The evolution of wireless communication system has led path for innovative antenna design specifically in wideband antenna for WiMax application. In this paper design and simulation of microstrip wideband circular patch antenna array operating between 2GHz to 4Ghz is presented. The circular patch antenna is designed to operate at 3GHz line feed and the ground is itched to achieve required wideband characteristics. The simulation is carried out in EM Flow solver, High Frequency Structure Simulator software. For a single patch antenna, the return loss, lesser than -10dB throughout the bandwidth. Later an antenna array is operating between 2GHz to 4GHz frequency is designed and simulated. The return loss is lesser than -12dBi throughout the band and a peak gain is 14.7dBi. Keywords: Microstrip Patch Antenna (MPA), High Frequency Structure Simulator (HFSS).