Evaluation of adaptive phased array antenna, far-field nullingperformance in the near-field region

A theory for analyzing the behavior of adaptive phased array antennas illuminated by a near-field interference test source is presented. Conventional phased array near-field focusing is used to produce an equivalent far-field antenna pattern at a range distance of one to two aperture diameters from the adaptive antenna under test. The antenna is assumed to be a linear array of isotropic receive elements. The interferer is assumed to be a bandlimited noise source radiating from an isotropic antenna. The theory is developed for both partially and fully adaptive arrays. Results are presented for the fully adaptive array case with single and multiple interferers. The results indicate that near-field and far-field adaptive nulling can be equivalent. The adaptive nulling characteristics studied in detail are the array radiation patterns, adaptive cancellation, covariance matrix eigenvalues, and adaptive array weights     

Properties of phase synchronizing sources for a radio camera

A distorted phased array can be made to operate as a diffraction-limited aperture if a compensating time delay and/or phase shift is added in each antenna element channel. When the distortion is not known a priori the correction mast be based upon phasefront measurements of the radiation from a source external to the array. The ideal adaptive synchronizing source is a point source radiating in free space. The phasefrouts of realistic sources are perturbed, however. Three types of practical sources and calculations of the conditions under which their radiation fields are acceptable for adaptive beamforming are discussed. The sources are the passive reflector, the active beacon, and radar ground clutter.     

一种级联结构的空时二维信号处理算法

在研究R．Klemm博士的级联抑制噪声干扰和杂波算法以及旁瓣对消算法的基础上,针对噪声干扰和地杂波同时存在的情况,提出了一种采用旁瓣对消结构级联抑制干扰和杂波的算法。该算法首先利用相控阵天线合成一个辅助天线和多个主天线,多个主天线共用一个辅助天线,针对每一对主辅天线,采用旁瓣对消算法在空域抑制噪声干扰;然后对多个主天线的输出结合时域进行STAP（空时二维信号处理）抑制地杂波。并且证明了该级联结构等效于一种同时抑制干扰和杂波的结构。计算机仿真结果及性能分析验证了该算法能有效地抑制干扰和杂波,且与其他级联结构相比,所提出的结构更利于工程实现。     

Linear array characteristics with one-dimensional reactive-regionnear-field scanning: simulations and measurements

A model for simulating the performance of a phased-array antenna with one-dimensional near-field scanning is addressed. Measurements and simulations in the reactive near-field region for a linear array with monopole elements are described. The array and near-field probe characteristics are simulated by using the method of moments. Measurements and simulations of the array near-zone received voltage, plane-wave spectrum, and far-field data, using centerline scanning at less than one wavelength distance from the antenna, are shown to be in good agreement. The presence of evanescent grating lobes in the plane-wave spectrum is observed. It is shown that a V-dipole theoretical probe antenna can accurately model a practical near-field measurement probe     

机载多通道天线SAR自适应杂波抑制

本文通过分析多通道天线SAR的空间几何关系,建立了完善的多通道天线SAR回波信号模型,提出了基于相控阵天线空域阵元混迭式结构形成多个接收通道天线的多通道天线SAR自适应杂波抑制方法和实现结构.理论分析和计算机仿真结果表明,利用多通道天线技术并结合时空二维自适应杂波抑制技术,可以在进行机载SAR成像中对慢速运动目标具有良好的检测性能.     

数字阵雷达天线波瓣图测试方法与试验验证

针对固定式相控阵雷达在中场法或远场法中不能实时得到天线波瓣图的问题,提出了采用扫描波瓣图替代天线波瓣图进行天线测试的方法。从理论上分别推导了和波束与差波束扫描波瓣图和天线波瓣图的解析式,研究了单元波瓣图对扫描波瓣图和天线波瓣图的影响,指出了在单元波瓣主瓣范围内扫描波瓣图和天线波瓣图近似等价。仿真和试验结果 均表明:扫描波瓣图和天线波瓣图在各项性能指标上都是等价的,可用于指导雷达总体依据扫描波瓣图对天线进行验收。     

