The performance study of rectangular micro strip patch antenna at X band frequency is presented in this paper. The resonant frequency is chosen at 10 GHz which is suitable for a variety of wireless applications. HFSS tool is used as the software environment to design and compare the performance of the antennas. It is found that the return loss of improved patch antenna is very low compare to simple rectangular patch antenna. In addition, the improved rectangular patch antenna has an improved VSWR value of 1.12 than that of the simple patch with VSWR 2.73.