Abstract: Magnonic crystals are periodic composites of magnetic materials for propagating spin waves. The periodic modulation in magnonic crystal plays a vital role in the formation of bandgaps at the Brillouin Zone (BZ) boundaries leading towards possible applications in spin wave filters. In this study, we explore the possibility of tailoring the magnonic bandgap in one-dimensional (1D) square antidot waveguide structures by micromagnetic simulation. The space-time variations of magnetization in these structures are obtained by solving the Landau-Lifshitz-Gilbert (LLG) equation using OOMMF by applying spatially and temporally varying “sinc” function normal to the waveguide plane in presence of a bias field of strength 1.01 and 0.505 T along the length of the waveguide. The dispersion relations are obtained by 2D discrete Fourier transform of the space-time data. We have investigated how the bias field affects the magnonic band structures and the corresponding bandgaps for four different materials. From the results we clearly observe a downward shifting of bandgaps towards lower frequency when the biasing field is decreased while the width of the bandgap remains same. Hence, it provides a simplest way for designing spin wave filters of different frequency regimes.