OFDM系统采样钟补偿算法及其FPGA实现

利用数字内插滤波器完成全数字域采样钟同步已广泛应用于OFDM数字接收机中.文中利用两个Farrow结构的内插滤波器,同时提高工作时钟对过采样信号进行数字域内插,完成接收端和发送端之间的采样时钟的完全匹配,并且根据硬件器件的特性和算法结构,逐级进行模块变量定点处理.基于实测数据的分析表明,该FPGA数字域采样钟补偿算法不仅有稳定的性能,而且其模块化设计也有利于更高阶算法或多通道系统的实现.     

Godard带通采样时钟恢复算法的研究

本文把Lyon的BECM时钟定时准则运用到带通采样中,推导出了Godard带通采样时钟恢复算法,但基于的准则跟Godard不同,算法推导过程比Godard的推导过程简单。文中给出了基于Lyon的BECM准则推导带通采样时钟恢复算法的完整推导过程,对Lyon准则和Godard准则的同一性进行了讨论,并对Godard带通采样时钟恢复算法作了进一步说明,最后通过matlab仿真验证了Godard带通采样时钟恢复算法可以有效地跟踪采样时钟的频偏和相偏,快速实现带通信号采样时钟的恢复。     

基于导频的OFDM时钟采样频偏估计

文中分析了OFDM系统时钟采样频偏对系统性能的影响,提出了一种基于导频的OFDM时钟采样频偏最大似然估计新算法,新算法只需一个OFDM符号就能精确的估计采样频偏,理论分析和仿真表明,新算法在低信噪比条件下仍具有很好的性能.     

高速采样信号数字内插理论与正弦内插算法研究

高速宽带数字化示波器在高扫速工作时,仅能采集信号的的少数样点.为了看清信号的全貌和精确测量其参数,必须在每两个样点之间进行插值(波形重构).本文从数字信号处理角度,研究了高速采样信号数字内插理论、插值滤波器结构、正弦内插算法.最后给出了计算机仿真的实例及其误差.     

一种基于内插采样的时差测量与基站同步技术

针对TDOA定位系统中的高精度时差测量问题,介绍并分析了一种基于内插采样的时差测量技术。与传统的时差测量方法相比,该方法将时钟量化误差转变为对基准信号相位的测量,从而消除了传统时差测量中的原理性误差。本文对该方法进行了理论分析与计算机仿真,仿真结果表明在当前的器件性能下能够实现70ps以内的时差测量精度。同时基于内插采样的高精度时差测量技术能够应用于TDOA定位系统中的基站时钟同步中,有效降低了基站时钟同步误差,进一步提高了时差定位系统的定位精度。     

二阶非均匀带通采样信号的快速恢复

本文讨论了实带通信号在二阶非均匀采样下的快速频域搬移，恢复，即用ＦＦＴ方法将实带通道恢复到两倍带宽（２Ｂ）内的复解析信号，而幅度和相位保持不变，最后经过简单的运算，得么原始频率，计算机模拟证实了上述方法。     

一种用于QAM解调的内插滤波器的设计

用频率响应最小均方误差的方法设计了一种用于数字电视QAM解调的插值滤波器,并提出了通过I/Q复用和部分模块的共用来实现插值滤波器的简化结构,节省了硬件资源。用Matlab对滤波器的性能进行了仿真,结果表明其对镜像信号的抑制达到-39dB,与其他类型的插值滤波器相比较,其对镜像信号的抑制性能更好。     

DVB系统中基于QAM调制的时钟恢复算法及实现

描述了DVB系统中接收端时钟恢复的作用,较详细地推导了时钟恢复的算法,并得出了时钟恢复的硬件实现电路,进而通过MATLAB仿真验证了算法的性能。     

用于光纤系统的数字突发方式时钟恢复技术

在这篇文章中我们提出了一种用于突发方式系统的时钟恢复技术，它完成时钟相位恢复，突发同步和定时告警产生的功能。     

采样时钟偏差对OFDM系统性能的影响

针对采样时钟同步偏差对正交频分复用（Orthogonal Frequency Division Multiplexing，OFDM）系统的影响，建立了数学模型，分别就采样定时偏差和采样频率偏差的影响进行详细分析；经过仿真，从星座图、误码率（Bit—Error—Rate，BER）及信噪比（Signal—to—Noise Ratio，SNR）损失等角度对采样频率偏差的影响做了揭示和验证。结果表明，采样频率偏差会引起信号幅度衰减和子载波间干扰（Inter—Carrier Interference，ICI），导致系统信噪比性能下降；这种影响与子载波位置有关，还会随着OFDM符号数的增多而加剧。     

高速OTDM系统的时钟恢复技术

介绍了高速光时分复用(OTDM)系统时钟恢复技术的三条实现思路，给出了具体的实验系统，指出了它们的适用场合。     

一种无需导频的适用于差分OFDM系统的符号与采样钟联合同步方法

该文提出了一种适用于OFDM系统的联合符号和采样钟同步校正方法,其中同步校正是在数字域通过改变对接收过采样信号的插值(interpolation)和抽取(decimation)实现的。这种方法在发送端相邻载波间采用差分QPSK调制,在接收端利用QPSK的差分解调信号获得同步误差信号,从而获得关于OFDM符号同步和采样钟同步调整的算法,其特点是无需专门的同步导频信号。所提出算法的同步性能在高斯白噪声信道和多径衰落信道均得到验证。     

