A novel technique for obtaining a single-layer single-feed dual frequency rectangular microstrip antenna with protruding semi ellipse for s-band communication is proposed and demonstrated. By protruding semi ellipse of appropriate dimension close to one of the edge, the rectangular patch has been shown to realize dual-frequency broadside radiations. This dual frequency operation increases its applications in radar and space communications. The range of the frequency ratio (FR) can be varied from 1.03 to 1.30 by changing the dimension of semi minor axis of protruding semi ellipse. Several optimizations are performed to attain the optimum values of the antenna physical parameters and then a prototype is fabricated. The presented antenna is compact having an area reduction greater than 15% and shows enhanced radiation characteristics compared to the standard rectangular patch. Details of the antenna design and experimental results are presented.