Box-Section Band Pass Filter with Planar Slow-Wave Resonators

A compact, narrow band planar filter is presented. It combines two noticeable characteristics, namely box-section coupling topology and open-loop slow-wave resonators. As a result high frequency selectivity, wide spurious-free stopband and compact size are achieved. The drawback is that direct electromagnetic optimization is required for the design, due to the small size and irregular configuration, but it is solved by means of a reduced order model-based algorithm