基于视线测量改进的主被动联合探测数据关联

针对主被动传感器异地配置情况,利用视线测量转换过程,对主被动联合探测的数据关联算法进行了改进:首先,计算视线垂足至主动传感器的距离,以方位测量与该距离之差(测量差)构造新的统计量,通过视线间距以及测量差两个统计量检验初选出候选关联集;接着,主被动视线交叉将不完整的被动测量补充为完整测量,用精度加权法实现多角度测量之间的融合,得到候选集的定位点估计,计算各定位点与目标的关联概率;然后,以视线间距和测量差构造测量距离,利用测量距离之和表征关联集内部各视线的紧密度,给出视线关联度;最后,用视线关联度修正关联概率,最大值搜索正确关联组合。仿真实验结果验证了算法的有效性。     

SuperDARN雷达的对流测量评估

通过与DMSP卫星测量的二维离子漂移矢量的比较,对SuperDARN雷达对流测量进行了评估.二维对流矢量的比较表明,两种观测手段的测量总体上相符,其中对流方向的相关性和一致性均优于对流大小;当对流较强时,SuperDARN测量值有偏低的趋势.进一步分析表明,SuperDARN的视线速度测量与DMSP离子漂移测量的一致性较高,暗示由视线速度推断对流矢量的模型存在局限性,不能有效地反映出对流图像的小尺度结构.     

红外稳定平台装调误差对视线角速度的影响分析

框架式稳定平台中的装调误差影响视线角速度的测量精度。给出了框架轴系偏差的数学描述,在此基础上研究了轴系偏差和陀螺敏感轴交叉耦合情况下三自由度框架式红外稳定平台对视线角速度的计算方法。并比较了这两类装调误差对视线角速度测量精度影响的大小。仿真结果表明,通过对装调误差补偿,视线角速度的测量精度可显著改善。所得结果对新型框架式稳定平台系统的误差指标分配具有重要的参考价值。     

捷联导引头视线角速率估计算法

研究了一种用于估计制导弹药与目标之间的视线角速率算法的推导与实现.低成本的捷联导引头的测量信息中包含了弹目在相对运动中形成的视线角和弹体姿态两部分信息,首先设计解耦算法将弹体姿态信息去除,然后采用扩展卡尔曼滤波(EKF)以及α-β滤波这两种算法分别对视线角和视线角速率进行估计,最终的仿真结果表明采用EKF算法能比α-β...     

空间目标相对运动角参数的天基光学测量方法

利用在轨光学相机对空间目标进行跟踪测量,目标相对运动角参数的测量精度决定了空间目标的定轨精度.针对轴系定向原理精度差、天文定向运算量大等问题.提出了基于星图识别的天基光学定向算法.根据空间目标及参考恒星在相机焦平面上成像角的位置关系.利用参考恒星的惯性天球坐标确定目标相对视线的惯性空间角(赤经、赤纬);建立了目标视线角...     

捷联成像寻的器ACDKF惯性视线重构

针对捷联成像寻的器的惯性视线重构问题,提出了一种基于自适应中心差分卡尔曼滤波(ACDKF)的惯性视线重构滤波器的设计方案.首先针对弹体本身的模态特性,结合CDKF非线性滤波理论,设计弹体姿态估计器实现弹体姿态的实时更新,然后利用弹体姿态估计的统计特性,结合Saga-Husa时变噪声估值理论,给出ACDKF惯性视线重构滤波器的设计方案.数字仿真结果表明,在已知速率陀螺组合测量特性的条件下,该算法有效提高了捷联寻的器惯性视线信息的提取精度,为捷联成像寻的系统的惯性视线重构开辟了一种新的处理途径.     

