音频测量系统的稳态分析研究

利用数字系统来实现数字音频测量系统中的正交检波分析,其关键在于如何选取当分析待测正弦信号中频域特性时的窗函数。在研究过程中,主要运用了BH窗、Blackman窗、三阶矩形自卷积窗和四阶矩形自卷积窗,同时使用Matlab进行了数值仿真计算,从而获得窗函数类型和加窗长度对于幅度及相位分析精度的影响,得出在数字音频测量系统中研究频率响应和失真时加余弦窗得到的精度比加矩形自卷积窗要高,这对保证测量结果的精确性很重要。为正弦稳态分析方法的正确使用提供了有意义的理论指导。     

基于混合卷积窗六谱线插值的多普勒信号处理

激光多普勒测速系统信号处理的过程中,通常采用快速傅里叶变换提取多普勒频移进而计算出被测物体运动速度,由于频谱泄露和栏栅效应的影响,会导致测量精度降低。本文提出了一种四项Nuttall窗和五项Rife Vincent窗的混合卷积窗函数结合改进的六谱线插值算法来降低频谱泄露和栏栅效应所带来的影响,从而提高激光多普勒信号处理精度。搭建了双光束后向散射差动式激光多普勒测速平台,通过仿真和实测得出在加入了RSN=-10dB的高斯白噪声的情况下使用该混合卷积窗所测量的最小相对误差为00027,而分别使用两个单一的窗函数测量的最小相对误差分别为00103和00461。从而验证了本方法的有效性。     

基于矩形卷积窗的声频测量系统谐波分析方法

研究卷积窗在声频测量系统高精度谐波分析中的应用,并将卷积窗与多种常用的经典窗函数进行比较.结果表明:与具有相同宽度的其他窗函数相比,当采样同步误差较小时,卷积窗的主瓣最窄,旁瓣衰减速率最大,具有更小的频谱泄漏效应,因此更适于声频测量系统的高精度谐波分析.通常声频测量系统的测量频率已知,通过选择合适的窗长,可以保证采样同...     

一种基于卷积核用于光刻模拟的计算稀疏空间点光强的方法

光学邻近校正(OPC)系统要求一种精确、快速的方法来预测掩模图形转移到硅圆片的成像结果.基于Gabor的"降解为主波"方法,一个部分相干成像系统可以用相干成像系统的叠加来近似,并用高斯过滤器来模拟光刻胶横向扩散和一些掩模工艺效应,由此提出了一种基于卷积核的精确、快速地用于光刻模拟的稀疏空间点光强计算方法.这种模型的简单性从本质上给计算和分析带来了好处.仿真结果说明这种方法是有效的.     

一种基于卷积核用于光刻模拟的计算稀疏空间点光强的方法

光学邻近校正 (OPC)系统要求一种精确、快速的方法来预测掩模图形转移到硅圆片的成像结果 .基于 Gabor的“降解为主波”方法 ,一个部分相干成像系统可以用相干成像系统的叠加来近似 ,并用高斯过滤器来模拟光刻胶横向扩散和一些掩模工艺效应 ,由此提出了一种基于卷积核的精确、快速地用于光刻模拟的稀疏空间点光强计算方法 .这种模型的简单性从本质上给计算和分析带来了好处 .仿真结果说明这种方法是有效的     

雷达信号处理系统建模方法研究

为解决雷达系统仿真过程中的高阶信号处理系统建模问题,对Levy最小二乘法、脉冲响应法,频域相乘法等进行了分析和实验。实验结果表明,这些方法很难得到准确的高阶雷达信号处理系统模型。为此,提出一种采用频率响应数据建立时域卷积数值模型的方法。仿真和实验结果表明,该方法具有适应性好,实现简单、模型准确等特点,可以大大提高系统仿真的准确性和精度,并可推广到其他高阶系统建模。     

An adaptive approach to spectral analysis of pattern-reversal visual evoked potentials

A method for spectral analysis of pattern-reversal visual evoked potentials (PRVEP's) is presented that results in spectral peaks of uniform width in the frequency domain for signals with a wide range of time-domain duration. Uniformity of spectral peak width is necessary for accurate comparison of spectra. The desired frequency domain characteristics can be achieved through the application of "tunable" data windows prior to transformation. The Io-sinh (Kaiser), Gaussian, and cosine-taper (Tukey) windows were evaluated as to their ability to produce power spectra with uniform spectral peak width. Objective comparison of power spectra is based on the "spectral parameter," which is a numerical index of power distribution. Application of the method to PRVEP waveforms of normal subjects (N = 20) and to a population of Alzheimer's Disease patients (N = 15) showed the Io-sinh window to be the most effective method, yielding correct classification of all normal and abnormal subjects. The Gaussian window also performed well, with only two misclassifications. Use of the rectangular window resulted in seven misclassifications. The tapered-cosine window was very limited in its applicability, and was about equal in performance to the rectangular window.     

