We propose a wide bandwidth antenna with a circular polarization for universal Ultra High Frequency (UHF) radio-frequency\nidentification (RFID) reader applications. To achieve a wide 3 dB axial ratio (AR) bandwidth, three T-shaped microstrip lines are\ninserted into the ground plane. The measured impedance bandwidth of the proposed antenna is 480MHz and extends from 660\nto 1080MHz, and the 3 dB AR bandwidth is 350MHz and extends from 800 to 1155MHz.The radiation pattern is a bidirectional\npattern with a maximum antenna gain of 3.67 dBi. The overall size of the proposed antenna is 114 Ã?â?? 114 Ã?â?? 0.8mm3.
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