捷联成像寻的器惯性视线重构精度分析

针对捷联成像寻的器,首先给出体视线和弹体姿态到惯性视线的映射关系,然后通过推导映射函数的雅克比矩阵,给出了从体视线和弹体姿态到惯性视线的误差传递公式。通过分析误差传递增益的范数,讨论了弹体姿态和弹目相对位置对惯性视线角计算的影响。由于体视线受到成像寻的器视场的约束,其角度测量值较小,合理简化了误差传递公式,给出了惯性视线误差的近似计算公式。最后应用蒙特卡洛实验,验证了近似计算公式的精度和结论。     

红外成像器视线漂移的自适应补偿研究

成像器视线稳定回路设计是一种高精度、高动态响应的伺服回路设计,对于速率陀螺稳定方案,视线的漂移角处于开环状态,由于轴间摩擦耦合、几何约束耦合,以及速率陀螺传感器测量精度的影响,成像器视线在载体扰动的条件下会发生视线角漂移,影响目标的识别.为实现较好的视线稳定精度,提出了一种自适应前馈补偿方案,通过自适应神经网络预测出光轴的漂移角,采用前馈实现对视线漂移的实时补偿,通过与单独的速率陀螺稳定方案、积分前馈补偿方案进行试验对比,结果表明采用自适应预测补偿方案,视线漂移明显减小,满足系统的指标要求.     

滚仰式红外导引头视线角速率提取方法研究

由于滚仰式导引头的结构特殊性,制导控制系统需要的视线角速率信息是不能够直接测量得到的,因此提出了一种基于跟踪微分器的视线角速率提取方法。根据滚仰式导引头的结构特点,分析了滚仰式导引头的运动学原理,并根据滚仰式导引头的结构推导出视线角与弹体姿态角、框架角和失调角的关系,然后设计了有限时间收敛跟踪微分器求解视线角速率信息。经数字仿真,对比了直接差分法和跟踪微分器法对视线角速率的提取效果,证明了利用跟踪微分器提取视线角速率的有效性。     

捷联末制导系统的控制与滤波模型研究

以半捷联寻的制导武器为对象,研究了捷联末制导系统中的捷联控制算法和制导信息滤波模型。首先分析了捷联末制导系统的工作原理,给出了捷联天线稳定平台的跟踪控制算法,然后针对捷联控制算法对目标视线角信息的需求,考虑仅有角度测量的被动制导情况,提出了一种基于M arkov随机模型的机动目标跟踪模型,通过推广Kalm an滤波技术可以获得目标视线角的估计。因为捷联末制导系统无法直接测量目标视线角速度,为了满足弹上比例导引的需要,提出了一个末制导系统角跟踪通道的数学模型,该模型可以采用常规的Kalm an滤波算法获得目标视线角速度的估计值。最后,通过一系列数学仿真验证了上述方法的有效性。     

Amplitude and phase scintillation measurements on 8.2 km line-of-sight path at 30 GHz

The letter summarises results of amplitude and phase scintillation measurements at 30 GHz on an 8.2 km line-of-sight path in the Netherlands. The measured results compare favourably with those obtained from weak-scattering theory.     

Statistical Prediction Modeling of Rain Induced Attenuation and Depolarization

Millimeter wave rain co-polarization attenuation, CPA, and cross polarization discrimination, XPD, measurements have been made at 35GHz and 94GHz over a line-of-sight link. On the basis of these experimental results, a study of this rain medium has been made with the method of link measurements. In this paper, we presented a statistical prediction modeling of rain-induced attenuation and depolarization from the statistical distribution of the rain intensity, and the size, and canting angle of raindrops. Our computational results are in good agreement with data of measurements.     

Polarization diversity in mobile communications

Signals in the vertical and horizontal polarizations at the base station have been measured by transmitting from a principally vertically polarized mobile. There was no direct line-of-sight path between the mobile and base. The envelopes were uncorrelated and the means differed by 7 dB and 12 dB when the mobile was in urban and suburban areas, respectively. The discussion of the results includes theoretical curves showing the relationship between the envelope correction coefficient and the mean levels difference of Rayleigh distributed signals in orthogonal linear polarizations at the base station. The variable parameters are the rotation angle of the base station antenna and the crosspolar discrimination of the incident fields     

Measurement and prediction of high spatial resolution indoor radiochannel characteristic map

This paper presents a new frustum ray tracing technique (FRTT) for the prediction of channel characteristic maps in a complex in-building environment. FRTT utilizes a fast line-clipping algorithm and does not rely on the conventional time-consuming ray intersection tests. Dielectric properties of building materials are empirically derived from in situ transmission coefficient measurements, which have enhanced the accuracy of prediction results. The FRTT is found to be more accurate and computationally efficient than the conventional ray tracing technique for area-type predictions. A detailed comparison has been made using measured narrow-band and wide-band channel characteristic maps with high spatial resolution (0.2 wavelength) at line-of-sight (LOS), non-LOS, and a corner transition region inside a multifloored building. The agreement between FRTT prediction and measurement appears to be excellent     

