基于漏波天线的分布式微波辐射计

为了缓解传统实孔径微波辐射计中性能指标与体积、重量间的矛盾, 解决综合孔径微波辐射计中高空间分辨率以系统结构、信号处理复杂度高为代价的难题, 提出了一种基于漏波天线的分布式微波辐射计系统。首先, 介绍了系统总体方案, 包括漏波天线和接收机方案; 其次, 详细分析了系统的关键指标——角分辨率和系统灵敏度, 并介绍了定标方案; 最后, 对系统进行建模并仿真分析。结果表明, 所设计的系统结构简单、复杂度较低、信号处理简单; 通过对系统进行建模仿真, 反演出的亮温值和真实亮温值误差很小。该系统可以作为一种新型的微波辐射计系统重点发展。     

毫米波超综合孔径辐射计成像技术

在深入了解超综合孔径辐射计的工作原理和成像性能的基础上,首次推导了超综合孔径辐射计在近场条件下采用傅氏反演方法进行成像的基本理论,并给出了超综合孔径辐射计的空间分辨率和灵敏度公式。随后,研制了由两个天线单元组成的最简单的毫米波超综合孔径辐射计原理样机,并分别用傅氏反演法和传统的匹配滤波法成功地反演得到了一维噪声点源的图像。实验结果验证了傅氏反演方法的正确性以及毫米波超综合孔径辐射计的成像能力,最后对超综合孔径辐射计和干涉式综合孔径辐射计的工作特点进行了比较。     

微波辐射计中异步量化技术的可行性分析

在微波综合孔径辐射计的数字相关处理系统中,多通道高速模数转换是关键环节。传统量化技术都采用具有同步逻辑的模数转换器,其性能优越,但消耗的系统资源相对较大,无法适应实际星载、机载等特殊环境要求。提出的异步量化技术能极大地简化系统设计,带来资源的节约,使得大规模的微波综合孔径辐射计系统可向实用方向发展。重点比较同步量化和异步量化技术在微波综合孔径辐射计中的差异,从理论上阐述异步量化技术引入的可行性,并通过Matlab建模仿真给出仿真结果验证理论分析的正确性。     

利用数字滤波技术的多视角分集数字图象重建

微波衍射层析是从多视角的微波衍射场值中推出介质体内部结构之分布,该方法对介质体内的折射指数之变化非常敏感,因而可用于测量介质体的介电参数之变化和生物医学上软组织之成象。在满足一定的条件下该方法成象最佳分辨率是照射波的波长之半。实际上很难达到这样高的分辨率,现有两种措施来提高成象的分辨率:一是微波层析,用多视角测量数据反演成的数字图象进行线性组合;二是用数字滤波技术和滤波逆传播算法来提高图象重建的质量。本文最后为证实上述方法的可行性,建立起X波段微波成象测量系统,并得到空气中介质体的实验结果。     

毫米波合成孔径辐射计末制导技术研究

针对弹上空间小且毫米波器件成本高,提出了把近程毫米波合成孔径辐射计被动成像技术应用于寻的末制导,并给出一种高性能制导系统。该系统采用二维最小冗余线性阵列天线,由7个接收阵元组成,可获得分辨率为6×6的像,大大节约了弹上资源和成本。同时引入了四阶累积量成像算法,不仅可以扩展孔径,而且使系统具有良好的抗噪能力。合成孔径辐射计可以即时成像,不需要扫描,满足制导的实时性要求。通过仿真表明,该系统在近距离时具有良好的探测性能。     

超综合孔径辐射计系统研究

分析了已有的超综合孔径分辨率表达式的不足之处,提出了更准确的空间分辨率表达式。首先将最小冗余线性阵列应用于超综合孔径天线系统,增加了超综合孔径天线系统的小基线部分,在空间频率覆盖方面表现为扩大了系统对低频部分的覆盖,从而达到抑制旁瓣,改善成像效果的目的。最后,通过仿真实验证明了改进的超综合孔径系统的性能相比于原始超综合孔径系统有很大的提高,主要表现在：一是天线阵列方面,阵列因子的旁瓣更低,主瓣更窄;二是成像方面,点源成像效果更好。     

微波毫米波辐射计宽带亮温定标系统研究

构建了国内首套微波毫米波辐射计宽带亮温定标系统,该系统由宽带标准黑体定标源、Dicke式标准辐射计、空间法黑体定标源发射率测量转台、高精度控温和测温装置组成。使国内具备了10 GHz~220 GHz频段辐射计校准、黑体定标源输出亮温值校准、微波亮温定标过程不确定度分析能力的实验研究平台。最后基于建立的微波辐射计定标系统亮温传递模型,给出了更为细致的随定标环境温度变化的微波亮温系统测量不确定度分析结果。     

