基于扰动理论的蒸发波导传播模态分析方法

A Mode Analysis Method of Evaporation Duct Propagation Based on Perturbation Theory

蒸发波导是形成海上微波超视距传播的主要机制,波导模态理论用于研究微波在蒸发波导中的传播特性,但求解过程复杂,计算时间较长不适于实时应用。根据蒸发波导折射率垂直剖面情况,提出了扰动理论和波导模态理论结合的方法,简化了求解过程,提高了计算效率。应用所编制的模态分析程序,仿真计算了蒸发波导高度不同时低阶模态的传播常数,并与算例比较,验证了方法的计算精确性和快速性。同时进一步分析并给出了信号频率与蒸发波导特性参数及场分布之间的关系。

The evaporation duct has been well recognized as a dominating mechanism for realizing over- the horizon microwave propagation at sea. Waveguide mode theory is used to study the characteristics of microwave propagation in the evaporation duct, but longer calculation time is not suitable for real - time applications. In this article, when calculating the shadow region field distribution, the waveguide mode theory is combined with perturbation theory according to vertical modified refractive profile condition of the evaporation duct, the calculation efficiency has been improved thereby. Several propagation constants of lower order modes for different evaporation duct height are carried out to confirm the accuracy of the method. Furthermore, the relation between transmitter frequency and evaporation duct characteristic parameter and the field distribution is analyzed.