A modified design approach for compact ultra-wideband microstrip filters

A modified design approach for compact ultra-wideband microstrip filters with cascaded/folded stepped-impedance resonators is described. The key feature of the proposed method is to facilitate stronger coupling between stepped-impedance resonators and, at the same time, eliminate the requirement of extremely small gaps in coupled-line sections, as found in traditional designs. Simulations and measurements demonstrate that the filters designed with this technique exhibit good reflection, insertion-loss, and group-delay performance within the 3.1–10.6 GHz band.