共查询到20条相似文献,搜索用时 140 毫秒
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主要对紫外光非视距通信系统的信道估计做了研究,采用最小均方(LMS)算法,通过自适应滤波的方式估计了紫外光非视距通信信道的脉冲响应.在多种条件下比较了该系统有、无信道估计技术时的误码率,得出了基于训练序列的信道估计技术能改善紫外光非视距通信系统性能的结论. 相似文献
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随着无线接入系统的工作频段越来越高,传输带宽越来越宽,非视距(Non Light Of Sight,NLOS)传输的限制就越来越大.研究非视距传播环境下抗衰落技术,对解决非视距无线接入条件下系统的可靠性和有效性,提高工程应用能力具有重要意义.非视距传输的关键实际上是抗多径衰落技术,包括OFDM、收发分集、子信道化、智能天线和自适应调制等技术.在分析非视距传播的条件和影响的基础上,对解决非视距传输问题的几个关键技术进行讨论,并对其在象WiMAX这样的宽带无线接入中的应用优势和影响进行了分析. 相似文献
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帧积分时间对微光电视观察视距的影响 总被引:2,自引:0,他引:2
微光成像系统在现代军事上起着越来越重要的作用,成像系统的探测视距一直是人们关注的焦点。分析了视距探测方程,提出了一种适用于慢运动目标的增大探测视距的方法——增加帧积分处理时间。基于修正的微光成像公式,从理论上分析了增加帧积分处理时间对于微光电视探测距离的影响,通过计算机模拟了不同照度下不同帧积分时间对探测视距大小的影响,例如四帧累加时:在10-4lx时,探测距离提高了1.57倍;在10-3lx时探测距离提高了1.31倍。通过在低照度下的现场实验数据验证了这种方法的可行性,证明增加帧积分时间对提高视距有很大的作用。 相似文献
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无人机视距数据链的信道特性与扩频技术 总被引:2,自引:2,他引:0
无人机视距数据链的信道类型主要是一个干涉型平衰落信道,但也可能发生频率选择性衰落、时间选择性衰落。限于无人机的使用特点和条件,视距数据链不同于一般通信系统,不适于极高的通信可靠度,也不要求很大的衰落储备。分析了扩频系统在无人机视距数据链中的特殊性并给出了解决方法。 相似文献
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在无线电视距工程应用中, 常用等效地球半径因子表征大气折射的影响.为深入分析我国不同区域大气折射对无线电视距的影响, 定义了一种无线电视距因子, 以表征无线电视距相对标准大气视距的变化.基于我国区域近地面65 m高度大气折射率梯度数据, 得到了不同时间概率下我国区域无线电视距因子的时空分布, 结合拉萨、重庆、厦门、渤海湾、西沙、乌鲁木齐典型地区无线电视距因子的时间概率分布和季节变化, 分析给出了我国区域无线电视距因子的时空分布特征.分析结果表明, 我国不同地域无线电视距存在显著的时空变化, 并可导致无线电系统最大覆盖区域的显著时空变化.这些结果可为我国不同区域无线电系统设计和覆盖性能评估等提供参考依据. 相似文献
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对国内复眼仿生学的发展做了简要的回顾,定义了复眼光学系统的视场角、角分辨能力和其通光孔径.理论计算了蜻蜓复眼的有效视距,分别给出了在蜻蜓复眼的有效视距之外的点目标以及在其有效视距之内的长条状目标的通光孔径,说明了并列型复眼多孔径光电系统具有定向和跟踪能力.最后展望了复眼仿生学应用. 相似文献
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本文分析并讨论了在非视距NLOS条件下,宽带无线通信系统能否部署?能否提供稳定可靠的高带宽连接?市面上有没有靠谱的高带宽非视距NLOS解决方案? 相似文献
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This paper investigated the implementation of an adaptive predictive controller using nonlinear dynamic echo state neural (ESN) model for a rotary crane system by the visual servo method. The control sequences within the control horizon were described using cubic spline interpolation to enlarge the predictive horizon. Verification of the proposed scheme in the face of exogenous disturbances and modeling error with inaccurate string length was demonstrated by both simulations and experiments. 相似文献
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新型红外地平敏感器非共轴红外光学系统的优化设计 总被引:3,自引:1,他引:2
从卫星用新型红外地平敏感器的视场设计出发,分析了光学膜厚度和锗红外光学材料的吸收对光学设计的影响,介绍了非共轴红外光学系统优化设计的方法,给出了其设计结果.试验表明,设计的非共轴红外光学系统完全满足卫星用新型红外地平敏感器的要求. 相似文献
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激光水平仪理论模型的建立 总被引:1,自引:0,他引:1
激光水平仪是一种新型的智能光电仪器,该仪器在二维空间实时产生一条激光扫描线,这这条的发描线总是与地平线平行。本文对激光水平仪的扫描控制模型进行了详细的介绍,采用该模型已成地完成了仪器的设计制做。 相似文献
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A system has been developed to measure the directivity patterns of full-scale antennas when located in their operational environments. The primary component of this system is an aircraft-towed multifrequency transmitter that is designed to approximate an elementary dipole antenna. An HF and a VHF version of this transmitter provide frequency coverage from 2 to 100 MHz. Techniques have been developed to measure the entire radiation pattern, from the horizon to the zenith, for several antennas simultaneously. Data derived from this system are processed to provide the radiation patterns as contour plots of the measured signal strength on azimuthal equal-area projections. The measurement hardware, data acquisition, and data processing techniques are described, and examples are given of measured and processed data derived from the system. 相似文献
