窄带中频数字接收机高速信号处理技术

窄带中频数字接收机在雷达对抗侦察中得到了广泛应用，其高速信号处理技术是目前研究的重点。本文详细介绍了数字雷达告警接收机高速信号处理技术的发展现状和关键技术，最后通过对该技术的全面分析指出了值得深入研究的领域。     

2‐Cyanoprop‐2‐yl dithiobenzoate mediated reversible addition–fragmentation chain transfer polymerization of acrylonitrile targeting a polymer with a higher molecular weight

The reversible addition–fragmentation chain transfer (RAFT) polymerization of acrylonitrile (AN) mediated by 2‐cyanoprop‐2‐yl dithiobenzoate was first applied to synthesize polyacrylonitrile (PAN) with a high molecular weight up to 32,800 and a polydispersity index as low as 1.29. The key to success was ascribed to the optimization of the experimental conditions to increase the fragmentation reaction efficiency of the intermediate radical. In accordance with the atom transfer radical polymerization of AN, ethylene carbonate was also a better solvent candidate for providing higher controlled/living RAFT polymerization behaviors than dimethylformamide and dimethyl sulfoxide. The various experimental parameters, including the temperature, the molar ratio of dithiobenzoate to the initiator, the molar ratio of the monomer to dithiobenzoate, the monomer concentration, and the addition of the comonomer, were varied to improve the control of the molecular weight and polydispersity index. The molecular weights of PANs were validated by gel permeation chromatography along with a universal calibration procedure and intrinsic viscosity measurements. ¹H NMR analysis confirmed the high chain‐end functionality of the resultant polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1272–1281, 2007     

A randomized voltage vector switching scheme for three-level powerinverters

In this paper, a feasibility study of a randomized space vector switching scheme for three-level inverters is reported. Based on the traditional space vector concept for pulse width modulation (PWM) inverters, the sequence of the space vector is randomized in this scheme. The overall vector, resulting from the randomization, is mathematically identical to that of the traditional space vector. It has been found that the randomized scheme can effectively spread the switching noise over a wide frequency range and at the same time keep the steady-state link capacitor voltage balanced. The proposed scheme has been implemented in real time in a digital controller and its features have been experimentally confirmed     

基于空间平滑的矩阵分解算法

本文研究了协方差矩阵分解算法解相关的问题,提出了一种修正的矩阵分解算法-基于空间平滑的矩阵分解（SSMD）算法。SMMD算法能在低信噪比条件下的估计相干信源,且估计精度比原修正的算法高,计算量比原修正算法小,最后通过大量的计算机仿真实验来说明矩阵修正算法的性能。     

全封离式低,中功率CO2激光器

本文回顾了过去十年来封离CO_2激光器使用射频(RF)激发技术方面的进展,并讨论了这一技术现状以及技术与市场的挑战。     

矩孔金属光栅矢量模式理论的数值计算

根据矩孔金属光栅的矢量模式理论，计算了不同入射方向，波长及偏振态情况下衍射场的分布，研究了不同光栅结构对衍射效率，偏振态变化的影响；同时，根据实际需要，加工制作了一批不同深度的矩孔光栅样品，进行了实验测量，并将计算值与实验值进行了比较，两者基本相符。     

OPNET的网络仿真机制及仿真建模方法

随着计算机技术和通信技术的迅猛发展，网络仿真已成为时下研究、规划、设计网络不可缺少的工具。本文以OPNET为例，在系统研究OPNET网络仿真机制的基础上，着重探讨了OPNET的网络仿真建模方法。     

高功率双工旋转场移相器

旋转场移相器具有移相精度高(均方根误差可小于1°)和温度稳定性好等特点,通过改进射频传输结构,可大大提高他的功率容量。利用旋转场移相器的互易特性和铁氧体圆极化器的非互易特性,设计出高功率双工旋转场移相器。其双工特性可将收/发信号分开,实现移相器和环行器的双重功能,用于天线的收发通道等场合时,可省去一个高功率环行器,结构紧凑。分析了双工旋转场移相器的工作原理,阐述了高功率应用下的设计方法,推导出了管状铁氧体的相移量计算公式,按此方法设计了实用的器件,并给出了试验数据。     

我国有线电视的网络媒体价值

阐述有线电视网络媒体的特点，有线电视网络媒体面临的困境及解决办法，最后展望有线电视网络媒体价值。     

DFB active filter/detector for multichannel FSK optical transmission

In a DFB laser amplifier, used simultaneously as narrow band optical filter and detector in O-FDM systems the increase of the input optical power induces distortion of the filter transfer function. The effect of such a distortion on the receiver sensitivity and dynamic range has been investigated in a 155 Mbit/s FSK direct detection experiment. A two-channel experiment is also reported for the first time. Owing to the effect of interference between the two channels, it has been found that a minimum channel spacing of about 15 GHz is required to maintain the bit error rate below 10/sup -9/.<>