弹载主被动复合雷达天线配置方案

针对弹载雷达发展需求,探讨了实现弹载主被动复合雷达天线的技术途径。针对双频反射面天线,提出了一种双频反射面天线的配置方案；针对宽带复合天线,研究了被动模式宽带天线的选型和主动模式天线的设计方案,提出了宽带复合天线的配置方案。     

基于Anristu 37347D矢量网络分析仪的雷达反射面天线远场测试系统

天线测量系统的设计必须充分考虑待测天线的结构和电性能指标,并以此为依据决定测试方法和系统配置,才能使系统满足测试要求。本文详细介绍了雷达反射面天线远场测试系统的配置和关键问题,详细分析了反射面天线远场测试系统的实现方法。     

极化滤波反射面隐身天线研究

介绍了一种极化滤波反射面天线,将天线工程中的周期结构反射面技术应用于解决飞行器天线的RCS问题,采用由金属丝栅网构成的周期结构作为天线主反射面,使其对正交极化的来波具有良好的透射性,从而降低了天线的RCS。给出了此天线辐射方向图和雷达散射截面(RCS)的实测结果,并与普通金属反射面天线的结果进行了比较。     

弹载共形相控阵天线拓扑结构分析

以弹载多模复合制导雷达导引头为应用背景,在未考虑极化的情况下,首先建立了任意有向阵列的方向图函数;然后,采用同心圆等角度、同心圆等间距以及矩形栅格 3种不同配置方式,建立了锥面共形相控阵天线模型,推导了不同配置方式下天线阵列方向图函数;通过比较其方位面及俯仰面的副瓣电平,得出结论:同心圆等间距配置方式是锥面共形相控阵雷达导引头天线单元的最优配置方式。     

星载网状天线反射面面型精度测试与分析

星载网状天线反射面作为大口径天线的重要结构部件,其面型精度直接影响天线的电性能。针对主要由抛物肋板、充气环、张力系统、中心鼓结构构成的网状天线反射面,采用数字摄影测试技术建立了反射面面型精度测试方案,获得了抛物肋板上普通标志点的空间坐标以及与最优抛物面之间的偏差,并开展了反射面面型精度的分析。为了提高网状天线反射面面型精度,提出了分阶段地依据各普通标志点偏差方向和大小调节肋板上节点至地面垂直距离的反射面面型调整方法。在阶段1至4中经过调整之后反射面面型精度分别提高了75.0%、54.3%、36.6%和37.4%,表明该天线面型调整方法的有效性。阶段4中网面的安装大大降低了抛物肋板的面型精度,同时抛物肋板的偏差趋势与阶段2偏差相近,所以前期阶段肋板的调整尤为重要,而反射面抛物肋板上的偏差主要分布于副肋。     

弹载天线旋转对接收信号多普勒偏差的影响

由弹体自旋产生的弹载天线的旋转是引起地面测控站多普勒测速误差的一个重要因素.根据线极化信号接收原理,对弹载天线旋转条件下接收的左旋和右旋信号多普勒偏差进行了理论推导和分析.分析结果表明：左/右旋接收信号将产生幅度相等、极性相反的多普勒偏差,多普勒偏差的均值与弹载天线旋转速率在数值上相等,多普勒偏差的方差随着目标视线与天线转轴之间夹角的增大而增大.为验证理论分析结果,开展了天线转台模拟实验,实验测量得到的多普勒偏差的均值和方差与理论分析结果基本一致.最后,根据理论分析和模拟实验结果,提出在实际任务中,可采用左旋和右旋多普勒偏差均值差的一半分别对左/右旋信号的多普勒进行补偿,以减小弹载天线旋转对测速精度的影响.     

大型深空测控天线副反射面控制技术

针对大口径、高频段深空测控天线主/副反射面变形引起的天线电性能下降问题,采用副反射面控制技术实现天线的电性能补偿。首先,在分析并联机构数学模型的基础上,结合并联机构坐标系定义,给出六自由度并联机构位姿的正、逆解;其次,根据变形后天线形状采用抛物面拟合法给出副反射面位姿与仰角的关系,这样在天线实时运动过程中,可根据仰角查找出副反射面位姿最佳工作点;最后通过六自由度并联机构正、逆解及控制算法控制副反射面到最佳位置和姿态上。理论分析和工程实践表明,副反射面控制技术通过控制副反射面中心到最佳焦点位姿上,可实现对天线电性能的有效补偿。六自由度并联机构控制具有自身承载力强,位置、姿态控制灵活等特点,适合于大型天线副反射面实时精密控制。     

