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V. A. Svetlichny O. V. Smirnova 《Journal of Communications Technology and Electronics》2018,63(7):761-769
A new numerical method for finding roots of the characteristic equation in problems of radio wave propagation in tropospheric ducts with a piecewise linear profile of the refractive index is proposed. For the selected model of the vertical profile of the refractive index of an surface duct, dynamics of propagation constants of modes and features of the behavior of the attenuation function of the electromagnetic field as functions of the troposphere parameters and the wavelength are studied. The contribution of the whispering gallery modes is also estimated. 相似文献
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The parabolic equation is a simplification of the wave equation that admits an efficient full wave solution to the problem of microwave propagation in a two-dimensional refractive index structure. Field strength diagrams for propagation in the presence of typical elevated ducting layers are given. The fields are significantly more complicated than can be predicted by one-dimensional mode methods 相似文献
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海洋大气波导是能够影响侦察预警探测装设备和常用民用航型保障设备的重要大气环境因素。本文采用一种基于激光探测遥感探测大气波导的技术,通过分析计算典型海洋大气多波长激光传输特性、光波波段折射率结构常数与激光探测大气波导机理模型。同时通过自主研制的激光雷达在三亚等地进行大量实践大气波导探测,并同步开展探空气球探测低空100m范围内的温度和湿度剖面,采用温度和湿度剖面获取折射率剖面和激光传输的消光系数垂直分布以及光波段的折射率结构常数分布,实验分析初步表明用激光探测大气波导尤其是海上大气波导尤其是蒸发波导的可行性。 相似文献
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Lo K.M. McPhedran R.C. Bassett I.M. Milton G.W. 《Lightwave Technology, Journal of》1994,12(3):396-410
We consider a dielectric waveguide or optical fiber having a real isotropic ambient refractive index. In addition, several isotropic and uniform embedded cylindrical regions of differing refractive index are considered. The radii, refractive indexes, and positions of the cylindrical subregions are arbitrary. We establish a rigorous method of determining the fields and propagation constants for the vector electromagnetic modes supported by this structure. We verify the accuracy of the method by comparing its results with those of other authors in particular cases, and exhibit direct demonstrations of convergence 相似文献
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海上大气折射率环境是影响电磁波传播、目标探测准确性的关键因素之一.文中利用南海的GPS探空数据评估了ERA-I(ERA-Interim)再分析数据计算的大气折射率,结果表明:3 000 m以下修正大气折射率整体标准差为9.2 M单位,相对误差为1.4%;在分布上修正大气折射率误差在低层偏小,并且会发生小幅震荡,边界层顶以上偏大,这与大气层内水汽分布密切相关,相关系数为0.94.此外两种数据识别的波导参数中,波导高度拟合斜率接近1,最准确;波导厚度和强度斜率不到0.5,波导厚度偏厚,而强度偏小.说明ERA-I再分析数据是较为可靠的数据源,可用来研究海上大气折射环境特性. 相似文献
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Demonstrates that although standard paraxial and wide-angle vector field propagation techniques lead to divergences for sufficiently small grid-point spacings and large refractive index differences, stability may be restored through either certain Pade approximates to the propagation operator or suitable boundary conditions. The authors also introduce a novel alternating directional implicit method applicable to less divergent discretizations of the vector wave equation 相似文献
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海上蒸发波导微波超视距电波传播对舰载雷达的运行具有重要的影响. 本文基于粗糙海面电波散射特征和海面高度分布概率密度函数,提出了一种考虑海面遮蔽影响的海上电波传播计算方法,并与两种不包含遮蔽影响的粗糙海面建模的计算结果进行了模拟和试验对比. 计算结果为:1)随着计算频率和风速的增大,不同粗糙海面处理方法的计算结果差异增大,对应位置的路径损耗差异可达10 dB;2)基于试验数据的对比初步显示采用考虑遮蔽影响改进的抛物方程模型预测的路径损耗精度相对较高,粗糙海面对电波的遮蔽效应是蒸发波导传播损耗计算中的一个重要因素;3)试验结果为不稳定大气时采用NPS蒸发波导模型、稳定大气时采用PJ蒸发波导模型预测大气折射率剖面,所预测的路径损耗要优于采用单一蒸发波导模型的结果. 本文所得结果对海上电波传播计算和大气波导的反演等具有参考价值. 相似文献
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The scalar wave equation for optical waveguides with arbitrary refractive index profiles is solved using a numerically stable integration method. The mode fields and the corresponding propagation constants are determined iteratively. Results for waveguides based on different well-known fabrication techniques are shown and the design of a new sensitive integrated optical switch is proposed. 相似文献
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An account is given of a theoretical investigation of radio wave propagation in a rock medium situated below a highly conducting plane boundary overburden, due to a vertically polarized electric dipole source immersed in the rock near the boundary. Excluded from this discussion are propagation modes in the rock guided between plane boundaries on top and bottom. Just as with dipoles in air above a plane ground, the rock wave can be considered as the result of a "direct wave," a wave "reflected' from the overburden and an "interface surface wave." Rock with complex phase constantk_{1} replaces air with real phase constantbeta_{0} . Of interest is the variation with depth below the boundary of the fields in the rock, analogous to "height gain" for fields in air. Of importance is the effect of the relative refractive index of overburden-to-rock. A sample calculation is given for a one-mile path assuming typical electrical constants for the rock and overburden media. At the VLF of interest, loss tangents in the media are large. These results may assist in determining whether or not a received signal is due predominantly to a rock propagated wave or to a possible "up-over-and-down" mode. 相似文献
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V. A. Batanov V. S. Petriv A. O. Radkevich A. Yu. Volkov 《Journal of Infrared, Millimeter and Terahertz Waves》1992,13(4):467-482
