直扩通信系统中FFT捕获算法的改进

直扩通信系统的解扩与解调都是依赖于有效的伪码捕获,为了实现伪码的快捕,对经典FFT捕获算法进行了部分改进。在经典FFT捕获算法的基础上采用了2倍码速率采样并且增加了一个多普勒频移控制器。首先对改进算法进行了理论分析,然后用MATLAB对其进行了仿真验证,仿真结果捕获图证明该算法在预设参数下可以实现有效快捕,而且在不降低捕获精度和抗干扰性能的同时缩短了捕获时间,从而进一步提高了FFT算法的捕获性能。     

快速时变信道下的OFDM信道估计方法

为解决正交频分复用(OFDM)系统在快速时变信道下引入的子载波间干扰(ICI)导致性能急剧下降的问题,提出一种基于带状矩阵的数据辅助型信道估计算法。通过分析由多普勒频偏引入的子载波间干扰矩阵,运用线性模型对信道冲击响应算法进行建模,对每个子载波设计带状补偿矩阵以最大程度消除ICI。数值仿真结果表明,该信道估计算法较最小均方误差(MMSE)算法复杂度大大减小,便于实现,满足快速时变信道下的估计精度需要。     

基于无线传感器网络的移动目标跟踪系统研究

脉冲多普勒雷达(PDR)是一个超宽带雷达系统,不仅能探测目标位置,也可通过多普勒效应测量其径向速度。然而,传统的雷达信号处理技术与极限计算和典型无线传感器微粒上的存储资源不相匹配。利用小型脉冲多普勒雷达作为传感器节点,通过设计一个新的目标跟踪系统来探索脉冲多普勒雷达和微型无线传感器节点的兼容性。该系统由几个PDR传感器节点组成,来检测移动目标的存在和位置,一个基站节点用来收集传感器节点的检测数据,一个算法来估计目标的位置。结果表明该系统有较小的偏差,可实现目标跟踪。     

基于剩余定理的数字干涉仪设计与实现

通过介绍一套外场应用条件下基于剩余定理的多基线数字干涉仪系统设计、仿真、实现和实验结论,说明剩余定理应用于干涉仪设计具有较为严密的逻辑性和准确性。将数字接收技术引入干涉仪系统合理可行,并且保证了较高性能,符合电子对抗发展趋势,使系统设计方法更具借鉴意义。该干涉仪采用超宽带数字技术实现,数字中频带宽达到400 MHz,已应用于某单站定位试验系统,效果良好。     

一般构型机载双站SAR回波信号特性分析

一般构型机载双站合成孔径雷达(SAR)的成像结构与系统参数使其回波信号具有新的特性,文中从残余距离徙动、多普勒参数、回波频谱三个方面对信号特性进行分析。研究结果表明,残余距离走动与残余距离弯曲具有方位向非对称性,宽场景成像中需按照残余距离徙动与二阶相位误差对观测场景进行成像区分块;多普勒质心具有二维扩散性,多普勒调频率与多普勒带宽具有二维扩展性;在距离频域-方位时域校正距离走动可削弱因双站斜视带来的回波信号距离-方位向二维强耦合,推导了距离走动校正后的回波频谱公式。仿真验证了一般构型机载双站SAR的信号特性与距离走动校正方法的有效性。     

差分反射因子测量误差分析

针对同时发射、同时接收体制双偏振多普勒天气雷达，论述了测量差分反射因子时雷达应满足的基本要求，提出了测景差分反射因子时能够引入误差的三类因素，即雷达测量基本要求不满足、接收机噪声和散射粒子相对运动引起的回波功率起伏、云雨目标对水平极化波和垂直极化波衰减的不同，并分别对影响差分反射因子测量误差的各种因素及其影响程度，进行了深入研究和分析。     

基于DDS的动态多普勒模拟器的设计与应用

在航天测控领域中,测控系统的动态捕获、跟踪性能和测量精度是非常重要的因素,为检测测控雷达的动态捕获、跟踪性能和测量精度,对直接数字频率合成技术进行了分析,提出基于DDS的动态多普勒模拟器的设计方案,产生70MHz为中心的高精度准确度的频率,达到对测控雷达中频单元动态测试的目的,此设计在工程中的应用效果良好。     

卫星通信中多普勒频偏的预校正

在低轨道卫星通信中，由于多普勒效应,无线电信号会产生频率偏移现象，这为接收机设计带来了一定的困难。一种新方法可用于消除多普勒频偏的影响：根据卫星与地面接收站之间的相对位置和速度，可预先计算出信号的多普勒频偏。据此实时地修正接收机中数字频率合成器输出的本振频率,以达到消除多普勒频偏的目的。     

