用DFT对连续信号谱分析的误差问题

谱分析是数字信号处理中的一个重要问题,初学者普遍对连续信号谱分析理解不深,尤其是在误差分析时缺乏统一示例,更容易产生困惑。介绍了用离散傅里叶变换(DFT)对连续信号进行谱分析的过程,并详细说明了误差产生的原因和减小误差的方法。而且通过对模拟信号谱分析的实例全面说明了各项误差的影响及解决方案,并应用Matlab直观地进行了分析和对比验证。     

小波包-能量谱在提取脉搏信号特征中的应用

小波包是继小波分析后提出的一种新型的多尺度分析方法。文章描述了小波包分析方法的基本原理及其实现算法,并从能量分布的角度出发,阐述了在脉搏信号特征提取中,利用小波包分析方法将脉搏信号进行量化、分解,从而便于处理、判断的一种新的应用途径。实验结果表明小波包-能量谱用于提取脉搏信号特征是行之有效的。     

FY-2云检测中动态阈值提取技术改进方法研究

针对固定分析区云检测阈值提取中存在的问题,采用滑动分析区和嵌套分析区的方法改进云检测阈值提取方法.个例分析表明,夏季多积云,较少出现大片层云覆盖情况,由基本分析区获取的有效云检测阈值为49%,分析区调整为滑动分析区和嵌套分析区后,有效云检测阈值的比例提高至78.7%;冬季易出现大片层云,且云雪混杂,由基本分析区获取的有效云检测阈值为43%,分析区调整为滑动分析区和嵌套分析区后,有效云检测阈值的比例提高至74.88%.分析结果说明,采用滑动和嵌套分析区的方法,可有效改善动态云检测阈值的提取比例,改进云检测效果.     

Analysis of Brain-Wave Generators as Multiple Statistical Time Series

An illustrative example of the spectral analysis of simultaneously recorded electroencephalograms(EEG's) is presented. The first topic is that of auto-spectral analysis, which is very similar to frequency analysis; then cross-spectral analysis is used to show that the major relationship among three of the traces analyzed is a linear one, while a fourth trace is nonlinearly activated. Two hypotheses suggested by this analysis are tested by methods of multivariate spectral analysis, a recently developed extension of the cross-spectral method.     

白盒SM4的分析与改进

差分计算分析(DCA)是一种应用于白盒实现安全性分析的侧信道分析手段,其高效性在白盒高级数据加密标准(AES)的分析工作中已得到验证。该文针对白盒SM4方案提出一种类差分计算分析的自动化分析方法,该分析以白盒SM4方案中的查找表结果为分析对象,采用统计分析的方法提取密钥,称为中间值平均差分分析(IVMDA)。相比于已有的白盒SM4的分析方法,中间值平均差分分析所需要的条件更少,分析效率更高。在对白盒SM4方案进行成功分析后,该文提出一种软件对策以提高白盒SM4方案的安全性,该对策利用非线性部件对白盒方案中的中间状态进行混淆,消除中间状态与密钥之间的相关性。实验证明该对策可以有效抵抗中间值平均差分分析。     

CCⅡ低通滤波器的PSpice仿真分析

用子电路模块代替电路中的关键元件,采用理论分析与PSpice的参数扫描分析和优化分析相结合的方法对电路进行最优化设计,结合一个CCⅡ低通滤波电路的设计实例,阐述了仿真分析方法的具体步骤,给出了滤波电路最优化设计的仿真分析结果,该结果符合设计理论分析值的要求。对优化后的电路进行了温度扫描分析、蒙托卡诺分析和最坏情况分析。仿真结果表明,该方法在电路设计中是可行的。     

A Fourier analysis for a fast simulation algorithm [for powerconvertors]

A powerful discrete modeling approach to the simulation of a switching converter that has appeared in power electronics literature over the last several years is briefly reviewed, and some desirable traits for its matrix exponential subroutine are discussed. The key result is a systematic and generic Fourier analysis that operates on the steady-state solution as provided by a discrete model. The Fourier analysis algorithm was tested on a phase-controlled parallel-loaded resonant converter which is useful as a fixed-frequency low-distortion AC source. Three verifications of the algorithm were made: a phasor analysis, an alternate closed-form analysis directed specifically to the problem at hand, and an analysis using experimental data. The performance of the algorithm was good for the case considered     

