Compact E-plane doublet structures for modular filter design

This paper presents a doublet structure for modular design of pseudo-elliptic microwave filters. Combinations of hairpin resonators etched on slab of dielectric substrate and septum are considered as insertions for conventional rectangular waveguide. Proposed structure is capable of producing two poles and two transmission zeros in upper and lower stopbands. The structure is applied in inline bandpass filter with non-resonating node and dual-band filter in order to prove feasibility of the structure at X-band. Experimental verification of simulated results is carried out.