猝发式直扩信号数字化接收机载波同步技术研究
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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。
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.
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。
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.
引文
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[2]韦惠民.扩频通信技术及应用[M].西安：西安电子科技大学出版社,2007.11.
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[4] G F Sage. Serial Synchronization of Pseudo noise systems. IEEE Trans. Commun. Technol, 1964. COM-12(12):123~127.
[5] Hurd, W.J.; Statman, J.I.; Vilnrotter, V.A. High Dynamic GPS Receiver Using Maximum Likelihood Estimationand Frequency Tracking. IEEE Transactions on Aerospace and Electronic Systems,1987, Vol.23(4):425-436
[6] Aghamohammadi, A.; Meyr, H.; Ascheid, G. Adaptive synchronization and channel parameter estimation using an extended Kalman filter. IEEE Transactions on Communications. 1989, Vol.37(4): 1212-1219
[7] [美] Floyd M.Gardner.锁相环设计(第三版)[M].北京：人民邮电出版社,2007.11.
[8] Costas, J.P. Synchronous Communications. Proceedings of the IRE.1956, Vol.44(12):1713-1718
[9] Natali, F. AFC Tracking Algorithms. IEEE Transactions on Communications. 1984, Vol.32(8): 935-947
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[42] Chung, B.-Y.; Chien, C.; Samueli, H.; Jain, R. Performance analysis of an all-digital BPSK direct-sequence spread-spectrum IF receiver architecture. IEEE Journal on Selected Areas in Communications.1993, Vol.11(7):1096-1107
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[50]王兰芳,吴长奇,高秀英.基于FLL与PLL级联的高动态载波跟踪技术[J].电子测量技术,2009年第3期.
[2]韦惠民.扩频通信技术及应用[M].西安：西安电子科技大学出版社,2007.11.
[3]管云峰.突发CDMA与突发OFDM接收机同步算法研究及实现[D].杭州：浙江大学,2003.
[4] G F Sage. Serial Synchronization of Pseudo noise systems. IEEE Trans. Commun. Technol, 1964. COM-12(12):123~127.
[5] Hurd, W.J.; Statman, J.I.; Vilnrotter, V.A. High Dynamic GPS Receiver Using Maximum Likelihood Estimationand Frequency Tracking. IEEE Transactions on Aerospace and Electronic Systems,1987, Vol.23(4):425-436
[6] Aghamohammadi, A.; Meyr, H.; Ascheid, G. Adaptive synchronization and channel parameter estimation using an extended Kalman filter. IEEE Transactions on Communications. 1989, Vol.37(4): 1212-1219
[7] [美] Floyd M.Gardner.锁相环设计(第三版)[M].北京：人民邮电出版社,2007.11.
[8] Costas, J.P. Synchronous Communications. Proceedings of the IRE.1956, Vol.44(12):1713-1718
[9] Natali, F. AFC Tracking Algorithms. IEEE Transactions on Communications. 1984, Vol.32(8): 935-947
[10]黄展.四相松尾环的研究与FPGA实现[D].哈尔滨：哈尔滨工业大学,2005.
[11]步如兰.扩频与解扩关键技术的研究与实现[D].西安：西安电子科技大学,2007.
[12]廖晓斌,第三代移动通信网络系统技术、应用及演进[M].北京：人民邮电出版社,2008.4.
[13]张高毅.中频直接带通采样数字相关器的研究[D].成都：电子科技大学,2006.
[14]李星.直扩系统发射机的设计与实现[D].西安：西安电子科技大学,2006.
[15] R Gold. Optimal binary sequences for spread spectrum multiplexing. IEEE Trans. Inform. Theory, 1967. IT-13(4)
[16]玉素甫·克依木.突发通信信号检测及同步技术研究[D].西安：西安电子科技大学,2010.
[17] Seong-Bok Park; Dhong-Woon Jang. A hybrid carrier synchronization scheme for PSK burst-mode communication systems. 11th International Conference on Advanced Communication Technology, 2009,Vol.2:1357-1360
[18]石代军.直接序列扩频突发信号同步算法研究及实现[D].成都：电子科技大学,2007.
[19]邹永.一种基于突发模式的DS/2DBPSK信号调制解调系统的研究[D].长沙：国防科学技术大学,2006.
[20] Efstathiou, D.; Aghvami, A.H. Preamble-less nondecision-aided (NDA) feedforward synchronization techniques for 16-QAM TDMA demodulators. IEEE Transactions on Vehicular Technology.1998, Vol.47(2):673-685
[21] Ahmad, J.; Jeans, T.G.; Evans, B.G. DSP implementation of a preambleless all-digital OQPSK demodulator for maritime and mobile data communications. IEE Colloquium on DSP Applications in Communication Systems.1993, 4/1-4/5
[22] Moeneclaey, M.; de Jonghe, G. ML-oriented NDA carrier synchronization for general rotationally symmetric signal constellations. IEEE Transactions on Communications.1994, Vol.42(8):2531-2533
[23]李骏.数字电视转发设备中数字中频技术研究及实现[D].杭州：杭州电子科技大学,2006.
[24]李宥谋,房鼎益. CRC编码算法研究与实现[J].西北大学学报（自然科学版）,2006年第6期.
[25]赵谨.短波猝发数传系统的研究与实现[D].西安：西安电子科技大学,2008.
[26]周希侠.卷积编码和维特比译码的FPGA实现[D].上海：复旦大学,2007.
[27]李江.机载无线通信中的盲均衡与差分编码技术研究[D].上海：上海交通大学,2008.
[28]文安平.平方根升余弦滚降数字滤波器的设计与实现[J].信息技术,2005年第9期.
[29]何秀慧.基于QPSK调制的扩频系统的FPGA实现[D].南京：南京理工大学,2007.
[30]李磊.基于DSP的QPSK通信系统研究[D].广州：华南理工大学,2007.
[31]李宏飞.直扩信号的同步与跟踪技术研究[D].西安：西北工业大学,2005.
[32]张静静.高动态下扩频系统的同步技术研究[D].南京：南京理工大学,2009.
[33]丁玲.短波猝发扩频通信系统的关键技术研究[D].西安：西安电子科技大学,2003.
[34]夏荥.高动态直扩信号载波同步技术[D].成都：电子科技大学,2008.
[35]施小茜.直扩接收系统中频数字化处理技术研究[D].西安：西安工业大学,2010.
[36]张爱民.直扩系统中基于DMF的伪码捕获和窄带干扰抑制技术研究[D].长沙：国防科学技术大学,2008.
[37]黄振,陆建华,杨士中.基于DMF直扩系统捕获性能的研究[J].电路与系统学报,2002年第1期.
[38]任江涛.北斗接收机基带信号的捕获算法研究[D].合肥：合肥工业大学,2010.
[39]黄福林.高动态环境下GPS跟踪算法研究及实现[D].西安：西安电子科技大学,2008.
[40] Spilker J J, D T Magill. The Delay-Lock Discriminator-An Optimum Tracking Device. Proc. IRE.1961,Vol.49(9):1403-1416
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