This paper presents dual-band circular plate antenna with an inserted annular-ring slot and four-paired rectangular slots excited by a feeding probe for RFID applications. The operating frequencies of the RFID system are 920 MHz to 925 MHz and 2.4 GHz to 2.5 GHz. It is found that at two bands, 922.5 MHz and 2.45 GHz, the |S11| are −14.7 dB and −23.2 dB, respectively. The radiation pattern of the proposed antenna radiates unidirectional beam with vertical polarization for both bands. The half-power beamwidths at 922.5 MHz in XZ-plane and XY-plane are 63.4 ° and 80.1 °, whereas ones at 2.45 GHz in XZ-plane and XY-plane are 35.5 ° and 57.6 °, respectively. The measured gain is higher than 5 dBi at both frequencies.
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