基于多层次MRF的多分辨率图像融合算法

图像数据融合的目的是恢复出分布在不同图像中的有用信息。在多层次MRF模型的基础上提出了一种多分辨率图像融合算法。该算法将定义在多层次图结构上的非线性因果Markov模型与贝叶斯SMAP(sequenti almaximumaposteriori)准则结合起来 ,弥补了MAP(maximumaposteriori)准则在多层次图结构上计算不合理的缺陷。实验部分中 ,对两种算法用于被高斯白噪声污染的合成图像的恢复结果进行了比较 ,并将该算法用于实际的多分辨率航空图像。实验结果表明了该算法的优越性。     

微波辐射探测仿真系统并行处理研究

对综合孔径微波辐射探测仿真系统进行了并行化研究.介绍了综合孔径微波辐射探测仿真系统各模块的实现方式,分析了各模块的计算复杂度,给出数据处理的瓶颈,并利用OpenMP技术对仿真系统进行并行化处理.实验结果显示,仿真速度提高3倍以上,并行效率达到70%以上,具有较高的加速性能.     

基于Curvelet变换的多光谱图像与全色波段图像融合

为了使融合后的多光谱Ms图像在保持原始Ms图像光谱特性的同时,最大可能地提高空间分辨率,提出了一种基于Curvelet变换的遥感影像融合算法。该算法首先采用Curvelet变换提取全色波段Pan图像的空间细节信息,然后采用基于内容的注入模型将提取的空间信息局部调整后添加到各波段Ms图像中去,得到具有高空间分辨率的Ms图像。算法在有效避免融合后Ms图像光谱失真的同时,能够显著提高融合图像的空间质量。采用IKONOS卫星遥感影像进行了仿真实验,实验结果结果表明,该算法在光谱保留和空间质量提高方面比传统的基于小波变换融合算法具有更高的性能。     

Super-resolution processing of passive millimeter-wave images based on conjugate-gradient algorithm

This paper designs a 3 mm radiometer and validate with experiments based on the principle of passive millimeter wave (PMMW) imaging. The poor spatial resolution, which is limited by antenna size, should be improved by post data processing. A conjugate-gradient (CG) algorithm is adopted to circumvent this drawback. Simulation and real data collected in laboratory environment are given, and the results show that the CG algorithm improves the spatial resolution and convergent rate. Further, it can reduce the ringing effects which are caused by regularizing the image restoration. Thus, the CG algorithm is easily implemented for PMMW imaging.     

修正的垂直航向运动补偿算法

机载毫米波高分辨合成孔径雷达(synthetic aperture radar,SAR)对运动补偿的精度要求很高。当前运动补偿算法在运动误差或斜视角大时对毫米波高分辨斜视SAR垂直航向运动误差补偿效果不明显。文中提出了一种修正的垂直航向运动补偿算法,通过先补偿包络和相位,然后产生一个附加的沿航向速度, 该附加沿航向速度和原始的沿航向运动误差一起补偿。毫米波高分辨斜视SAR仿真结果表明,所提方法在30°斜视角时仍能较好补偿垂直航向运动误差,补偿效果显著优于已有算法, 实测数据成像结果也进一步验证了所提方法的正确性和有效性。     

逆合成孔径成像激光雷达系统建模及成像仿真

逆合成孔径成像激光雷达能突破传统成像激光雷达扫描体制的限制,实现对运动目标实时高分辨成像,对运动目标的探测与识别具有重要意义。分析了逆合成孔径成像激光雷达的高分辨成像原理,并综合考虑系统结构、大气衰减、背景噪声、目标散射特性等多方面因素,建立了仿真模型,对成像流程与分辨能力进行了详细分析。仿真实验证明了逆合成孔径成像激光雷达具有优于微波波段逆合成孔径雷达的成像效果以及文中建立的仿真模型的有效性。     

Novel imaging methods of stepped frequency radar based on compressed sensing

The theory of compressed sensing (CS) provides a new chance to reduce the data acquisition time and improve the data usage factor of the stepped frequency radar system. In light of the sparsity of radar target reflectivity, two imaging methods based on CS, termed the CS-based 2D joint imaging algorithm and the CS-based 2D decoupled imaging algorithm, are proposed. These methods incorporate the coherent mixing operation into the sparse dictionary, and take random measurements in both range and azimuth directions to get high resolution radar images, thus can remarkably reduce the data rate and simplify the hardware design of the radar system while maintaining imaging quality. Experiments from both simulated data and measured data in the anechoic chamber show that the proposed imaging methods can get more focused images than the traditional fast Fourier transform method. Wherein the joint algorithm has stronger robustness and can provide clearer inverse synthetic aperture radar images, while the decoupled algorithm is computationally more efficient but has slightly degraded imaging quality, which can be improved by increasing measurements or using a robuster recovery algorithm nevertheless.     

