COMPACT MULTIBAND TRANSVERSAL BANDPASS FILTERS WITH MULTIPLE TRANSMISSION ZEROES

Novel compact multiband microstrip transversal bandpass fllters (BPF) using short-circuited or open-circuited stub-loaded half- wavelength resonators (SLR) are presented. The dual-band BPF consists of two SLRs and two T-shaped feedlines, and the tri-band BPF can be implemented by a simple reconflguration of adding one resonator above the original circuit of the dual-band BPF. Multiple transmission zeroes are created to improve the selectivity of the fllters. Furthermore, the high degree of design freedom obtained for every passband of dual- or triple-band BPF is achieved by independent resonators and independent signal paths. To verify the proposed concept, two dual-band bandpass fllters (fllter I and II) and one tri- band bandpass fllter (fllter III) are designed and fabricated. Both theoretical and measured results are presented, with good agreements.