Design and analysis of low pass microwave filter using metamaterial ground structure

An improved periodic complementary split ring resonator (CSRR) structure at ground plane is investigated for low pass filter (LPF) application. The realisation in microstrip configuration consists in making the equivalence between the geometry of a CSRR structure and a parallel resonator circuit. Initially, we design a low pass filter without CSRR on the ground plane. We have simulated the results and observed that the results are deviated from the ideal low pass filter and we also obtain the ripples in the passband and the attenuation in the stop band is not infinite. Then we used 3 identical, square shaped CSRR in the ground plane equally spaced with respect to each other. Varying empirically the dimension of the CSRR we obtained an improvement of frequency response. The results show that the latter exhibit the better stopband performance. For suppressing ripples in the passband we switch to higher order low pass filter.