基于内插的OFDM系统采样时钟恢复研究

数字内插滤波器全数字化恢复采样时钟已广泛应用于OFDM系统数字接收机中.文中给出了基于数字内插采样时钟恢复的完整推导过程,采用Farrow结构的数字滤波器,同时用拉格朗日内插方法对采样信号进行数字内插,完成收发两端之间采样时钟的完全匹配.仿真结果表明,该方案能够很好地跟踪采样时钟偏差,快速实现采样时钟的恢复.     

非相干重采样技术及应用

从基本原理、实现方法两个方面对多速率信号处理中的重采样技术进行了详细分析,说明了几种内插滤波器的特点及选择依据,最后介绍了非相干重采样技术在多载波调制和在时钟恢复中的应用。相对于利用DA和AD转换芯片实现采样率变换的方法,采用数字重采样技术实现采样率变换的方法具有性能稳定可靠、灵活性好、功耗低、复杂度低等特点。     

基于内插滤波器符号同步的实现

比较了同步采样和异步采样条件下符号同步实现方法的不同,在全数字接收机中需要采用内插方法来实现符号同步,内插滤波器是一种线性时变滤波器,在工程中可以采用多项式内插函数来近似,采用FARROW结构实现。在此基础上介绍了内插法符号同步环路的结构,组成单元,其中详细介绍了内插控制器和定时误差检测器的原理。在AWGN信道中针对QAM64信号进行了仿真和实现,眼图和星座图恢复良好,该符号同步环路可以应用于侦察接收机的解调器中。     

高阶重采样滤波器的多项式近似实现

可变载频带限信号的重采样,一般归结为按转换比P/Q(P为内插比,Q为抽取比)对原采样序列做内插和抽取。当P值很大时,需要多路内插滤波器,由于抗镜像的需要,滤波器系数矩阵非常庞大,使得高阶重采样难以实现。该文提出一种多项式近似滤波器的方法,用一组低阶多项式近似内插滤波器系数矩阵,简化了滤波器的结构,运算效率高,且内插延迟可任意改变。计算机仿真的结果表明:该结构适用于可变延迟的高阶带限内插滤波器。在一定条件下,误差在容许的范围之内。     

基于全相位IDCT滤波器的内插重采样分层编码技术

该文提出了一种基于全相位逆离散余弦变换(APIDCT)内插滤波器的重采样分层编码技术。全相位数字滤波器(APDF)是一种新型的线性相位滤波器。该文给出了APIDCT的设计方法,并通过比较几种APDF的性能,证明APIDCT在图像内插方面性能优异。在此内插方法基础上,结合重采样和自适应算术编码形成了分层图像编码技术,这种技术算法简单,适用于空间可分级编码。实验结果表明仅用其中3层,重建图像的峰值信噪比和压缩率就可达到略优于JPEG的效果,并且压缩率高时也不会出现块效应。     

高速数字示波器中的插值算法的研究

高速数字示波器只能采样原信号的少量点数.为了很好的恢复和重建原信号,必须对采样信号进行插值运算,本文介绍了数字内插的基本概念,对线性内插与正弦内插两种内插方法进行研究,通过模拟对其在正弦波、方波、三角波的实际用中的均方误差进行了计算和比较.     

一种宽带恒定束宽DBF技术实现方法

针对常规DBF方法不适用于宽带信号的问题提出一种宽带恒定束宽DBF方法.根据空间重采样理论将均匀线阵视为空间离散采样,利用内插定理得到各阵元在不同频点上的加权系数矩阵.利用维纳滤波理论设计宽带波束合成器拟合加权系数矩阵,实现宽带内波束指向一致,宽度相等.给出了理论分析依据及仿真结果,仿真结果表明了该方法具有计算复杂度低、稳健性强的优点.     

一种星上多载波APSK信号定时恢复方法

APSK信号应用在基于MF-TDMA星上处理的卫星通信系统中增加了系统的灵活性,多载波APSK信号定时恢复是实现星上整体解调处理的一个关键步骤。针对多载波APSK信号的特殊性和星上资源的有限性,提出了一种基于2倍采样加内插的多载波APSK信号定时恢复方法,在多载波情况下该方法与常规的定时恢复方法相比能够减小一半的数据缓存量,为星上处理节约了大量宝贵的存储空间,具有处理时延小和对信号幅度不敏感的优点。通过仿真给出了本方法性能与内插滤波器阶数和运算数据长度的关系。仿真结果表明,该方法能够较好地完成星上多载波APSK信号的定时恢复。     

DVB-C中可变速率符号的定时恢复

介绍了一种在DVB-C接收机中应用的基于非同步采样用内插技术实现的符号同步方法,完成了可变速率的符号同步,用Matlab实现其仿真性能,并在QAM/BPSK解调器中成功实现.     

