and real wavelet packet and SDC based MC-CDMA system. Xiangbin Yu received the M.S degrees in Communication and Information Systems from Hohai University, Nanjing, China, in 2001; and his Ph.D. in Communication and Information Systems in 2004 from National Mobile Communications Research Laboratory at Southeast University, China. Now he is working as a Postdoctoral Researcher in Information and Communication Engineering Postdoctoral Research Station at Nanjing University of Aeronautics and Astronautics, Nanjing, China. His research interests include multi-carrier digital communication, space-time coding and digital signal processing in modern communications. Xiaodong Zhang received the M.S degrees from Nanjing University of Posts and Telecommunications, Nanjing, China, in 1998. In 2002, he received the Ph.D. degree from Southeast University, Nanjing, China. His research interests include contemporary signal processing and digital communications. DaZhuan Xu received the M.S degrees and Ph.D. in Communication and Information Systems from Nanjing University of Aeronautics and Astronautics in 1986 and 2001, respectively. He is now a full professor in Nanjing University of Aeronautics and Astronautics, Nanjing, China. Prof.Xu is a Senior Member of China Institute of Electronics (CIE). His research interests include digital communications, soft radio, coding theory, medical signal processing. Guangguo BI was graduated from Nanjing Institute of Technology, Nanjing, China, in 1960. He is now a professor in the Department of Radio Engineering of Southeast University, Nanjing, China. Prof.Bi is a fellow and a member of the board of Director of the China Institute of Communications, and a senior member of IEEE. His research interests include digital communications, personal communications network, spread spectrum communications, and intelligent information processing. He has published more than 200 papers in above areas.