The Vivaldi antenna is developed as an ultra-wideband antenna with a directive pattern and high gain, which is attractive for radar application and microwave sensing. We have modeled various kinds of Vivaldi antenna and attempted to achieve linear or constant phase center. We realized that the phase center can be controlled by controlling the distribution of fields in level and around the antenna leading to phase control. Also, Vivaldi antennas are used in radar bands and are studied in this paper. In this review paper, we have focused on two main methods for phase controlling and we have debated on their basic theory. In addition, mutual coupling is considered as one of the benefits of these antennas. The open aperture and the photonic band gap substrate are known as two main methods for achieving the constant phase center. The first method discusses combining horn antenna with Vivaldi antenna, and so we have obtained a higher gain and directivity and in parallel way the PBG is used for phase controlling and it shows more gain and directivity enhancement. Here, we compare them and discussed in the background theory of this method. In contrast, we suggest five categories for phase center modification.

中文翻译：

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Vivaldi天线中的相位中心控制：故事的回顾和发展

Vivaldi天线被开发为具有定向模式和高增益的超宽带天线，对于雷达应用和微波感测具有吸引力。我们已经对各种Vivaldi天线建模，并尝试实现线性或恒定相位中心。我们意识到，可以通过控制天线中水平和天线周围的磁场分布来控制相位中心，从而实现相位控制。此外，Vivaldi天线也用于雷达频段，并在本文中进行了研究。在这篇综述文章中，我们集中于两种主要的相位控制方法，并对它们的基本理论进行了辩论。另外，相互耦合被认为是这些天线的优点之一。已知开口孔径和光子带隙基板是实现恒定相位中心的两种主要方法。第一种方法讨论了将喇叭天线与Vivaldi天线组合在一起，因此我们获得了更高的增益和方向性，并且并行地将PBG用于相位控制，它显示了更多的增益和方向性增强。在这里，我们将它们进行比较，并在此方法的背景理论中进行了讨论。相反，我们建议将相位中心修改分为五类。