Design of a compact dual-band folded-waveguide bandpass filter using multilayer waveguide resonators
A novel compact dual-band bandpass filter based on multilayer folded-waveguide (FWG) structure is presented in this article.In this design, slots are used to realize direct coupling between adjacent resonators and apertures are adopted to implement cross coupling between non-adjacent resonators.A new technique of external quality factor of FWG resonator and coupling coefficients between different resonators are studied using full-wave simulator. In order to demonstrate the proposed technique, a four-pole dual-band bandpass filter is designed, fabricated and measured using vector network analyzer. Measurement results which are well agreed with simulation results are presented. Moreover, four-pole substrate integrated folded waveguide SIFW dual-band bandpass filter, using two layers of slotted folded waveguide resonators, is demonstrated. The proposed filter has a compact size and it is excellent candidate for the application of wireless communication systems.  2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:780788, 2015.
sifw folded-waveguide resonators microwave filters dual passband filter