Design of dual circularly polarized antenna with high isolation for RFID application

Abstract

In this paper, a dual-fed circularly polarized antenna design with high isolation is presented for radio frequency identification (RFID) reader. The proposed antenna is excited by two fed ports connected with a circular split-ring microstrip line underneath the ground plane. A radial aperture in the ground plane provides coupling between the split-ring microstrip and radiating patch. For multiple RFID band requirements, the dimension of the aperture can be modified to obtain high isolation on different RFID Band. Finally, an antenna prototype for China RFID Band (920-925 MHz) is fabricated. The measured results agree well with simulation, and show 10-dB matching bandwidth of 18% (820-1000 MHz), 3-dB axial ratio (AR) bandwidth of 11% (854-960 MHz), and 25-dB isolation bandwidth of 11MHz (917-928MHz).