A compact circularly polarized slot antenna is proposed in this paper, which has a much wider operation bandwidth compared to the antennas with similar sizes. This antenna is designed for universal ultrahigh frequency (UHF) radio frequency identification (RFID) reader applications. The antenna is CPW-fed by an L-shaped feeding line. To achieve good impedance matching and broadband CP operation, two L-shaped strip lines are inserted into the circular slot in the ground plane. The measured 10-dB return loss bandwidth is 380 MHz (618-998 MHz, 47.0% centered at 808 MHz). The measured 3-dB axial ratio bandwidth is about 332 MHz (791-1123 MHz, 34.7% centered at 957MHz). The overall size of the antenna is 120 × 120 × 0.8 mm 3 .

This article proposes a circularly polarized monopole slot antenna which is suitable for ultra‐high frequency (UHF) radio frequency identification (RFID) reader. In this antenna design, a meandering slot is being placed in the ground plane to produce good circularly polarized radiation characteristics, and the microstrip line feed can be adjusted to achieve good impedance matching. Measurement results showed that the 10‐dB return loss bandwidth of the antenna is 10.3% (0.857–0.95 GHz), and the 3‐dB axial ratio bandwidth of the antenna 7.4% (0.878–0.945 GHz). The maximum gain and efficiency of the antenna is 2.09 dBic and 76%, respectively. The overall antenna size is 120 × 80 × 0.8 mm3. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1102–1105, 2016