超宽带雷达树丛穿透干扰抑制算法

由于超宽带雷达受树丛对电磁波衰减作用,目标的反射回波很弱。本文首先分析人体运动多普勒特征与周围环境的区别设计频域滤波器,提出了一种基于滤波器,小波变换以及EMD的干扰抑制方法,实验结果表明,提出算法可以有效抑制干扰。     

超宽带噪声穿墙雷达成像与实验研究

设计了一个超宽带噪声穿墙雷达样机,工作频率为350 MHz～750 MHz,既能够获得较好的距离分辨率,又能够保证一定的穿透性和作用距离.采用后向投影(BP)算法对接收回波与发射噪声的互相关信号进行相干成像,实现目标信号的空间能量聚焦.实验结果表明该方法对超宽带噪声穿墙雷达行之有效,能够实现墙壁后面目标的隐蔽探测和成像.     

超宽带雷达时域成像算法及仿真

基于远场散射理论，将Radon变换理论引人到远场微波成像领域。给出超宽带雷达信号的概念，提出由超宽带雷达信号散射远场重建理想导体目标简捷的时域成像公式和实现算法。经计算机模拟，实现得到导体球清晰的像，表明该方法是远场雷达成像系统的一种有效方法。     

基于超宽带雷达的丛林目标探测无人机系统分析

探测和识别丛林目标并对其准确定位是复杂的技术问题,解决这一问题的需求十分迫切。首先对具备叶簇穿透能力的超宽带(UWB)雷达的技术构成和性能特点进行描述,然后对适合加装超宽带SAR的无人机提出要求。在此基础上对叶簇穿透超宽带SAR无人机的系统实现进行分析,分解需关注和解决的技术问题,探讨工作方向和重点。     

超宽带穿墙探测雷达的反向投影成像算法

在SAR BP（Back Project反向投影）成像算法的基础上,结合超宽带穿墙探测雷达应用中存在的特定条件（如墙体的反射、折射及其对宽带信号的色散影响,因天线阵的天线数目有限而使获得的信息量小等）,提出了一种超宽带穿墙探测雷达的BP成像算法。该算法考虑了超宽带电磁波穿透墙体传播的特性,能够去除墙体对成像的影响,并有效抑制了天线阵天线数目较少时的拖尾现象。通过仿真成像,分析了舍成孔径长度对可成像区域和成像精度的影响：合成孔径长度增加,成像精度提高,而可成像区域减小。     

基于超宽带雷达的三维成像技术研究

为了获取障碍物后或建筑物内恐怖分子的位置和分布信息并将目标清晰成像,在现有二维成像技术的基础上,采用超宽带无线电技术及时控阵雷达技术,对三维成像技术进行设计研究,并对其进行实验测试与仿真。仿真结果表明,该方案能够进一步提高雷达的探测精度和成像能力,成像效果显著提高。     

基于快速后向投影的超宽带冰雷达数据成像算法

该文提出一种新的冰雷达成像算法,该算法可以在获得高分辨率冰下剖面图的同时,拥有较高的处理效率。该算法是一种基于快速后向投影的超宽带(UWB)冰雷达成像方法,其修正了多层媒质情况下的雷达与目标之间的距离,以及因多层媒质造成的距离徙动几何变化。该文分析了算法的原理,给出了算法实现的具体步骤,并将其应用于点目标仿真和航空冰雷达数据实验,验证了算法在冰下成像中的有效性。此外,将该方法与现有常用冰雷达算法的成像结果在方位向杂波抑制能力、计算时间和方位向分辨率3个方面进行了对比,证明该算法能够在不降低方位向杂波抑制能力和方位向分辨率的前提下,有效提高计算效率。     

连续波穿透雷达柱面成像的干涉条纹抑制研究

在进行单频连续波表层穿透雷达的柱面2维无损检测成像扫描时,发现明暗相间的条纹现象,这是雷达成像扫描的一种主要干扰,会严重降低目标的成像效果。该文简单分析了曲面干涉条纹的产生机理,并且基于柱面与目标的谱域分布特性差异,提出谱域干涉条纹滤波方法。针对小目标具有较规律的谱域角度分布特性,沿角度进行谱域插值的补偿,以消除谱域滤波丢失目标谱信息的影响。此外,结合波前成像算法,给出了实现简单、处理高效的谱域滤波成像处理流程。通过仿真分析和实测数据实验,结果表明该文方法能够有效去除柱面的干涉条纹,形成清晰的目标图像。与传统的减平均方法的对比证实该文方法更有效。     

Two-dimensional superresolution radar imaging using the MUSICalgorithm

The multiple signal classification (MUSIC) algorithm developed by Schmidt [1986] is applied for two-dimensional radar imaging. The performance of the MUSIC algorithm using spatial smoothing for decorrelation is demonstrated. Two-dimensional radar images are generated for a simulated target as well as a target measured in the compact range at the University of Pretoria, South Africa     

