Novel Broadband Bow-Tie Antenna Based on Complementary Split-Ring Resonators Enhanced Substrate-Integrated Waveguide

This paper presents a broadband bow-tie antenna based on the metamaterial-inspired periodic structure of coupled complementary split-ring resonators substrate-integrated waveguide for the first time. The CSRRs and two branches of the bow-tie patch are etched on the top and bottom metal surfaces of the substrate. The CSRRs produce a resonant frequency, which can be combined with the two resonant frequencies produced by the bow-tie patch and the feedline of the bow-tie patch. The bandwidth can then be broadened. In order to enhance the gain in the low-frequency bandwidth, the gap width g of the CSRR is decreased without destroying its broadband characteristic. By decreasing g from 1 to 0.5 mm, the minimum gain in the low-frequency bandwidth is increased from 3.4 to 5.2 dBi, and the flat gain characteristic is obtained in the whole operating frequency range. The experiment results show that the realized antenna can operate from 7.3 to 10.3 GHz with the gain of 5.1 to 6 dBi. The absolute bandwidth is about 3 GHz, and the relative bandwidth is about 34.1%. Compared with the results for dipole antennas based on traditional SIW which with a series of metalized via holes embedded in a thin metal-backed dielectric substrate as the side walls, the relative bandwidth is improved about at least 17.7%.