Use of discontinuities in ground planes or in micro strip lines is currently employed to improve the performance of different passive circuits. It includes size reduction of amplifiers, enhancement of filter characteristics and applications to suppress harmonics in patch antennas. This paper presents an improved method of size reduction of a micro strip antenna using Defected Micro strip Structure. It does so by introducing imperfections in the micro strip antenna on the conducting layer using a DMS designed defect. The design was simulated using IE3D Electromagnetic Simulator. The results are very encouraging as it increases the number of components in a given constant area. On the other hand, a new proposal, called defected micro strip structure (DMS), has been successfully used in reducing the size of, and can be further used as tuning technique for, rectangular patch antennas.