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毫米波/红外复合制导共口径天线需要使用二向色镜,用于透射微波/毫米波、反射红外,提出了用分形频率选择表面(FSS)实现二向色镜的方法,设计了一种Ku波段和Ka波段双频带通的Y环分形FSS,基于频域有限差分法(FDFD)和周期边界对其进行了仿真分析,并进行了实物研制,仿真和测试结果表明,该分形FSS结构具有稳定而优良的频率特性,同时圆极化性能好、工程实现简单,而且对大于5 μm的红外信号反射率最高接近90%. 相似文献
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毫米波/亚毫米波临边探测仪中的辐射计通常需要工作在多个频段,如多频段共馈源,则其带宽往往不能达到要求。当多个探测频段共用一个主反射镜,采用准光学技术实现探测频率分离,则可以节省很大的空间。准光极化线栅和准光频率选择器相配合用来分离频率范围在118 GHz~340 GHz 的4个频带,准光极化线栅是一个准光功率分配/合成器,将4个频段的信号分为(183 GHz/240 GHz)和(118 GHz/340 GHz)2组信号。准光频率选择器是一个高频频率选择表面,可以将高频段的电磁波透射,低频段的电磁波反射。反射和透射的电磁波分别进入2个频段的接收模块,实现信号的接收。本文利用HFSS仿真软件对周期单元的结构参数进行仿真优化,并通过仿真结果完成了准光极化线栅和准光频率选择器的技术实现。实测结果与毫米波/亚毫米波临边探测仪的设计要求一致。 相似文献
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毫米波/红外复合制导半实物仿真中需要使用二向色镜,用于透射毫米波、反射红外,提出了用分形频率选择表面(FSS)实现二向色镜的方法,设计了一种8 mm和3 mm波段双频带通的Y环分形FSS,基于频域有限差分法(FDFD)和周期边界对其进行了仿真分析,并进行了实物研制.仿真和测试结果表明,该分形FSS结构具有稳定而优良的频率特性,同时圆极化性能好、工程实现简单,而且对大于5 μm的红外信号反射率最高接近90%.特别是这种二向色镜可以同时应用于8 mm和3 mm波段毫米波/红外半实物仿真系统,具有良好的复用特性,因此有很好的应用前景. 相似文献
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为了研究手征超表面在中红外波段的非对称传输特性,设计了一种基于L型结构的手征超表面单元。利用CST电磁软件进行仿真分析,结果表明在68.92~88.68 THz范围内非对称传输参数大于0.8,在73.25 THz处非对称传输参数达到极值为0.88,由此可知该结构在中红外波段具有良好的非对称传输特性;通过分析表面电流分布和透射场相位分布,阐明了该手征超表面的极化选择性反射和交叉极化透射机理;对单元结构手征强弱和非对称传输特性的关系进行了讨论,并研究了介质层、金属层的厚度以及电磁波入射角度对非对称传输特性的影响。 相似文献
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提出了用于测量吸波材料吸收雷达波性能的新型探头。引入高次模,采用相位分析法,克服了多变量干扰,简化计算。在固定区间求偏差和方差最小值,得到平缓电场。仿真结果证明新型探头口径电场平缓,波动小,近似平面波。新型探头的平面波范围与口径比为53%,比现有厘米波探头扩大了17.2%,能精确地模拟雷达对材料的辐射,减小测量误差。此探头尺寸较小,可广泛应用于户外测量材料吸收毫米波雷达电磁波的性能。 相似文献
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石墨烯由于其优异的电学性能,在微波、毫米波、太赫兹波等领域显示出潜在的应用前景。本文设计了毫米波和亚太赫兹波频段的基于石墨烯的相位和幅值波导调制器。该石墨烯调制器可以通过调节石墨烯的表面阻抗来调控电磁波在波导中传播的振幅和相位;分析了石墨烯片的长度和位置对电磁波在波导中的透射和反射系数的影响,同时还分析了石墨烯化学势对电磁波在波导中传输和反射的影响。结果表明,通过调节石墨烯片的长度及其在矩形金属波导中的位置,可以调控调制器的反射系数、透射系数和透射相位调制范围,并满足器件级应用需求。 相似文献
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Blanchard P.M. Greenaway A.H. Harvey A.R. Webster K. 《Lightwave Technology, Journal of》1999,17(3):418-425
Passive millimeter-wave imaging requires large apertures to achieve an angular resolution comparable to that of typical infrared imagers. Aperture synthesis offers a route to achieving high resolution without using a single large aperture, by interferometrically combining the signals from a number of smaller distributed apertures. In such a system the individual millimeter-wave signals must be transported to a common location with good phase fidelity and combined to form the image. This paper discusses a technique called coherent optical beam forming which performs optical transport of the up-converted millimeter-wave signal and direct image formation at the optical frequency. Proof of principle experiments are described that demonstrate coherent optical beam forming with a point source and a method of self-calibrating the array to remove phase errors 相似文献
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Liquid crystal (LC) lens cells are fabricated using a nematic LC material with a positive dielectric anisotropy and semicircle-shaped metal substrates as quasioptical millimeter-wave devices. The millimeter-wave focusing properties of the LC lens are measured at 94 GHz and its convergent effects caused by the lens-shaped configuration are then observed. Changes in the focusing properties by applying an external electric field are confirmed 相似文献
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《Microwave Theory and Techniques》1987,35(8):748-752
