A novel dual‐band ring coupler based on dual‐band phase inverter

A novel dual‐band ring coupler based on dual‐band phase inverter is proposed. And two types of dual‐band phase inverters (Type I and Type II) are designed in this article. The design method of dual‐band ring coupler is simpler than the traditional ways like replace the single‐band λ/4 transmission line with dual‐band λ/4 transmission line. Its main idea is replacing the wide‐band phase inverter with dual‐band phase inverter. Two dual‐band ring couplers (0.9/2.88 and 0.9/2.43 GHz) using the two types of dual‐band phase inverter, respectively, are simulated and measured. The measured results validate the proposed method.     

高光谱遥感图像波段选择研究进展综述

高光谱成像遥感技术可获取地物的光谱、辐射和空间信息,在国民经济的各个领域得到广泛的应用.但其狭窄的波段间距带来丰富光谱信息的同时,也带来了信息冗余,增加了数据处理的难度.因此,高光谱遥感数据在进行实际应用前,需要进行波段选择并提取光谱特征,降低数据维数.对高光谱遥感图像的波段选择研究进展进行了综述,在分析、归纳波段选择...     

ZY-3东北界河地区影像特征分析

对资源三号卫星(ZY\|3)数据影像特征进行科学分析与应用研究,为ZY\|3数据优化利用与广泛应用提供可靠的借鉴。分别从单波段数据信息量、多波段数据相关性及各波段数据地类间可分性分析原始数据,ZY-3多光谱数据以band4信息量最丰富,与其他波段相关性小,地类间光谱距离最大,其次是band3与band2,而band1各项指标最差。将band4、3、2组合后,进行多光谱数据与全色数据分辨率融合,进一步分析融合后数据,对于土地覆被调查,主成分分析影像视觉最好,而乘积方法信息量最丰富。
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Factor analysis approach for composited ASTER band ratios and wavelet transform pixel-level image fusion: lithological mapping of the Neoproterozoic Wadi Kid area,Sinai, Egypt

In this study, we have adopted an approach for objective optimization of the selection of band ratios in forming Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) band ratio composites, based on factor analysis loadings and specific variances. The factor loadings and specific variances of all 72 possible spectral band ratios of the visible and near infrared (VNIR) and the short-wave infrared (SWIR) of ASTER data from Wadi Kid, southeastern Sinai Peninsula, Egypt, were utilized to construct two separate rankings of band ratios in an ascending manner in order to determine the best ASTER band ratio combinations for lithological mapping in the study area. Two ASTER band ratio composites ((band 6/band 3–band 1/band 3–band 9/band 5) and (8/6–8/7–4/7) in blue–green–red (BGR)) were built, based on the rankings of factor loadings and specific variances, respectively. These two composites were fused together based on a discrete wavelet transform (DWT) decomposition, which enables decomposition of an image into (high-pass) details and (low-pass) approximations at various levels of resolution, resulting in improved lithological discrimination of granitic and meta-sediments rock units and a reduction in the BGR imprints of topographic reliefs.     

Spot5影像统计分析及最佳组合波段选择

遥感影像特征分析是影像融合和解译的基础,而对遥感数据源各个波段进行定量分析是图像融合的前提。本文以SPOT5为遥感数据信息源,在湖南省资兴市天鹅山林场进行了图像特性和波段组合的实验研究。研究主要采用了典型地物的光谱数据采集分析和遥感数据定量分析相结合的方法,计算出各波段之间的熵、相关系数和协方差。研究结果表明:SPOT5各波段的标准差大小顺序为:波段3>波段4>波段2>波段1,熵值的大小顺序则为:波段4>波段1>波段2>波段3;波段3与波段4的协方差最大,而且两波段又处在红外区域,说明红外波段之间独立性较强;从光谱辐射仪采集的数据来看,水体、草地、裸土地的光谱反射率就有很大的差异性。乔木树种的光谱反射率在可见光区域内非常接近,在红外———近红外区域内具有一定的差异,红外———近红外区域波谱对林业遥感研究具有极其重要的意义;利用联合熵和最佳指数方法确定了最佳波段组合为1(R)4(G)3(B)波段。     

利于目标识别的高光谱影像波段选择方法

遥感图像数据量大、波段数目多、信息冗余多等特点给图像的进一步解译带来了困难.为了解决这个问题,在使用相邻波段间的互信息量与全部波段间的相关系数矩阵相结合的方法对波段进行分组的基础上,运用波段指数和光谱角制图算法,提出了针对某个感兴趣目标的波段选择方法.首先对校正后的全部有效波段进行分组(划分子空间),然后提取出各个子空间中指数最大的波段,最后依据地物光谱可分性选取最佳的波段组合.通过试验及与常见的波段选择方法进行比较的结果显示,所提方法目标提取效果明显.     