一种简便的MIMO阵列雷达CFAR检测器

本文提出了一种适用于MIMO阵列雷达的简便的CFAR检测器,它利用了MIMO阵列雷达观测空间维数高的特点,通过直接滤除杂波干扰子空间的方式抑制杂波和干扰。该检测器的简便性在于杂波子空间可以离线估计与存储,而干扰子空间的估计也只需在低维空间上进行,而其原因是在估计杂波和干扰子空间时没有利用距离参考单元观测样本,而是利用了已知的系统参数、杂波子空间结构以及干扰协方差矩阵的模块对角性质。仿真结果表明,在杂波的理想模型条件下,选择适当的估计方法可以获得较高的杂波子空间估计精度,由此得到的CFAR检测器的性能也非常接近于已知杂波干扰子空间条件下的检测性能。      

Adaptive arrays in airborne MTI radar

The ability of an AMTI (airborn moving target indication) radar to reject clutter is often seriously degraded by the motion of the radar. An adaptive receiving array can compensate for platform motion and provide excellent AMTI performance. Scattering from aircraft structure can also distort antenna patterns and reduce AMTI capability. The technique described here can adapt the element weights to compensate for near-field scatterers and element excitation errors. Another important advantage is the ability to null out discrete active interference sources without significantly degrading AMTI performance.     

Control of peak sidelobe level in adaptive arrays

Adaptive beamforming techniques are now widely used to reject interference (jammer/clutter) signals in radar, communication, and sonar applications. In adaptive arrays using the sample matrix inversion (SMI) algorithm, inadequate estimation of the covariance matrix results in adaptive antenna patterns with high sidelobes and distorted mainbeams. In this paper, a method is proposed to precisely control the peak (rather than average) sidelobe level of adaptive array patterns. The proposed method is also generalized to adaptive array antennas with moderate bandwidth and large random amplitude and phase errors. Theoretical analysis and simulation results are provided to illustrate the performance of the method proposed     

机载雷达时-空二维自适应处理新方法

本文针对机载侧面相控阵雷达的杂波谱特点,提出了一种基于列子阵结构的先时后空局域联合二维信号处理方法。文中对该方法的原理和性能作了较详细的讨论,并与其它两种方法作了比较,理论分析和计算机模拟均表明新方法的性能和容差能力较好,特别是在主杂波附近区域的改善因子有明显的提高。     

三维空时自适应处理的信号模型

空时自适应处理(STAP),是用于动目标检测的一项关键技术,文中通过对三维STAP雷达天线阵列模型的描述,详细分析了接收信号的表达式及其格式化表示,其中不仅分析了阵列天线的方向图,而且详细分析了噪声、干扰和杂波的信号模型,为深入研究三维STAP提供了理论基础.     

空载雷达杂波抑制自适应阵列技术

文中对一个采用联合局域化－通用似然比准则的自适应阵列雷达与一个采用相移中心孔径（ＤＰＣＡ）技术的雷达作了比较。对目标的实验结果表明，在严重的非均匀杂波及干扰环境中，普通的自适应处理技术是不适用的。     

Near- and Far-Field Characterization of Planar mm-Wave Antenna Arrays with Waveguide-to-Microstrip Transition

We present the design and characterization of planar mm-wave patch antenna arrays with waveguide-to-microstrip transition using both near- and far-field methods. The arrays were designed for metrological assessment of error sources in antenna measurement. One antenna was designed for the automotive radar frequency range at 77 GHz, while another was designed for the frequency of 94 GHz, which is used, e.g., for imaging radar applications. In addition to the antennas, a simple transition from rectangular waveguide WR-10 to planar microstrip line on Rogers 3003? substrate has been designed based on probe coupling. For determination of the far-field radiation pattern of the antennas, we compare results from two different measurement methods to simulations. Both a far-field antenna measurement system and a planar near-field scanner with near-to-far-field transformation were used to determine the antenna diagrams. The fabricated antennas achieve a good matching and a good agreement between measured and simulated antenna diagrams. The results also show that the far-field scanner achieves more accurate measurement results with regard to simulations than the near-field scanner. The far-field antenna scanning system is built for metrological assessment and antenna calibration. The antennas are the first which were designed to be tested with the measurement system.     

