【作者】 朱凯里；

【导师】 张福洪；

【作者基本信息】 杭州电子科技大学 ， 电子与通信工程， 2012， 硕士

【摘要】 扩频通信技术因其具有很强的抗人为干扰，抗多径干扰和抗截获的能力，而被广泛应用于对保密性要求高和通信时电磁环境恶劣的军事通信领域中。猝发通信是指在通信时将信息以较短数据帧的形式在随机时间点上进行发送，由于信号的发送时间不确定和发送持续时间短，进一步增强了信号的抗截获和抗侦听能力。将猝发通信技术和扩频通信技术相结合，可以有效地提高通信系统的保密性和抗干扰能力。载波同步是数字化接收机中的一项关键技术，它是接收机能正确解调接收数据的前提和基础，并决定了整个通信系统能否正常工作。本文在一猝发式直扩通信系统科研项目的背景下，主要研究了在数字化接收机中针对低信噪比和大频偏条件下的猝发式直扩信号，如何在有限长的导频序列内完成载波同步，进而正确解调出后续的信息数据，实现收发双方正确通信。本文首先介绍了扩频技术和载波同步技术在国内外发展现状和趋势，扩频通信的基本原理和直接序列扩频技术的相关理论。然后给出了本文所采用的猝发信号的帧结构，全文的研究始终围绕着这一信号结构，同时还给出了本文所研究的猝发式直扩通信系统中发射机和接收机的总体框图，并对其中的重要模块做了简要说明。接着讨论了基于数字匹配滤波器（DMF）的猝发式直扩信号的捕获方法，定量分析了多普勒频移对信号捕获过程所产生的巨大影响，对本文所采用的伪码相位联合多普勒频率的二维搜索策略作了说明，并简要介绍了伪码相位跟踪环的基本原理。之后对本文的重点：载波同步技术进行了深入研究，结合猝发信号的帧结构，设计了两种不同的混合载波同步方案：FFT校频+松尾环结构和锁频环（FLL）+松尾环结构，并在Matlab上对算法进行了仿真，仿真结果表明在系统要求的技术指标下，两种方案都能在规定的猝发信号导频符号长度内，完成载波同步，正确解调出后续的信息数据，设计的方案切实有效，具有一定的实际应用价值。最后，对全文作了总结，指出了下一步要完成的任务。更多还原

【Abstract】 Spread spectrum communication technology is widely used in the military communicationfield which requires high confidentiality and is coupled with a bad electromagnetic environment,due to its excellent capacity of anti-artificial interference, multi-path interference and intercept.Burst-mode communication means that the transmitter sends the information in the form of shortdata frames on the random time points in the communication process, because of the uncertain andshort transmitting time, the anti-intercept capacity of the signal is enhanced. By combining theSpread spectrum communication technology with burst-mode communication technology, we canimprove the communication system’s confidentiality and anti-interference capacity efficiently.Carrier synchronization is a key technology in the digital receiver, which is the premise andfoundation for receiver to correctly demodulate the received data, and decide the whole system canwork normally or not.This paper mainly researches how to fulfill carrier synchronization in the limited pilotsequence for burst-mode DSSS signal in the digital receiver under the situation of low SNR andlarge carrier frequency offset, then to correctly demodulate the follow-on information data, andestablish a reliable communications link. The research is done under the background of aburst-mode DSSS communication system research project.Firstly the paper introduces the development status and trend at home and abroad of spreadspectrum technology and carrier synchronization technology. The basic theories of spread spectrumtechnology and the technology of direct spread spectrum also have also been introduced.Secondly the frame structure of the burst-mode signal used in this paper is provided, theresearches which we did are around this signal structure from beginning to end. The general blockdiagram of the transmitter and receiver in the burst-mode DSSS communication system which weresearched is also provided, and we give some simple explanations to the important components ofthe block diagram.Then the capture method based on DMF of the burst-mode DSSS signal is discussed. Aquantitative analysis is done to the Doppler frequency shift which will produce a huge effect duringthe acquisition process. And the two dimension search strategy which combines the PN code’sphase with Doppler frequency is put forward and the basic theories of DLL are also introduced.After that, we develop this paper’s key further: carrier synchronization technology, and designtwo hybrid carrier synchronization schemes based on the frame structure of burst-mode signal: FFT+SongWeiLoop and FLL+SongWeiLoop, thereafter, the algorithm is simulated on Matlab. Thesimulation result shows that all two schemes can fulfill the carrier synchronization in the requiredpilot sequence of the burst-mode signal, under the system’s technical indicators, correctlydemodulate the follow-on information data, so the schemes which we designed is effective, and ofpractical value.Finally, the paper makes a summary about the finished work and indicates the following work.更多还原