Design of broadband multi-frequency antenna based on the defected ground plane

A new miniaturized wide-band multi-frequency antenna is proposed. The proposed antenna can generate three separate impedance bandwidths to cover all the 2.4/5.8 GHz Bluetooth/WLAN/RFID operating bands and the 2.5/3.5/5.5 GHz WiMAX bands. The proposed microstrip-fed antenna mainly consists of four semicircular rings, a circular ring, a rectangle strip, and a defected ground plane. By adding a circular ring in the four semicircular rings, 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.