Integral equation formulation for the impedance representation of aperture-coupled devices with finite wall conductivity

Recently a method, which is based on the integral equation technique, has been proposed to compute an admittance or impedance representation of planar transitions between waveguides. Although the method provides satisfactory simulation results when compared to measurements, it does not take into account the ohmic losses due to a finite conductivity in the transition walls. In this paper, we propose a simple and easy to implement extension to this method in order to include in the impedance representation the missing ohmic losses of the waveguide junction. Though the method has been developed in the framework of waveguide devices, like filters, it is applicable to any aperture-coupled structure based on metallic surfaces with finite conductivity, e.g. slot antennas.