机载相控阵雷达近程杂波抑制的俯仰向空域自适应算法

该文针对机载平面阵列相控阵雷达的动目标检测提出了一种俯仰向空域自适应的近程杂波抑制算法。该方法利用平面阵列天线在俯仰向的自由度,在近程杂波的支撑区域内沿着多普勒单元选取训练样本估计协方差矩阵,计算俯仰向空域最优权。在存在距离模糊的情况下,该方法可以自适应地滤除近程杂波,保留远程杂波,从而增强了杂波的距离均匀性,有利于提高后续的方位空域和时域STAP的性能。     

便于工程实现的机载雷达空时二维自适应处理方法

本文提出了一种便于工程实际实现的机载雷达空时二维自适应处理方法,其特点为在主杂波区增加辅助阵元。经理论分析和计算机模拟表明,这种方法可以通过空时两方面有效地抑制地杂波,获得优良的系统性能,同时运算量小,实现方便,具有工程应用前景。同时本文还对在主杂波区增加辅助波束的方法进行了分析研究。     

基于频率分集阵列的多功能一体化波形设计与信号处理方法

频率分集阵(FDA)是在相控阵基础上的一次体制革新,其通过在发射天线阵元间进行频率步进,得到的发射方向图是角度、距离、时间的多维函数,显著提升了波束控制能力与信号处理维度,经过收发联合处理后,可应用于多维参数联合估计、主瓣欺骗式干扰抑制、模糊杂波抑制、高分宽幅成像等方面。该文从系统层面出发,研究基于FDA的多功能一体化波形设计与信号处理方法,重点对其在检测与估计一体化、解模糊与抗干扰一体化、合成孔径雷达(SAR)成像与动目标检测一体化的信号处理新方法进行综述、评述及研究,并对FDA多功能一体化系统的应用前景进行展望。      

机载雷达杂波特性及工程中的目标检测技术

针对机载雷达地杂波谱的分布特性,讨论了机载PD和相控阵两种体制雷达的工程可实现的地面目标检测方法,重点研究了空时二维处理技术在机载相控阵雷达杂波抑制中的应用,仿真结果证明3DT-SAP方法能有效改善杂波抑制性能,具有良好的工程应用价值.     

某型地基相控阵天线指向系统性误差分析

相控阵天线的指向精度决定着雷达系统对目标的探测精度,甚至会影响跟踪、截获目标的成败。以一种地基相控阵天线为例,详细分析了机电混合扫描天线的指向系统性误差来源：1)热形变导致的单元间距误差,2)空气折射,3)伺服机械转动误差,4)天线内部温度场变化等。从理论上分析了上述因素对天线指向精度的影响,并提出了完整的远场误差校准方法和误差修正流程。试验结果表明,误差来源分析准确,所提出的校准方法可以明显改善天线指向精度,从而提高雷达系统跟踪精度和威力,对于地基乃至移动平台相控阵天线的设计与应用具有重要的参考价值。     

Study on Clutter Model and Characteristics of Airborne Radar with Parabolic Conformal Phased Array

The studies on clutter modeling and suppression of airborne radar with a parabolic conformal array are uncommon due to the complexity of this type of antenna array configuration. The correct understanding of clutter characteristics for airborne radar with a parabolic conformal antenna array is the prerequisite and foundation of optimal suppression of this type of clutter. This paper establishes the model of clutter echo of airborne parabolic conformal phased array radar and analyzes the structure characteristics and the distribution features of this type of clutter. The simulation results show that this type of clutter has the following characteristics: 1) The main lobe on the azimuth is seriously broadened, 2) the power spectrum presents strong heterogeneity, and 3) the freedom degrees are high. Based on the existing related clutter suppression methods, we verified the correctness of the constructed clutter model. This work has an important guidance to further study on clutter suppression methods in airborne parabolic conformal array radar.     

一种减小相控阵天线球面近场测量截断误差的方法

在相控阵天线球面近场测量中,有限扫描面和相控阵天线波束扫描将会引起较大的截断误差.为了解决这一问题,提出利用基于遗传算法参数优化的余弦窗函数对近场数据进行加权处理的方法来有效减小截断误差.以半波振子组成的矩形平面阵作为待测天线,对相控阵天线球面近场测量进行了计算机模拟.模拟结果表明,通过对近场数据进行加余弦窗的处理并用遗传算法对参数进行优化能够大大减小相控阵天线波束扫描时的有限扫描面截断误差,从而证实了文中所提出方法的正确性和有效性.