Design of compact multilevel folded-line bandpass filters

A simple design methodology for compact multilevel multiconductor folded-li ne bandpass filters is presented in this paper. Several new compact folded- line filter topologies in single, as well as multilevel environments are pr oposed. Simple closed-form design equations are presented for the extractio n of an equivalent coupled transmission line representing the folded-line f ilter section. The folded-line filter designs are validated by full-wave el ectromagnetic simulation, as well as by measurement for a four-section maxi mally flat four-coupled-line bandpass filter. The new folded-line filters e xhibit a significant reduction in footprint compared to the conventional de signs.