Theoretical aspects of radar imaging using stochastic waveforms

In this work, we develop the theory of radar imaging using stochastic waveforms, such as random noise or chaotic signals. Specifically, we consider one-dimensional (1-D) (range profiles) and two-dimensional (2-D) (range-Doppler) radar imaging performed with a random signal radar, in which the transmit signals are assumed to be stationary random processes. We calculate the 1-D and 2-D point-spread functions as the expected value of the radar return. We show that the 2-D point-spread function is spatially invariant; however, the reduction in height and broadening of the mainlobe is small in the case of bandlimited noise. We also derive a formula that is useful in calculating the variance of the radar return under the assumption that the transmit signal is real valued and Gaussian     

3-D radar imaging using range migration techniques

An imaging system with three-dimensional (3-D) capability can be implemented by using a stepped frequency radar which synthesizes a two-dimensional (2-D) planar aperture. A 3-D image can be formed by coherently integrating the backscatter data over the measured frequency band and the two spatial coordinates of the 2-D synthetic aperture. This paper presents a near-field 3-D synthetic aperture radar (SAR) imaging algorithm. This algorithm is an extension of the 2-D range migration algorithm (RMA). The presented formulation is justified by using the method of the stationary phase (MSP). Implementation aspects including the sampling criteria, resolutions, and computational complexity are assessed. The high computational efficiency and accurate image reconstruction of the algorithm are demonstrated both with numerical simulations and measurements using an outdoor linear SAR system     

High-resolution radar imaging using 2-D linear prediction

An algorithm for radar imaging is described. The algorithm is based on two-dimensional (2-D) linear prediction of 2-D Cartesian frequency spectra. It is shown that the algorithm provides much better resolution than the ISAR image obtained using a 2-D inverse Fourier transform. The algorithm is especially useful for imaging targets using small-bandwidth RCS data over limited aspect angle regions     

利用140 GHz雷达实现目标缩比模型的RCS测量与成像

构建了140 GHz频段的单基雷达用于缩比模型的高分辨力成像和雷达散射截面积(RCS)测量。雷达的相干收发机用全固态的方式实现,其发射信道采用一个Ka波段频率源驱动的倍频链作为本振,在5 GHz的带宽内实现了0.5 mW的输出功率,接收机采用基于肖特基二极管的次谐波混频器实现相干接收。该雷达RCS测试系统显示出高信噪比的特点,获得了大于100 dB的动态范围和3 cm的成像分辨力。除了可实现对目标的逆合成孔径成像,该系统还可完成对旋转目标全方位角的RCS测量。利用该系统对某航空母舰1/720th模型进行了成像实验和RCS测量,模拟了全尺寸目标在P波段的结果。所获得的数据根据缩比定律可为P-波段雷达设计提供参考。     

Automatic aircraft landing using interferometric inverse syntheticaperture radar imaging

This paper presents an interferometric processing of an aircraft's monostatic and bistatic inverse synthetic aperture radar (ISAR) signatures for automatic landing. The aircraft's squint angle in this ISAR imaging problem is near 90 degrees . We show that this extreme squint angle does not pose any problem for the ISAR Fourier-based (wavefront) reconstruction algorithm. In fact, the aircraft can be imaged accurately, and without any erroneous shifts in the cross-range domain, within the imposed theoretical resolution. Moreover, the algorithm is accurate enough such that one can utilize the phase of the ISAR monostatic and bistatic measurements for interferometric processing. The resultant interferometric ISAR image is used to detect undesirable rotations in the aircraft's orientation.     

Time-domain imaging of airborne targets using ultra-wideband orshort-pulse radar

A time-domain physical optics inverse scattering identity is derived for real-time use in ultra-wideband radar systems. It is shown that using the band-limited impulse response of a radar target provides an edge-enhanced image. A simulation based on stepped-frequency, multiaspect measurements of aircraft models produces clear images with highly-defined edges     

利用奇异值特征的激光成像雷达目标识别

随着激光技术的发展,激光成像雷达在现代战争复杂战场环境中逐渐获得了广泛的应用,目前激光成像雷达目标识别技术已成为国内外研究的热点.基于激光成像雷达的距离像,以地面军事目标为识别对象,提出了针对奇异值特征的激光成像雷达目标识别算法.利用奇异值特征表征图像具有良好的稳定性,通过分析识别率与奇异值特征数目的关系,从激光成像雷...     

Time-domain imaging of radar targets using algorithms forreconstruction from projections

A time domain bistatic inverse scattering identity based on the Radon transform and the space-time magnetic integral equation is derived for real-time use in short pulse radar systems. It is shown that using a sine-modulated exponential pulse (SILIEP) and algorithms for reconstruction from projections provides an edge-enhanced image. A simulation based on stepped frequency, multi-aspect measurements of aircraft models produces clear images with highly defined edges. Images using data from a restricted range of aspect angles are also demonstrated     

Time-domain imaging of radar targets using sinogram restoration forlimited-view reconstruction

The time-domain image reconstruction problem can be formulated as a sinogram recovery problem. The sinogram recovery problem is to find a complete sinogram based on the measured incomplete sinogram. In this paper, we solve the sinogram recovery problem by using linear prediction techniques. Since the scattered field of a target can be written as a superposition of distinct specular reflections arising from scattering centers on the target, the trace of the scattering centers can be predicted using linear prediction with the change of the observation angle. Thus, the missing data may be predicted before reconstructing the image. Some useful results obtained using the proposed method are presented