Carrier Frequency Recovery Technique in OFDM Systems

Orthogonal frequency division multiplexing (OFDM) systems are highly sensitive to carrier frequency errors. In this paper, a new method utilizing pilots to do frequency synchronization in frequency domain is proposed with large estimation range. It needs no such prerequisite assumption that a perfect symbol timing synchronization [IEEE Transactions on Communications 42 (1994) 2908; 45 (1997) 1613] has been done before performing integer carrier frequency synchronization. Also, a new adjusting model for fine carrier frequency is proposed. Simulation and performance analysis show that our overall frequency estimator has high accuracy. The corresponding FPGA circuit through test in high definition TV (HDTV) prototype in Team of Expert Engineering Group (TEEG) in China proves its availability and feasibility.Bo Ai (M2001) was born in Shannxi Province in China on February 7, 1974. He received a B.Sc. degree from Engineering Institute of Armed Police Force and a Master degree, a Ph.D degree from Xidian University in 1997, 2002 and 2004 in China respectively. He has once participated in the key research project on HDTV in TEEG (Team of Engineering Expert Group) of China, and has published over forty papers in his research area till now. He is senior member of Chinese Electronics Institute (CIE), an editorial commitee member of journal of Computer Simulations. His current interests are the research and applications of OFDM technique with emphasis on synchronization.Jian-hua Ge was born in September, 1961 in JiangSu Province in China. He received the B.Sc., Master and Ph.D. degree from Xidian University in 1982, 1985 and 1989 respectively. He is now the professor in both Xidian University in Xian and Shanghai Jiaotong University in Shanghai. He is the senior member of Chinese Electronics Institute. He has won lots of scientific and technical prizes in China and published many papers. His interests are transmission communications and web security.Yong Wang (M2003) was born in Shannxi Province in China in 1976. He received a B.Sc. and Master degree from Xidian University in China in 1997 and 2002 respectively, and is now working towards the Ph.D. degree on communications in the Key Laboratory of ISN in Xidian University. He has once participated in the key research project on HDTV in TEEG of China and his interests are broadband multimedia communications.Dian-fu Zhang was born in Shannxi Province in China in 1954. He received a B.Sc. degree from Xidian University in China in 1977. He is now working as a professor and the chairman of the telecommunication department in Engineering College of Armed Police Force. His interests are mobile communications.Jun Liu was born in Beijing in China in 1963. He received his B.Sc. degree from Nanjing University Of Aeronautics and Astronautics in China in 1984. He is now a professor in Engineering College Of Armed Police Force. His research interests include integrated circuit design and artificial intelligence.     

一种环路带宽自适应调整的时钟数据恢复电路

针对SONTE OC-192、PCIE3.0、USB3.2等协议在串行时钟数据恢复时对抖动容限、环路稳定时间的要求,提出了一种环路带宽自适应调整、半速率相位插值的时钟数据恢复电路(CDR)。设计了自适应控制电路,能适时动态调整环路带宽,实现串行信号时钟恢复过程中环路的快速稳定,提高了时钟数据恢复电路抖动容限。增加了补偿型相位插值控制器,进一步降低了数据接收误码率。该CDR电路基于55 nm CMOS工艺设计,数据输入范围为8～11.5 Gbit/s。采用随机码PRBS31对CDR电路的仿真测试结果表明,稳定时间小于400 ns,输入抖动容限大于0.55UI@10 MHz,功耗小于23 mW。     

基于随路时钟恢复的多源数据光纤传输系统

针对数据互联网络中多源高速并行数据实时传输的问题,提出了一种基于随路时钟恢复的多源数据光纤传输系统,详细介绍了其工作原理和设计思想.系统将现场可编程逻辑门阵列(FPGA)内部高速收发器与专用数字锁相环相结合,给出了随路时钟恢复与数据流量控制的具体实现过程.相比于现有的各类高速并行数据传输解决方案,该系统具备可软件定义的数据接入能力,也能支持更加灵活的随路时钟动态范围.同时,通过设计精简合理的帧结构,推导数据位宽与随路时钟之间的约束关系,有效提高了系统传输带宽.测试结果表明,该系统工作稳定可靠,实时传输效果好,时钟恢复精度可达100 fs,扩展了串并转换与并串转换技术的应用领域.     

OTDM中时钟提取技术的发展及前景

光时钟提取是光时分复用的关键技术之一，得到了广泛的关注。目前，OTDM系统中用于时钟提取的技术方案有多种，本文对各种光时钟提取技术进行了综述和分析，并对其发展前景进行了展望。     

全光再生中的时钟恢复技术

随着超高速大容量的光网络的发展,全光再生技术成为目前的研究热点.其中全光的时钟恢复是全光再生技术的重要组成部分, 是全光再生中定时、整形的基础.文章在阐述了目前各种全光时钟恢复技术研究所取得的进展的基础上,分析了各类技术的优缺点,并对进一步研究作了展望.