Side-Coupled Shorted Microstrip Line for Compact Quasi-Elliptic Wideband Bandpass Filter Design

This letter presents a novel structure composed of a shorted quarter-wavelength microstrip line side-coupled to two open-ended stubs. The proposed topology exhibits a quasi-elliptic wideband response with two transmission zeros enhancing the selectivity. To verify the design concept, one filter example has been designed, fabricated and measured. Good insertion/return losses, flat group delay, sharp transition, excellent DC-choked property, simple topology, and compact size are achieved as demonstrated in both simulation and experiment.