A NOVEL GAIN-ENHANCED ANTENNA WITH METAMATERIAL PLANAR LENS FOR LONG-RANGE UHF RFID APPLICATIONS

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 × 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.