Compact arc-shaped slotted circularly polarized microstrip antenna for RFID readers

A compact arc-shaped slotted circularly polarized (CP) microstrip antenna is presented for ultra high frequency (UHF) radio frequency identification (RFID) handheld reader applications. Four unequal arc-shaped slots are cut diagonally onto the square patch radiator for CP radiation and compact size. The antenna prototype is with an overall antenna size of 90 × 90 × 4.572 mm³ (0.277λ₀ × 0.277λ₀ × 0.0141λ₀ at 924 MHz). The measured 3-dB axial-ratio (AR) bandwidth of around 8.0 MHz with and 10-dB return loss bandwidth of 24.0 MHz are achieved. The gain is up to 3.7 dBic.