共查询到19条相似文献,搜索用时 187 毫秒
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应用有限元仿真软件HFSS,建立了准确的3维螺旋线行波管耦合阻抗仿真模型。应用该模型,对微扰实验法在微扰杆内电场所做出的4个假设和近似,进行了定量的分析和讨论:电场在轴向是均匀的,忽略掉轴向高次空间谐波的存在;电场在角向是均匀的,忽略掉角向高次空间谐波的存在;忽略掉电场中TE波部分,认为电场角向分量为零;假设微扰前后的电场是相等的。同时,对微扰杆的尺寸和介电常数与耦合阻抗的依赖关系进行了模拟分析。结果表明:当微扰法所引入的假设和近似逐步消失后,微扰法的结果最后收敛于定义法。 相似文献
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在Sheath模型下,采用严格的场匹配法,结合积分形式的边界条件,推导了自由矩形螺旋线的色散方程和耦合阻抗表达式,并与近似理论进行对比。结果表明:与近似理论相比, 严禁场匹配法具有更高的准确性,且采用场匹配法的数值计算结果与3维商业电磁仿真软件结果吻合得很好。从而证明了所采用理论方法的有效性。同时分析了矩形螺旋线横截面尺寸、螺距、螺旋角、纵横比对色散特性和耦合阻抗的影响,结果表明:只有当矩形螺旋线横截面纵横比大于4时,才可忽略横截面的宽度对高频特性的影响,通过调节结构的参数可以改善色散和提高耦合阻抗。 相似文献
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在Sheath模型下,采用严格的场匹配法,结合积分形式的边界条件,推导了自由矩形螺旋线的色散方程和耦合阻抗表达式,并与近似理论进行对比。结果表明:与近似理论相比, 严禁场匹配法具有更高的准确性,且采用场匹配法的数值计算结果与3维商业电磁仿真软件结果吻合得很好。从而证明了所采用理论方法的有效性。同时分析了矩形螺旋线横截面尺寸、螺距、螺旋角、纵横比对色散特性和耦合阻抗的影响,结果表明:只有当矩形螺旋线横截面纵横比大于4时,才可忽略横截面的宽度对高频特性的影响,通过调节结构的参数可以改善色散和提高耦合阻抗。 相似文献
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本文从阻抗微扰的概念出发,把Unger在研究H01波通过弯曲及截面变形波导管时所得到的耦合系数,在不同表面阻抗时平方和不变的原理推广到更普遍的情况,这样,使计算相关距离十分小的各种随机公差和接头公差变得十分简便,对于不同类型波导精确度的计算,可由统一的公式出发,此外在一般情况下,得到了两两耦合系数之间的相互关系。在计算均匀不规则波导的精确度时,利用阻抗微扰的形式,得到尤许阻抗微扰量与附加衰减的关系,从而可以按照各种不规则性与阻抗微扰的关系决定均匀公差。 相似文献
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We propose an approach to optical microscopy that enables full control over the three-dimensional polarization vector at the focal spot of a high-numerical-aperture lens. The input field to the lens is linearly polarized and no polarization optics are needed. This technique utilizes the azimuthal spatial degree of freedom of the input field. We find that only a small set of low-order azimuthal spatial harmonics contributes to the focused field on axis, and a simple transformation exists between the linear vector space of these harmonics and the three-dimensional polarization-vector space. Controlling the relative complex weights of these azimuthal harmonics produces any desired three-dimensional state of polarization. 相似文献
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Uhriandt D. Winkler R. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2001,29(3):462-470
The cylindrical column plasma of a neon dc glow discharge under the influence of a weak longitudinal magnetic field is studied. An extended, fully self-consistent model of the column plasma has been used to determine the kinetic quantities of electrons, ions and excited atoms, the radial space charge field, and the axial electric field for given discharge conditions. The model includes a nonlocal kinetic treatment of the electrons by solving their spatially inhomogeneous kinetic equation, taking into account the radial space charge field and the axial magnetic field. The treatment is based on the two-term expansion of the velocity distribution and comprises the determination of its isotropic and anisotropic components in the axial, radial, and azimuthal direction. A transition from a distinctly nonlocal kinetic behavior of the electrons in the magnetic-field-free case to an almost local kinetic behavior has been found by increasing the magnetic field. The establishment of the electron cyclotron motion around the column