Programmi di riduzione su calcolatore elettronico delle osservazioni astronomiche di tempo e di Azimut

In this paper a program is described for the reduction of the astronomical time and azimuth observations. The program is based on the Mayer's formula and allows a separate computation of the clock correction and instrumental azimuth. As regards this last quantity the program foresees three interesting procedures for the utilization of each observed azimuth utilising polar or equatorial stars. Besides by means of this program is possible to utilise the valnes of the time transit obtained by a totalizator chronograph. The various approximations introduced in the program are discussed, putting in evidence the great accuracy of the program.      

基于SoPC的复合信号幅频测试仪

设计了一种基于SoPC的复合信号幅频测试仪,给出了基于Hamming窗频谱函数比例查表法,有效解决了FFT变换中栅栏效应问题。依靠IQMath函数库在NiosⅡ软核上进行了高速FFT运算,实现了在1.5 s内对复合频率信号的主次分量频率、幅度信息的精确计算,同时通过SoPC系统的DDS组件配合滤波电路实现了复合频率信号的精确重建。     

一种推广形式的自适应算法

在某些实际问题中,如地震勘探信号处理等,对于非最小相位系统相位特性辨识,及非正 态分布随机信号的处理问题,用非二次范数为准则可以得到比传统的最小二乘法更好的结果, 但这常导致解一组非线性方程使计算复杂.本文提出一种新的最陡梯度下降自适应算法,它 是LMS法的推广,计算简单,可以误差的任意次范数为目标函数.文章证明了算法的收敛性 及其收敛结果,并给出了实验结果.     

一种扩频通信系统模型设计

移动通信的发展当前正处于一个关键时期,新的业务和技术不断涌现,客户的需求也不断增长。同时,因特网迅速发展成为真正的超级高速公路,数据多媒体通信发展迅猛,所以第三代移动通信的目标是宽带通信,也就是扩频通信。本文讨论了多相正交序列波应用于扩频通信系统的可能性。构造了基于多相正交序列波的扩频通信系统模型,并用Simulink软件对其通信过程进行仿真。结果表明,接收端恢复的信息数据保持了发送端信息数据的特征。     

基于Zoom-FFT的改进Rife正弦波频率估计算法

Rife算法是正弦波频率估计的一种经典算法,但其根本缺陷在于低信噪比且被估计频率接近量化频率点时估计性能差。本文通过分析Zoom-FFT的基本原理,验证了其具有可控的局部频谱放大功能,进而提出了一种改进的Rife频率估计算法。通过对信号进行Zoom-FFT处理实现以被估计频率为中心的较窄频段频谱的大幅度细化和放大,然后利用Rife算法进行精确频率估计。仿真结果表明,该算法具有高于传统Rife及其改进算法的估计精度和抗噪声性能,且对真实频率与量化频率点的位置关系不敏感,但计算复杂度有一定增加。     

一种低复杂度的鲁棒自适应波束形成算法

传统基于干扰噪声协方差矩阵（interference-plus-noise covariance matrix,INCM）重构的鲁棒自适应波束形成（robust adaptive beamformer,RAB）算法在多种样本数据协方差矩阵误差和信号导向向量误差的失配环境中具有较强的鲁棒性,但目前主流的INCM重构法都是对信号和干扰的导向向量通过建立凸优化模型来估计,这带来了很高的计算复杂度。为了解决这个问题,提出了一种低复杂度的基于INCM重构的RAB算法。该算法首先将干扰信号的导向向量分解为对应标称项和误差项的和,然后通过一种子空间方法估计得到误差项的单位向量。接下来对一个Capon空间谱功率最大问题进行求解,得到误差项的模值,以此得到重构的INCM。同时利用Capon空间谱中残差噪声的存在,使用交替投影法估计得到期望信号的导向向量,最后得到所提算法的权重向量。仿真实验表明所提算法在多种误差环境下具有较强鲁棒性的同时,还具有较低的计算复杂度。     

谱消除法在MEMS陀螺仪信号处理中的应用

介绍了数字信号处理中谱消除法的基本原理.结合MEMS陀螺仪漂移信号的频谱特点,给出了谱消除法在MEMS陀螺仪漂移信号处理中的应用.用此方法对不同频率的动态正弦信号进行仿真,信号的标准差可以从326.8(°)/h降低到36.9(°)/h.与传统的Kalman滤波、小波变换等去漂移方法相比,该方法具有运算简单,适时性好,易于硬件实现等优点.     

