Design and implementation procedure of a wideband aperture coupled microstrip antenna in L-band frequency is introduced. To improve radiation performance of the microstrip antenna four structures are proposed. The measurement and simulation results show better performance in terms of matching bandwidth for the structure constructed with air substrate. Experimental results of frequency bandwidth and radiation patterns of the optimum structure are in agreement with the simulation results. The proposed patch antenna creates a directive radiation pattern with a gain of 8.SdB. In addition, it provides a quite large frequency bandwidth of greater than 25%, and FIB better than 15d8 as well. This aperture coupled microstrip antenna has been used as an element of Sxt microstrip array antenna for SSR systems. The array antenna gain, SLL and azimuth HPBW are: 17.SdB, less than 24d8 and 10°, respectively.