This document describes the design and simulation of a dual band triangular slotted planar monopole circular antenna for WiMAX applications. The antenna consists of a circular radiating patch with an isosceles triangular slot, printed on an FR-4 substrate. A defected ground plane is used to improve bandwidth. Simulation results show the antenna resonates at 3.5GHz and 5.3GHz with return losses below -30dB, meeting WiMAX bandwidth requirements. Measured results agree well with simulations. The antenna has omnidirectional radiation patterns and gains of 2.19dBi at 3.5GHz and 3.63dBi at 5.3GHz, making it suitable for short range wireless communications.