Circularly Polarized Broadband Co-Planar Waveguide fed Antenna for 2.45 GHz RFID Reader

Abstract

In this paper, a bi-directional coplanar-waveguide (CPW)-fed antenna with circular polarization (CP) is presented for radio frequency identification (RFID) reader applications. By incorporating an inverted L-shaped arm at the left side and a and tuning stub at the right side of ground plane in a conventional CPW-fed monopole antenna, a wide impedance bandwidth and axial-ratio bandwidth (ARBW) is achieved. The antenna geometry is square in shape and printed on one side of FR4 substrate only, which consumes an overall dimension of $60 \times 60$ mm2 with a thickness of 1.5 mm. The antenna is simulated and the simulation results shows an impedance bandwidth $(\mathrm{S}11 \lt -10$ dB) of 40.2% (2.18–3.28 GHz) and ARBW ($\lt3$ dB) of 28.3% (2.03-2.7 GHz), respectively. The peak gain of the proposed antenna is 3.17 dBi in both ±Z direction. The antenna is suitable for Internet of Things (IoT) based RFID applications.