Tri-band bandpass filter using shorted stub-loaded dual-mode resonators

A compact tri-band bandpass filter (BPF) using three shorted stub-loaded dual-mode resonators (SSLDMR) is presented. To verify the approach, three single-band filters with only one folded SSLDMR and the same pair of meandering feed lines are each simulated by using the Ansoft HFSS simulator. All the other dimensions are fixed except the stub lengths. Since the coupling paths of the three passbands are isolated, the center frequency and bandwidth of all three passbands can be flexibly controlled by tuning the electrical length of the corresponding resonators and shorted stubs, respectively. Moreover, each passband can be independently adjusted without affecting the other two. A prototype of a tri-band BPF centered at 2.4, 3.5 and 5.2 GHz has been designed and fabricated with six transmission zeros. Six transmission zeros on either side of three passbands are located at 2.17, 2.62, 3.04, 3.94, 4.55 and 5.65 GHz.

Duke Scholars

Author William T. Joines Electrical and Computer Engineering