Hybrid metamaterial technique for performance improvement of monopole antenna for WLAN

Abstract

A technique of hybrid metamaterial for performance improvement of a quarter wave monopole antenna is proposed in this paper. The hybrid metamaterial is comprised of two-structure, namely the metallic holes structure for bandwidth and impedance matching improvement and the vertical wire medium structure added circle around the monopole for increasing gain and profile of a quarter wave monopole antenna at the operating frequency of 2.45 GHz for WLAN applications. Metallic holes structure is a specific type of metamaterial in which frequency selective surfaces (FSS). These surfaces are periodic structures normally applied as superstrates in antenna to enhance its performance, especially bandwidth and impedance matching. While, the wire medium structure, wire metamaterial, demonstrates a large type of artificial electromagnetic structures, which can be considered as dense arrays of aligned metal wires or rods embedded into dielectric matrices. The improvement of antenna gain of the wire medium technique is to transfer the electromagnetic fields from a quarter wave monopole through this vertical wire medium placed surrounding of the monopole, therefore, the phases of electromagnetic wave transmission are equal resulting in ultimate resonance. When the hybrid metamaterial structures, metallic holes and vertical wire medium structures, are placed circle around the monopole with suitable parameters and optimized spacing, we found that this proposed monopole antenna not only provides a better bandwidth and impedance matching, but also a high gain improvement of 9.81 dB or raised up around 6.37 dB when compared with a basic monopole.