Extrapolation of Time and Frequency Responses of Resonant Antennas Using Damped Sinusoids and Orthogonal Polynomials

An extrapolation technique is presented which reduces the computational demands of obtaining a wideband electromagnetic response from a resonant antenna using traditional computational electromagnetic methods. It has been shown that a wideband response can be extrapolated by fitting early-time and low-frequency data with a summation of orthogonal polynomials. However, representing responses characteristic of resonant structures in practice proves computationally inefficient and can lead to numerical instabilities. This paper outlines the incorporation of damped sinusoids to efficiently, accurately, and reliably extrapolate both time- and frequency-domain responses of resonant antennas due to a wideband source. A genetic algorithm is used to select the necessary extrapolation parameters. The wideband driving-point current response of several resonant antennas is accurately extrapolated. The transmission-line matrix method and the method of moments are used to compute early-time and low-frequency data, respectively. Fundamentally different discretizations of the structure of interest are used, illustrating in principle the independence of the technique and the choice of computational methods used to provide the directly-computed data.     

Doubly-Selective Channel Estimation Using Data-Dependent Superimposed Training and Exponential Basis Models

Channel estimation for single-user frequency- selective time-varying channels is considered using superimposed training. The time-varying channel is assumed to be well- approximated by a complex exponential basis expansion model (CE-BEM). A periodic (non-random) training sequence is arithmetically added (superimposed) at low power to the information sequence at the transmitter before modulation and transmission. In existing first-order statistics-based channel estimators, the information sequence acts as interference resulting in a poor signal-to-noise ratio (SNR). In this paper a data-dependent superimposed training sequence is used to cancel out the effects of the unknown information sequence at the receiver on channel estimation. A performance analysis is presented. We also consider the issue of superimposed training power allocation. Several illustrative computer simulation examples are presented.     

一种正交多项式混沌全局建模方法

本文研究了一种正交多项式混沌全局建模方法 ,所用正交多项式集以吸引子不变测度为核 .通过对H啨ｎｏｎ映射数据和电离层参数实测数据的分析 ,表明在待建模系统不很复杂时 (其内在机理可用较低阶多项式表达 ) ,这种全局建模方法能得到系统动力学特性 .在低噪声情况下模型还能充分精确地重构系统方程式 .在噪声较大或系统内在机理很复杂时建模结果仍可用于一步预测 ,且具有较好效果     

Power Estimation Using Probability Polynomials

We describe a method of polynomial simulation to calculate switching activities in a general-delay logic circuit. This method is a generalization of the exact signal probability evaluation method due to Parker and McCluskey, which has been extended to handle temporal correlation and arbitrary transport delays. The method can target both combinational and sequential circuits.Our method is parameterized by a single parameter l, which determines the speed-accuracy tradeoff. l indicates the depth in terms of logic levels over which spatial signal correlation is taken into account. This is done by only taking into account reconvergent paths whose length is at most l. The rationale is that ignoring spatial correlation for signals that reconverge after many levels of logic introduces negligible error. When l = L, where L is the total number of levels of logic in the circuit, the method will produce the exact switching activity under a zero delay model, taking into account all internal correlation.We present results that show that the error in the switching activity and power estimates is very small even for small values of l. In fact, for most of the examples, power estimates with l = 0 are within 5% of the exact. However, this error can be higher than 20% for some examples. More robust estimates are obtained with l = 2, providing a good compromise between speed and accuracy.     

GPS高精度测速方法探讨

主要介绍了4种GPS测速方法,给出了各种方法的特点与适用范围,得出了4种方法的测速结果.中心平滑微分求速方法克服了常用微分平滑求速方法计算速度慢以及当部分位置数据出现较大跳跃时,计算出的载体速度严重偏离实际速度的缺点.通过对某次试验的GPS实测数据进行处理,采用中心平滑微分求速,得出的载体速度精度高,能够满足绝大部分领域的测速要求.     

