超宽带TEM喇叭天线的低频分离回路设计

在超宽带TEM喇叭天线的设计中，往往由于低频性能优化和天线小型化两者难以兼顾，而使得其应用受到限制。该文针对低频的反射问题，基于带通滤波器并联的设计思路，且区别于传统天线末端的低频反馈回路结构，提出在超宽带TEM喇叭天线馈电过渡结构上设计低频分离回路结构，减少低频分量在天线末端的反射，从而改善天线的低频性能。采用该设计思路，对一款超宽带TEM喇叭天线的结构进行改进并实现其优化设计。通过对比改进前后的天线性能，其阻抗带宽的低频降至0.1 GHz，拓展了12.5%，同时天线端口馈电效率提升10%，结果验证了该设计思路和方法对于超宽带TEM喇叭天线低频优化的有效性。最终，对阻抗特性以及该结构在不同频点下电流分布的分析，进一步证实新思路的可行性。

Design of Low-frequency Separation Structure for Ultra-wideband TEM Horn Antenna

In the design of ultra wideband TEM horn antenna, it is difficult to combine both the character optimization in low frequency and the miniaturization of an antenna, which always limits the usage of TEM horns in some applications. For the problem of low-frequency reflection, a structure, which is referred to the principle of band-pass filters in parallel and different from the conventional ones, is proposed in this paper for separating a fraction of low-frequency electric field component on the plates linking excitation port to radiation plates. It can greatly reduce the reflection of low-frequency component at the edge of radiation plates to improve the low frequency character of the antenna. In this paper, an ultra-wideband TEM horn antenna improved with the proposed structure is presented. Finally, the comparison of the improved antenna and the original one is exhibited, which shows that the impedance bandwidth is 12.5% wider with the low-cutoff frequency decreasing to 0.1 GHz and simultaneously the port-feed efficiency is increasing by 10%. The results confirm the validity of the proposed design to optimize the low frequency character. The feasibility is also validated in the end by analyzing the impedance and the magnitude distribution of currents in different frequencies, respectively.