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太赫兹探测技术发展与展望 总被引:1,自引:0,他引:1
介绍了太赫兹探测技术的发展概况,简要阐述了太赫兹波的探测方法、主要特点、重要的学术应用价值和主要产品,并综述了国内外在太赫兹波领域的研究进展,对未来的发展与应用进行了乐观的展望. 相似文献
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由于地球同步轨道(GEO)的衰减周期长,累积效应突出,空间碎片对卫星安全产生日益严重的威胁,特别是地基设备无法观测的危险空间碎片。根据碎片分布与运动特性,开展地球同步轨道星载太赫兹雷达碎片预警技术研究。针对工作波长、目标尺寸与雷达截面积(RCS)、观测范围与工作方式进行论证,完成雷达系统方案和仿真分析。雷达采用有源相控阵天线,天线尺寸为250 mm×250 mm,工作频率为140 GHz,平均功率为190 W。雷达能够在方位与俯仰±15°、距离为1.95~24.12 km内搜索与跟踪尺寸为6.8 mm~15 cm的碎片,并对将要产生的撞击进行预警,预警时间4~35 s。 相似文献
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太赫兹回旋管的现状及其发展 总被引:2,自引:1,他引:2
太赫兹回旋管一种具有重要发展前景的高功率太赫兹源。简要介绍了回旋管的结构和基本原理,并且评述了国内外太赫兹回旋管的发展状况和趋势;同时指出了太赫兹回旋管发展中存在的关键问题及一些建议。 相似文献
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针对星载云雷达对冰云探测可行性分析的需求,分析了非球形冰晶对340 GHz电磁波的单散射特性,基于不同的体积散射模型,研究了非球形冰晶云的回波特性以及94\340 GHz云雷达双波长比,假定冰云垂直分布的情况下,探讨了星载94\340 GHz云雷达双波长比随高度的变化以及可以穿透的冰云厚度。相较于94 GHz及220 GHz,冰晶粒子对340 GHz电磁波的散射能力增强,但是同时云对其的衰减也大大增加,340 GHz的衰减系数约是94 GHz的5~130倍;340 GHz云雷达可以探测浅薄的含水量较小的冰云,基本可以探测云厚2 km、冰水含量在 0.000 1-0.2 g/m3的冰云。含水量较多的厚云由于衰减,造成电磁波穿透能力大大降低,在假定的冰水含量垂直分布下,当最大冰水含量为1 g/m3时,可探测厚约5 km内云厚的40%以上;衰减也造成不同高度上相同滴谱的云有不同的双波长比,冰水含量的大小及垂直分布影响了双波长比的大小及电磁波探测云的厚度。衰减随着冰水含量增大而增大,高频云雷达电磁波衰减大,使得双波长比变大,从而使双波长比和谱的数浓度N0有关,因此利用双波长比反演时,衰减订正非常重要。 相似文献
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太赫兹技术的发展现状及应用前景分析 总被引:1,自引:0,他引:1
简要介绍了太赫兹辐射源和太赫兹探测器,特别是THz量子级联激光器(QCL)和THz量子阱红外光子探测器(QWIP)的原理、特点及研究现状.分析了太赫兹技术工程应用前景及限制因素.指出作用距离是决定太赫兹技术应用的关键因素之一.如果太赫兹辐射在大气对流层内传输时的衰减问题不能得到有效解决,那么太赫兹技术在地面或海上的应用可能受到严重制约.基于机载或星载平台的太赫兹雷达或通信,则具有诱人的应用前景. 相似文献
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近年来,随着太赫兹(THz)技术的快速发展,它在安检、航空航天、生命科学、化学等领域展现了巨大的应用前景.在安检领域.由于许多炸药及其相关材料在太赫兹波段具有特征吸收谱.许多非金属、非极性材料对太赫兹波是透明的.因此爆炸物太赫兹光谱探测技术具有巨大的潜力,受到了国内外的高度重视.介绍了国内外利用太赫兹波进行爆炸物光谱探... 相似文献
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Chandrasekar V. Wanyu Li Zafar B. 《Geoscience and Remote Sensing, IEEE Transactions on》2005,43(5):1078-1086
The Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar uses surface reference method to estimate the attenuation encountered in the observation of radar reflectivity. The cumulative attenuation estimated from the surface reference method can be distributed along the radar range using a power law relation between the specific attenuation (k) and reflectivity factor (Z). A physical interpretation of the variability in the k-Z relation can be provided with the normalized drop size distributions. This paper describes an algorithm to estimate the drop size distribution (DSD) parameters from the measured attenuation and reflectivity values obtained from TRMM precipitation radar observations. Coincident data collected with ground polarimetric radar during the TRMM field campaigns is used to cross-validate the estimates of drop size distribution parameters obtained from the TRMM precipitation radar. The results of cross validation show fairly good agreement with the drop size distribution parameters retrieved from TRMM precipitation radar and the ground-radar-based estimates. The algorithm is subsequently used to generate monthly global maps of DSD. The global distribution of DSDs is critically important for development of retrieval algorithms used by the Global Precipitation Mission Radiometers. 相似文献
