Ab stract- M odern wireless systems are placing greater emphasis on antenna designs for future development in communication technology because of antenna being the key element in the whole communication system. The microstrip antenna in a system serves as the transducer between the controlled energy residing within the system and the radiated energy existing in free space. This antenna is very good for wireless communication due to it’s light weight, low volume and low profile planer configuration which can be easily made conformal to host surface. Additionally, some of it’s characteristics like low fabrication cost, supportive nature for both linear and circular polarization, and low sensitivity to manufacturing tolerance make this antenna very important for next generation. However, a major disadvantage of this type of antenna is that it has very narrow band width. In this paper, we remove such type of disadvantage of rectangular microstrip antenna by adding a PBG structure. We first describe briefly the properties of the microstrip antenna & photonic band gap structure and after this we design a rectangular microstrip antenna with PBG structure using cavity model method. Then the results are simulated with IE3D based on MOM method. At the end, we compare the simulated and measured results. We find that the bandwidth of microstrip antenna is enhanced by adding a PBG structure . K eywords: Bandwidth, Directivity, Microstrip Antenna, Method of Moment (MOM), Photonic Band Gap Structure.