Full band waveguide turnstile junction orthomode transducer with phase matched outputs

A >40% bandwidth fully scalable turnstile‐based waveguide orthomode transducer having excellent phase performance is described for the WR75 standard rectangular waveguide. Flexible bandwidth tuning is achieved through the use of an interchangeable stepped scattering element. Reduced height waveguide topology provides a simple, compact, and robust design against mechanical tolerances. The intrinsic broadband nature of half‐height E‐plane bends and single‐step power combiners assures high order mode free increased bandwidth in balanced phase operation. The designed orthomode transducer exhibits a return loss better than 23 dB at any port, an insertion loss less than 0.06 dB, and an isolation of 50 dB over the full bandwidth. Moreover, the phase difference between orthogonal polarizations is lower than 0.7° over the band, thus enabling applications where phase‐matched outputs are required. This design has been chosen for the QUIJOTE cosmic microwave background experiment due to its cost‐effective, compact design, and high‐quality performance as well as being readily scalable to the WR51 and WR28 waveguide bands. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

Simultaneous measurements of normal spectral emissivity by spectral radiometry and laser polarimetry at high temperatures in millisecond-resolution pulse-heating experiments: Application to molybdenum and tungsten

Spectral radiometry and laser polarimetry are two independent techniques for the measurement of spectral emissivity of materials. In this paper, a high-speed system is described for the rapid measurement of normal spectral emissivity of a specimen based on the simultaneous utilization of the two techniques. One of the goals of this work to ascertain the accuracy of the laser polarimetry technique in measurement of normal spectral emissivity at high temperatures. To accomplish this goal, the normal spectral emissivities, in the vicinity of 0.633m, of molybdenum and tungsten were measured by the two techniques over the temperature range 2000 to 2600 K. The results obtained by the two techniques are in agreement within 1%. The total uncertainty (two-standard deviation level) in measurement of emissivity by either spectral radiometry or laser polarimetry technique is estimated to be not more than + 2%.     

雷达多视极化检测器性能对比分析

雷达极化检测器性能对比分析可为极化检测器的工程设计提供重要参考,但目前针对其检测性能的评估理论仍不完善,尤其缺乏多视情形下的分析结果.文章以极化雷达多视协方差矩阵的复Wishart分布为基础,采用蒙特卡洛仿真与理论推导得到了7种经典极化检测器的多视检测性能曲线,并构建曲线下面积（Area Under Curve,AUC）指标对检测性能进行自动排序.仿真实验结果表明4视处理时的检测性能排序为:最优极化检测器＞极化白化滤波器≈似然比检验＞最佳能量检测器＞极化匹配滤波器≈多视极化能量检测器＞单通道检测器.理论推导结果表明,具有线性加权形式的极化检测器,其检测与虚警概率都具有两类等价的数学表达式,其中基于Gamma函数的表达式可用于快速计算出恒虚警检测门限.最后采用全极化合成孔径雷达实测数据,对上述结论进行了验证.     

A novel operation mode for spaceborne polarimetric SAR

A novel operation mode for spaceborne polarimetric SAR,named polarization space-division adding polarization code-division (PSD-PCD) operation mode,is proposed in this paper through combining polarimetric SAR with elevation digital beam-forming (DBF) on receive.In a pulse repetition interval the up-chirp LFM sub-pulse is transmitted with horizontal polarization antenna,and with some delay the down-chip LFM subpulse is transmitted with vertical polarization antenna to realize code division.After every sub-ap...     

基于目标相干散射特性的极化SAR图像分解分类方法

基于对目标极化相干散射特性的分析,我们改进了Cloude和Lee等人提出的极化特征分解及非监督分类算法,以适应高分辨率极化SAR图像中复杂的地物细节特征。实验结果表明,相对传统方法,该方法更能够保留目标的细节特征、准确地估计目标极化相干矩阵,因此能够获得更好的分解分类结果。另外,该方法还具有较好的收敛性和鲁棒性。     

Orientation Mechanism Based on Insect Polarization Navigation

A method to determine the direction angle for bionic navigation is proposed. In order to do it,observation models of polarized light were obtained through full-sky imaging polarimetry,and the symmetry line (solar meridian) was detected firstly; then the angle between solar meridian and the system moving direction was derived from simultaneous model,and the relative position of the sun was calculated by astronomical knowledge; finally,the direction angle for bionic navigation was evaluated by utilizing sun a...     

目标散射的去取向理论和应用(一)去取向理论

提出目标全极化散射的去取向分析理论,通过对目标散射矢量的变换将目标旋转到一个确定的取向,使得原本取向不同、但特征相同的目标能具有相同的散射信息,凸现目标本身特性.对于SAR图像的像素中随机分布目标的目标主散射矢量作去取向分析,凸现该像素中随机分布目标的平均特性.第一部分推导了目标散射矢量的去取向变换公式,并解析定义参数u,v,ω,ψ,由单个或随机分布非球形粒子的全极化散射数值分析了ψ,u,v及熵H的表征意义.在第二部分将用(u,v,ψ)-H设计地表无监督分类模型,先用u,v,H将地表分类不同类别,再对每种类别由ψ分析其取向情况.该分类方法应用于中国广东省惠阳地区的SIR-C数据及加拿大Bo-real地区的AirSAR数据,得到较好的地表分类结果,与传统的α-H方法对比,分类性能明显提高.     

基于特征选择与GOPCE的舰船检测方法

原始的广义相对最优极化(GOPCE)中,通过最大化目标与背景极化参数融合结果的比值,而求取极化参数的最优系数向量,但没有考虑参数融合结果中目标与杂波的分布。为提高基于极化合成孔径雷达图像的舰船目标检测性能,提出了一种基于极化特征选择及改进 GOPCE的目标检测方法。首先提出了一个改进的优化准则,同时考虑了最大化信杂比与最小化目标与杂波分布的方差。基于改进的优化准则,选择了3个最优极化特征,并求解对应的最优系数向量,获取了目标与背景区分度更大的融合图像。实验结果表明,该方法有效提高了目标的检测性能。     

利用SVM的极化SAR图像特征选择与分类

该文提出一种新的利用SVM的特征选择算法,并将其融入到极化SAR图像分类过程中,构成一种新的基于SVM的分类方法。其中,特征选择算法利用支持向量个数作为特征评估指标,并以顺序后退法作为搜索策略。真实数据的实验结果表明,该分类方法能有效降低SVM分类器对自身参数的敏感性,与利用原始特征集和经典的RELIEF-F的分类方法相比,该方法能以更少(或相当)的特征个数,在更广泛的SVM参数取值范围内获得更高的分类精度。