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本文根据综合脉冲/孔径雷达采用多个天线同时向全空域辐射多个载频信号,而在接收端通过信号处理获得发射方向图的特点,提出一种新的多基地“无源”定位雷达系统。该系统既利用在岩上发射,在舰船上接收而构成岩-舰多基地雷达,又由于在接收站不发射信号而相当于无源定位系统,本文介绍该系统的基本组成,工作原理及其与常规地波超视距雷达、双/多基地雷达相比的显著特点,给出计算机模拟结果;最后讨论了该雷达需解决的关键问题。 相似文献
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基于外辐射源的运动目标探测、定位与成像技术是目前新体制雷达研究的热点之一。文中介绍了基于外辐射源的无源雷达对运动目标成像的研究现状,分析了利用电视或调频广播等外辐射源信号作为机会照射源的多基地无源雷达成像系统的构成和基本原理,并且选取了12个电台信号作为外辐射源,利用无源雷达成像技术对运动目标进行了仿真实验,最后探讨了该无源雷达成像体制的若干关键技术和应用前景。 相似文献
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基于复倒谱技术的无源雷达直达波提纯方法 总被引:3,自引:0,他引:3
利用民用FM广播信号为无源雷达的外辐射源时,由于信号在空间传输时产生严重的多径干扰,导致接收站获取的直达波参考信号与目标反射的回波在后继匹配滤波时出现失配现象,严重影响了雷达的目标检测性能。文中首先建立了基于FM广播外辐射源的双基地雷达模型;然后提出了一种在复倒谱域对直达波参考信号进行提纯处理后再进行匹配滤波的方法;最后给出了一个基于FM广播的外辐射源雷达实验系统,通过该实验系统采集的数据进行仿真,其结果表明了该方法与未提纯时相比,输出信噪比约有6dB的改善,在工程上有参考价值。 相似文献
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介绍了一种无源定位机场场面监视雷达时差接收机,该接收机采用了微波光电技术。微波光子学是一项被认为为未来高性能雷达、电子战系统提供一种非常具有吸引力的新技术领域,具有更远的传输距离和更大的带宽。目标微波信号通过多子站接收、传输至中心站进行幅度检测和时间测量,接收子站简单便捷、布站灵活,同时解决了多站时间同步问题,结合波分复用时间校准,实现高精度时差测量。目前该接收机已完成样机研制和应用试验,定位精度明显优于传统时差接收机,文中给出了实验数据和研制结果。 相似文献
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双星无源定位系统对地海面雷达辐射进行定位时,存在脉冲信号频差参数提取的模糊问题。提出了一种基于虚拟双星的双时差粗定位方法,可有效解决频差测量的模糊,再结合时差/频差联合定位方法,分析了双星系统对雷达辐射源无源定位的可行性,给出了一些有用的结论。 相似文献
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针对脉冲骨架周期固定的雷达脉冲信号辐射源无源定位问题,该文提出一种基于虚拟时差的运动阵列空间无源定位算法,采用运动单阵列接收目标辐射源信号,通过多次测量侦察站不同位置的脉冲到达时间来估计目标辐射源位置。分别针对脉冲骨架周期已知和未知两种情况,提出了一种基于高阶统计量的无源定位算法,并推导了不同情况下定位精度的克拉美罗界。仿真实验表明,不同情况下定位算法定位精度逼近克拉美罗界,且脉冲骨架周期已知时虚拟时差无源定位算法定位精度优于同孔径实阵列TDOA无源定位算法定位精度,脉冲骨架周期未知时虚拟时差无源定位算法定位精度低于同孔径实阵列TDOA无源定位算法定位精度。 相似文献
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在人烟稀少、边远山区和高原等地区,无线基站覆盖面较小导致无线传输通道环境恶劣,无法有效实现远程高清音视频的实时播放.前端无线手持设备多采用Android操作系统,因此Android系统高质量实时传输高清音视频成为远程视频监控的关键问题.为保证高清音视频的稳定传输,解决网络拥塞和画面延迟抖动等问题,在Android系统上采用RTMP协议传输高清音视频,优化RTMP的数据传输策略,实现了高清音视频的无线传输.在严重丢失帧的恶劣环境下测试该系统,系统运行稳定,显著提高了音视频播放的流畅性和传输的服务质量. 相似文献
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This paper describes several methods to realize passive and active networks. with linear phase frequency response applicable to the video signal processing circuit especially for the FM transmission system. The methods are based on employing the hyperbolic tangent function realized by using passive LC ladder networks. They are also based on a time base conversion technique which provides the zero phase network. Using these methods, video signal processing circuits with linear phase property such as pre-emphasis and de-emphasis networks for the FM transmission TV system are introduced. 相似文献
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中波广播天线周围存在的无源干扰,主要来源于场地内其它频率的发射天线和场地周边高压架空输电系统的影响。本文采用矩量法作为计算的数值方法,建立中波广播发射天线和高压输电线路的仿真模型,通过FEKO软件仿真,分析场地内其它频率发射天线和场地外110kV高压输电线路对江苏广播585kHz中波天线的无源干扰影响,为中波广播发射台合理规划天线场地提供理论依据。 相似文献
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Kato S. Kubota S. Kazama H. Morikura M. 《Selected Areas in Communications, IEEE Journal on》1992,10(6):1054-1065
