Performance enhancement of novel antipodal Vivaldi antenna with irregular spacing distance slots and modified-w-shaped metamaterial loading

This paper proposes a novel enhanced far-field performance antipodal Vivaldi antenna (AVA) by including slots into the flare with irregular spacing distance between each other and modified-w-shaped metamaterial (MWSM) unit cells etched on both sides of the substrate. The MWSM unit cell is simulated in finite element method commercially available software HFSS version16 and the effective parameters of the meta-atom are extracted by homogenization retrieval method based on transmission and reflection coefficients. Electric field and surface current distribution are displayed to qualitatively explain the occurrence of near-zero index permittivity, permeability and refraction index in 10 GHz. The unloaded and loaded modeled AVA simulation is provided, respectively, in detail and manufacturing procedure is conducted to verify the effectiveness of the suggested ideas. The return loss measurement indicated a good impedance match between the bare AVA and the loading composite MWSM unit cells despite little discrepancy compared to the simulation results. Numerical simulation reveals that the gain of the composite AVA increases from 7.5 to 11.52 dB after loading with the irregular spacing distance slots in the flare and MWSM unit cells etched substrate. The half-power beamwidth decreased from 72.4° to 41.4° for the E -plane and reduced to 33.38° from 63.4° for the H -plane, respectively. The measured results of the fabricated prototype are consistent with the simulated ones with slight discrepancy. This presented strategy will combine the advantages of the lens effect of metamaterial on the AVA and modified radiating flare, thus keeping the low profile of the whole structure all the time.