The propagation of spatially modulated IR pump and FIR generated waves interacting in the active gas medium of Raman laser is simulated numerically. Stationary nonlinear diffraction of monochromatic beams is studied for the isolated homogeneously broadened three-level system without any limitations on the values of field strength and frequency offset. It is shown that FIR radiation is trapped in the active wave guide induced owing to the nonlinear refractive index mechanism and gain inhomogeneity across the pump wave beam. Nonlinear focus positions and on-axis focal intensities for both fields are calculated. 相似文献
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大气湍流对对流层内微波的传播具有重要影响,正确认识大气湍流的特性有助于提高电波传播模型预测的准确性和可靠性. 本文利用天气数值预报(weather research and forecasting,WRF)模式预测气象要素,计算微波波段大气折射率结构常数,研究对流层内大气湍流的时空分布特性,并探讨其与温度、相对湿度和修正大气折射率的变化关系. 研究表明:近海面微波湍流强度具有明显的日变化特征;对流层内微波湍流的垂向结构具有较为明显的分层;大气环境出现逆温减湿现象,湍流活动较强. 这些研究成果可为微波在大气环境中传播的准确预测提供理论支持. 相似文献
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A fast numerical method using Gaussian quadrature, which takes only seconds on a microcomputer, is presented for calculating the fundamental mode sizes in optical channel waveguides. Variational expressions for the square of the propagation constant, β2 , of the TE- and TM-like modes are derived using the vector wave equations. For channel waveguides with gradual refractive index distributions, these expressions approach the variational expression obtained using the scalar wave equation. To show the usefulness of the numerical technique the authors present the results for titanium indiffused lithium niobate channel waveguide which are commonly used in integrated optical circuits. Since these waveguides have gradual refractive index distributions, both types of expressions give the same results; however, it takes less time to compute the mode sizes when using the variational expression obtained from the scalar wave equation. The authors find the calculated mode sizes are in good agreement with published measurements. From the comparison process, best fit parameters are obtained, which give mode sizes close to the values published in the literature. For one special case the authors are able to obtain an analytical variational expression and they use it to test the accuracy of the numerical method. They find that the values of β2 given by both methods agree to six significant figures 相似文献
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针对阵列波导光栅设计中自由传播区模式有效折射率的确定问题,提出了一种采用加权等效模式折射率作为自由传播区模式有效折射率的方法。通过引入慢变包络近似条件并采用吸收边界条件的一阶Galerkin有限元法,给出了阵列波导光栅自由传播区仅含有磁场分量的全矢量波动方程组。在此基础上,基于三维全矢量束传播法对自由传播区光场进行了模式分析,并结合导模传输分析法,推导给出了加权等效模式折射率的表达式,为阵列波导光栅设计中自由传播区模式折射率的确定提供了一个理论依据。 相似文献
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为了研究无衍射光波在特异材质内的传输特性,实现更优良的光波通信,将传统右手材料和双负折射率材料相结合,提出了一种轴向阶跃变化周期圆形介质结构。基于广义惠更斯-菲涅耳光学积分公式,结合光学传输矩阵,分析了艾里光束在这种传输媒质中出射表面光强分布特性和侧面传输光强分布图;分析了负折射率参量对这类光波演变的影响及其补偿机理;分析了实现输出光波完美还原时,负折射率大小同介质单元长度的定量关系。结果表明,当介质孔径逐渐减小时,有限艾里光束衍射效应越来越严重,并且出射光强外形轮廓逐渐从艾里光束过渡到高斯光束;当双负折射率材料的折射率nl的绝对值大于右手材料的折射率nr时,出射表面实现光波完美还原的双负折射率材料单元层越长,反之则越短。该研究对分析周期或准周期轴向阶跃变化的圆形平板介质光波通信是有帮助的。 相似文献
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In two-dimensional optical waveguides with the varied refractive index along the transverse direction, the wave propagation is accurately computed. The asymptotic mode solutions are taken as initial guesses for Rayleigh Quotation iteration. More accurate solutions by considering leaky modes and both wave propagation in the transverse electric (TE) and transverse magnetic (TM) are obtained. Numerical simulations demonstrate that the results from Rayleigh Quotation iteration with the asymptotic solutions are better than ones from Lapack solver when the norms of modes are large enough. Thus, it is the best way to combine the two solvers together. This method is particularly useful to the design and simulation of micro waveguide with core layer refractive index fluctuation. 相似文献
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Won Jay Song Song G.H. Byung Ha Ahn Minho Kang 《Antennas and Propagation, IEEE Transactions on》2003,51(6):1185-1198
We have applied the effective index method to reduce the two-dimensional (2-D) refractive index profile into the 1-D refractive index structure and modified the wave equations to obtain the paraxial wave equations. Then, transverse electric (TE) and transverse magnetic (TM) polarized fields in the curved single-mode planar waveguides are analyzed by using the scalar beam-propagation method (BPM) employing the finite-difference method with a slab structure. The bending loss in bent waveguides is analyzed for optical fields obtained from the BPM and comparisons are made between the loss for the waveguides with various radius of curvature and refractive index difference. The outward shift of the optical field, which is generated at the connection between a straight and a bent waveguide, is obtained from the results of calculation of location of the maximum optical intensity. The transition loss can be reduced by introducing an optimized inward offset at a straight-to-bend junction. The birefringence for TE and TM polarized fields in bent waveguides is calculated from the phase difference of the optical fields. The wavelength shift due to the birefringence of TE and TM polarized fields in bent waveguides is also calculated. 相似文献