In this paper, the authors propose a method based on the combination of inverse fast Fourier transform (IFFT) and modified particle swarm optimization for side lobe reduction of a thinned mutually coupled linear array of parallel half-wave length dipole antennas with specified maximum return loss. The generated pattern is broadside (φ= 90 degree) in the horizontal plane. Mutual coupling between the half-wave length parallel dipole antennas has been taken care of by induced emf method considering the current distribution on each dipole to be sinusoidal. Directivity, first null beamwidth (FNBW), return loss of the thinned array is also calculated and compared with a fully populated array. Two cases have been considered, one with symmetric excitation voltage distribution and the other with asymmetric one. The method uses the property that for a linear array with uniform element spacing, an inverse Fourier transform relationship exists between the array factor and the element excitations. Inverse Fast Fourier Transform is used to calculate the array factor, which in turn reduces the computation time significantly. The element pattern of half-wave length dipole antenna has been assumed omnidirectional in the horizontal plane. Two examples are presented to show the flexibility and effectiveness of the proposed approach.