Patch antennas are one of the most attractive antennas for integrated RF front end systems due to their compatibility with microwave integrated circuits. To fulfill the demand of integrated RF front end systems, a design of microstrip patch antenna with optimum performance at 12 GHz is investigated. It is also investigated how the performance properties of a microstrip patch antenna are affected by varying the dielectric constant of substrate and width to length ratio of the patch. In this present work a liquid crystal polymer substrate with dielectric constant of 3.1 is taken and the total simulation is done using the software Ansoft-HFSS.