多进制小波变换及其在影像分析中的应用

首先简要地介绍了多进制小波基本理论并分析了其变换特征,然后阐述了其在影像缩小、边缘检测中的应用。     

A novel reconfigurable FSS applied to the antenna radar cross section reduction

Active reconfigurable FSS using pin diode for the antenna radar cross section (RCS) reduction is proposed. The reconfigurable FSS reflector is presented in this article. The proposed reconfigurable FSS reflector is able to be switched between band‐stop FSS with OFF‐state diodes and band‐pass FSS with ON‐state diodes around 3.8 GHz. The using of band‐stop FSS reflector corresponds to the out‐band RCS reduction during radar operating, and the using of band‐pass FSS reflector corresponds to the in‐band RCS reduction during radar nonoperating. Therefore, the state of the antenna scattering can be switched according to the working state of radar. The results show that the reconfigurable FSS reflector can contribute to the switchable RCS reduction between in band and out band of the antenna. The radiation performance of the antenna is preserved when the diodes are ON state. The monostatic RCS of the antenna with FSS reflector with ON‐state diodes can be reduced more than 25 dB at operating band, and the out‐band RCS reduction can be achieved with ON‐state diodes.     

Mode investigation of parasitic annular ring loaded dual band coplanar waveguide antenna with polarization diversity characteristics

This document presents a dual band dual polarized coplanar waveguide (CPW) antenna with single port feed. Lower resonating band is circular polarized, while the upper band is linear polarized. A novel concept of realizing dual polarization by suppressing the undesired modes is introduced in this work. Orthogonal Even/Odd modes are excited at lower band and a phase difference of 90° is maintained between them. Hence, circular polarization behavior is realized for lower operating band. For upper band, Odd mode is suppressed by introducing step shaped modifications in the ground plane at left side of the feed line, resulting in linear polarized upper band. Dual band nature of the antenna is confirmed by 10 dB impedance bandwidth extending from 3.91‐5.31 GHz to 7.51‐8.72 GHz. Circular polarized nature of lower band is confirmed by enclosure of lower band by 3 dB axial ratio bandwidth extending from 4.01 to 5.59 GHz. Advantages of proposed antenna involves the use of single port feed for generating dual polarization performance along with compact antenna size.(30 × 30 × 1.6 mm³).     

高光谱影像波段选择算法研究

基于高光谱影像数据的特点,分析了高光谱数据的降维方法。着重探讨了波段选择的若干算法:熵及联合熵、最佳指数因子、自动子空间划分、自适应波段选择、波段指数和最优波段指数等算法。分析了各种算法的有效性、局限性和计算复杂度,并针对波段指数的不足,设计了最优波段指数(OBI)波段选择新算法。最后通过具体的试验,验证了各种算法的性能。     

A Multiband antenna using plus‐shaped fractal‐like elements and stepped ground plane

A multiband planar symmetrical plus‐shaped fractal monopole antenna with stepped ground plane is presented in this study. Measured results show that the proposed antenna operates with 10 dB return loss bandwidths from 1.630 to 1.88 GHz and from 4.5 to 8.5 GHz covering The Global System for Mobile Communications (GSM) 1800 MHz 2G spectrum band, 4400 to 4900 MHz 5G spectrum band adopted by Japan and China for future 5G communication in sub‐6 GHz band, 5.15 to 5.925 GHz LTE band 46, WLAN IEEE 802.11 y/a/h/j/n/P bands, and 5.8 to 7.707 GHz military band. The antenna gain varies between 1.73 and 1.97 dB in lower band and 3.6 to 5.05 dBi in upper band with radiation efficiencies more than 90% in lower band and more than 80% in upper band. The antenna has more than 64 and 28 dB isolations between the copolar and cross‐polar radiation patterns in the lower and upper bands, respectively.     