基于MATLAB的伪随机序列的产生和分析

MATLAB由于其强大的功能而被广泛应用于很多工程领域。在扩频通信中通常的做法是用一扩频序列与信号相乘,从而得到频谱的扩展或压缩,因而扩频序列的性能直接决定着通信质量。伪随机序列中的m序列和Gold序列最常用作扩频序列。该文首先简单介绍了m序列和Gold序列的原理,性能和构造方法,接着在MATLAB中用M语言编程实现它们的产生和分析。仿真结果验证了该方法的正确性和可行性。该方法简练直观,适合工程技术人员参考。     

Computing Interpolation Weights in AMG Based on Multilevel Schur Complements

This paper presents a particular construction of neighborhood matrices to be used in the computation of the interpolation weights in AMG (algebraic multigrid). The method utilizes the existence of simple interpolation matrices (piecewise constant for example) on a hierarchy of coarse spaces (grids). Then one constructs by algebraic means graded away coarse spaces for any given fine-grid neighborhood. Next, the corresponding stiffness matrix is computed on this graded away mesh, and the actual neighborhood matrix is obtained by computing the multilevel Schur complement of this matrix where degrees of freedom outside the neighborhood have to be eliminated. The paper presents algorithmic details, provides model complexity analysis as well as some comparative tests of the quality of the resulting interpolation based on the multilevel Schur complements versus element interpolation based on the true element matrices.     

Un particolare metodo per la determinazione di autovalori di matrici tridiagonali simmetriche

In this paper we given an algorithm of low computational complexity which determines the eigenvalues of a symmetric tridiagonal matrix. The algorithm uses the technique of spectrum slicing together with methods for finding the zeros of polynomials. An application of algorithm for computing Gauss quadrature formulas is given.

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Lavoro svolto nell'ambito del Gruppo Nazionale di Informatica Matematica del C.N.R.     

基于多段分频等长信号融合的频率估计方法

多段采样信号十分常见,对其进行信息融合能有效提高信号处理的精度,尤其适用于低信噪比、被测频率持续时间短的情况。为提高多段采样信号频率估计的精度和扩展已有方法的适用范围,给出一种多段分频等长信号融合方法。在该方法中,因各段信号的被测频率不等,故生成频域分析参数矩阵以实现同频化效果;因同频化后各段信号之间仍然相位不连续,故设计相位差补偿因子矩阵以达到相位连续信号的效果;因相位差补偿因子矩阵包含未知参数,故生成搜索频率序列以用于实际计算并得到具有特定形式的功率谱矩阵。为验证方法的正确性,给出了数学证明。针对多种应用环境状态进行了仿真实验,结果表明该方法具有普适性,抗噪性好,频率估计精度比现有方法有较大提高。     

Numerical methods for nonlinear integro-parabolic equations of fredholm type

This paper is concerned with iterative methods for numerical solutions of a class of nonlocal reaction-diffusion-convection equations under either linear or nonlinear boundary conditions. The discrete approximation of the problem is based on the finite-difference method, and the computation of the finite-difference solution is by the method of upper and lower solutions. Three types of quasi-monotone reaction functions are considered and for each type, a monotone iterative scheme is obtained. Each of these iterative schemes yields two sequences which converge monotonically from above and below, respectively, to a unique solution of the finite-difference system. This monotone convergence leads to an existence-uniqueness theorem as well as a computational algorithm for the computation of the solution. An error estimate between the computed approximations and the true finite-difference solution is obtained for each iterative scheme. These error estimates are given in terms of the strength of the reaction function and the effect of diffusion-convection, and are independent of the true solution. Applications are given to three model problems to illustrate some basic techniques for the construction of upper and lower solutions and the implementation of the computational algorithm.     