axis increasingly restricts the radial electron energy transport and reduces the radial ambipolar current. The complex interaction of these transport phenomena with the alterations in the charge carrier production leads finally to a specific variation of the electric field components. The axial field increases by applying weak magnetic fields, however, decreases with increasingly higher magnetic fields. At higher magnetic fields, the radial space-charge field is considerably reduced 相似文献
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为了在介质壁加速器中增大轴向加速电场, 提高加速梯度的同时抑制径向电场对束包络的扩张, 提出了在每个加速电极上添加金属栅网结构。采用基于粒子云网格方法的电磁粒子模拟软件对不加栅网与添加栅网的电极结构进行了数值仿真, 分析了不同结构下加速管道中的电场分布和束包络变化。通过实验对比了两种不同结构下经过相同的加速长度获得的粒子能量。结果表明:添加金属栅网结构相对于不加栅网的金属小孔式结构, 轴向加速电场强度提高20%, 同时径向电场得到有效抑制;栅网结构下, 被加速的粒子束在自由漂移空间中的径向发散基本得到抑制;在相同的加速长度下加速H3+粒子, 栅网结构得到的能量增益提高了一倍。 相似文献
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为了在介质壁加速器中增大轴向加速电场, 提高加速梯度的同时抑制径向电场对束包络的扩张, 提出了在每个加速电极上添加金属栅网结构。采用基于粒子云网格方法的电磁粒子模拟软件对不加栅网与添加栅网的电极结构进行了数值仿真, 分析了不同结构下加速管道中的电场分布和束包络变化。通过实验对比了两种不同结构下经过相同的加速长度获得的粒子能量。结果表明:添加金属栅网结构相对于不加栅网的金属小孔式结构, 轴向加速电场强度提高20%, 同时径向电场得到有效抑制;栅网结构下, 被加速的粒子束在自由漂移空间中的径向发散基本得到抑制;在相同的加速长度下加速H3+粒子, 栅网结构得到的能量增益提高了一倍。 相似文献
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Pedro J. Castro Joaquim J. Barroso Rafael A. Corrêa 《International Journal of Infrared and Millimeter Waves》2000,21(4):633-645
A study of the electrodynamical properties of a Ka-band gyrotron open resonator was experimentally conducted. Experiments were accomplished to measure resonant frequencies and their respective loaded quality factors for TE modes in the frequency range from 26 to 40 GHz. In particular, a perturbation technique was used to determine the axial, radial and azimuthal electric field profiles, as an identification method of the TE021 mode operating around 35 GHz. In any experimental event, good agreement with the values predicted by theory was found. 相似文献
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Ahmed E. Radwan 《Journal of magnetism and magnetic materials》1992,110(3):331-336
The electrodynamic instability of a self-gravitating dielectric fluid penetrated by a uniform axial electric field surrounded by a self-gravitating vacuum pervaded by a varying electric field is investigated. A general eigenvalue relation valid to all possible (symmetric and asymmetric) modes of perturbation for all (short and long) wavelengths is derived and discussed in detail. The model is gravitationally stable to the pure asymmetric disturbances modes while to symmetric modes it is as if the longitudinal wavenumber normalized with respect to the jet radius is equal to or greater than 1.0668 and vice versa. The axial electric fields pervaded interior and exterior to the cylinder are stabilizing for all disturbances modes according to some restrictions. The transverse varying electric field is purely stabilizing in the symmetric disturbance for all wavelengths, while it is stabilizing in the asymmetric disturbance under some restrictions. The electrodynamic force has a strong stabilizing influence in the symmetric mode and can suppress the gravitational instability above a certain value of the basic electric field. 相似文献