共查询到20条相似文献,搜索用时 218 毫秒
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对数周期偶极子天线全空间可变相位中心 总被引:2,自引:0,他引:2
导出了直线阵列在全空间中存在可变相位中心的条件,得出了由非相似单元组成的直线阵列(如对数周期偶极子天线)不存在全空间可变相位中心,但在E面和H面独立存在各自的可变相位中心的结论.证明了对数周期偶极子天线(LPDA)在E面和H面有不同的可变相位中心.采用矩量法(MoM)分析了LPDA的E面和H面可变相位中心,计算结果表明:虽然在LPDA的主波束范围内其相位中心变化很小,可以作为"视在相位中心",但是这种"视在相位中心"仍然在E面和H面是不重合的.此外,"视在相位中心"随着频率沿着集合线移动. 相似文献
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为了提高计算对数周期偶极子天线(LPDA)视在相位中心的速度和精度,提出一种计算LPDA视在相位中心的变步长法,井计算LPDA的E面、H面视在相位中心,给出了E面、H面方向图半功率波瓣宽度内的最大相位差.最后,根据计算出的相位中心重新计算LPDA在E面、H面的相位方向图,在天线功率波瓣宽度内相位值平坦,表明该方法是有效的. 相似文献
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用改进的多普勒中心跟踪法进行ISAR运动补偿 总被引:14,自引:2,他引:12
针对ISAR运动补偿中的相位补偿,本文在多普勒中心跟踪法的基础上,引入Wahl等的相位梯度自聚焦算法,提出了改进的多普勒中心跟踪法,该方法通过在像域的循环移位,隔离和迭代等步骤,巧妙地消除目标转换相位分量对平动相位分量估计的影响。 相似文献
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像素匹配是在线三维测量中的关键技术之一,提出了基于归一化等相面的在线三维测量像素匹配方法。仅投一帧正弦光栅条纹到在线运动的物体上,由CCD再依次移动相同步距时刻同步采集受物体调制的变形条纹图。利用FTP方法预测物体不同位置的相位信息并进行归一化,再以二值化等相面协助像素匹配,不仅实现了物体在各帧条纹图中的像素坐标一一对应,而且归一化减少了由于物体运动产生的不同位置相位展开起始点不一致导致的不同位置相位展开的差异性而引入的误差,同时节省了像素匹配计算量。对最大高度为8 mm的peaks函数型物体的模拟结果表明:均方差为0.021 mm,像素匹配时间上,该方法较直接用FTP方法预测得到的相位为模板进行像素匹配缩短了近2倍,同是实物测量也验证了该方法的有效性和可行性。所提方法不仅可以保证在线三维测量的精度,而且有效地提高了测量速度。 相似文献
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Under the circumstance of optical axis being in the incident plane,the evanescent wave of total reflection is studied when an extraordinary beam is incident from an isotropic medium upon a uniaxial crystal by using the general characteristics of uniaxial crystal and electromagnetic field.This paper presents the propagation directions of equiphase plane and the images of evanescent wave,and reveals that the equiamplitude plane and the equiphase plane are not in quadrature any more,and the phase difference between longitudinal wave and transversal wave does not equal π/2,either.But the reflectivity is still kept at 100. 相似文献
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对两点源诱偏反辐射导弹的效果进行了研究.推导了两点源作用下的合成电磁场模型,在地面雷达站球面坐标系下建立了合成场等相面梯度矢量方程;利用直角坐标系与球面坐标系的转换关系及弹体坐标系与地面雷达系的转换关系,建立了反辐射导弹导引信号的模型.通过仿真得出两点源诱偏成功与两点源间距之间的关系曲线,给出了两点源的最优配置. 相似文献
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相控阵雷达反演口径分布实现方位超分辨 总被引:1,自引:0,他引:1
为了实现普通相控阵雷达的方位超分辨,需要知道天线阵面的幅相分布。通过对相控阵天线单元进行时序Walsh-Hadamard相位权重可以反演该天线阵面的幅相分布。在此基础上再采用超分辨算法就可以得到目标的超分辨方位信息。所采用的超分辨算法是抗噪性和鲁棒性均较好的逐次逼近算法。为了得到平缓的相位分布,减少相位权重次数,对于不在正常方的目标采用了附加线性相位分布波阵面地准的方法,经数值仿真,对于一个X波段 相似文献
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基于光线传输矩阵理论,结合高斯光束特征参数,研究了球面镜曲率半径和腔体长度变化对环形腔子午面和孤矢面内束腰半径的影响.结果表明:两束腰半径均随曲率半径和腔体长度的增大而增大.在此基础上,分析了这种变化对环形腔内光强分布、多横模耦合和光波传输等相位面大小的影响. 相似文献
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通过运用连续渐变线代替多节阻抗变换器,实现了一种改进的宽频带功分器的设计与实现的形式和方法;功分器的设计利用平行耦合带状线,结合渐变线耦合形式,给出了宽频带等功率分配器的设计电路,同时通过有限元法仿真计算了散射矩阵的参数,并进行了实测,结果显示设计的功分器在9个倍频的宽频带范围内性能良好.采用该方法对于宽频带不等幅功分器的电路进行了设计,并给出了有限元仿真计算的散射矩阵参数的结果(包括幅度和相位),在超宽频带范围内较好地解决了功分器在幅度不等分的情况下的相位差大问题. 相似文献
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《Antennas and Propagation, IEEE Transactions on》2006,54(10):2854-2861
The synthesis of classical dual-reflector antennas suited to provide omnidirectional coverages with arbitrary main-beam direction in the elevation plane is discussed. Both sub- and main reflectors are bodies of revolution generated by axis-displaced conic sections, so to transform a spherical radiation emanating from the antenna principal focus (at the symmetry axis) into an equiphase field distribution over a conical aperture. Closed-form design equations are presented for the geometric-optics synthesis of all possible configurations. Several case studies are investigated and analyzed by the accurate method of moments technique in order to validate the proposed design procedure. 相似文献
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An alternative to individually phase-stabilised links for distribution of local oscillator (LO) signals in large arrays of radio telescopes is considered. An array is illuminated from an elevated optical source, intensity modulated at the LO frequency. LO phase feedback from the centre of the illuminated zone counteracts tower and atmospheric instabilities, locking a fixed phase at zone centre, and hence a template of constant phase contours around the zone centre point. Other LO detector planes are aligned to equiphase contours, providing a phase coherent LO to all telescopes aside from differential optical path effects. A local PLL at each site reduces the remaining noise from differential slant path variations 相似文献
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Feng Kongyu 《电子科学学刊(英文版)》1984,1(4):225-233
The conventional requirements on the antenna are reviewed. The importance of the phase pattern of the antenna in modern science
and technology is pointed out. Under such a background, the problems concerning the phase characteristic of the radiation
pattern and the current distribution of the antenna aperture are attempted to be systematized on the basis of previous works,
namely, the phase reference point, the transformation of the radiation patterns corresponding to different phase reference
points of an antenna, the null level and the phase difference between the adjacent lobes, and the resolution of current distribution
of a linear source, are summarized and discussed. The general condition of the equiphase lobe and the condition of the symmetric
lobe of a linear source are proposed and proved theoretically. Some theorems are proposed by induction from the above and
the overall discussion is termed the phase theory of radiation pattern. 相似文献