Low pass filters with stepped impedance resonators and DGS structures

Two different methods to design microstrip low pass filter operating at 6 GHz are discussed in this paper. In the first method filter structure is designed without any slots on the ground plane and the second method consists of interdigital slots on the ground plane. Interdigital slot consists of metal fingers, which enhances the performance of the filter. The resonant frequency can easily be changed by tuning the length of the metal fingers. Based on the comparative study, it is found that in the second method the return loss is enhanced to -22.5 dB. The insertion loss is found to be 0.1 dB in the passband. It is inferred that the filter becomes compact and the return loss is improved, using interdigital slots in the design.