Terrain elevation mapping results from airborne spotlight-mode coherent cross-track SAR stereo

Coherent cross-track synthetic aperture radar (SAR) stereo is shown to produce high-resolution three-dimensional maps of the Earth surface. This mode utilizes image pairs with common synthetic apertures but different squint angles allowing automated stereo correspondence and disparity estimation using complex correlation calculations. This paper presents two Ku-band, coherent cross-track stereo collects over rolling and rugged terrain. The first collect generates a digital elevation map (DEM) with 1-m posts over rolling terrain using complex SAR imagery with spatial resolution of 0.125 m and a stereo convergence angle of 13.8/spl deg/. The second collect produces multiple DEMs with 3-m posts over rugged terrain utilizing complex SAR imagery with spatial resolutions better than 0.5 m and stereo convergence angles greater than 40/spl deg/. The resulting DEMs are compared to ground-truth DEMs and relative height root-mean-square, linear error 90-percent confidence, and maximum height error are reported.     

基于复图像的稀疏SAR成像方法在高分三号数据上的验证

基于稀疏信号处理的合成孔径雷达(SAR)成像(稀疏SAR成像)是稀疏微波成像的一个重要研究方向,相较于经典SAR,稀疏SAR成像在提升成像性能等方面具有重要优势。然而,受困于较大计算代价,其难以用于大观测场景的稀疏恢复,这极大限制了其应用范围。此外,无论军用还是民用,各国星载SAR系统的技术性能指标均是保密的,因此相较于原始回波,通常的公开数据都是经匹配滤波算法重构的SAR复图像。因而如何基于复图像数据进行稀疏成像,对提升现有SAR图像质量、降低稀疏成像计算代价具有重要意义。高分三号是我国首颗1 m分辨率C波段多极化SAR卫星,它具有成像分辨率高、幅宽大等优势,对提升我国灾害监测、海洋监视等能力具有重要作用。该文将一种基于复图像数据的稀疏SAR成像技术引入到高分三号SAR复图像的性能提升当中。实验结果表明,经稀疏处理后的图像拥有更低的旁瓣、更高的信杂噪比以及更优的目标可分辨率能力。且类似于匹配滤波算法重建图像,稀疏恢复结果也可以很好地保持图像统计分布及相位信息,使得稀疏重构的高分三号SAR图像仍适用于干涉、恒虚警率检测等应用。      

Microstrip antennas for SAR applications

This paper discusses various methods of implementing a shared-aperture dual-frequency dual-polarized array antenna for spaced-based synthetic aperture radar (SAR) applications. After evaluating the use of several potential array architecture concepts and radiating elements, a design using interlaced C-band microstrip patches and X-band printed slot elements was chosen as the best choice for the present system requirements. Layout considerations for the two arrays and their associated feed networks are addressed in terms of a practical design. A dual-frequency (C- and X-band), dual-linear polarized SAR array antenna prototype was designed, fabricated, and tested. The principal goal of this effort was to demonstrate the viability of the dual-band dual-polarized array concept, and this has been accomplished. Test results are shown with good correlation between measured and predicted results, validating the design approach used. This work demonstrates that a dual-frequency dual-polarization SAR antenna within a single aperture is a feasible approach to meeting user requirements in future SAR spacecraft     

星载SAR系统参数设计过程自动化方法研究

针对星载合成孔径雷达（Synthetic Aperture Radar，SAR）系统参数设计过程中部分参数仍需手工选取，并且系统根据设计结果无法做出反应的问题。本文提出了一种星载SAR系统参数自动化设计的方法。首先，针对脉冲重复频率（Pulse Repetition Frequency，PRF）和波位位置等重要参数进行了优化选取设计。然后，利用比例?积分?微分（Proportion?Integral?Differential，PID）控制器对系统参数结果作自动化调节。仿真和实验结果表明，与传统的星载SAR系统参数设计方法相比，该方法具有便捷高效、易于实现的特点，提高了星载SAR系统设计过程中参数选取的自动化程度，实现了当系统技术指标的评测结果不满足用户要求时的参数自动调节。     

弹载俯冲大前斜SAR成像几何校正参数误差影响分析

弹载合成孔径雷达(Synthetic Aperture Radar, SAR)成像需依托弹道参数完成斜距图像向地距图像的几何校正,在俯冲大前斜SAR成像模式下的几何校正性能对弹道参数的精度非常敏感。针对弹载俯冲大前斜视SAR成像模式下成像斜距图为距离多普勒类型图像的几何校正算法,从理论上分析了多维弹道参数误差带来的几何校正畸变量,通过仿真验证了算法及畸变量分析的有效性。该研究对雷达导引头的系统设计、目标识别技术需求等提供了理论依据,具有重要的工程应用价值。     

