An electromagnetic model for post-wall waveguide building blocks

During the past five years, dielectric and metallic post-wall waveguides (PWWGs) have been analyzed at TNO Defence, Security and Safety, using both an integral equation approach and a modal approach. The model developed focuses on TEn0 modes facilitating the analysis of infinitelylong, straight PWWGs as well as finite PWWGs with arbitrary post positioning. Quite recently, we introduced an alternative approach for dealing with complex propagation constants, so that PWWG losses, and the scattering matrices of PWWG sections can be computed. These sections are represented by ‘current matrices’ that relate the ‘incoming’ electric and magnetic surface currents on predefined ports to the ‘outgoing’ surface currents. The derivation of the current matrices is based on Lorentz’s reciprocity and Love’s equivalence theorems. Both the ‘incoming’ and ‘outgoing’ surface currents are represented by rooftop bases. The scattering parameters of a PWWG section are determined by expressing waveguide modes in terms of these bases. Finally, the corresponding software code can be integrated in a circuit simulator, a familiar platform for microwave designers.