Tri-band microstrip bandpass filters for GSM and WiMAX applications

This paper presents the design and development of two distinct microstrip tri-band bandpass filters (BPFs) operating at 1.8 GHz, 4.5 GHz and 7.6 GHz for GSM and WiMAX applications. The first modified filter consists of a pair of open loop resonators with loaded inner stubs and, the second one is based on a pair of open loop resonators and two dumbbell-shaped defected ground structure (DGS) units. The simulated results of the proposed tri-band BPFs are compared with the previous published works. The proposed filters are smaller in size and provide better performance in terms of small insertion loss and good passband selectivity than those reported in the literature.