Accurate measurements were taken of the leakage constant of a leaky-wave structure based on nonradiative dielectric (NRD) waveguide in order to verify the theory derived in the companion paper, part I. Although the structure is intended for millimeter-wave use, measurements were made on a model scaled to X band (lambda = 3 cm) to improve the accuracy of the experimental results. The measurements were taken by probing the electric near field strength along the longitudinal direction. Comparisons with accurate theoretical data are presented for different frequencies and geometrical parameters, and very good agreement is found between the measurements and the theory. 相似文献
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共孔径光学结构可以充分利用长焦距、大孔径光学系统高分辨率的特点,是光学系统发展的重要方向之一。文中设计了一套可见光成像、激光成像和激光测高共孔径的跟踪引导系统。共孔径设计结合了高分辨率的可见光系统与高测量精度的激光系统,使系统既可以获得目标的高清图像,又可以得到目标的相对位置信息。同时,共孔径光学结构可以压缩系统尺寸,降低光学系统在跟踪过程中的转动惯量,有利于系统的整体实现。可见光子系统的焦距1 200 mm,F数6,视场1.2;1 064 nm激光成像子系统焦距1 500 mm,F数7.5。各系统的成像质量均接近衍射极限,并通过公差分析验证了系统的公差分配结果。 相似文献
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《Microwave Theory and Techniques》1983,31(2):199-209
At theoretical procedure well suited for generating design data on dielectric grating antennas for the millimeter-wave region is presented. The procedure utilizes the effective dielectric constant (EDC) method to determine the phase constant of the leaky modes supported by the antenna structure of finite lateral width. The radiation or leakage constant of these modes is obtained from the relatively simple boundary value problem of dielectric grating antennas of infinite width. For single-beam radiation, the practicably interesting case, the phase and leakage constants completely determine the field distribution in the antenna aperture, from which the directivity gain and radiation pattern are then calculated. The dependence of the antenna characteristics on the dimensions of the radiating structure is presented and discussed for epsilon = 12, the dielectric constant of typical millimeter-wave materials, such as silicon and GaAs. 相似文献
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Optoelectronic switching and gating of millimetre-wave signals at 94 GHz by optically generated plasma in silicon dielectric waveguides are reported. A pulsewidth for millimeter-wave signals as short as one nanosecond and variable to tens of nanoseconds can readily be obtained by this technique. 相似文献
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实验研究了一种基于相位调制器(PM)并级联强度调制器(IM)实现40 GHz毫米波传输正交频分复用(OFDM)信号的光纤无线通信(ROF)系统。在中心站,采用20 GHz的射频(RF)信号驱动PM,调节驱动信号的强度,使输出的信号经光纤布拉格光栅(FBG)滤除中心载波后再送入IM。2.5 Gbit/s的OFDM信号直接调制在光毫米波上,经过50 km标准的单模光纤(SSMF)传输到基站。在基站,光调制信号经光电转换器(PD)转换成电调制信号,再与RF信号混频,恢复出基带OFDM信号。实验结果表明,在无色散补偿、误码率(BER)为10-3的条件下,下行链路中2.5 Gbit/s的OFDM信号经光纤传输50 km后,其功率代价小于1 dB,而且信号的星座图依然较好。 相似文献
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A new type of millimeter-wave imaging technique, passive millimeter-wave microscopy is proposed and demonstrated. Passive millimeter-wave imaging techniques when combined with scanning near-field microscopy enable direct observation of millimeter-wave signals thermally emitted from the viewed object with a spatial resolution below the diffraction limit. Details of our passive microscope system operating at Ka-band frequencies are explained. Millimeter-wave images obtained with the system are presented to demonstrate the feasibility of this new imaging technique. 相似文献