基于MIMO-ISAR的弹道目标结构参数估计方法

传统的单站逆合成孔径雷达(inverse synthetic aperture radar, ISAR)成像为实现方位向的高分辨,往往会增大成像时间,但对于高速运动的弹道目标而言,此方法并不适用。针对这一问题,提出利用多输入多输出逆合成孔径雷达(multiple input multiple output ISAR, MIMO-ISAR)在空间上的多分布来达到时间上积累的效果。在得到多通道回波信号后,利用时频图和时间距离像对弹道目标锥顶散射点进行匹配。然后根据锥顶散射点信息对多幅ISAR像进行配准融合,得到一幅高分辨的融合ISAR像。最后利用不同雷达视线下的目标投影长度和目标几何参数之间存在的映射关系,反演出弹道目标的几何结构参数。通过仿真结果可以验证算法的有效性。     

Super-resolution processing of passive millimeter-wave images based on adaptive projected Landweber algorithm

Passive millimeter wave(PMMW)images inherently have the problem of poor resolution owing to limited aperture dimension.Thus,efficient post-processing is necessary to achieve resolution improvement.An adaptive projected Laadweber(APL)super-resolution algorithm using a spectral correction procedure,which attempts to combine the strong points of all of the projected Landweber(PL)iteration and the adaptive relaxation parameter adjustment and the spectral correction method,is proposed.In the algorithm,the PL iterations are implemented as the main image restoration scheme and a spectral correction method is included in which the calculated spectrum within the passband is replaced by the known low frequency component.Then,the algorithm updates the relaxation parameter adaptively at each iteration.A qualitative evaluation of this algorithm is performed with simulated data as well as actual radiometer image captured by 91.5 GHz mechanically scanned radiometer.From experiments,it is found that the super-resolution algorithm obtains better results and enhances the resolution and has lower mean square error(MSE).These constraints and adaptive character and spectral correction procedures speed up the convergence of the Landweber algorithm and reduce the ringing effects that are caused by regularizing the image restoration problem.     

Circular SAR processing using an improved omega-k type algorithm

An improved circular synthetic aperture radar (CSAR) imaging algorithm of omega-k (ω-k) type mainly for reconstructing an image on a cylindrical surface is proposed. In the typical CSAR ω-k algorithm, the rage trajectory is approximated by Taylor series expansion to the quadratic terms, which limits the valid synthetic aperture length and the angular reconstruction range severely. Based on the model of the CSAR echo signal, the proposed algorithm directly transforms the signal to the two-dimensional (2D) wavenumber domain, not using approximation processing to the range trajectory. Based on form of the signal spectrum in the wavenumber domain, the formula for the wavenumber domain interpolation of the ω-k algorithm is deduced, and the wavenumber spectrum of the reference point used for bulk compression is obtained from numerical method. The improved CSAR ω-k imaging algorithm increases the valid synthetic aperture length and the angular area greatly and hence improves the angular resolution of the cylindrical imaging. Additionally, the proposed algorithm can be repeated on different cylindrical surfaces to achieve three dimensional (3D) image reconstruction. The 3D spatial resolution of the CSAR system is discussed, and the simulation results validate the correctness of the analysis and the feasibility of the algorithm.     

Super-resolution processing of passive millimeter-wave images based on adaptive projected Landweber algorithm

Passive millimeter wave （PMMW） images inherently have the problem of poor resolution owing to limited aperture dimension. Thus, efficient post-processing is necessary to achieve resolution improvement. An adaptive projected Landweber （APL） super-resolution algorithm using a spectral correction procedure, which attempts to combine the strong points of all of the projected Landweber （PL） iteration and the adaptive relaxation parameter adjustment and the spectral correction method, is proposed. In the algorithm, the PL iterations are implemented as the main image restoration scheme and a spectral correction method is included in which the calculated spectrum within the passband is replaced by the known low frequency component. Then, the algorithm updates the relaxation parameter adaptively at each iteration. A qualitative evaluation of this algorithm is performed with simulated data as well as actual radiometer image captured by 91.5 GHz mechanically scanned radiometer. From experiments, it is found that the super-resolution algorithm obtains better results and enhances the resolution and has lower mean square error （MSE）. These constraints and adaptive character and spectral correction procedures speed up the convergence of the Landweber algorithm and reduce the ringing effects that are caused by regularizing the image restoration problem.     

基于超材料天线的超分辨关联成像的改进

近几年新型的超材料天线相比于传统的相控阵有着多方面的优势，但是由于超材料天线的正常工作必须要有变频信号的辅助，而目前的超分辨成像算法没有补偿由于频率变动产生的误差，导致成像质量严重下降甚至不能成像。此外，回波信号中频率的变动和不同的距离互相耦合，导致不能简单的直接补偿掉误差相位。因此，提出一种基于压缩感知的超分辨关联成像算法的改进方法，将基于压缩感知的超分辨关联成像算法和超材料天线结合在一起，实现了低系统复杂度、低成本、高分辨率的微波关联成像。通过设计仿真实验证实了所提方法的正确性，并且验证了此方法对于二维和三维成像均可以处理。