Implementation of hybrid fractal metamaterial inspired frequency band reconfigurable multiband antenna for wireless applications

In the present paper authors propose the design and analysis of a hepta band metamaterial inspired octagonal shape antenna using hybrid fractals for wireless applications. Multiband characteristics in the designed antenna is accomplished by introducing of slotted octagonal shape radiating part with hybrid fractal form of Moore curve and Koch curve and two SRR cells. The frequency band reconfigurability is obtained with aid of PIN diodes placed inside the strips connected between Moore curve (fused with centered Koch curve) and feedline. During ON mode of PIN diode antenna operates at seven microwave frequency S‐band WiMAX (3.4~3.69 GHz—IEEE 802.16e)/Lower C‐band terrestrial fixed and mobile broadband application (4.25~4.76 GHz)/C‐band WLAN (5.15~5.35/5.75~5.825 GHz—IEEE 802.11a] (5.4~5.9 GHz)/Lower X‐band Earth exploration‐satellite service ITU region 2 (7.9~8.4 GHz)/Upper X‐band Amateur satellite operating band (10.45~10.50 GHz)/Lower Ku‐band Radar communication application (13.25~13.75 GHz)/Middle Ku‐band Geostationary satellite service (14.2~14.5 GHz) covering various wireless applications. Proposed design exhibit hexa/hepta band features during OFF/ON mode of PIN diode. An acceptable gain, stable radiation characteristics, and good impedance matching are observed at all the resonant frequencies of the proposed structure.     

A printed dual‐band dipole filtenna with flexible frequency ratio and improved band‐notched performance

A printed dual‐band dipole filtenna with flexible frequency ratio and improved band‐notched performance is proposed. It consists of a driven dipole and three parasitic elements. For the driven dipole with short and long arms, a radiation null is found between two passbands, which achieves a band‐notched filtering characteristic. Two parasitic elements are introduced to enhance the passband bandwidth and an additional parasitic element is utilized to improve the band‐notched performance. In addition, the characteristics of the proposed design including flexible frequency ratio, independent controllable operating frequency, and controllable band‐notched bandwidth have also been demonstrated. A filtenna prototype is fabricated and tested. Measured results show that a fractional bandwidth of 21.1% and 18.1% is obtained in the lower and upper passbands, respectively. The measured efficiency is 84% in the lower band and 74% in the upper band but the efficiency sharply decreases to about 13% within the notched band.     

基于多进制小波变换的图象放大方法

多进制小波是近几年发展的小波分析理论的一个新分支，为了更好地进行图象的放大，提出了一个基于多进制小波变换的图象放大方法，并用三进制小波变换进行了图象的放大试验，通过与常用的插值放大方法进行比较的结果表明，基于多进制小波放大的图象能较好地保持原来图象的特征，优于一般的插值放大方法。     

Multi‐band pattern reconfigurable Yagi‐Uda antenna

In this study, novel designs of single‐band and tri‐band pattern reconfigurable antennas are proposed. The design of single‐band pattern reconfigurable antenna is accomplished by the use of varactor diodes with the parasitic elements placed on both sides of the driven conventional printed dipole antenna. By tuning the capacitance of varactor, the antenna operates in four different configurations of radiation pattern which include bi‐directional end‐fire, broadside, and uni‐directional end‐fire radiation patterns. The tri‐band pattern reconfigurable antenna design is achieved by the use of parasitic elements on both sides of a tri‐band driven dipole antenna. Dual‐band LC resonators are used as loading elements along the arms of printed dipole to get two lower order modes in addition to the reference dipole mode, resulting in a triband operation of the driven element. The electrical lengths of the parasitic elements with respect to the tri‐band driven element are controlled by suitably embedding varactor and PIN diodes with them. The proposed tri‐band antenna operates in ten different configurations of radiation patterns in the three operating bands. Fully functional prototypes of single‐band and tri‐band pattern reconfigurable antennas along with the DC bias networks have been fabricated to validate the results obtained in simulation.     

