Design of a microstrip patch antenna to achieve the dual polarization by using ground plane, having a square backed cavity in order to increase and achieve the bandwidth with good isolation is proposed in the paper. In this proposed model we are using the proximity coupling mechanism as the feeding technique. The antenna in the paper has four feed lines which are electromagnetically coupled with the patch and now the pair of the two feed lines which are in the same direction are excited out of phase which results in high isolation between the pair of ports. The cavity which is made in ground plane acts like another radiator in order to enhance the bandwidth. The results which obtained shows a very good isolation and the bandwidth is enhanced by using the square backed cavity. The applications of these model are seen weather radar. © 2017 IEEE.