Generally high antenna gain and directivity are required for satellite based communication systems. This study proposes improving the directivity and gain of microstrip patch antenna at Ku-Band (12 GHz). In order to optimize these parameters, Omega-Shaped metamaterial (OSM) is designed as a flat lens in front of Microstrip Patch Antenna (MPA) that tuned to 12 GHz resonance frequency. Computer simulation technology Microwave Studio (CST MWS) was used for modeling and simulation. The permeability and permittivity of the designed metamaterial are extracted from the S parameters by using Matlab.