Miniaturized coplanar waveguide‐fed disk monopole antenna for ultra‐wideband applications with improved wireless local area network band rejection

In this article, we first propose a miniaturized coplanar waveguide‐fed disk monopole antenna with overall size of 14 mm × 22 mm. Measurement results show that the antenna has an ultrawide impedance bandwidth from 3 to 12 GHz and omnidirectional radiation pattern. Next, we introduce two U‐shaped slots in the ground plane of the antenna to provide an improved band rejection in the wireless local area network frequency band. Experimental results indicate that the proposed band notch antenna has maximum voltage standing wave ratio (VSWR) of 25 in the desired rejection band. Measured gain for the proposed band notch antenna is around 0 dB and reduces to ?15dB in the desired rejection band. Time domain performance of both the initial antenna and band notch antenna is also examined and the best detection template is presented. Computed total fidelity factors for both the initial and band notch antenna are greater than 0.9. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013     

多模式雷达在矿区沉降监测中的应用研究

合成孔径雷达差分干涉测量(DInSAR)技术在地表形变监测方面已得到广泛应用。介绍了将差分InSAR技术运用于矿区地表沉降监测,获得了河北峰峰煤矿地表Envisat/ASAR和ALOS/PALSAR的雷达形变干涉相位图,并对Envisat C波段和ALOS L波段的形变干涉相位图进行了相干特性和相位特性的分析。通过综合考虑C波段和L波段的优势与不足,将两者联合使用,实验表明利用多模式雷达数据对矿区地表沉降进行检测的可行性。同时,通过对雷达干涉相位图的分析,能够及时提供正在进行地下开采活动的矿区地理位置。     

Generalized band matrices and their inverses

The idea of defining the generalized band matrices is based on the recognition that several pattern matrices and their inverses have low rank submatrices in certain domains. Theoretical considerations concerning the generalized band matrices enable us to give uniform treatment for several well known classes of matrices like band matrices, block band matrices, band matrices with low rank corrections, sparse matrices and their inverses. Making use of the new notions of information content and of compact representation of matrices, the concept of proper matrices is extended for generalized band matrices. Some reduction algorithms are presented which help to discover certain hidden structural properties of the generalized band matrices. The theoretical results are enlightened by a large number of figures illustrating numerical examples. Work supported by the Progetto Finalizzato Calcolo Parallelo e Sistemi Informatici of CNR. Visiting Professor at the University of Pisa under the support of GNIM-CNR.     

Volterra series‐based model for concurrent dual‐band power amplifier using dynamic memory depth

In this article, a dynamic dual‐band baseband equivalent Volterra (DDBE) model is proposed to compensate the nonlinear distortions of the concurrent dual‐band power amplifier (PA). The DDBE model is obtained by improving the discretized dual‐band baseband equivalent Volterra model which can describe the output characteristics of concurrent dual‐band PA completely in theory but is lack of practicability. Three simplification rules are proposed in the article, and the relevance between in‐band intermodulation and in‐band cross modulation is employed to simplify the establishment complexity of the model. Then the dynamic kernels are categorized into three groups, and based on this, DDBE models with different level dynamical kernels are derived. In addition, draw on the experience of single‐band PA behavioral model, even‐order kernels are introduced into DDBE models. Digital predistortion performances of a wideband PA, which works in concurrent dual‐band mode, are evaluated to verify the feasibility and advantages of the proposed model.     

A state‐of‐art review on band‐notch characteristics in UWB antennas

Ultra‐wideband technology has experienced a rapid growth over the last decade for its contribution in different sectors of human society. Printed antennas are considered as preferred platform for implementing this technology because of its alluring characteristics like light weight, low cost, ease of fabrication, integration capability with other systems, etc. Antennas developed for ultra‐wideband applications are desired to have notch characteristics for avoiding interference with other existing radio communication systems. The techniques related to design and developments of printed band‐notched antennas are continuously upgraded for improving the antenna performance. In this article, a comprehensive review has been carried out on ultra‐wideband antennas with band notch characteristics proposed in around last decade. The band notched UWB antennas available in the literature have broadly been classified into five different categories based on their notch characteristics like single band‐notch, dual band‐notch, triple band‐notch, quad/multiple band‐notch, and reconfigurable/tunable band‐notch, respectively. This review exercise may be helpful for beginners working on ultra‐wideband band‐notched antennas and also such a review process is not available in the open literature to the best of author's knowledge.