Efficient analysis of lossy substrate integrated waveguide structures

As frequency increases, conductor losses become an important loss mechanism in substrate-integrated-waveguide (SIW) based devices and may significantly degrade their performance. Therefore, one needs a general, reliable and efficient analysis tool that could properly take the aforementioned effect into account and consequently be used in design and optimization. In this presentation we propose a general analytical scheme for rigorous modeling of conductor losses in SIW devices within the recently proposed hybrid modematching/method of moments framework (M. Casaletti et al., IEEE-Trans. Antenna Propag., 11/2013; 5575-5588) for the fast and accurate analysis of multilayer SIW guiding/radiating structures. In particular, we extend the mode-matching part, originally accommodated to PEC boundaries, by generalizing it to boundaries describable in terms of Leontovich impedance boundary condition, which is able to incorporate the effects of both conductor losses and surface roughness. This mode-matching implementation can be subsequently incorporated in the general hybrid method. The description of lossy or rough metal surfaces as impedance surfaces allows the analytical derivation of the cylindrical wave vectors associated to the Parallel Plate Waveguide (PPW) hosting the SIW structure. This latter non-orthogonal complete basis set is used to represent, as a series expansion, the corresponding PPW Green´s function and the field scattered by a general lossy/dielectric cylinder inside the PPW. The scattered field amplitudes are then obtained using an optimized mode-matching method. Special care is also needed for the derivation of the port parameters. Differences with the PEC case will be presented during the presentation. To validate our approach and demonstrating the necessity of incorporating the conductor losses in the modeling, several examples of lossy SIW devices will be considered, and the comparison with commercial software in terms of accuracy and resources will - e presented.