Wideband Single-Fed Circularly Polarized Antenna for RFID Application

A novel single-fed wideband stacked circularly polarized (CP) microstrip antenna with a perturbated square ring is proposed in this work. This antenna has a relatively small size since four symmetric square slots and a cross-shaped slot are incorporated into the square patch, which extends the current path and reduces the overall size. The antenna bandwidth is substantially enhanced with the combination of a perturbated square ring and a slot-loaded parasitic patch. All the substrates are made by low-cost FR4 material. LHCP radiation is implemented by choosing the position of the structure perturbation in the square ring. Good agreement is observed between measurement and simulation. The measured −10 dB bandwidth, 4 dB axial ratio and peak gain is 15.3 % (853–993 MHz), 880–945 MHz, and 7.2 dBic, respectively. The proposed CP antenna demonstrates advantages of a compact size, low-cost, wideband, and good radiation performance, which is suitable for RFID reader application.