A spirally complementary split-ring resonators antenna for circular polarization and RFID reader application

A spirally complementary split-ring resonators (CSRRs) circular polarization antenna fed by a microstrip line is proposed. The antenna size is compact with an area of 100 × 100 mm² (0.305 λo × 0.305 λo), which is very suitable for the handheld UHF RFID reader system. The measured impedance bandwidth (|S₁₁|= -10 dB) is ~13.8% (900-1035 MHz) and the 3-dB axial ratio bandwidth is ~3.7% (905-940 MHz).