机载无线电罗盘垂直天线电参数分析

从机载无线电罗盘垂直天线的实际应用出发，首先对垂直天线的电参数进行了简单的介绍和说明，然后依据等效电路理论对天线的各项参数的相互关系进行了详细的分析和推导，并列举了相关的试验方法和试验结果，进一步说明了垂直天线电性能是其相关电参数折衷的结果，最后对非独立垂直天线设计中的关键问题提出了相关建议。     

频率选择表面机载雷达天线的研究

研究了降低机载雷达天线散射截面的频率选择表面(FSS)极化扭转板。根据Floquet定理利用模式电压概念建立矢量模式,对二维周期阵列的频率选择表面进行理论分析和计算。设计并加工了一种降低机载雷达天线散射载面的频率选择表面极化扭转板结构。计算和实验表明:频率选择表面的极化扭转板在雷达天线工作通带内保持与原极化扭转板的性能不变,而在工作通带外具有降低雷达散射载面的效果。降低雷达散射截面7～10dB。     

一种基于神经网络的前馈控制器设计

本文根据文献的思想，以弹载雷达天线伺服系统为应用背景，针对具有确定性结构和多数，但不易准确建模的实际系统，设计了一种控制结构。数字仿真试验表明，该方案对上述系统具有可行性及良好的控制性能。     

Effectiveness of MMW aerosols in defeating a battlefieldsurveillance radar: field demonstration preliminary results

The US Army ERDEC is developing advanced aerosol systems to combat threat surveillance, fire control, and seeker systems operating in the visible, infrared, and millimeter wave portions of the electromagnetic spectrum. One such system is the M56 multispectral smoke generator, which presently operates in the visible and infrared portions of the spectrum; a millimeter wave (MMW) Module is in development to extend the M56 spectral range. This paper documents preliminary results of a field demonstration test of the M56 MMW Module. An MMW instrumentation radar was modified to simulate the scan pattern and radar parameters of a tactical battlefield surveillance radar system. A test grid was populated with both stationary and moving tactical targets, and the radar scanned the grid to simulate a surveillance radar in operation. Once a realistic tactical engagement scenario was developed, MMW aerosols were deployed to demonstrate the impact such aerosols could have on radar detection and classification performance     

MMW scanning antenna

Cost reduction is one of the most important considerations in millimeter-wave (MMW) radar development. Hardware, especially the phase-shifters, for electronic beam scanning in the MMW band presents very complex fabrication challenges that dramatically raise the device cost. A typical mechanically-scanning antenna contains one or more hinged parts (lenses, mirrors or feeds). In operation they experience strong mechanical accelerations and other forces that sharply limit the scanning speed. We propose a solution to this problem, using a leaky-wave periodically loaded antenna design and a new architecture. This paper presents the basic design, and discusses related issues     

Neural network learning of low-probability events

In the problem of stationary target identification (STI) via millimeter wave (MMW) seeker radars in heavy clutter environments, it is often necessary to use nonparametric identification procedures, as detailed parametric models of clutter and target returns are generally unavailable. Neural networks provide an attractive approach to perform nonparametric identification. However, when identifying low-probability events, the computational overhead associated with training a neural network can become excessive. This is because low-probability events must be adequately represented in the training sample. We present a modified backpropagation training algorithm based on a likelihood ratio weighting function (LRWF) to train the neural network using a much smaller training set than that required using the standard backpropagation algorithm This algorithm is closely related to the importance sampling technique used in digital communication systems to obtain probability of error estimates by using a much smaller number of simulation runs than what is required with standard Monte Carlo simulation. The modified backpropagation technique results in a significant reduction in computational overhead in training the network, resulting from a substantial reduction in the size of the training set required to achieve a given level of performance. We demonstrate the performance of the algorithm on simulated data for the STI problem in MMW radar     

A track filter for reentry objects with uncertain drag

A filter was developed for maintaining track on ballistic missiles whose drag profiles are unknown or deviate significantly from prior predictions. The filter employs an innovative form of a seven-state Kalman filter in which object drag is included as a state to be estimated. Using measurements of range, azimuth, and elevation, the filter can track endo- and exo-atmospheric targets on a wide variety of trajectories without requiring a priori tuning to account for variations in reentry angle, drag history, measurement signal-to-noise ratio, etc. The filter was designed to be implemented at the millimeter wave (MMW) radar (a high-range-resolution, narrow beamwidth, Ka-band radar) located at Kwajalein Missile Range (KMR) in the Marshall Islands. Extensive testing and comparisons using a high fidelity simulation showed the new filter to be robust to a wide variety of trajectories and substantially better than track filters presently used at KMR. The filter was coded to run efficiently in real time, installed at the MMW radar, and successfully used to track an intercontinental ballistic missile (ICBM) with varying drag characteristics through exo-atmospheric and reentry phases. The filter yielded a more accurate and responsive track than possible with the previously used filter on a similar trajectory     