带热流密度限制的推力可控导弹三维制导律

传统三维制导律设计通常将三维空间分成垂直面和水平面分别考虑,容易导致耦合信息的缺失,同时没有考虑导弹红外导引头对导弹头部热流密度的限制和终端速度约束。针对以上问题,基于具有推力可控能力的导弹,在视线旋转坐标系的视线瞬时旋转平面内进行制导律设计。该制导律包含根据运动伪装理论设计的一种新的满足运动伪装条件的视线法方向加速度指令,以及通过变系数加权法综合考虑导引头热流密度限制及终端速度约束的视线方向加速度指令。数值仿真结果表明了存在导引头初始对准误差时,该制导律在满足红外导引头对导弹头部的热流密度限制、终端速度约束以及轴向过载限制下对高速机动目标制导性能良好,视线角速率可控制在3（）/s以下,具有一定的工程应用价值。     

Fade statistics measured by ETS-V in Japan for L-band land-mobilesatellite communication systems

Fade statistics were measured along 4095 km of expressways using a 12 dBi gain antenna with an automatic tracking system. The results show that the line-of-sight statistics, which were available for more than 90% of total distance, can be described by a Rician distribution with Rician factors of 15 to 25 dB     

The Impact of Antenna Directivity on the Small-Scale Fading in Indoor Environments

Results obtained from using a geometrically based, single-bounce propagation model are presented to characterize small-scale fading in indoor propagation channels when directional antennas are used. The model is verified by comparing simulated results to measured results. The model is then used to obtain, via simulation, fading statistics for an indoor, line-of-sight channel. The results show that when directive antennas are used, the parameters of the Nakagami- or Rician-distributed small-scale fading vary with separation between the transmit and receive antennas. Furthermore, the strength of the variation depends on antenna directivity. Some physical mechanisms for this effect are discussed     

Co-channel Interference Assessment for Line-of-Sight and Nearly Line-of-Sight Millimeter-Waves Cellular LMDS Architecture

Behavior of co-channel interference in fixed wireless cellular systems, such as millimeter-waves Local Multipoint Distribution Service (LMDS), is different compared to what has been established for mobile microwave systems. This is due to utilization of a high-gain antenna for the subscriber. In this paper, first the analysis of signal-to-interference ratio (SIR) is presented for line-of-sight and nearly line-of-sight LMDS architecture. In this analysis, the effects of precipitation and foliage attenuation and depolarization have been considered. These two parameters have negligible effect on the microwave mobile systems but in millimeter-wave range are among the most important factors in the link budget. To mitigate the fading due to shadowing by buildings and trees, a highly overlapped architecture and macro-diversity are proposed. After analysis of downlink SIR in previously proposed cellular systems, a cellular architecture is proposed based on polarization interleaving and frequency segmentation which has a much higher SIR yield. The statistical assessment of SIR is accomplished by assuming lognormal distribution for the received signals.     

Frequency correlation of line-of-sight signal scintillations

The frequency autocorrelation of amplitude and phase scintillations of radio signals propagated over turbulent line-of-sight paths is calculated theoretically. The single scattering (Born) approximation to the electromagnetic response of the turbulent irregularities is used, limiting the results to small amplitude and phase variations. However, the results are valid for both Fresnel (near zone) and Fraunhofer (far zone) scattering. The calculations are made for an arbitrary model of the turbulent irregularities by using the spectrum method, which postpones the specialization of the analysis to a particular turbulence model until the wave-propagation aspects of the problem are completed. It is shown that the signal variations on adjacent carrier frequencies have high correlation for frequency separations comparable to the carrier frequency for all propagation conditions, indicating that the "medium bandwidth" for line-of-sight paths is very large. This also means that there should be negligible pulse distortion for high-speed data links or high resolution radars operating on line-of-sight paths. These predictions are compared with the few available experimental results.