A DETACHED ZERO INDEX METAMATERIAL LENS FOR ANTENNA GAIN ENHANCEMENT

Abstract

In this paper, a detached zero index metamaterial lens (ZIML) consisting of metal strips and modifled split ring resonators (MSRRs) is proposed for antenna gain enhancement. The efiective permittivity and permeability of the detached ZIML are designed to synchronously approach zero, which leads the ZIML to having an efiective wave impedance matching with air and near-zero index simultaneously. As a result, neither does the detached ZIML need to be embedded in horns aperture nor depends on auxiliary re∞ectors in enhancing antenna gain, which is quite difierent from conventional ZIMLs. Moreover, the distance between antenna and the detached ZIML slightly afiect the gain enhancement, which further conflrms that the ZIML can be detached from antennas. Simulated results show that the efiective refractive index of the detached ZIML is near zero in a broad frequency range where the efiective relative wave impedance is close to 1. The detached ZIML is fabricated and tested by placing it in front of an H-plane horn antenna. One flnds that evident gain enhancement is obtained from 8.9GHz to 10.8GHz and the greatest gain enhancement reaches up to 4.02dB. In addition, the detached ZIML can also work well at other frequencies by adjusting its geometric parameters to scale, which is demonstrated by designing and simulating two detached ZIMLs with center frequencies of 2.4GHz and 5.8GHz, respectively.