锥面共形阵列信源方位和极化参数的联合估计算法

该文用交叉电偶极子对在锥面共形载体表面构造极化敏感阵列,在建立其快拍数据模型的基础上实现了信源方位和极化参数的联合估计。算法首先通过合理的矩阵变换将阵列流形中的信源方位和极化信息去耦合,然后分别根据秩损理论和旋转不变子空间思想对其进行估计,最后通过一种轮换比对配对方法实现信源方位和极化参数的联合估计。Monte-Carlo仿真实验表明,所提算法可以很好地解决锥面共形阵列的多参数联合估计问题。     

Analysis of an anisotropic plate Faraday rotator coated with multilayer dielectric plates

The analysis of an anisotropic plate Faraday rotator coated with multilayer dielectric plates is presented by means of the matrix methods in conjunction with Fourier transformation technigues. It provides a closed-form representation of the electromagnetic field over the whole multilayer regions. The treatment does not limit the direction of the biased magnetic field and the numbers of the coated dielectric plates. Numerical results are presented and compared with that calculated with the method in ref.[1], and full-waveguide-band bandwidth for 47.5°±1.5° rotation angle is obtained for transmission type rotator in W band. Calculation for reflection type rotator is also presented and compared with the experiments.     

对低信噪比非稳定信号的参数估计MESPRIT

对振幅衰减和信噪比极低的信号进行参数估计,最常用的傅氏变换以及大多数现代信号参数估计方法(如,最大熵法MEM、线性预测奇异分解法LPSVD等),其结果都不能令人满意.本文针对信号衰减、信噪比极低的特点,改进了基于旋转不变技术的信号参数的估计方法(MESPRIT),并给出几种估计方法的对比仿真结果.     

The UCB/MPE cassegrain submillimeter heterodyne spectrometer

The UCB/MPE Submillimeter Heterodyne Spectrometer is a system for ascronomical spectroscopy in the high-frequency atmospheric windows from 500 to 1000 GHz. It contains a molecular laser local oscillator, a cooled Schottky open structure mixer, a quasi-optical coupling system, and an acousto-optical spectrometer. The compact receiver mounts at the Cassegrain focus of large infrared astronomical telescopes. The receiver noise temperature on the telescope is approximately 3500 K (DSB) during observations of the CO J=76 line at 806.652 GHz. The spectrometer's frequency resolution and instantaneous bandwidth (<2 MHz resolution across 1.1 GHz) are well suited for observations of molecular emission lines from a variety of astronomical sources.     

Global Optimization For Molecular Clusters Using A New Smoothing Approach

Strategies involving smoothing of the objective function have been used to help solve difficult global optimization problems arising in molecular chemistry. This paper proposes a new smoothing approach and examines some basic issues in smoothing for molecular configuration problems. We first propose a new, simple algebraic way of smoothing the Lennard-Jones energy function, which is an important component of the energy in many molecular models. This simple smoothing technique is shown to have close similarities to previously-proposed, spatial averaging smoothing techniques. We also present some experimental studies of the behavior of local and global minimizers under smoothing of the potential energy in Lennard-Jones problems. An examination of minimizer trajectories from these smoothed problems shows significant limitations in the use of smoothing to directly solve global optimization problems.     

Ray tracing on extended hemispherical and elliptical silicon dielectric lenses

In this paper, extended hemispherical and elliptical silicon dielectric lenses are compared by means of ray tracing. It is shown that the optical focuses of two lenses are not at same position though the elliptical lens is synthesized from an extended hemispherical lens by carefully choosing a particular extension length as stated in ref[1]. It may be used to explain why the best compromise between alignment, directivity and Gaussian-coupling effciency will be obtained if the feed antenna is placed at the region between 2.2 mm and 2.4 mm of extension length (for 13.7 mm diameter lens, dielectric contant = 11.7).     

教育虚拟演播室技术

虚拟演播室是在高速图形计算机和视频色键基础上发展起来的演播室技术.在虚拟演播室系统中,现场视频可以实时地与计算机产生的三维图形完美无缺地集成在一起,是对传统的教育电视演播室技术的一次重大变革.本文讨论了虚拟演播室系统的原理、技术途径以及系统评价等问题.     

基于软计算集成的入侵检测技术

软计算技术越来越广泛地应用于解决各领域的实际问题。文章将多种不同软计算技术的集成应用于入侵检测。由于网络攻击事件的日益增多，建立有效的入侵检测系统对保护信息安全是非常必要的，但要实现这一点仍面临巨大的挑战。分析了两种类型的软计算技术：人工神经网络和支持向量机。实验证明这两种方法的集成在入侵检测的检测精度方面要优于单一方法。     

卫星导航系统中的BOC调制和接收技术分析

BOC调制是一种新的调制方式,能够实现频谱分离并能够充分利用整个频带,比传统的BPSK调制拥有更好的自相关特性,以至于能够改善定位精度。由于BOC调制信号在载波频率点处有较低的功率谱密度,因而,在未来的卫星导航系统中使用BOC调制信号将能够减少信号间的干扰。本文详细地分析了BOC调制信号的特点,通过对功率谱密度函数、自相关函数、Gabor带宽和码跟踪精度等参数的分析和仿真,验证了BOC调制信号在相关特性、抗干扰能力和码跟踪精度方面的优越性。并针对BOC调制信号自相关峰的多峰带来的跟踪不确定性会使捕获复杂度增加和带来跟踪误差的问题,本文介绍了几种BOC调制信号的接收技术,可为我国自主研发的导航系统的信号体制设计和系统优化提供技术支撑。     

一种基于旋转不变子空间算法的非模糊参数配对方法

针对多维旋转不变子空间算法(ESPRIT)信号参数估计存在失配的问题,该文提出一种基于特征值分维的参数配对方法。该方法首先对包含待估计参数信息的多维特征值进行线性组合并构造判断矩阵,再根据矩阵维数对应关系进行配对。相比于其他配对算法,该文提出的算法结构简单,没有模糊参数,在特定情况下具有较高的鲁棒性,能实现参数的自动配对。最后通过对比仿真验证了该文配对算法的优越性。