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A compact circularly polarized patch antenna excited by an open circular ring microstrip line through multiple slots is investigated. The lengths of the slots were chosen equal to the diameter of the ring. It was observed that circular polarization (CP) performance and input impedance bandwidth can be improved with the number of slots. A radio frequency identification reader (RFID) antenna with 36 slots and operating at 902-928 MHz was designed and tested. Measured impedance bandwidth of 75 MHz (18%) and 3 dB axial ratio bandwidth of 28 MHz (3%) for the antenna are observed.