New kinds of fractal iterated and miniaturized narrowband bandpass filters for wireless applications

In this paper, some new type of compact and highly selective microstrip dual mode narrowband bandpass filters are proposed and compared for modern wireless applications. The filters are proposed by integrating the concepts of dual mode with slotted square patch resonator, Seirpinsky Carpet Fractal Geometry applied to the conventional microstrip square patch for achieving miniaturization and addition of perturbation for obtaining the bandpass characteristics. These type of microstrip fractal narrowband bandpass filters show the advantage of providing the much narrower bandwidth, more miniaturization, high Q-value and high selectivity than that of single mode resonator and conventional square patch filter. The performance of proposed filters based on Seirpinsky Carpet Fractal Geometry and dual mode slotted square patch resonator up to third iterations have been evaluated using full wave based on CST microwave studio. The simulation results show that at the same operating frequency and same substrate material, the proposed filter after third iteration provides a considerable low insertion loss, more miniaturization i.e less effective area of filter, high Q-value, high selectivity and sharper response of about 1.29% fractional bandwidth as compared to the conventional microstrip square patch filter of 2.04% fractional bandwidth. The Comparative Simulation results also show that as the number of iterations increase, the insertion loss, 3dB fractional bandwidth, compactness of filter and Q-value shall also be improved i.e the comparative study shows that these filter structures offer the better performance in terms of above mentioned parameters as compared to other types of non-fractalized filter structures.