Left-handed metamaterial incorporated with microstrip antenna

Abstract

Left-handed metamaterial (LHM) is an artificial material where the permittivity and permeability are simultaneously negative at a certain range of frequency. One of the unique properties of the LHM is its negative refraction index which produces focusing effect to the wave propagating through the LHM. With this unique property, the LHM structures are used to increase the low gain of the microstrip antenna. In this work, an LHM structure consists of a modified split ring resonator (MSRR) and two capacitance loaded strip (CLS) is proposed. The MSRR has four slots in the middle of the structure which create wider range of negative permittivity and permeability. The MSRR exhibits negative permeability while the CLS exhibits negative permittivity. The well-known modified Nicolson-Ross-Wier (NRW) approach has been used to determine the values of permittivity and permeability. Parametric study on the parameters of the LHM has been carried out. The gap between the CLS – MSRR, the MSRR length and the CLS width show strong influence to the resonant frequency and the range of negative permittivity and permeability. A series of LHM structures are then incorporated with different antenna type such as single patch antenna, linear polarized 2x2 array patches antenna and circular polarized 2x2 array patches antenna at operating frequency of 2.4 GHz. The simulation and measurement results such as return loss, bandwidth, gain, half power beamwidth and radiation pattern are analyzed. The gain of the antennas increased upto 4 dB while the half power beamwidth decreased upto 37 % and became directional. The bandwidth of the antennas also increased upto 60 %.