Physics‐based spectral sharpening through filter‐chart calibration

The spectral overlap of color‐sampling filters increases errors when using a diagonal matrix transform, for color correction and reduces color distinction. Spectral sharpening is a transformation of colors that was introduced to reduce color‐constancy errors when the colors are collected through spectrally overlapping filters. The earlier color‐constancy methods improved color precision when the illuminant color is changed, but they overlooked the color distinction. In this article, we introduce a new spectral sharpening technique that has a good compromise of color precision and distinction, based on real physical constraints. The spectral overlap is measured through observing a gray reference chart with a set of real and spectrally disjoint filters selected by the user. The new sharpening method enables to sharpen colors obtained by a sensor without knowing the camera response functions. Experiments with real images showed that the colors sharpened by the new method have good levels of color precision and distinction as well. The color‐constancy performance is compared with the data‐based sharpening method in terms of both precision and distinction. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 564–576, 2015     

基于解相干的改进MUSIC算法DOA估计

MUSIC算法是一种子空间分解算法。在非相干的情况下,经典MUSIC算法能准确进行波达方向（DOA）估计,但当信号源在相干的情况下时算法失效。在对经典MUSIC算法进行理论分析研究的基础上,对其阵元接收数据阵做相应变换,得到共轭重构后的协方差矩阵,通过特征值分解再进行DOA估计。就经典的MUSIC和改进算法的DOA估计性能进行了仿真分析。结果表明,改进后的算法在信号源相干的情况下也能精确地估计信号的波达方向。     

近似解相关多用户检测算法的FPGA实现

简要介绍了近似解相关 (AD)多用户检测算法 ,通过对算法的分析 ,建立了该算法的实现框架 ,给出了用 FPGA技术实现该算法模块的详细方案 ,并从实际硬件量的角度分析了其复杂度。最后以DSP2 6 2 1EA评估板为基本硬件平台对该方案进行测试 ,测试结果和理论分析基本吻合 ,说明了该方案是可行的。     

Monitoring mine collapse by D-InSAR

For harmful ground collapse and its special deformation characteristics,which causes SAR images to lose coherence,InSAR technology cannot be applied in monitoring surface collapse in mining areas.We took the Shenmu mining area in northern Shaanxi province as an example to study subsidence in mining areas and proposed an interpolated multi-view processing method.The results show that this method can improve the detectable deformation gradient to a certain extent and can become a good reference value for monitoring large scale gradient deformation.We also analyzed the rules for temporal decorrelation in mining.     

干涉SAR的基线干损和极限基线分析

基线是干涉SAR工作原理中的关键概念。它反映干涉测高原理的本质，既是相干性的来源，也是导致基线干损的根源，它还用极限基线给出了干涉存在的条件。本文详细分析了基线、基线干损、极限基线，以及它们之间的关系，并引入新一个的概念；相干角，来更加准确和深入地分析上述关系，指出了它们在频域和图像域中的表现。     

A Combined Antenna Array and Multi-User Detection DS-CDMA Receiver in Single-Path and Multi-Path Fading Channels

An adaptive antenna array is incorporated into a decorrelatingmulti-user detector to effectively increase the DS-CDMA system capacity.Capacity improvement is due to beamforming gain, spatial diversity gain(assuming large angle spread), and the decorrelating effect. Thereceiver has been analyzed for the cases of sufficiently andinsufficiently spaced receiving antennas. The receiver consists of afront-end beamformer for every user in the cell and has knowledge of allusers' signature sequences. The beamformer estimates the desired userchannel vector, enhancing its signal and reducing the co-channelinterference from other directions. The multi-user detection, exploitingknowledge of other users, rejects those interferers whose arrival anglesare close to that of the desired user. The average uncoded Bit ErrorRate (BER) as a function of the number of in-beam active users, theaverage antenna Signal-to-Noise Ratio (SNR), and the number of receivingantennas is examined in both single-path and multi-path Rayleigh fadingchannels. Analysis shows an increase in system capacity proportional tothe number of receiving antennas.     

精确提取InSAR时间去相关分量的方法

提出了一种干涉合成孔径雷达(InSAR,Synthetic Aperture Radar Interferometry)回波信号时间去相关分析的新方法,该方法主要包括三个步骤:采用自适应区域增长算法(IDAN,Intensity-Driven Adaptive Neighborhood)估计所有干涉子集的相干性;利用迭代最小二乘去除估计量偏差;采用相干性分解技术对无偏样本相干性进行分离,获得精确的时间去相关分量.以美国南加州洛杉矶地区的ENVISAT ASAR数据集为例,对新方法和现有方法进行了比较研究.结果表明,新的融合算法能够获得更加可靠、精度更高的时间去相关分量,并具有非阈值和近乎完全的自适应性.本文的研究将有利于改善与时间相干性有关的地球物理参数反演,也有利于地表变化周期性和随时间变化的气候环境实时监测等.     

探地雷达回波信号的特征提取和分类

探地雷达的回波信号具有非平稳特征.为实现非平稳信号的检测和分类,采用了二进小波变换、主分量分析与Fisher线性判别分析和前馈多层感知器分类器分别对探地雷达回波信号进行小波分解、去相关与特征选择和分类.实验结果表明,该算法具有很好的分类效果.     

基于迁移策略的分布式遗传算法多用户检测器

针对简单遗传算法多用户检测器的收敛速度慢和“早熟”问题,利用解相关算法的抗多址干扰能力和分布式遗传算法的快速全局寻优优势,提出了一种基于迁移策略的分布式遗传算法解相关多用户检测器。计算机仿真结果表明:该多用户检测器的检测性能明显优于简单遗传算法多用户检测器和解相关多用户检测器,更易于实现。     

基于非线性空时编码系统的自适应信道估计

用非线性分组编码，在时间选择性衰落信道环境下，将基本LMS自适应算法推广到对二维空时编码信号的权矩阵自适应迭代估计，分析了对输入信号序列编码所生成的非线性编码矩阵之间的相关性，运用解相关LMS自适应算法对衰落信道进行估计．在不同噪声情况下，根据估计信道和噪声统计量，推导了对非线性编码进行解码的最大似然决策方法．仿真试验表明，采用扩展LMS算法和解相关LMS算法跟踪时变衰落信道响应具有较强的鲁棒性和快速收敛性，非线性空时分组编码系统相对干线性编码系统提高了编码系统性能，运用最大似然决策方法进行解码降低了系统误码率．