卷积窗及其在电力系统参量估计中的应用

利用矩形窗的多重卷积,导出一类新的窗函数,称其为卷积窗,并研究其在电力系统的参数估计中的应用.误差分析和数值模拟表明: 若采用k阶矩形卷积窗(矩形窗的k重卷积),各电气参量测量值的误差正比于相对频偏的k次方.在电力系统中,只需取4阶窗函数,便可将因非同步采样引起的测量误差降低到10^-7的量级,而不必采用任何同步采样措施.     

适用于超深亚微米光刻仿真的建模和优化

提出了一种新颖的利用版图轮廓的超深亚微米光刻工艺建模流程.该流程采用的方法主要包括:首先将代表纯光学模型的传输交叉系数矩阵通过圆极化采样正交投影成更小规模的矩阵,同时用该组相同的极化采样基表示掩模图形;然后用目标电路版图的严格3D仿真结果或其SEM轮廓图对该新系统进行半经验化的校正.在模型校正过程中引入了基于遗传算法的全局优化算法. 实验结果显示,该方法能够快速有效地模拟用传统方法不能准确模拟的超深亚微米新出现的一些畸变效应.由于最终的模型是用一批卷积核的形式表示,建成的模型能够满足光学邻近校正对准确性和快速性的要求.     

适用于超深亚微米光刻仿真的建模和优化

提出了一种新颖的利用版图轮廓的超深亚微米光刻工艺建模流程.该流程采用的方法主要包括:首先将代表纯光学模型的传输交叉系数矩阵通过圆极化采样正交投影成更小规模的矩阵,同时用该组相同的极化采样基表示掩模图形;然后用目标电路版图的严格3D仿真结果或其SEM轮廓图对该新系统进行半经验化的校正.在模型校正过程中引入了基于遗传算法的全局优化算法. 实验结果显示,该方法能够快速有效地模拟用传统方法不能准确模拟的超深亚微米新出现的一些畸变效应.由于最终的模型是用一批卷积核的形式表示,建成的模型能够满足光学邻近校正对准确性和快速性的要求.     

MATLAB在电力电子电路仿真中的应用

MATLAB软件是当今控制系统的设计与仿真中重要的工具软件。讨论了交直流控制系统中利用Matlab／Simulink软件平台进行仿真研究的方法,具体给出了基于MATLAB软件,对直流调速系统中的转速负反馈调速系统的起动过程及其在各类扰动作用下系统的动态过程进行了仿真分析,说明了MATLAB在电力电子电路仿真中的应用;详细给出了在Matlab软件平台下如何搭建控制模型以及电力电子电路中常用的整流桥、晶闸管、交直流电动机的仿真方法。实践证明,应用MATLAB实现对电力电子电路的仿真方法简便,易于实现。     

The discrete Fourier transform method of solvingdifferential-integral equations in scattering theory

An accurate and efficient numerical method is presented for solving many differential-integral equations arising from electromagnetic scattering theory. It uses the discrete Fourier transform technique to treat both the derivatives and the convolution integrals which often appear in these equations. As a consequence, this method is extremely simple to implement, uses less computer memory than comparable methods, and yields accurate predictions. The differential-integral equation is recast into a periodic form conducive to application of the discrete Fourier convolution theorem. The differential operators are approximated by appropriate finite-difference and discrete-convolution operators. All these quantities are computed by using the fast Fourier transform. An approximate solution is obtained by using the conjugate gradient method. Results are compared to experimental data or analytical solutions for a 3λ×3λ metal plate (where λ is the wavelength), a homogeneous and a layered infinite circular dielectric cylinder, and a dielectric sphere. The accuracy of the method is further illustrated by comparing predictions with independent measurements by R.A. Ross (1966) on a 2λ×1λ metal plate at grazing incidence. In all cases, agreement is excellent     

Multiple Edge Responses for Fast and Accurate System Simulations

High-speed input/output (I/O) link performance is limited by random noise as well as signal integrity issues such as dispersion, reflections, and crosstalk. Hence, accurate prediction of system performance including these random and deterministic noise is crucial in high-speed link design. This paper presents a novel, fast, and accurate method to simulate the time-domain system response. The presented method calculates the system response using multiple edge responses (MER) based on linear superposition. Being able to take into account system nonlinearity more accurately, the presented method significantly improves simulation accuracy compared with the other published fast simulation techniques based on either single bit response (SBR) or double edge responses (DER), while at the same time maintaining equivalent numerical efficiency. Furthermore, peak distortion analysis, which is commonly used to find the worst-case data pattern based on SBR, is extended for DER and MER using dynamic programming. A multiphase worst-case data pattern approach is also introduced in this paper in order to determine the worst-case system performance under both timing and voltage consideration.      

