Abstract

Abstract—Novel compact multiband microstrip transversal bandpass filters (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 reconfiguration of adding one resonator above the original circuit of the dual-band BPF. Multiple transmission zeroes are created to improve the selectivity of the filters. 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 filters (filter I and II) and one tri-band bandpass filter (filter III) are designed and fabricated. Both theoretical and measured results are presented, with good agreements. 1.