A Compact and Low-Profile High-Gain Multilayer Vivaldi Antenna Based on Gradient Metasurface Superstrates

This letter presents the design, analysis, and implementation of an electrically compact high-gain multilayer Vivaldi antenna. The multilayer antenna comprises gradient metasurface superstrate layers arranged on the top and bottom of a central electrically compact Vivaldi antenna via low-loss polyethylene foam spacers. The overall electrical dimensions of the antenna are $\text{0.36}\lambda _{0}$ × $\text{0.29}\lambda _{0}$ × $\text{0.06}\lambda _{0}$, covering a bandwidth from 450 MHz to 10 GHz with an average measured forward gain of more than 15 dBi ($\lambda _{0}$: free-space wavelength at 450 MHz). The unit pixel dimensions of the gradient metasurface layer have been optimized to achieve a high-flat gain profile within the desired bandwidth of the antenna. The metasurface layers are printed on thin Kapton polyimide boards to minimize the system's weight. The prototyped antenna is extremely low-profile and weighs 182 g, making it ideally suited for lightweight ultrawideband (UWB) applications needing a very high forward gain.