Performance analysis of joint voice-data PRMA over random packeterror channels

We consider a joint voice-data packet reservation multiple-access (PRMA) system with transmission errors. Two analysis methods are presented. The first is a combined Markov and equilibrium point analysis. In this method, equilibrium point analysis is used to obtain the equilibrium number of backlogged data terminals, while Markov analysis is used to compute the stationary state probability distribution, assuming the number of backlogged data terminals is equal to the equilibrium value. The second is a Markov analysis using an approximate marginal distribution of backlogged data terminals. System performance measures, namely, voice packet dropping probability, data packet delay, and throughput, are derived in the presence of transmission errors. Computation complexity and accuracy are compared for the two analysis methods. Simulation results are also presented for comparison with analysis results, and good agreement is observed, especially when the packet header error rate is small     

Advanced types of the sensitivity analysis in frequency and time domains

The majority of standard tools for computer-aided design can perform only limited types of the sensitivity analysis: Spice determines operating-point sensitivities, and SpectreRF contains a parametric sensitivity analysis that can be used for determining the phase noise, for example. In the paper, some new types of the sensitivity analysis in frequency and time domains are described. These types of the analysis are not implemented in the standard circuit simulators.In the frequency domain, a procedure for determining the sensitivities of the noise figure is suggested. First, an improvement of the method for computing the noise figure is presented, which incorporates necessary circuit matching and eliminates the subtraction of output noise from the load at each frequency. Second, a simple formula is derived for computing the sensitivities of the noise figure. The sensitivity analysis in the frequency domain is generally demonstrated by means of a distributed microwave amplifier. The application of the sensitivity analysis of the noise figure for improving the noise properties of a monolithic microwave amplifier is described.In the time domain, a new recurrent formula is derived for the sensitivity analysis that efficiently uses high-order expressions of the algorithm for implicit numerical integration. Since the chosen integration algorithm is more flexible than the more frequently used Gear's one, the suggested formula leads to more efficient procedure. The sensitivity analysis in the time domain is important for analyzing symmetrical microwave circuits, because their operating-point sensitivities are zero in principle. For this reason, the significance of the proposed method is demonstrated by an analysis of a symmetrical radio-frequency CMOS multiplier. As an unusual example of exploiting the method, a temperature sensitivity analysis of a power operational amplifier is described.     

学习质量的智能分析模型

学习质量分析是一个复杂的过程，首先探讨了影响成绩质量的几种不确定性因素，给出了直观分析模型、概率分析模型、概率推理分析模型等3种成绩分析模型，通过学生的学习成绩较系统地分析了学生的学习质量，最后利用MYCIN概率推理分析模型对一具体实例进行了智能分析。     

基于某伺服转台的摇臂设计分析

桁架是工程及建筑中常见的一种结构形式,由于其在结构中的重要作用,设计后必须对其进行力学分析。以桁架的结构形式设计了一个伺服转台摇臂,利用ANSYS Workbench软件对其进行强度分析、屈曲分析以及模态分析,得到合理的结构。通过强度分析确定摇臂的结构形式,然后结合屈曲分析得到摇臂的合理尺寸,最后再对摇臂进行模态分析。     

Fixed-point error analysis of CORDIC processor based on the variance propagation formula

This paper presents a fixed-point mean-square error (MSE) analysis of coordinate rotation digital computer (CORDIC) processors based on the variance propagation method, whereas the conventional approaches provide only the error bound which results in large discrepancy between the analysis and actual implementation. The MSE analysis is aimed at obtaining a more accurate analysis of digital signal processing systems with CORDIC processor, especially when the design specification is given by the signal-to-noise ratio or MSE. For the MSE analysis, the error source and models are first defined and the output error is derived in terms of MSE in the rotation mode of the conventional CORDIC processor. It is shown that the proposed analysis can also be applied to the modified CORDIC algorithms. As an example of practical application, a fast Fourier transform processor using the CORDIC processor is presented in this paper, and its output error variance is analyzed with respect to the wordlength of CORDIC. The results show a close match between the analysis and simulation.     

基于Hadoop的海量电信数据云计算平台研究

传统的数据分析方法面对海量电信数据存在管理和分析难的问题.Hadoop是一个可实现大规模分布式计算的开源框架,具有高效、可靠、可伸缩的优点,被广泛应用于云计算领域.本文在对云计算和Hadoop进行分析和研究的基础上,提出了一种针对海量电信数据的分布式云计算方法,建立了基于Hadoop的海量电信数据云计算平台.实验证明,该平台能够有效完成海量数据的管理和分析任务,提高海量数据分析的速度和效率.     