SPRI: simulator of polarimetric radar images

Simulator of polarimetric radar images (SPRI) consists of a suite of image processing programs for producing realistic millimeter-wave (MMW) radar images artificially on a workstation. The heart of the simulation approach is a polarimetric Rayleigh clutter simulator coupled to a clutter database. The simulator produces high resolution single-look polarimetric images. Hard targets can then be embedded into this clutter map, and the resultant image can be degraded in resolution, number of looks, polarization, etc. to match that which would be observed by a real sensor. Examples of simulated images, and comparisons of these simulations to actual images, are presented. The MMW Clutter Database is the most comprehensive to-date database of over 3500 Mueller matrices for many kinds of terrestrial clutter measured at 35 and 95 GHz, many of which are at incidence angles close to grazing. The database can be accessed via a World Wide Web flexible interface that enables data to be combined in new and unique ways specified by the user, and displayed in either tabular or graphical format. The structure and access procedure to the database are described     

Aircraft ice accretion measurement: a Phase I, SBIR study usingmillimeter wave radar (MMWR)

Discusses Phase I bids to study the feasibility of using MMW radar techniques to measure the amount of ice accumulated on aircraft wings and rotors. It appeared to the authors that this sensor technology might have the potential to solve some of the problems of sensors that are currently available. A proposal and program strategy was adopted capitalizing on the prior research in the area wherever it could be found from unclassified sources     

双层柱壳和单层柱壳战斗部侵彻性能对比分析

采用数值模拟的方法对双层柱壳和单层柱壳的半穿甲爆破型战斗部的侵彻性能进行了对比分析。计算发现：侵彻20 mm厚靶板时,采用双层柱壳不会对战斗部侵彻性能产生明显影响,但是在侵彻较厚的25 mm靶板时,双层柱壳战斗部的侵彻性能要比单层柱壳战斗部略差;而焊接强度对双层柱壳战斗部侵彻性能的影响比单层柱壳要大。     

毫米波无人直升机避障雷达系统研究

由电力线所引起的无人直升机事故频频发生,因而确保无人机飞行安全一个很重要的方面就是对电力线的检测。文章采用毫米波宽带线性调频技术实现了对高压线小目标的探测分辨,研制了毫米波无人直升机避障雷达系统,解决了无人机低空巡线飞行的安全问题。通过实际挂飞试验说明,该系统可靠有效,满足装备要求。     

空间进动目标动态散射特性的实验研究

研制了进动目标模型,构建了紧凑场微波暗室动态测量系统,通过暗室实验的方法研究了空间进动目标的动态散射特性,给出了若干典型条件下的全极化宽带测量结果。通过实验可以观察到目标进动引起的多普勒频移,证明了微波雷达对进动目标微多普勒的可观测性,同时观察到弹头常见结构引起的非理想点散射现象。实验结果的分析表明,该实验系统能够有效地揭示进动目标的目标特性和回波调制特性,从而为弹道中段目标的动态电磁散射特性、目标结构反演、运动参数提取和逆合成孔径雷达(ISAR)成像的研究奠定了基础,对于弹道中段目标识别的研究具有重要的意义。     

天基光学平台下弹头与气球诱饵中段观测运动差异分析

为了解决弹道导弹在中段释放气球诱饵伴飞,以干扰天基光学防御系统对导弹目标进行精确跟踪识别的问题,基于弹头和气球诱饵质阻比的差异,利用美国NRLMSISE-00(Naval Research Laboratory Mass Spectrometer and Incoherent Scatter radar Exosphere,海军研究实验室质谱仪和非相干散射雷达大气经验性模型)对气球诱饵进行相应动力学分析,得出气球诱饵在弹道中段的大气阻力模型.然后给出了J2摄动下,气球诱饵经过阻力修正后较精确的中段运动模型,并将结论引入到天基光学平台中,进行观测仿真实验.结果表明,在200 km以上的高空,大气阻力对于弹头和气球诱饵的影响微弱,可忽略不计,在观测像平面中表现为一块难以区分的亮斑;而在100～200 km高度范围内,气球诱饵受大气阻力影响剧烈,在观测像平面内的运动与弹头存在较大差别,具有较强的可区分性.