利用卷积神经网络进行毫米波图像违禁物体定位

随着毫米波器件的成熟,毫米波成像雷达已经应用于人体安检.但毫米波图像中违禁物体的定位仍然是一个艰巨的任务,这极大地限制了毫米波成像雷达的应用.文章将卷积神经网络(Convolutional Neural Network,CNN)应用于毫米波图像,自动定位毫米波图像中的违禁物体,如枪、刀等.利用滑动窗口在输入图像上滑动,并通过CNN得到各个子图块存在违禁物体的概率.图像块是相互交叠的,将各子图块的概率值累积起来,得到概率累积图.概率累计图反映了违禁物体的位置.由于CNN和概率累积图的应用,在实验中,该方法获得了很高的定位准确率,验证了该方法的有效性.     

An FDTD formulation for dispersive media using a current density

A novel finite-difference time-domain (FDTD) formulation for dispersive media called the JE convolution (JEC) method is derived using the convolution relationship between the current density J and the electric field E. The high accuracy of the JEC method is confirmed by computing the reflection and transmission coefficients for a nonmagnetized plasma slab in one dimension. It is found that the new method has an accuracy comparable to the auxiliary differential equation (ADE) while having the same computational efficiency as the less accurate recursive convolution (RC) method. Numerical simulations also show that the JEC method exhibits significantly higher accuracy than the RC method in modeling wave attenuation inside the plasma     

Wavelet-based time-domain solution of multiconductor transmission lines with skin and proximity effect

A time-domain wavelet-based method for the analysis of transmission lines (TLs) characterized by the presence of skin and proximity effects is presented. The method is based on the time domain TL equations, expressed in terms of transient resistance and convolution operator. A formulation of the convolution in the wavelet domain is presented here, and is used to expand the TL equations in the wavelet domain. In this way, the TL equations, properly discretized in the space variable, are reduced to an algebraic system characterized by a sparse block matrix whose blocks are easily calculated. The solution of the system is conveniently performed using standard techniques, avoiding step by step procedures. The method can be applied to linear and nonlinear problems, characterized by conductors of different shapes. The results obtained are compared with standard techniques, showing both accuracy and CPU time reduction.     

Convolution-Based Trigonometric Interpolation of Band-Limited Signals

This paper presents a method to obtain a trigonometric polynomial that accurately interpolates a given band-limited signal from a finite sequence of samples. The polynomial delivers accurate approximations in the range covered by the sequence, except for a short frame close to the range limits. Besides, its accuracy increases exponentially with the frame width. The method is based on using a band-limited window in order to reduce the truncation error of a convolution series. It is shown that the polynomial can be efficiently constructed and evaluated using algorithms designed for the discrete Fourier transform (DFT). Specifically, two basic procedures are presented, one based on the fast Fourier transform (FFT), and another based on a recursive update algorithm for the short-time FFT. The paper contains three applications. The first is a variable fractional delay (VFD) filter, which consists of a short-time FFT combined with the evaluation of a trigonometric polynomial. This filter has low complexity and can be implemented using CORDIC rotations. The second is the interpolation of nonuniform Fourier summations, where the proposed method eliminates the need to interpolate any kernel sample. Finally, the third can be viewed as a generalization of the FFT convolution algorithm and makes it possible to interpolate the output of an finite-impulse-response (FIR) filter efficiently.      

Delay analysis of various service disciplines in symmetric tokenpassing networks

An approach to the delay analysis of various service disciplines in symmetric token passing networks is presented. It is shown that exact or approximate accurate expressions for the average packet delay of different service disciplines can be directly derived by the delay expression of the exhaustive service system. This can be accomplished by inflating, by an appropriate factor, the packet size of the discipline whose performance is analyzed and then using the inflated packet in the delay expression of the exhaustive service system. The method is applied to the analysis of the limited service and TTS disciplines, and its accuracy is verified by simulation results. The advantages of the analytic method presented are its generality, higher accuracy over previous analytic methods, and insensitivity to network latency and other system parameters     

有限元分析在CCD制冷封装设计中的应用

采用有限元分析方法对制冷封装CCD工作在低温时光窗外表面温度过低产生露珠的现象进行了研究,分析了光窗与芯片表面(冷端)不同距离时光窗的最低温度以及内部填充不同气体时光窗的最低温度.通过有限元分析得到了光窗不产生露珠时的最优封装设计结构.