A Miniaturized and High Gain Double-Slot Vivaldi Antenna Using Wideband Index-Near-Zero Metasurface

In this paper, a wideband, miniaturized, and high gain double-slot Vivaldi antenna is proposed. First, a corner cutting technique is adopted to broaden the frequency band. Second, a pair of defected ground slots is added to the edges of the antenna to extend the low-end frequency limitation from 2.27 to 1.15 GHz, which provides a great design freedom. Third, a novel unit cell of an index-near-zero metasurface is proposed in our design. The unit cell is a two-stub-loaded split-ring resonator, which has a compact size, a wide frequency band, and a good reflection coefficient. The gain of the double-slot Vivaldi antenna is improved over a wide frequency band by the inclusion of the index-near-zero metasurface in the aperture, without changing the overall dimensions or compromising the whole frequency band performance of the antenna. Finally, to verify the design method, an ultra-wideband double-slot Vivaldi antenna with defected ground slots and metasurface was fabricated and measured. The circuit has an overall size of 0.76 λg × 0.41 λg × 0.005 λg. The modified antenna exhibits a measured gain of 0.7-14 dBi over the frequency band of 1.13-12 GHz.