This paper describes the design procedure of a compact wideband waveguide filter, based on stepped impedance resonators (SIR) and a combined usage of capacitive and inductive coupling irises, that provides a significant improvement in the out-of-band response of the filter with respect to the state-ofthe-art. In addition to theory, several filter prototypes have been designed and manufactured. A detailed sensitivity analysis has been also carried out. Finally, simulations and measurements are compared, showing very good agreement, thereby fully validating the new filter topology. Index Terms-Aggressive space mapping, band-pass filters, hybrid (inductive and capacitive) irises, stepped impedance resonator and wideband.