【作者】 陈胜明；

【导师】 陈吉忠；

【作者基本信息】 南京航空航天大学 ， 通信与信息系统， 2006， 硕士

【摘要】 软件无线电技术是一门新兴的通信技术,极具潜力。其在移动通信中的应用前景广阔,但受器件水平所制,进展较慢。扩频通信技术是一种在军用和民用方面都有广泛的应用的成熟的通信技术。直接序列扩频通信就是扩展频谱通信技术的一种通信方式,具有优良的性能,适合军用和民用。将软件无线电思想与扩频通信技术结合起来,就产生了一种新的通信平台:软件无线电扩频电台,更适合变化无常的移动通信世界。在软件无线电直接序列扩频电台接收机中,扩频码同步部分是关系到接收机性能的重要部分。扩频码同步包括捕获和跟踪两个内容,其中捕获最为困难和重要。目前的捕获方法从实现结构上可分为并行捕获、串行捕获和兼有并行结构与串行结构的混合结构捕获;从处理域上可分为时域捕获、频域捕获;从解扩运算方法上可分为基于相关器的捕获和基于匹配滤波器的捕获。本质上,各种捕获技术均利用伪码的自相关特性,由本地产生一个伪码副本与接收伪码进行相关运算,如果门限检测识别出相关峰则捕获完成。为了改善捕获性能,本文对两种常用的捕获系统进行改进。理论研究证明,改进的单积分顺序搜捕系统在低信噪比条件下比原系统大大减少了捕获时间;改进的匹配滤波器捕获系统比原系统在相同检测概率和虚警概率条件下信噪比有2dB改善,系统只增加了一个延时单元,简单的改进大大改善了接收机的性能,更适合应用于软件无线电直接序列扩频接收机系统。更多还原

【Abstract】 The Software Radio technology which has potential development is an new communication technology. Its application has broad prospect in mobile communication. For limited parts of an apparatus, the Software Radio technology is developed slowly. The Spread Spectrum Communication technology is mature and widely used in military and civil application. One kind of the communication is the direct Sequence Spread Spectrum communication which has good performance. When the Software Radio and the Spread Spectrum technologies combined, a new communication Platform is produced, that is the spread spectrum receiver based on Soft Radio which is more adaptive the wireless mobile communication world.In the system of the DSSS receiver based on Software Radio, PN code synchronization is the most important part. It can affect the receiver’s performance. The synchronization of spreading code includes acquisition and tracking, thereinto, acquisition is more difficult and important. At present, practical implementation can be parallel, serial, or hybrid. And it can be viewed as time region, or frequency region. Also, it can be based on correlator, or matched filter. In substance, all of the technologies are similar for using the PN code self-correlation characteristic. When the locally generated PN code phase is correlated with the received-signal PN codes’and the threshold detector finds the max correlated peak value, the PN code acquisition is finished, and the followed is tracking.In this paper, two PN code acquisition systems in common use are modified for getting better performance. The theoretic research proves that the first modified system based on single integral sequence acquisition system has less acquisition-time in low SNR condition and the second modified system based on differential non-coherent matched filter system has 2dB SNR advantage at the same probability of false alarm and probability of detection, only increasing a delay cell. The simple modification improves the performance of the relevant receiver, so it is more suitable for the Software Radio receiver.更多还原