电力系统暂态稳定分析方法的现状与发展

随着电力系统的发展,互联电力网络变得越来越大,暂态稳定性问题日趋严重,而电力系统安全运行的关键之一是可靠的暂态稳定分析。通过介绍电力系统暂态稳定分析常用的几种方法,回顾电力系统暂态稳定的发展历史和现状,对比分析了几种方法的特点及适用范围,并在此基础上对电力系统暂态稳定分析的发展前景进行了展望。最后指出,小波分析用于电力系统暂态稳定分析具有广阔的发展空间,特别是在处理暂态信号方面,更是一个很有应用价值的研究方向。     

A unified approach for the steady-state analysis of resonantconverters

A generalized approach for the steady-state analysis of resonant converters is presented. Different resonant converter tank circuit configurations are combined into a single tank circuit referred to as a generalized tank circuit. The load presented to this tank circuit is represented by an AC equivalent resistance, and simple complex circuit analysis is used to analyze such a generalized tank circuit. This type of unified approach simplifies the method of analysis for different configurations and eliminates the need for analysis of different schemes separately. In addition, in a computer program, the results for a particular scheme can be obtained by opening or shorting the nonrequired tank circuit components of the generalized scheme. The effect of high-frequency transformers and other parasitics can be taken into account in the analysis. A design example is presented to illustrate the method of designing a converter, and experimental results are presented to verify the analysis     

高功率激光装置靶场光学系统的误差分析

基于高功率激光装置主激光束精确打靶的需要,应用误差分析方法为装置的工程实施和单元技术的改进提供理论指导.针对装置在每发打靶前多应用自动准直技术来消除存在的误差,而传统的误差分析方法即随机误差和传统误差又未能进行全面系统的分析,提出了新的激光瞄准误差分析方法:静态误差和动态误差的划分.通过对靶场光学系统全面的误差分析,获得激光瞄准精度的普适性公式,并验证了该误差分析方法的正确性和可行性.     

试卷分析的统计学原理与软件设计

试卷分析是教学考试的重要组成部分,是有效提高教学质量不可或缺的环节,是测试诊断试题与试卷质量的有效性,从而保证试卷具有较高客观性的必要手段。从学生成绩统计分析、试题质量分析与试卷质量分析3个方面探讨了试卷分析的统计学原理,设计了科学实用的试卷分析程序软件,开发过程中研究应用了基于COM组件的VC＋＋6.0与Matlab7.0混合编程方法,实现了考试成绩频率直方图分析的图形绘制,对教学管理及软件设计人员均具有较大参考价值和指导意义。     

电波传播的抛物方程近似分析法

文中提出了一种电波传播模式分析方法. 通过对PJ (Paulus-Jeske)波导进行参数估计,实现蒸发波导的完备性建模;采用抛物方程法分析气象环境中的二维电波传播路径损耗分布,利用最大值池化降低数据量,并采用自适应聚类分析实现电波传播模式分析,进而建立海杂波衰减规律与电波传播模式之间的映射,统计条件概率. 结果表明,蒸发波导环境下海杂波衰减与电波传播模式之间具有相关性,分析结果能够展示蒸发波导中的电波传播模式,并且能够为海杂波反演大气波导提供先验条件概率分析.     

A new approach to the design of critically sampled M-channeluniform-band perfect-reconstruction linear-phase FIR filter banks

A new approach is presented for the design of uniform-band M-channel perfect-reconstruction (PR) FIR filter banks employing linear-phase analysis and synthesis filters. The technique designs on the impulse responses of the analysis filters directly. The design problem is formulated as an optimization program. The filter bank's PR feature can either be implicitly enforced through a set of mathematical relationships among the analysis filters' coefficients or through a set of constraints in the optimization program. The former approach results in a filter bank whose PR feature's dependency on hardware and software is eliminated or, at least, minimized. The synthesis filters are then obtained by a set of relationships that describe each synthesis filter as a function of the analysis filters. The criterion for optimality is “least-squares,” where the square of the difference between the ideal and actual frequency responses is integrated over the appropriate frequency bands for all M analysis filters and minimized     

CDMA系统下行链路容量研究

本文从基本的码分多址(CDMA)理论出发,根据WCDMA系统建立系统模型,从基站发射功率受限和小区间的相互干扰与影响的角度入手,结合计算机仿真,对CDMA系统的下行链路的容量特性作了分析与计算,分析了传播环境、小区半径、切换门限等参数对下行容量的影响,并使用计算机仿真对分析结果作了验证.对比表明,该分析结果与计算机仿真所得结果吻合的较好,可以作为分析、设计CDMA网络的基础.