This study presents a design of 4x1 rectangular microstrip array antennas operation in different applications within the context of ISM bands (specifically 2.4 and 5.8 GHz bands). High gain and radiation pattern characteristics are obtained by using parallel-fed network technique. Insetfed and quarter-wave impedance transformer techniques are used for impedance matching. Dimensions of the radiating top conductor are taken as 250 x 90 mm2 and dielectric constant and thickness of the substrate FR4-epoxy insulating material as 4.4 and 1.6mm respectively. Less than 2 VSWR value, 11.3dB of gain with a directivity of 12dB have been achieved. Simulation results are obtained and examined by using the microstrip antenna model ANSYS High Frequency Structure Simulator v.15