Microwave multi-path dual-passband filters for wide-band applications

Two configurations of microwave dual-band bandpass planar filters for wide-band applications are reported. They are based on signal-interference multi-path circuit stages operating as dual-passband transversal filtering sections (TFSs). These TFSs, by means of signal-interaction concepts, allow dual-band bandpass filtering profiles with transmission zeros to be obtained. Analytical equations and rules for the design of the described dual-passband TFSs are given. Also, two synthesis examples of multi-stage wide-band dual-passband filters are shown. Moreover, for experimental validation, a 1.5/2.5-GHz microstrip prototype with ultra-wideband (UWB) passbands is built and tested.