Design of a Circularly Polarized Patch Antenna for RFID Applications

A compact microstrip circularly-polarized (CP) slotted antenna is presented in this paper. The antenna is having wider operational bandwidth from 713 MHz to 1673 MHz. The antenna is designed with Coplanar-waveguide feed with T-shaped feeding line. Two L-shaped lines are introduced into the slotted area of the ground plane to achieve proper impedance matching. Here four L-shaped slots are incorporated at corners of the ground plane for achieving meandering effect. It shows 80% of fractional bandwidth centered at 1190 MHz with a maximum gain of 4.3 dB. It has 3 dB axial-ratio (AR) bandwidth of approximately 400 MHz i.e. from 1450 MHz to 1859 MHz in higher frequencies of the described frequency band and around 118 MHz i.e. from 590 MHz to 708 MHz. The efficiency is more than 95%. The dimension of the antenna is 0.59 lambda(g) x 0.59 lambda(g) x 0.003 lambda(g), where lambda(g) is the guided wavelength corresponding to lowest cutoff frequency. The antenna is covering ultrahigh frequency band (UHF) and suitable for radio-frequency identification (RFID) reader applications.