Novel Dual-band Band-Pass Filters Based on Surface Plasmon Polariton-like Propagation Induced by Structural Dispersion of Substrate Integrated Waveguide

In this paper, we present two novel dual-band bandpass flters based on surface plasmon polaritonlike (SPP-like) propagation induced by structural dispersion of substrate integrated waveguide (SIW). Both flters are realized as a three-layer SIW where each layer represents a sub-SIW structure with intrinsic efective permittivity that depends on its width and flling dielectric material. The layers are designed to have efective permittivities of opposite signs in certain frequency ranges, which enables SPP-like propagation to occur at their interfaces. Since three layers can provide two distinct SPP-like propagations, the flters exhibit dual-band behaviour. A detailed theoretical and numerical analysis and numerical optimization have been used to design the flters, which were afterwards fabricated using standard printed circuit board technology. The independent choice of geometrical parameters of sub-SIWs and/or the corresponding dielectric materials provide a great freedom to arbitrarily position the passbands in the spectrum, which is a signifcant advantage of the proposed flters. At the same time, they meet the requirements for low-cost low-profle confguration since they are realized as SIW structures, as well as for excellent in-band characteristics and selectivity which is confrmed by the measurement results.