A Dual-Band Circularly Polarized Antenna With a Dual-Band AMC Reflector for RFID Readers
Sayan Sarkar, Bhaskar Gupta
Abstract
This letter proposes a circular patch antenna with dual-band circular polarization at the UHF-RFID and WLAN bands. Two perpendicular slots are etched on the patch to down-shift the first resonance to 915 MHz (UHF-RFID band) and introduce a new resonance at 2.45 GHz (WLAN band). Four slits are etched on the ground plane to improve axial ratio (AR) mainly in the first band. A dual-band AMC reflector having 25 unit cells is placed a small distance below the patch to reduce the backlobe level and improve the gain at both bands. Measured 3 dB AR bandwidths of 5.25% and 2% are achieved at UHF-RFID and WLAN bands respectively with gains of 3.1 dBi (UHF-RFID) and 6.25 dBi (WLAN). The antenna system can be used with RFID readers for detecting tags and sending information via the WLAN band.