游标测距在LFM全相参脉冲雷达中的应用

游标测距技术是一种新颖的相位测距技术，可以提供精密的径向距离测量值，其随机误差小于1／4波长。文中首先讨论了游标测距在线性调频全相参脉冲雷达中应用的可行性问题，然后利用计算机仿真进行了误差分析，最后得出游标测距在线性调频全相参脉冲雷达中应用时所需的测量数据和对该测量数据的要求。     

Measurement and Statistical Analysis of the Temporal Variations of a Fixed Wireless Link at 3.5 GHz

This paper presents the measurement and statistical analysis of the temporal variations of the radio channel defined by a fixed link at 3.5 GHz in suburban areas. The analysis provides the required information about the temporal stability of the channel, the probability of occurrence and depth of fades, the Doppler spectrum and, in general, the influence of the environment on the signal behaviour. In particular, the effect of fast traffic on a motorway in the neighbourhood of the receiver is investigated, obtaining some general conclusions particularly useful in wireless communication systems design. Rafael P. Torres was born in M′laga, Spain, in 1961. He received his MS degree in Physics from the University of Granada (Spain) in 1986 and his Ph.D. from the Telecommunications Engineering School at the Polytechnic University of Madrid (UPM) in 1990. From 1986 to 1990 he was with the Radio Communication and Signal Processing Department of the UPM as a research assistant. During this time, he worked about numerical methods in electromagnetics, and its applications to design of passive microwave devices like radomes, circular polarizer, rotators and planar lenses. He became an associate professor in the Department of Communication Engineering of the University of Cantabria (Spain) in 1990. From this time to the present, he has participated in several projects about RCS computation, on board antennas analysis, electromagnetic compatibility, and radio-propagation. He is co-author of a book about the CG-FFT method, author of several chapters in different books, more than 20 papers, and about 80 conference contributions. He has been the leader of the group that have developed the code CINDOOR, Computer Tool for Planning and Design of Wireless Systems in Enclosed Spaces. His current research interests include radio-propagation for wireless and mobile communications, as well as the simulation and design of new wireless communications systems. Beatriz Cobo was born in Santander, Cantabria (Spain), in October 1974. She received the M.Sc. degree in telecommunications engineering from the University of Cantabria, Spain, in 2000. During the period 2000-2004 she developed her research work in the Department of Communications Engineering in the Higher Technical School of Industrial Engineering and Telecommunications at the University of Cantabria. During the first two years she was an assistant researcher of the FEDER project “Subsystems of Radar and Radiocommunications in Maritime Traffic Services” and the last two years she worked in the project “Systems and Applications WLAN and WPAN”. At the moment she is a Ph.D. student at University of Cantabria and from October 2004 she is an assistant professor at University of Oviedo. Her areas of research include high-frequency methods, applied to the characterization of the natural scenarios where a radar can be located. Dimas Mavares received B.S. degrees in electronic engineering from la Universidad Politécnica Antonio José de Sucre, Venezuela, in 1994, and M.S. degree in electronic engineering form la Universidad Simón Bolivar, Venezuela, in 1997. From 1997 to 2001 he worked as an instructor in la Universidad Politécnica Antonio José de Sucre. Since 2002 he has been pursuing a Ph.D. degree in Communications Engineering from the Universidad de Cantabria, Spain. His research interests include MIMO wireless communications, channel estimation, space-time coding and neural networks. Francisco Medina was born in Santander, Cantabria (Spain), in July 1974. He received the M.Sc. degree in telecommunications engineering from the University of Cantabria, Spain, in 2002. During three months in 2002 he hold a scholarship to stay at Bordeaux (France) and to work in the company Thalès Systèmes Aéroportés. Nowadays he works as a sales engineer at the Export Department of Nexans in Malia?o, Cantabria (Spain), an expert company in cables and cabling systems. Susana Loredo was born in Gijóon, Spain, in 1972. She received the M.S. and Ph.D degrees in telecommunications engineering from the University of Cantabria, Spain, in 1997 and 2001 respectively. From 1998 to 2001 she was with the Department of Communications Engineering as a Research Assistant. During this time, she worked on numerical and high frequency methods applied to the characterization of the radio-propagation channel, and also on the narrowband and wideband experimental characterization of the indoor radio channel. In 2001 she joined the Department of Electrical Engineering at University of Oviedo, Spain, as a Research Scientific. From this time to the present, she has been working on MIMO channel characterization using high frequency approaches and source reconstruction methods to characterize the antenna radiation.