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滚动时域控制是一种考虑整个固定时域范围的控制方法,对于每次由优化算法得到的最优控制序列,仅取序列中的第一个元素作为当前此时刻的控制率。滚动时域控制是一种基于模型、滚动优化并结合反馈校正的优化控制算法。在由控制自由变量的非线性函数组成的非线性优化问题中,该控制自由变量的求取可采用凸优化理论中的相关算法来获取,进而采用滚动时域的思想来重新组合控制变量,以得到最优的控制变量。对于非线性系统中滚动时域控制所得到的最优化问题,分析非线性系统的滚动时域控制是否存在最优解,利用凸优化理论中的基本知识分别推导出此最优化问题在无和有集合约束条件下存在最优解的充要条件,并将此充要条件与经典优化理论中现有的最优条件进行对比,得出该充要条件的优势,最后将凸优化理论在无人机航迹规划算例中进行仿真验证。 相似文献
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Chunling Du Lihua Xie Yeng Chai Soh 《Signal Processing, IEEE Transactions on》2000,48(6):1760-1768
This paper deals with H∞ filtering of two-dimensional (2-D) linear discrete systems described by a 2-D local state-space (LSS) Fornasini-Marchesini (1978) second model. Several versions of the bounded real lemma of the 2-D discrete systems are established. The 2-D bounded real lemma allows us to solve the finite horizon and infinite horizon H∞ filtering problems using a Riccati difference equation or a Riccati inequality approach. Further a solution to the infinite horizon H∞ filtering problem based on a linear matrix inequality (LMI) approach is developed. Our results extend existing work for one-dimensional (1-D) systems to the 2-D case and give a state-space solution to the bounded realness of 2-D discrete systems as well as 2-D H∞ filtering for the first time. Numerical examples are given to demonstrate the Riccati difference equation approach to the 2-D finite horizon H∞ filtering problem and the LMI approach to the 2-D infinite horizon H∞ filtering problem 相似文献
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This paper is concerned with finite impulse response (FIR) filtering problem for discrete-time linear system which possesses
stochastically jumping parameters described by a finite-state Markov process. An FIR filter processes the measured inputs
and outputs on a finite receding horizon linearly and the filter gain is obtained by minimizing variance of the error between
real state and estimated one. According to inverse computation, system matrix is always assumed to be non-singular. In terms
of engineering application, we must have complete access to the current time jump mode. The FIR filter is presented in batch
form and recursive form, respectively, and Kalman filter is also addressed for comparison. Finally, a numerical example is
given to illustrate the design procedure and their effectiveness. 相似文献
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介绍了基于米散射多普勒测风激光雷达的基本原理。测风激光雷达系统一般由发射系统、接收系统、信号发射接收光学系统、控制系统组成,其中接收系统在整个系统中最重要,起到信号鉴频的作用。基于测量误差最小和实际加工工艺的考虑,设计了标准具的参数和米散射测风激光雷达接收机的结构,并且把该接收机用于米散射测风激光雷达系统中并进行了标准具透过率的测量,用Pseudo?鄄Voigt函数拟合出标准具的各个参数,与理论设计相差在5 %以内。同时进行了风廓线的初步测量,与风廓线雷达Airda16000进行了比对,两者符合很好。 相似文献
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The linear quadratic Gaussian (LQG) control for one-dimensional (1D) systems has been known to be one of the fundamental and
significant methods in linear system theory. However, the LQG control problem for two-dimensional (2D) systems has not been
satisfactorily solved due to their structural and dynamical complexity. In this paper, sufficient conditions for evaluation
of the quadratic performance indices of 2D systems in terms of the system state and control variables are proposed. Using
these conditions, systematic design methods for finite horizon and infinite horizon LQG controls of 2D systems are developed
using a convex optimization method. 相似文献