This book describes about the experimental and simulation work carried out on rectangular microstrip antennas (RMAs). The various RMAs have been designed and fabricated on easily available, low cost FR4 dielectric material at S-band frequency. The patch element (radiator) is excited using co-axial probe feed technique. The effect of slots, slits, stubs in enhancing the various antenna parameters such as compactness, impedance bandwidth and gain are studied in detail. Compactness, impedance bandwidth and gain of RMA has been enhanced using various techniques such as patch with slots, slits on patch, stubs loaded patch on 0.16 cm thick dielectric material with inverted patch configuration having air as a substrate medium. With these techniques, a compactness of 78%, 12.41% of bandwidth. It is also concluded that by etching the various slits on the patch having a superstrate thickness of 0.24 cm (2.4 mm thick Yagi-RMA and 2.4 mm thick H-RMA). This technique reduced the maximum physical size (compactness) of the antenna upto 98.3 % with a gain of 7.13 dB.These antennas may find applications in the wireless, microwave communication systems operating in L and S band of frequency range.