A miniaturized multi-frequency antenna is proposed. The proposed antenna can generate three separate impedance bandwidths to cover all the 2.4/5.8 GHz WLAN/RFID operating bands and the 2.5/3.5/5.5 GHz WiMAX bands. The proposed microstrip-fed antenna mainly consists of a circular ring, four semicircular rings, a rectangle strip, and a defected ground plane. By adding four semicircular rings in the circular ring, the antenna excites two resonant modes and is with miniaturization structure. Because of the introduction of the cambered ground plane with an circular-defect, the third wide band with better impedance matching is obtained. A prototype is experimentally tested, and the measured results show good radiation patterns and enough gains across the operation bands.
