A novel design of a multi band microstrip antenna is presented in this work. The double modified U slots planar patch antenna is designed, simulated and fabricated to operate at 2.8 GHz (between 2.794 to 2.846 GHz), at 3.1 GHz (between 3.145 to 3.196 GHz), at 3.6 GHz (between 3.56 to 3.3.644 GHz), at 4.7 GHz (between 4.684 to 4.772 GHz) and at 5.4 GHz (between 5.423 to 5.526 GHz) for WiMAX/WLAN applications. One of the main challenges was keeping a low profile and low cost substrate (1.2mm and FR4 respectively) with penta-band frequency response without scarifying these characteristics. Each resonant frequency is accomplished by modifying each U slot and patch radiator itself. Simulations had been conducted using HFSS software and measured parameters such as reflection coefficient (S11 parameter) was performed with a vector network analyzer. Measured results confirm simulated results that the antenna could work within mentioned frequencies. Parametric study was conducted in order to study the effect of slots variation over the design.