FSS reflector-based RFID reader antenna for UHF/SHF applications

Abstract

In today’s world, RFID (Radio Frequency Identification) technology is growing increas- ingly, especially in sectors such as logistics, healthcare, access control, and localization. A dual-band circularly polarized RFID reader antenna consisting of two layers and operates at the UHF/SHF band using FSS is designed to be used for long read range RFID applications. The first layer is a dual-band CP antenna with dimensions 120 × 140 × 0.817mm3. The antenna is CPW-fed within L-shaped line. The antenna consists of an L-shaped line inserted and aligned with a square rotated at an angle of 45◦ so that the lat- ter is also aligned With a curved line and an L-shaped strip line to the left of the circular slot. Two inverted L-shaped strip lines to the top left of the circular aperture have two gaps to achieve circular polarization, and three L-shaped strip lines to the bottom to the right of the circular slot. Two inverted L-shaped strip lines to the top left of the circular aperture have two gaps to achieve circular polarization, and three L-shaped strip lines to the bottom to the right of the circular slot. The operation bandwidth of this antenna is 881-942 MHz, centred at 915 MHz and 2.32-2.52 GHz, centred at 2.45 GHz. The antenna shows a broadside circularly polarized (CP) radiation with a gain of -1.26 dBic at 915 MHz and 3.26 dBic at 2.45 GHz. To enhance the antenna gain in both the two operating bands, a second layer of a frequency selective surface (FSS) structure is added, with a periodic array of double square loops. The FSS size and the distance between the two layers are optimized to realize the field positive superposition. The simulated results show that the gain is enhanced to 3.74 dBi at 915 MHz and 7.11 dBi at 2.45 GHz. The proposed antenna shows high capabilities of high gain and dual-band in circularly polarized radiation.