共查询到19条相似文献,搜索用时 187 毫秒
1.
地下水平电偶极子在均匀球形地面产生的侧面波 总被引:3,自引:2,他引:1
讨论了位于地下的水平电偶极子在均匀球形地面上产生的侧面波(Lateral wave)。从位于球形地面场的垂直电偶极子和磁偶极子在地面上建立的电磁场出发,利用互易定理,获得了地下水平电偶极子在地面上和地面下产生的既方便于数值计算又具有足够精度的电磁场的解析表达式。计算结果表明,由于地球曲率的影响,沿球形地面传播的侧面波比沿平行地面传播的侧面波衰减的快,当收发地点的距离超过40km后,地球曲率对传播的影响就不能被忽视,对地下通信以及潜艇通信有一定指导意义。 相似文献
2.
在理想化的均匀球面通过进一步地与具有突变边界的均匀各向同性同心球面电离层条件下的LF天波全波解的基础上,考虑由海陆之差引起的地面导电率的变化、大气和低电离层的不均匀性以及由地磁场引起的各向异性特性等因素的影响,推导出了较严格预测实际地与低电离层条件下场强与传播相延精确预测的完善公式。 给出了一些低电离层模式参数的实测结果。这些模式参数为参考高度h0、参考浓度N0与梯度参数α。由罗兰-C天波信号场强与相位的精细测量数据求得的。 相似文献
3.
4.
5.
6.
本文利用模式匹配技术得到侧面波沿森林覆盖的平面-曲面-平面地带上传播时的绕射与散射的解。当曲面地带的半径远小于地球的半径时,这种地带可以被看成平面-曲面-平面地带的组合。利用阿里函数的计算机程序可以计算高频侧面波沿森林覆盖的平面-曲面-平面地带上传播时的衰减因子。 相似文献
7.
8.
9.
调频连续波雷达(FMCWR)具有分辨率高、信号动态范围大、对周围电磁环境干扰小、抗干扰能力强等特点,得到广泛应用,特别适用于海事交通管制系统(VTS)。由于调频连续波雷达发射的是连续波,不能像脉7中式雷达那样可以采用电开关来控制天线的收发转换,而必须将发射天线和接收天线分隔开来,因此接收天线对发射天线的隔离度就成为FMCWR雷达设计的重要指标。本文根据洛伦兹互易定理,结合平面波谱法(PWS),推导出调频连续波雷达收发天线间的隔离度公式,通过对比仿真计算结果和实测结果,达到了较好的一致,验证了计算方法的有效性。 相似文献
10.
11.
Curves for ground wave propagation over mixed land and sea paths 总被引:1,自引:0,他引:1
Specific numerical results are presented for ground wave propagation over paths which are part sea and part land. The problem is idealized to the extent that the earth is a smooth spherical surface. The method is based on a previous formulation in terms of mutual impedance between two vertical electric dipoles on an inhomogeneous spherical earth. Amplitude and phase of the ground wave are given for various combinations of the following parameters: frequency 1000, 100, and 20 kc; land conductivities 100 and 10 mmhos/meter; and a sea conductivity of 4 mhos/meter. Most of the curves exhibit the well-known recovery effect which occurs beyond the coast line for propagation from land towards the sea. 相似文献
12.
通过对球面波复射线展开的物理图象的分析,将球面波的复射线展开转化成了对单个复射线束振幅的求知(均匀波)或加权求和(非均匀波)问题,从而方便地给出了弱非均匀球面波的展开系数,而均匀球面波则作为其特例给出。 相似文献
13.
You-Lin Geng Xin-Bao Wu Le-Wei Li Bo-Ran Guan 《Antennas and Propagation, IEEE Transactions on》2005,53(12):3982-3989
Electromagnetic scattering by an inhomogeneous plasma anisotropic sphere is formulated and obtained, where the inhomogeneous plasma anisotropic sphere is divided into (s-1) homogeneous anisotropic spherical layers. The electromagnetic fields in the inner spherical multilayers and outer free space of the inhomogeneous plasma anisotropic spherical structure can be expanded in terms of the spherical vector wave functions in plasma anisotropic medium and in isotropic medium, respectively. By applying the continuous boundary conditions of electromagnetic fields on the spherical interfaces of the (s-1)-layered homogeneous anisotropic plasma medium, the unknown expansion coefficients of fields in the multilayered plasma spherical structure are obtained, and then the electromagnetic field distributions are calculated. Numerical results for the very general inhomogeneous plasma dielectric material sphere are given and the data in a special case are obtained using the present method and the method of moments accelerated with the conjugate-gradient fast-Fourier-transform approach and compared to each other to verify the correctness and applicability of the present analysis. 相似文献
14.
Constant impedance boundary conditions have been used by many authors to obtain mode reflection and transmission coefficients for propagation across a land-sea discontinuity. The impedance boundary conditions are here replaced by exact boundary conditions and similar formulae are obtained for propagation between a diffuse inhomogeneous isotropic ionosphere and a homogeneous isotropic earth. These formulae permit the use of any ionospheric model with vertical inhomogeneity although some simplification results if impedance boundary conditions are used at the ground. A numerical example is given to illustrate the significance of the formulae. 相似文献
15.
实测大气模型下雷达定位公式的解析式兼论有效地球半径 总被引:1,自引:0,他引:1
实测大气模型,只能用多个线性成层大气模型的总和来代表。据此导出了实测大气模型下,目标视在距离的精确解析求和式。从而当初始视在仰角为零时,可得到目标视在距离的精确解。该文指出,使用中值近似是获取大气折射精确解的一种途径,而且通过积分中值近似可导出有效地球半径。对有效地球半径的推导方法和应用进行了讨论。 相似文献
16.
《Microwave Theory and Techniques》1976,24(7):404-409
An approximate theory on the propagation of modes in an arbitrarily inhomogeneous optical waveguide embedded in a homogeneous medium is presented. Simple formulas are given, whereby the propagation constants can be determined assuming that the analytic solution is known in the absence of cladding. The results obtained applying the theory to a truncated parabolic-index profile are shown to be in good agreement with those obtained by the rigorous analysis. The theory is also applied to the propagation of TE and TM waves in truncated near-parabolic-index media. 相似文献
17.
由平直有耗地面上垂直电偶极子产生地波场的解析解和互易原理,本文导出了用FDTD方法处理目标地波散射问题时的近一远场外推公式。在数值结果验证了该公式的正确性之后,对海上一金属半球的地波散射场进行了求解,并以此与李清亮等(1997)提出的工程应用方法相对比,考察了工程应用方法的适用性。 相似文献
18.
A new variational expression is derived for the propagation constant of inhomogeneous shielded and open planar lines with gyrotropic lossy substrates. It yields rapidly convergent results even when higher order modes are considered. Results obtained on open and shielded lines and structures agree very well with experimental results. The efficiency of the formulation is such that calculations are made on-line on a regular PC 相似文献