The authors propose a satellite video signal transmission system that uses a time division multiple access (TDMA) scheme for digital video signal transmission and a code division multiple access (CDMA) scheme for voice signal transmission from a video signal reception-only earth station (backward voice signal transmission). The adoption of a TDMA scheme makes it possible to transmit video signals from various places and to communicate in multipoint-to-(multi)point mode. For backward voice channel transmission from video signal reception-only earth stations, a superposed CDMA voice signal transmission over TDMA video signals by using the same transponder is proposed. The employment of high coding gain forward error correction and development of a cochannel interference cancellation technique have made it possible for the proposed system to transmit a practical number of voice channels. The performance of the proposed system has been experimentally evaluated and the results show the proposed scheme can transmit about 20 CDMA voice channels simultaneously 相似文献
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《Wireless Communications, IEEE》2002,9(5):100-110
We consider the real-time transmission of encoded video from distributed, uncoordinated wireless terminals to a central base station in a multicode CDMA system. Our approach is to employ the recently proposed simultaneous MAC packet transmission (SMPT) approach at the data link layer (in conjunction with UDP at the transport layer). We consider the real-time transmission of both video encoded in an open loop (i.e., without rate control) and video encoded in a closed loop (i.e., with rate control). We conduct extensive simulations and study quantitatively the trade-off between video quality, transmission delay (and jitter), and number of supported video streams (capacity). We find that the simple-to-deploy SMPT approach achieves significantly higher video quality and smaller delays than the conventional sequential transmission approach, while ensuring high capacity. In typical scenarios, with SMPT the probability of in-time video frame delivery is more than twice as large as with sequential transmission (for given delay bounds). Our results provide guidelines for the design and dimensioning of cellular wireless systems as well as ad hoc wireless systems. 相似文献
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雷达在电子对抗中起着极其重要的作用。本文针对T-R型双基地跟踪雷达,分析了系统的特殊性及要解决的关键技术问题,介绍了发射站和接收站之间的时间同步、频率同步和空间同步技术,分析了传统的单基距解算方法的不足,讨论了基于调整发射站触发脉冲和接收站测距同步脉冲两种距离解算方法,对双基地雷达测量值的校准方法进行了描述,最后对双基地雷达的定位准确度及采用联网多基地雷达系统提高距离的定位准确度进行了研究。仿真结果表明,联网双(多)基地雷达的数据融合,可明显改善基线附近的单基距准确度。 相似文献
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Subcarrier multiplexing (SCM) transmission has been widely used for analog video transmission in CATV systems. As digital video technology rapidly advances, there is a strong need to transmit digital video over the same SCM system. Since digital video such as HDTV requires a much larger bandwidth, multilevel signaling becomes an important approach. As the number of levels increases, however, the noise margin decreases and the system is more subject to adjacent channel interference (ACI). In this paper, we analyze the spectrum efficiency and power penalty of multilevel SCM transmission. We found that using pulse shaping can make multilevel signaling attractive. Depending on the ACI that can be tolerated, results show that multilevel amplitude-shift keying (ASK) of 5-7 b/symbol can give the optimum spectrum efficiency using the raised-cosine pulse. The price paid is a slight power penalty of 0.4 dB to reduce intersymbol interference (ISI) to zero 相似文献
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数字高清电视转播车作为移动式演播室系统在广电行业已经广泛使用,以12信道数字高清电视转播车为例,介绍了高清电视转播车视频系统构成,阐述了系统的设计原则以及视频系统、PFU微波传送设备、同步系统的选型和配置、应急方案等。 相似文献