A novel gain-enhanced antenna with metamaterial planar lens for long-range UHF RFID applications

Abstract

A novel gain-enhanced microstrip antenna (MSA) with metamaterial planar lens for longrange radio frequency identification (RFID) applications for the 902-928 MHz UHF frequency band is proposed in this paper. The antenna is a combination of a new general-purpose circularly polarized MSA and a novel effective negative refractive index metamaterial (NIM) slab of 25 unit cells, arranged in a 5 x 5 layout, working as a planar lens for gain enhancement. The general-purpose MSA has an impedance frequency band of 828-1015 MHz, a maximum gain of 8.43 dBi at 915 MHz, an axial ratio frequency band of 896-931 MHz, and excellent performance for short and medium range RFID applications. The new infinite periodicity NIM slab has a negative refractive band of 886-1326 MHz, a negative electric permittivity band of 888-3406 MHz, and a negative magnetic permeability of band 885-1065 MHz. Together, the general-purpose MSA and the NIM planar lens results in the low-cost gain-enhanced antenna for long-range RFID applications, with an 843-993 MHz impedance frequency band and a maximum broadside gain enhancement of 48.27%, resulting in a 12.5 dBi gain at 902 MHz. Finally, the parametric studies conducted during the design process of the gain-enhanced antenna with metamaterial planar lens are presented.