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为了实现圆极化波到线极化波的高效率转换,提出了一种由两种圆极化波调制模块构成的复合结构单元频率选择表面圆-线极化转换器。采用天线-馈线-天线结构设计了左-左旋和左-右旋两种圆极化调制模,并将二者组合形成具有左旋圆极化波接收、左旋和右旋圆极化波同幅同相辐射功能的圆-线极化转换器。仿真与测试结果表明,该极化转换器能够将入射左旋极化波转换成线极化波,3 dB传输系数相对带宽大于19.8%,工作带宽内的圆-线极化转换率大于0.99。该极化转换器具有插入损耗低、设计原理易于推广等优势。 相似文献
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提出了一种采用圆偏振光的偏振复用通讯系统。其基本设想是信号光在空间中以左
旋和右旋圆偏振光的形式进行传播,在接收端将这两种偏振光区分并分别接收。本文详细论证了在两个相对运动点之间采用圆偏振光实现偏振复用激光通讯的可行性。 相似文献
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研究了周期量级的圆偏振激光在空气中成丝产生太赫兹辐射的偏振特性。将中心波长1.8 m、脉宽8.6 fs 的圆偏振红外激光脉冲聚焦到空气中,形成等离子体细丝,产生太赫兹辐射。通过测量太赫兹辐射的偏振状态,和偏振方向与驱动激光载波-包络相位的关系,发展太赫兹波偏振控制的方法。实验结果表明,太赫兹辐射为椭圆偏振,而且偏振平面随着驱动激光载波-包络相位的变化而转动。这对太赫兹波的偏振控制有重要意义,并为周期量级激光载波-包络相位的测量提供了新方法。 相似文献
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圆偏振光有良好的“偏振记忆”效应,为了验证在 强散射介质中通过圆偏振光的旋性 差异可以有效抑制散射光的影响,实现复杂背景下的目标探测功能。从经典的米氏散射 理论和菲涅尔反射理论出发,结合偏振蒙特卡罗方法,构建了主动式圆偏振光在散射介质中 探测目标的模型,通过追踪每个光子的偏振态变化,统计分析了圆偏振光经过介质散射和目 标反射后的Stokes矢量信息。仿真结果表明,文中建模方法可以明显区分出散射介质中是否 存在被探测目标;不同的介质环境和不同的探测距离都会对目标的偏振成像造成不同程度的 衰减,而圆偏振差分成像及圆偏振度成像均可实现偏振成像的增强处理。文中建模方法可以 为全偏振探测的理论研究及实际应用提供借鉴。 相似文献
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激光诱导击穿光谱(LIBS)是一种快速、实时的元素成分分析技术。为了提高LIBS的灵敏度,人们已经提出多种方法来提高LIBS的光谱强度。本文采用飞秒脉冲激光烧蚀黄铜产生LIBS,对比了圆偏振和线偏振下LIBS光谱的强度,结果发现圆偏振下的光谱强度比线偏振下的强,光谱强度大约提高了15%。采用飞秒激光照射金属时,金属内部的自由电子吸收光子的能量。在线偏振飞秒激光场中,电子在脉冲的每个光学周期中经历交替的加速和减速;而圆偏振飞秒激光可以连续加速电子,因此电子可以获得更高的能量,这使得圆偏振飞秒激光产生的光谱强度不同于线偏振飞秒激光产生的光谱强度,圆偏振激光有助于改善飞秒LIBS信号的强度。 相似文献
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基于Mie散射理论利用偏振相关的Monte Carlo仿真方法对圆偏振光在水平大气中传输进行建模仿真。仿真结果表明:在大气能见度为5 km、传输距离为11.16 km条件下,接收光斑中心处保偏性能很好,且优于接收光斑边缘处保偏性能。进行了11.16 km水平大气链路左旋圆偏振光退偏实验,实验结果表明:在大气能见度为5~10 km,大气折射率结构常数Cn2=1.82510-13 m-2/3条件下,左旋圆偏振光经过长距离水平大气信道传输后偏振旋向不发生改变;接收光斑中心处保偏性能良好,优于接收光斑边缘处,和仿真结果趋势一致。 相似文献
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An inclined planar panel, which is generally anisotropic, intercepting a circularly polarized beam introduces loss and phase shift, and depolarizes the received signal. Orthogonal linearly polarized waves aligned to the symmetry planes are often used in the measurement of such panels. Using these data, convenient graphs are presented to illustrate the loss and phase shift of a circularly polarized beam, as well as the amount of depolarization into an orthogonal circularly polarized channel, without explicitly determining the intermediate axial ratio or polarization ellipse tilt angle of the emerging wave 相似文献
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传统的圆极化阅读器天线采用单馈电微带天线方式设计,频带窄、极化特性较差。在单馈电微带天线的基础上,采用探针馈电曲线贴片的方式,在圆形铁片上开了4个对称的方形缝隙,最终设计出一种新型的UHF RFID圆极化阅读器天线。天线的结构尺寸为167.5 mm×167.5 mm×3 mm,阻抗带宽为870~936 MHz,3 dB轴比带宽为900~918 MHz,最大增益为3.5 dB。与传统的圆极化阅读器天线相比,设计的天线频带宽,且极化特性得到良好改善,能够满足工程上的应用需求。 相似文献
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In this work, we study the realization of realistic polarization transformers formed by long metallic helices. To this end, we propose a new homogenization model to characterize the propagation of electromagnetic waves in a medium formed by infinitely long helices. We derive approximate analytical expressions for the effective permittivity, effective permeability and the magnetoelectric tensor of the composite material, taking into account the effects of spatial dispersion. We apply the new homogenization model to characterize novel linear-to-circular polarization transformers. Our results show that the metamaterial screen may be designed in such a way that an incoming linearly polarized wave may be transformed into a circularly polarized transmitted wave, and that the transmission efficiency of such polarization transformer may be as high as 95%. 相似文献
