异型截面波导模式变换技术

异型截面波导具有特殊的模式传输特性，理论上能够扩展现有的变模技术，推动多频点、宽带宽和紧凑化模式变换器的发展。但由于其结构复杂，难以通过数学方法直接获得准确描述模式耦合过程的解析表达，从而抑制了此类技术的发展。从麦克斯韦方程组出发，重新推导并给出了基于矢量波形函数的弯曲波导耦合波方程组以及耦合系数的表达式，结合数值求解矢量波形函数的方法即可解决异型波导模式变换器的优化问题。为验证该技术途径的有效性，设计了一个工作在X波段的椭圆波导TM₀₁-TE₁₁模式变换器。仿真与数值计算结果一致，表明该模式变换器变模效率高于95%的带宽为10%，最高转换效率高于99%，较经典的圆波导变模器件有着更好的性能表现。

The Mode Conversion Technology of Special-Shaped Section Waveguide

The special-shaped section waveguide has special mode transmission characteristics. In theory, it can expand the existing mode conversion technology and promote the development of multi-frequency point, broadband and compact mode converter. However, due to its complex structure, it is difficult to directly obtain the analytical expression to accurately describe the mode coupling process through mathematical methods, which inhibits the development of this kind of technology. Based on Maxwell's equations, the coupled wave equations of curved waveguide and the expression of coupling coefficient based on vector waveform function are deduced and given. Combined with the numerical solution of vector waveform function, the optimization problem of special-shaped waveguide mode converter can be solved. In order to verify the effectiveness of this technical approach, this paper attempts to design an elliptical waveguide TM₀₁-TE₁₁ mode converter working in X-band. The simulation and numerical results show that the mode conversion efficiency of this mode converter is higher than 95%, the bandwidth is 10%, and the maximum conversion efficiency is higher than 99%. It has better performance than classical circular waveguide mode converters.