Two dimensional metamaterial slot antenna for improved directivity

Abstract

Directivity of an antenna is a figure of merit which shows how effective an antenna is at transmitting / receiving in a desired direction. A highly directive antenna is useful for applications such as satellite communications and radar systems. Directivity is usually achieved using either large antenna apertures or array systems comprising lots of antenna elements. More recently, metamaterials have been investigated for improving the directivity of different types of antennas such as linear wire antennas, patch antennas and horn antennas. Electromagnetic metamaterials are manmade materials which have unusual fundamental properties not readily available in nature. In this thesis, we investigate the possibility of improving the directivity of a slot antenna with a metamaterial substrate. We consider a two-dimensional metal waveguide with a slot and a metamaterial substrate with a point source excitation inside the substrate. The metamaterial substrate is modeled as a Debye medium with dispersive permittivity and permeability. The refractive index of the substrate is (a) negative at frequencies below the plasma frequency; (b) zero at the plasma frequency; and (c) positive at frequencies above the plasma frequency. Transverse magnetic mode wave propagation is simulated using finite difference time domain techniques with perfectly matched boundary conditions. Far field radiation patterns of the antenna are estimated from the electric field at the aperture of the slot. The effect of antenna parameters, such as the length of the aperture, the height of the substrate and the choice of the plasma frequency of the metamaterial, on the bandwidth and directivity of the antenna are studied. The results indicate that reduced beamwidth is achieved for a bandwidth of frequency around the plasma frequency when compared to a conventional slot antenna with an air substrate.