In this paper, a circular microstrip antenna with a novel angular unconnected Defected Ground Structure (DGS) is proposed. In the absence of DGS the structure is found to resonate at the WLAN band i.e 5.8 GHz. When the DGS is introduced, the antenna is observed to resonate at the Bluetooth band i.e. 2.4GHz. Gradually as the length of the DGS is modified, the antenna is made to resonate at WiMAX band i.e. 3.5GHz and at IMT band i.e. 3.8GHz. Thus the antenna has been frequency tuned by modifying the length of the DGS to resonate at the Bluetooth, WiMAX and IMT bands respectively.