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《Electron Devices, IEEE Transactions on》1980,27(11):2152-2155
A new method for profiling of optically active defects is presented. Traps in a depletion region are illuminated with chopped extrinsic light(hnu < E_{g}) . The resulting ac photocurrent in the external circuit originates from a small part of the depleted layer. The trap profile is obtained by changing the bias voltage which moves the active traps with respect to the semiconductor surface. The method is illustrated with measurements made on an MOS tunnel device. 相似文献
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太赫兹雷达散射截面测量研究进展 总被引:1,自引:0,他引:1
太赫兹雷达散射截面(RCS)测量技术是当前太赫兹重要的应用技术之一。利用太赫兹源,不仅可以测得目标太赫兹波段的RCS,还可以通过对缩比模型的RCS测量,获得微波波段全尺寸目标的RCS值。基于RCS定义及测量的一般要求,介绍了国外太赫兹RCS测量的主要成果;重点介绍三类测量装置及测量目标;给出部分代表性的测量结果。最后分析了利用飞秒激光器抽运晶体的太赫兹时域谱系统、CO2激光抽运太赫兹激光器的逆合成孔径雷达系统和信号合成器的相干探测系统在工作频率、待测目标尺寸和小型化等方面的特点。为我国太赫兹RCS测量技术的发展提供技术借鉴。 相似文献
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The bright band is the enhanced radar echo associated with the melting of hydrometeors in stratiform rain. To simulate this radar signature, a scattering model of melting snow is proposed in which the fractional water content is prescribed as a function of the radius of a spherical mixed-phase particle consisting of air, ice, and water. The model is based on the observation that melting starts at the surface of the particle and then gradually develops toward the center. To compute the scattering parameters of a nonuniform melting particle, the particle is modeled as a sphere represented by a collection of 64/sup 3/ cubic cells of identical size where the probability of water at any cell is prescribed as a function of the radius. The internal field of the particle, used for deriving the effective dielectric constant, is computed by the conjugate gradient and fast Fourier transform (CGFFT) numerical methods. To make computations of the scattering parameters more efficient, a multilayer stratified-sphere scattering model is introduced after demonstrating that the scattering parameters of the nonuniformly melting particle can be accurately reproduced by the stratified sphere. In conjunction with a melting layer model that describes the melting fractions and fall velocities of hydrometeors as a function of the distance from the 0/spl deg/C isotherm, the stratified-sphere model is used to simulate the radar bright-band profiles. These simulated profiles are shown to compare well with measurements from the Precipitation Radar (PR) aboard the Tropical Rainfall Measuring Mission (TRMM) satellite and a dual-wavelength airborne radar. The results suggest that the proposed model of a melting snow particle may be useful in studying the characteristics of the bright-band in particular and mixed-phase hydrometeors in general. 相似文献