SAR图像质量外场试验与评估技术

SAR图像质量评估是评判SAR系统性能的关键指标,常用SAR图像质量评估参数包括目标分辨率、峰值旁瓣比和积分旁瓣比等。首先介绍了SAR图像质量评估参数的定义;其次分析了SAR图像质量评估参数测试误差,给出了单个角反射体时积分区间对积分旁瓣比的影响,以及多个角反射体时图像质量评估参数测试误差,并进一步给出了定标场地设计要求;最后介绍了SAR图像质量评估软件系统。SAR图像质量评估技术研究已在SAR系统试验中得到应用,开发的评估软件系统在sAR图像质量评估中具有一定的推广价值。     

Seasat Synthetic-Aperture Radar Data Reduction Using Parallel Programmable Array Processors

This paper presents a digital signal processing system that produces the SEASAT synthetic-aperture radar (SAR) imagery. The system consists of a SEL 32/77 host minicomputer and three AP-120B array processors. The partitioning of the SAR processing functions and the design of softwae modules is described. The rationale for selecting the parallel array processor architecture and the methodology for developing the parallel processing scheme on this system is described. This system attains a SEASAT SAR data reduction speed of 2.5 h per 25-m resolution 4-look and 100 km X 100 km image frame. A prelininary performance evaluation of this parallel processing system and potential future applications for remote sensing data reduction are described.     

FM—CW SAR系统及其发展概况

FM-CW SAR是一种新近被提出来的成像雷达体制，它结合连续波与合成孔径成像技术，具有体积小、重量轻、成本低、分辨率高等一系列优点。文章概述了FM-CW SAR系统及其信号处理特点，讨论了FM-CW SAR系统实现的难题所在；归纳了目前FM-CW SAR的几种应用背景及其主要参数；根据FM-CW SAR发展概况，讨论了FM-CW SAR进一步的发展趋势。     

弹载合成孔径雷达动态海面成像模拟研究

海面成像模拟是对海作战导弹弹载合成孔径雷达(SAR)成像制导全过程动态仿真的重要组成部分,对于系统的性能分析和优化设计具有重要意义。研究了弹载情况下SAR对海成像模拟问题,提出了基于三维海面波动模型及弹载SAR工作过程的成像模拟方案。出于逼真性及运算速度的考虑,仿真时动态海面选用基于海浪谱的双尺度模型,海面散射模型选用双尺度散射模型。结合一组典型弹载SAR系统参数,分别在正侧视和斜视模式下对三种典型海况的动态海面进行了成像模拟,并利用实际海面SAR图像的统计特性验证了模拟结果的有效性。     

Synthetic Aperture Radar Imaging from an Inclined Geosynchronous Orbit

Images of Earth can be produced with an assumed synthetic aperture radar (SAR) on a satellite platform undergoing a nutating relative motion from geosynchronous altitude. From a 50° inclined circular orbit, the contiguous United States can be imaged in about 3 h of segmented operation at 100-m resolution with 4-azimuth-look averaging. The 2450-MHz transmitter radiates 1312 W of average power from a steerable 15-m-diam antenna. The SAR can image daily an area bounded longitudinally and latitudinally.     

极化干涉SAR的研究现状与启示

阐述极化与干涉结合的基本考虑,介绍极化干涉SAR相干最优和相干目标分解的基本思想,总结分析极化干涉SAR技术、典型星载极化SAR系统研制和极化干涉SAR应用的研究现状,以得到开展极化干涉SAR技术研究的启示。     

Synthetic aperture radar

A short introduction to the background and theory of synthetic aperture radar (SAR) imaging is given. Some of the key issues in SAR design are discussed and possible future developments involving SAR operation with phased arrays are suggested     

SAR复图像域上的噪声抑制和目标特征提取

基于SAR图像的稀疏先验,提出了一种基于l_k范数的复图像域正则化方法,用于SAR复图像的噪声抑制和目标特征提取.文中通过算法设计及其收敛性的研究,保证了该方法的可行性和稳健性.同时,基于正则化方法与广义岭估计的契合之处,提出了一种新的正则化参数的选取方法.理论分析和实验结果均表明,本文方法可操作性强,具有有效的噪声抑制和目标特征稀疏表示寻优功能.     