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The electromagnetic field radiated by an arbitrary source is represented as the multipule expansion of the left-hand circularly polarized and of the right-hand circularly polarized modal fields. In particular, the multiarm log-spiral antennas have been investigated using such an approach. With approximated current distributions, the multipole coefficients and the circularly polarized field patterns for a few typical log spirals are computed and compared with the measured results. Generally, only a few dominant modes are sufficient to describe the major radiating characteristics of the log spirals; therefore, a better insight as to the polarization and the angular dependence can be gained through the modal-field point of view. 相似文献
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A novel gain improvement method for a circularly polarized array antenna consisting of linearly polarized elements is proposed. It is verified that the gain of a circularly polarized array antenna can be increased by adjusting the array arrangement of the individual linearly polarized elements. The gain of a multiring array antenna consisting of the above mentioned circular array can also be increased by properly combining the directions of the linear polarization of the individual circular arrays. The gain improvement of the single-circular array antenna and the two-ring array antenna using the proposed method are verified by the measured results 相似文献
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《Vehicular Technology, IEEE Transactions on》1973,22(4):237-239
Land mobile systems currently use vertically polarized antennas while trying to solve the problem of small sector signal variations, which are greater for vertical polarization than for either horizontal or circular polarization. This difference in small sector variations is shown from results of tests at 430 MHz. The variations at 900 MHz should be more rapid and have amplitudes at least as great as those shown for 450 MHz. At 900 MHz antennas can be made small for mobile service and the improvements noted here may spur developments in circularly polarized antennas. 相似文献
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Land mobile systems currently use vertically polarized antennas while trying to solve the problem of small sector signal variations, which are greater for vertical polarization than for either horizontal or circular polarization; This difference in small sector variations is shown from results of tests at 430 MHz. The variations at 900 MHz should be more rapid and have amplitudes at least as great as those shown for 450 MHz. At 900 MHz antennas can be made small for mobile service and the improvements noted here may spur developments in circularly polarized antennas. 相似文献
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在核磁共振陀螺系统中,需要用圆偏振光来泵浦碱金属(例如铷)原子,使其产生极化。然而实际应用中的泵浦光不是理想的圆偏振光,为了研究泵浦光椭圆度与铷原子极化率的变化关系,推算了泵浦光经过四分之一波片后的表达式,并由此得出泵浦光照射铷原子气室前的椭圆度,建立了数值仿真模型,研究了椭圆度对铷原子极化率的影响。同时通过实验得到了铷原子极化率与椭圆度的关系曲线。仿真和实验结果表明,泵浦光椭圆度越大,铷原子极化率越大,随着椭圆度的进一步增大,铷原子极化率增速变慢逐渐饱和;此外,相同的椭圆度下,铷原子极化率随着泵浦光功率的增大而增大。 相似文献