A Method for Increasing the High Frequency Gain of a Traditional Vivaldi Antenna

This paper presents an approach to improve the high band gain of a conventional Vivaldi antenna. In a conventional Vivaldi antenna, the circular slot at the end of the tapering slot serves to impedance match with the microstrip line and to reflect a small portion of the backward-radiating electromagnetic wave. In this paper, by improving the circular slot into a fin-type slot, the reflection of the backward-radiating electromagnetic wave by the slot line is enhanced, the backward radiation of the antenna is reduced, and the forward radiation is enhanced, so that more currents are gathered in the high-frequency radiating area of the antenna, and thus the antenna’s gain in the high-frequency band is improved. The bandwidth of the antenna is improved by loading rectangular slots on both sides of the tapering slot line. The size of the proposed antenna is $0.75 \lambda_{0} * 0.53 \lambda_{0}$ ($\lambda_{0}$ is the wavelength in free space corresponding to the lowest operating frequency) and the antenna operates in the $4.1 \mathrm{GHz}-13.75 \mathrm{GHz}$ band. The gain of the proposed antenna is more than 8 dBi in $6.6 \mathrm{GHz}-13.7 \mathrm{GHz}$. The gain in the high band is improved by 3dBi compared to the conventional Vivaldi antenna.