NMOS管Snapback特性ESD仿真模型研究

随着集成电路特征尺寸的不断缩小,ESD的问题始终困扰着芯片设计师们。文章提出了一种宏模型用于ESD的snapback仿真,它包含一个MOS管、一个NPN晶体管和一个衬底电阻,没有外部的电流源。简化的宏模型没有必要使用行为级的语言,如Verilog-A、VHDL-A。这使得仿真速度和收敛性得到提高。同时比较了三种先进的BJT模型:VBIC、Mextram、HICUM。模型参数可以通过模型参数提取软件(BSIMProPlus、ICCAP等)提取。     

Investigation of High-Accuracy Indoor 3-D Positioning Using UWB Technology

There are many challenges in building an ultra-wideband (UWB) indoor local positioning system for high-accuracy applications. These challenges include reduced accuracy due to multipath interference, sampling rate limitations, tag synchronization, and antenna phase-center variation. Each of these factors must be addressed to achieve millimeter or sub-millimeter accuracy. The developed system architecture is presented where a 300-ps Gaussian pulse modulates an 8-GHz carrier signal and is transmitted through an omni-directional UWB antenna. Receiver-side peak detection, a low-cost subsequential-sampling mixer utilizing a direct digital synthesizer, high fidelity 10-MHz crystals, and Vivaldi phase-center calibration are utilized to mitigate these challenging problems. Synchronized and unsynchronized experimental results validated with a sub-millimeter accurate optical tracking system are presented with a detailed discussion of various system errors.     

Space-Time Diversity Using Orthogonal and Amicable Orthogonal Designs

In this paper we consider the utilization of multiple transmitterand receiver antennas for space-time diversity. The optimalSNR scheme, which also provides the best diversity, is outlined.This scheme however involves a reduction in the data rate. Coding schemes are then presentedwhich not only achieve the optimal SNR but also mitigate the reductionof data rate. The proposed schemes are based on the theory of Orthogonal Designsand Amicable Orthogonal Designs.     

Analysis and Simulation of a Digital Mobile Channel Using Orthogonal Frequency Division Multiplexing

This paper discusses the analysis and simulation of a technique for combating the effects of multipath propagation and cochannel interference on a narrow-band digital mobile channel. This system uses the discrete Fourier transform to orthogonally frequency multiplex many narrow subchannels, each signaling at a very low rate, into one high-rate channel. When this technique is used with pilot-based correction, the effects of flat Rayleigh fading can be reduced significantly. An improvement in signal-to-interference ratio of 6 dB can be obtained over the bursty Rayleigh channel. In addition, with each subchannel signaling at a low rate, this technique can provide added protection against delay spread. To enhance the behavior of the technique in a heavily frequency-selective environment, interpolated pilots are used. A frequency offset reference scheme is employed for the pilots to improve protection against cochannel interference.     

基于正交基分解算法的航空磁探方法

航空磁探中,将潜艇目标以磁偶极子模型代替。针对目标信号信噪比较低的情况,利用正交基分解检测算法,大幅提高了水中磁性目标信号的信噪比,有效地检测到磁性目标。采用双L型航空磁探方法,确定磁性目标的运动位置、航向和航速。仿真试验表明,该方法具有一定的工程应用价值。     

Zernike多项式波面拟合精度研究

光学表面检测的绝大多数情况中,被测光学表面或光学系统的出射波面总是趋于光滑且连续的,这样的波面函数一定可以表示成一个完备的基底函数的线性组合。因此常用Zernike多项式作为基底函数对测量得到的离散数据进行拟合,把实际波面或面形表示为Zernike多项式各项的线性组合。文中研究了Zernike多项式阶数对拟合精度的影响,以及采样点数对拟合精度的影响。得出Zernike多项式拟合波面并非阶数越高越好,阶数过高会使拟合结果出现病态。因此拟合波面要选择合适阶数的Zernike多项式。当多项式阶数选定时,采样点数多有利于提高拟合精度,但采样点的多少并不是提高拟合精度的先决条件。     

基于方向正交小波基的声源定位

引入一种光滑性可调的对信号的方向性敏感的周期基插值小波,先对其进行正交化处理,构成二维空间的方向正交小波基,同时对相应的滤波器周期化,给出了快速方向小波变换的算法。对于方向性弱的声音信号可以选择阶数相对高的周期基插值小波来分析,而对于方向性强的信号只要阶数低的周期基插值小波就可以。用传声器阵列对声音信号进行采集,对采集的数据进行快速方向正交小波变换,通过角度和半径方向的图,得到两条比较清晰的半径线,它们的交点唯一确定声源的位置。     

