单负材料填充包层的矩形波导模式特性

【目的】通过求解矩形波导模式特征方程,计算矩形波导横向场分布,研究电磁波在单负材料矩形波导中的传播特性以及该波导参数对其导模Exmn的影响规律。【方法】基于电磁场的波动理论和马卡梯里假设,利用图解法对波导有效折射率及横向电场分布进行求解,并分析波导模式的频率色散关系。【结果】该矩形波导的传播模式Ex0n和Ex1n为x方向衰减的表面模,仅当m1时,波导的传播模式才是振荡导模;固定波导芯子层厚度不变,当导波频率增大时,高阶模向高频方向移动的速度比低阶的快;保持m1,当m或n增大时,Exmn模式的截止点均向波导孔径增大的方向移动,且相邻模式的截止间距相等。【结论】单负材料包层的矩形波导既支持存在低阶表面模的条件,也支持存在高阶振荡导模的条件,波导孔径大小对导波模有很好的调制效果,可实现宽孔径多模传输和小孔径单模传输的功能。

Properties of Guided Modes in Rectangular Waveguides with Single Negative Materials

Objective] The propagation properties of electromagnetic wave and the regulation of waveguide parameters to the guided mode E_mn^xare studied by solving the equation of waveguide mode and calculating the transverse field distribution in rectangular waveguide with single negative materials.Methods] Based on the electromagnetic wave theory and the assumption of Marcatili''s, the effective index and the transverse field distribution are solved, and the frequency dispersion of guided mode is obtained numerically by using the graphical method.Results] The propagation modes of E_0n^x and E_1n^x in the rectangular waveguide are the surface modes in x-axis direction, and wave-guide propagation mode will be oscillating mode only when m>1;when the wave-guide core layer thickness is fixed, the translational speed of high-order mode moves to higher frequency and is quicker than the low order with the frequency of guided mode increasing; when keeping m>1, the cut-off point of E_mn^x mode moves to the direction of widen wave-guide aperture with m or n increasing, and the cut-off distance is the same of the adjacent mode.Conclusion] The rectangular waveguide with single negative materials supports both high-order guided modes and low-order surface modes.The modulation effect of waveguide aperture size to wave guided mode is very well, which can realize the function of wide aperture multi-mode transmission and small aperture single-mode transmission.