蒸发波导环境下风浪对电磁波传播影响的数值模拟研究

INFLUENCE OF WIND SPEED ON ELECTROMAGNETIC WAVE PROPAGATION UNDER EVAPORATION DUCT CONDITION BASED ON SEA SURFACE MODEL

蒸发波导是一种特殊的大气波导,在其中传播的电磁波信号会被陷获在近海大气层中,实现超视距传播。受海表面温度、湿度、风速、微波频率等因素的影响,海洋蒸发波导环境中的微波传播特性起伏变化很大,规律十分复杂。以往的工作主要通过计算这些气象因素对蒸发波导条件下大气折射率剖面的影响来分析它们对路径损失的作用,其结果与实验数据仍有较大差异。本文在一定的蒸发波导条件下,利用一维分形海面模型产生海面“地形”,将其作为抛物方程电磁波传播模型的边界条件进行计算,得到相应的路径损失,并与传统计算方法进行对比,分析了不同蒸发波导高度、不同频率及不同接收天线高度时的数值模拟情况,可为舰艇通信系统或者雷达系统的设计提供相应的依据。

An evaporation duct is a kind of atmospheric ducts in which electromagnetic wave could be trapped to achieve over-the-horizon propagation.Affected by temperature,humidity,wind speed,and microwave frequency above sea surface,the characteristics of microwave propagation in an ocean evaporation duct are very complicated.Previous works focus on the effects of meteorological factors on the refractive index profile of the evaporation duct,and the simulation results are biased from the observation.Therefore,we analyzed the influence on the propagation path loss and found that the calculated results are quite different from the experimental data using a one-dimensional fractal sea surface model to generate sea surface“topography”.In addition,we input the calculated results to the parabolic equation propagation model,compared the corresponding path loss with that of traditional method,and analyzed the outputs under different evaporation duct heights,frequencies,and receiver heights.When the frequency of microwave propagating in the evaporation duct is less than 4.5 GHz,wind speed has little influence on the propagation path loss.When the microwave frequency is about 6-10 GHz,the path loss difference becomes more obvious.The findings of this study could be applied to the design of ship communication system or radar system.