Abstract
This article presents a synthesis of the ultra‐wideband bandpass (UWB) filters consisting of two short‐circuited stubs combined with two stages of stepped impedance resonators (SIRs).The practical and theoretical transfer functions of the proposed UWB filters are derived. An example filter is firstly theoretically‐designed by the proposed synthesis procedure, then optimized by EM simulator, fabricated in microstrip line and finally characterized by a network analyzer. A good agreement between the theoretical and experimental results validates the proposed synthesis procedure successfully. In addition, the results of the designed filter show that the characteristics of the new filter is even better than those of a conventional filter composed of three‐stage of SIRs but without stubs. This means the proposed filters have compact sizes compared with the conventional ones. The designed filter also exhibits good characteristics of low insertion losses, quite sharp skirts, a flat group delay, deep attenuations in stopband (especially in lower one), and satisfies even FCC outdoor specifications. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1268–1271, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25172