Blind-velocity SAR/ISAR imaging of a moving target in a stationarybackground

A synthetic aperture radio/inverse synthetic aperture radar (SAR/ISAR) coherent system model and inversion to image a target moving with an unknown constant velocity in a stationary background are presented. The approach is based on a recently developed system modelling and inversion principle for SAR/ISAR imaging that utilizes the spatial Fourier decomposition of SAR data in the synthetic aperture domain to convert the SAR system model's nonlinear phase functions into linear phase functions suitable for a computationally manageable inversion. It is shown that SAR/ISAR imaging of a moving target can be converted into imaging the target in a stationary squint-mode SAR problem where the parameters of the squint-mode geometry depend on the target's velocity. A method for estimating the moving target's velocity that utilizes a spatial Doppler analysis of the SAR data within overlapping subapertures is presented. The spatial Doppler technique does not require the radar signal to be narrowband, so the reconstructed image's resolution is not sacrificed to improve the target's velocity estimator.     

多角度极化SAR图像散射特征分解及SVM分类

在极化合成孔径雷达（synthetic aperture radar,SAR）图像理解和解译中,地物分类是重要的应用方向之一.为了研究多角度极化SAR图像的地物分类,文中基于极化统计特征差异性顺序,给出了多角度极化分解特征序列构建方法.首先,采用基于Wishart分布的统计量对非各向同性散射中心进行检测,并逐像素生成基于散射特征差异的新序列图像.然后,面向多种极化特征分解模型,提出通用的多角度极化特征一阶差分序列描述方法及编码方法,包括Yamaguchi四分量分解、Krogager分解以及H/A/Alpha分解,得到多维特征参数序列.最后,通过两种方法对比后最终选用支持向量机（support vector machine,SVM）方法对特征序列进行分类.通过机载P波段极化SAR开展360°观测试验,验证了该方法的有效性,并展示出在地物分类方面的应用潜力.     

一种基于压缩感知的稀疏孔径SAR成像方法

 高分辨大场景合成孔径雷达(SAR)成像给数据存储和传输系统带来沉重负担.本文针对条带式SAR成像,提出一种基于压缩感知技术的稀疏孔径SAR成像方法.该方法沿方位向以部分子孔径采样的方式获取降采样的原始数据,然后在距离向采用传统匹配滤波方法实现脉冲压缩处理,在方位向则利用小波基作为场景散射系数的稀疏基,并通过求解最小l₁范数优化问题重构方位向散射系数.该方法在存在多普勒参数误差情况下,能够有效实现多普勒参数估计,具有良好稳健性.仿真和实测数据成像结果表明所提算法在方位向严重降采样条件下仍能够实现无模糊的SAR成像,具有较强的有效性与实用性.     

System-level microwave design projects

The teaching laboratory can be an invaluable component of an undergraduate electromagnetics curriculum. This goal of this article is to illustrate several simple but effective microwave-design laboratory projects, involving both system- and component-level design experiences, based upon radar and wireless communications applications. The projects highlighted include a Doppler radar, a simple synthetic aperture radar (SAR), and wireless links using amplitude and frequency-modulation schemes. Students use modern computer-aided design (CAD) tools, coupled with planar technology     

数字阵列合成孔径雷达

回顾了数字波束形成（DBF）技术与合成孔径雷达（SAR）逐步结合的技术发展进程,讨论了DBF技术在SAR系统的典型应用模式、性能改善和功能提升,分析了DBF SAR系统构成及工程实现的主要技术问题,并提出了相应的解决方案。     

Focused synthetic aperture radar processing of ice-sounder datacollected over the Greenland ice sheet

The authors developed a synthetic aperture radar (SAR) processing algorithm for airborne/spaceborne ice-sounding radar systems and applied it to data collected in Greenland. By using focused SAR (phase-corrected coherent averaging), they improved along-track resolution by a factor of four and provided a 6-dB processing gain over unfocused SAR (coherent averaging without phase correction) based on a point-target analysis for a Greenland ice-sounding data set. Also, They demonstrated that the focused-SAR processing reduced clutter and enabled them to identify bedrock-interface returns buried in clutter. Using focused-SAR technique, they processed data collected over a key 360-km-long portion of the 2000-m contour line of southwest Greenland. To the best of their knowledge, these are the first high-quality radar ice thickness measurements over this key location. Moreover, these ice-thickness measurements have been used for improving mass-balance estimates of the Greenland ice sheet