数字传感器信号采样技术研究

为了提高数字传感器输出信号的采样精度,简化采样处理,提出了一种将脉冲宽度测量和脉冲计数测量相结合的复合采样方法,给出了该方法的基本原理,并依据信号采样理论,推导了该方法的基本计算公式,讨论了它的采样精度、性能和参数选取限制.结合实际应用情况,给出了可以节省处理量的基于整数运算的改进算法和可以使采样精度最大化的动态精度自适应算法.该方法已成功地应用到实际系统中,实测数据表明,该方法有较好的精度和适应性.     

声门激励信号的获取及其应用

声门激励信号是语音信号的源信号,可用于语音特征参数的有效提取。研究了从观测语音获取声门激励的两种方法——线性预测法和倒谱法;用实际录制的语音做计算机仿真实验,比较了两种方法的性能和特点。结果表明倒谱法获取声门激励、由它提取基因周期等激励特征参数的精度高,但计算量相对较大;线性预测法由于采用高效算法,不仅获取声门激励的速度快,而且可同时获取声道模型参数、语音功率谱等重要参数,是获取声门激励的常用方法。     

基于局部均值分解的信号非线性趋势项剔除方法及应用

本文提出了一种基于样条插值的局部均值分解(LMD)法剔除趋势项的途径,并研究了其在发动机瞬时转速信号处理中的应用。通过与常用的最小二乘法(LSM)和小波分解法(WM)进行比较,表明了基于样条插值的局部均值分解法在去除信号中趋势项的问题上,具有剔除与真实信号频谱重叠的趋势项的优势。这对提高发动机瞬时转速信号预处理精度具有重要意义。     

Un metodo per la determinazione di un albero con lati pre-assegnati o meno in un grafo non-orientato descritto mediante la matrice di adiacenza

A computer oriented algorithm is given for the determination of a tree in a nondirected linear graph described by its adjacency matrix. The algorith allows two types of constraints for the tree to be found; it can be requested: 1. to involve some given edges. 2. not to involve some other given edges. The computation speed can be improved, when a centre of the graph is nown; an optimization of the procedure is given for this case. The storage requirement is pratically reduced to the only required by the adjacency matrix.     

基于DFT的相位差估计精度与改进方法

相位差是传感器信号处理中重要的检测参数。针对相位差高精度估计要求,在阐述DFT相位差估计原理基础上,分析了影响估计精度的主要因素,推导出估计方差与信噪比、采样长度、频率偏差及对称窗型窗长的具体关系,并给出了满足精度要求的信噪比、采样长度和和频率偏差条件。提出一种校正谱泄漏的相位差估计方法,先通过比值法计算出频率偏差,然后考虑负频率泄漏影响进行相位差估计,校正了短程和长程两类谱泄漏影响,给出了加矩形窗或Hanning窗的估计式和方法步骤。实验结果验证了估计精度分析及本文方法性能,科氏流量计应用实验表明了方法的工程可行性和实用价值。     

Calcolo di funzioni di matrice ad elementi reali mediante matrici costituenti reali

Sommario SeA è una matrice ad elementi reali edf(λ) una funzione analitica reale, si fornisce per la matricef(A) una espressione in termini di sole matrici costituenti reali. Successivamente si espone un algoritmo per il calcolo dif(A).

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A definition off(A) by means of real constituent matrices is given for any real matrixA, and any analitic real functionf(λ). An efficient algorithm forf(A) computation is shown.

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Lavoro eseguito presso la Fondazione Ugo Bordoni, come da convenzione in atto tra l'Amministrazione P. T. e la Fondazione Ugo Bordoni.     

轨道目标ISAR中频回波模拟技术研究

该文目的是研究一种空间目标宽带ISAR雷达回波的模拟实现方法，为空间目标探测雷达的研制及空间目标特性的研究提供信号来源。该文首先深入研究了空间目标的运动特性，给出了弹道目标轨道方程的计算方法，由目标的轨迹可以确定任意时刻目标的姿态，从而得到目标的散射中心分布。然后分析了目标在大时宽带宽雷达照射下的回波信号特性，结合目标轨道计算提供的散射中心分布信息，模拟出目标的中频回波信号。最后，提出了一种轨道目标ISAR雷达回波模拟器的实现方案，给出了实验结果。在实际应用中证明，用该方法模拟空间目标宽带雷达回波完全可行。