可变速率符号定时恢复在QAM解调器中的实现

随着数字通信技术的发展,不同速率业务的相继推出,传统的符号定时恢复方法已不能满足要求,提出了一种基于非同步采样,用内插技术实现的符号同步方法,完成了可变速率的符号同步,并在QAM解调器中成功实现.     

脉冲激光测距中阈值—峰值双通道时刻鉴别方法

脉冲激光测距系统由于其精度高、抗干扰能力强等优点,广泛应用于激光雷达、激光引信等领域,但是常用的时刻鉴别法存在误差,制约了动态测距精度的提升,主要原因是回波脉冲的衰减和展宽。针对这一问题,提出一种采用恒阈值和峰值双通道的时刻鉴别新方法。该方法通过引入激光发射脉冲的理论方程,建立了回波波形的时域分布模型,可以实现不受到衰减和展宽的影响的准确回波鉴别。在此基础上设计了双通道时刻鉴别的脉冲激光测距系统。实验结果表明,采用双通道时刻鉴别方法可以将近程测距的误差控制在3 cm以内,并可通过多次测量对精度进一步提升,解决了时刻鉴别误差制约测距精度提高的瓶颈问题。     

色散控制WDM孤子通信系统中的定时抖动

采用拉格朗日变分法在同时考虑本信道放大自发辐射 (ASE)噪声、相邻信道信号对本信道信号和ASE噪声等多种因素影响的情况下 ,分析了色散控制孤子的传输演化特性 ,给出了准稳态色散控制孤子传输动力学方程和定时抖动解析表达 ,并给出了三种扰动因素影响程度的比较。     

SDH／非SDH接口界面的定时

同步数字系列ＳＤＨ的迅猛发展及传统准同步数字系列ＰＤ 量共存，导致了许多业务须在ＳＤＨ及非ＳＤＨ接口界面上传送。非ＳＤＨ接口定时一秀从传统的ＰＤＨ２０４８ｋｂｉｔ／ｓ数据信号中提取但ＳＤＨ网络中由于指针调整机制的引入，使得２０４８ｋｂｉｔ／ｓ数据不再能传递定时信息，这就给ＳＤＨ／非ＳＤＨ接口界面的定时带来问题，本文提出了再定量及改进解同步器等２种解决这一问题的方法，并给出了应用实例。     

激光成像系统高精度目标距离和强度信息提取

为提高脉冲激光3D成像系统中提取目标距离和强度信息的精度,对时刻鉴别和峰值保持电路进行了深入研究。在简要分析激光测距体制及探测器选择的基础上,给出了激光3D成像系统结构框图:激光器输出信号经半反半透棱镜,反射光线触发参考APD作为计时起始信号,以提高计时基准。给出了恒定阈值鉴别与恒比定时鉴别相结合的时刻鉴别电路,在提高时刻鉴别精度的同时可有效消除噪声对电路的影响。峰值保持选取基于OPA861的跨导型峰值保持电路。在实验室搭建了回波信号模拟系统,并在此基础上对电路性能进行测试。最后,给出了实验结果。结果显示:时刻鉴别电路精度优于1 ns;当输入窄脉冲峰值信号低于800 mV时,峰值保持电路保持精度优于2.63%。整个结果满足后续实验要求。     

Linear mappings ofn-dimensional uniform recurrences ontok-dimensional systolic arrays

We propose two methods for the synthesis of systolic arrays from uniform recurrence equations. First, we discuss a synthesis method for mappingn-dimensional uniform recurrence equations ontok-dimensional systolic arrays with a two-dimensional system clock. In this method we are led by the idea that all space-time conflicts caused by a scalar valued causal timing function and an allocation function can be rule out by a second scalar valued timing function. Stacking both timing functions yields a two-dimensional clock. Second, we develop a method to synthesizek-dimensional arrays with a scalar valued clock from a large subclass ofn-dimensional uniform recurrence equations containing important algorithms from signal and image processing. This method is based on a decomposition of the domain of the uniform recurrence equations into subdomains according to a given procesor allocation which allows the construction of a timing function for the whole domain from timing functions for the subdomains. In this way, the problem of finding optimal timing functions is reduced to finding optimal functions for the subdomains which are usually easier to establish. This synthesis method exhibits simplicity but its drawback lies in its limited applicability.     