心电模拟波形发生系统的设计

以32位低功耗的ARM9微处理器为核心,移植了嵌入式Linux操作系统设计的一个心电模拟波形发生系统,实现了心电信号的实时采集和波形显示功能。Qt是KDE等项目使用的GUI支持库,所以许多基于Qt的X Window程序也可以非常方便地移植到Qt/Embedded版本上,因此系统采用Qt进行软件界面的开发。该系统设计主要包括ARM9处理器、信号采集模块、D/A转换模块、右腿驱动、低通滤波等模块。采用嵌入式Linux操作系统作为软件开发平台,充分利用ARM9的高效性和低功耗性能,很好地模拟正常的人体除颤的过程,并且能够模拟34种常见的异常心电波形,输出波形都达到了医学相关要求。     

开关磁阻风力发电系统最大风能跟踪控制仿真研究

介绍了开关磁阻发电机工作模式并选用了他励发电模式。在此基础上搭建了以跟踪最大风能为目的开关磁阻风力发电系统模型。针对开关磁阻电机的特点,选择了转速反馈控制方案来实现系统的风能跟踪。在阵风、渐变风、随机风三种典型风速变化下对所搭建系统进行了仿真研究,证明该系统能够完成最大风能跟踪。     

Orthogonal Basis Expansion-Based Phase Noise Estimation and Suppression for CO-OFDM Systems

In coherent optical orthogonal frequency- division-multiplexing systems, the laser phase noise which induces common phase error (CPE) and intercarrier interference (ICI) is a major impairment to the system's performance. In this letter, we propose an orthogonal basis expansion-based phase noise suppression algorithm which can mitigate CPE as well as ICI effectively. The proposal can significantly reduce the bit-error-rate floor caused by ICI.      

应用半导体激光器缩比仿真微波着陆系统辐射源研究

针对微波着陆系统仿真试验的辐射源模型选用问题,提出以大的缩比系数将半导体激光器作为微波系统辐射源缩比仿真模型,研究了微波系统和半导体激光器辐射信号的物理相似性,分析了二者的辐射强度、频谱特性、信号场型以及极化方式等主要相似性能,并采用三菱激光器进行了微波着陆系统辐射源缩比模型的仿真实验,实现了对微波着陆系统工作过程的模拟,验证了运用半导体激光器缩比仿真微波电磁系统辐射源的可行性,为在实验室以较小的空间缩比仿真大型电磁系统性能提供了新的方法手段,同时也丰富了电磁缩比仿真理论。     

ModelMaker建模研究

ModelMaker是专为Delphi设计的Case工具，它为Delphi的类和组件包均开发提供了一种全新的途径。ModelMaker全面支持Delphi的ObjectPascal语言，已经被应用于实时技术和数据库应用中。利用模型制作工具创建一个模型后，这个模型将会自动地转换成Delphi代码。文章主要介绍ModelMaker模型的主要组成部分及其之间的关联，并给出了一个ModelMaker建模实例。     

基于正交多项式不变矩的图像描述

通过对大图像、小图像、噪声图像的重建,比较了泽尼克矩、正交的傅里叶-梅林矩.畸变的雅可比-傅里叶矩的图像描述能力,最后得出:畸变的雅可比-傅里叶矩有着最强的图像描述能力.在实验中还发现:在噪声图像的重建中,随着重建阶数的提高,图像的重建误差并不是一直减少,而是和有噪声图像一样,是一个先降后升的过程,并对此现象作了解释:在离散空间中连续正交多项式矩并不是完全意义上的正交,是这种正交误差造成了此现象.     

Constructing Space-Time Trellis Codes Using Orthogonal Designs

In this paper we consider the design of space-time trellis codes usingorthogonal designs. We derive a condition on the codewords to obtainthe maximum received signal energy and show that the codes based onorthogonal designs satisfy this condition.We consider in detail the design of a trellis code for two transmitantennas. The new code we develophas a higher diversity in fast fading and a higher coding gain in quasi-static fading when compared to otherexisting space-time codes. We also consider a turbo implementation ofthe new trellis code which results in very high diversity gains infast fading channels.     

一种基于正交小波包变换的数据压缩方法

本文将最优小波包基变换应用到数据压缩方法的研究工作中,针对不同频率的小波包系数之不同统计特性设计了相应的标量量化和矢量量化方法,并对一组实际测量数据运用我们建议的方法进行压缩,在失真率较小的情况下,得到较高的压缩比.