A novel miniaturized ultrawideband (UWB) half-mode Vivaldi (HM-Vivaldi) antenna based on mirror image theory is proposed in this letter. The antenna consists of half a modified radiating arm and two rows of metallized vias, which are equivalent as the perfect electric wall. According to the mirror image theory, the induced current on the electric wall can replace the mirror image current of the radiating arm at its symmetrical position, which will result in the HM-Vivaldi structure. The antenna size of 0.35λ0L × 0.54λ0L (λ0L is the free-space wavelength at the lowest operating frequency) is reduced by 33% compared to the original antipodal Vivaldi antenna size. In addition, the continuous exponential curved edge on the ground is improved to retain the wideband impedance match characteristic. The operation theory and parametric analysis of this HM-Vivaldi antenna are presented with a prototype being measured. An UWB from 5.3 to 40 GHz with the reflection coefficient lower than –10 dB is experimentally achieved except that |S11| is slightly higher than –10 dB at several frequencies, and the maximum gain reaches 11 dBi.

中文翻译：

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基于镜像理论的小型化超宽带半模Vivaldi天线

这封信提出了一种基于镜像理论的新型微型超宽带（UWB）半模维瓦尔第（HM-Vivaldi）天线。天线由半个改进的辐射臂和两排金属化过孔组成，相当于完美的电墙。根据镜像理论，电墙上的感应电流可以代替辐射臂对称位置处的镜像电流，从而形成HM-Vivaldi结构。0.35λ0L × 0.54λ0L（λ0L为最低工作频率下的自由空间波长）的天线尺寸比原来的对映Vivaldi天线尺寸减小了33%。此外，对地面连续指数曲线边缘进行了改进，保留了宽带阻抗匹配特性。该 HM-Vivaldi 天线的工作原理和参数分析与正在测量的原型一起展示。除了 |S11| 之外，通过实验实现了从 5.3 到 40 GHz 反射系数低于 –10 dB 的 UWB。在几个频率下略高于–10 dB，最大增益达到11 dBi。