Linear mappings ofn-dimensional uniform recurrences ontok-dimensional systolic arrays

We propose two methods for the synthesis of systolic arrays from uniform recurrence equations. First, we discuss a synthesis method for mappingn-dimensional uniform recurrence equations ontok-dimensional systolic arrays with a two-dimensional system clock. In this method we are led by the idea that all space-time conflicts caused by a scalar valued causal timing function and an allocation function can be rule out by a second scalar valued timing function. Stacking both timing functions yields a two-dimensional clock. Second, we develop a method to synthesizek-dimensional arrays with a scalar valued clock from a large subclass ofn-dimensional uniform recurrence equations containing important algorithms from signal and image processing. This method is based on a decomposition of the domain of the uniform recurrence equations into subdomains according to a given procesor allocation which allows the construction of a timing function for the whole domain from timing functions for the subdomains. In this way, the problem of finding optimal timing functions is reduced to finding optimal functions for the subdomains which are usually easier to establish. This synthesis method exhibits simplicity but its drawback lies in its limited applicability.     

中国的毫秒脉冲星计时观与建议

回顾了国际上脉冲星计时观测研究的进展与成果,评述了中国的毫秒脉冲星计时的学术观和进展,给出了应用小波分析方法在研究时间尺度方面的创新性成果。深思了进行高精度计时需进一步研究的一些问题,并对国际间合作进行脉冲星计时与应用研究的工程问题等提出建议。     

一种基于机器学习的众工艺角延迟预测方法

在不同工艺角下,关键路径呈现显著差异,因此需要进行大量的静态时序分析,从而导致时序分析运行时间较长。与此同时,随着工艺尺寸的缩小,静态时序分析的精度问题变得不容忽视。本文提出一种基于机器学习的适用于众工艺角下的延迟预测方法,考虑工艺、电压和温度对时序的影响,利用基于自注意力Transformer模型对关键路径进行全局聚合编码,预测众工艺角下关键路径的统计延迟。在EPFL基准电路下进行验证,结果表明该方法的平均绝对误差范围为5.8%～9.4%,有良好的预测性能,可以提高时序分析的准确度和效率,进而缩短数字电路设计周期和设计成本。     

Symbol synchronization technique in COFDM systems

In this paper we focus our research on the symbol timing synchronization technique in COFDM systems. A new method utilizing pilots to do coarse symbol timing is proposed. It overcomes the problem of fluctuation of the estimated symbol start position with cyclic prefix correlation method. The symbol timing error with the proposed method is within only /spl plusmn/10 samples. Different from previous algorithms in , we utilize the known pilot information to estimate the residual symbol timing offset with low system complexity. This paper also proposes a new control model for the sampling clock adjustment, different from the phase-locked loop (PLL), or delay-locked loop (DLL) method. The simulation and correspondent Field Programmable Gate Array (FPGA) circuit through test in HDTV prototype in Team of Engineering Expert Group (TEEG) proves its feasibility and availability. The proposed method is also suitable for burst mode transmission systems such as Wireless Local Area Network (WLAN) and Fixed-Broadband Wireless Access (F-BWA).     

A new ignition timing control method using dual-slope integration

A potentially useful method of reducing pollutants in automobile exhaust gas and reducing fuel consumption is the optimum control method for ignition timing of the mixture. Optimum ignition timing varies with the state of engine operation. Moreover, it is a complex function involving parameters of engine operating state. Ignition timing is usually expressed as the measure of angular displacement of the engine shaft with varying rotational speed, so that its control must depend on continuous phase control techniques. Dual-slope integration as a method of this phase control is proposed. A special feature of this method is that the phase angle between signals for each reference angle input intermittently can be determined in terms of linear functions of repetition frequency of the signals. By varying the time constants of integration and the level of comparison with the integration value, even more complex multivariant functions can be generated. The principle of phase control by dual-slope integration is described. An ignition timing controller applying this principle is discussed, the controller meeting the optimum ignition timing characteristics required in actual automobiles.