A NOVEL TRI-BAND FILTER USING STUB-LOADED OPEN LOOP RING RESONATORS

摘要

In this article, a novel type of compact tri-band filter using stub-loaded open-loop ring resonators (OLRRs) is presented. With the open stub loaded, the resonant frequency of the OLRR can be tuned by the tapped location and length of the loaded stub, which makes the OLRR more compact. Making use of the microstrip open-ended feed line, proper external couplings are provided to each passband by magnetic coupling. A tri-band filter centered at 2.0 GHz, 3.2 GHz, and 4.3 GHz is designed, fabricated and measured. Predicted results are verified by the experiments.