Electric Green´s dyadics for modeling resonance and surface wave effects in a waveguide-based aperture-coupled patch array

Electric Green´s dyadics for a semi-infinite partially filled rectangular waveguide are developed for the full-wave analysis of a waveguide-based aperture-coupled patch amplifier array. The Green´s functions are derived in the form of a double series expansion over the complete system of eigenfunctions of the Helmholtz operator. In this representation, the one-dimensional characteristic Green´s functions along the waveguide provide a physical insight on resonance and surface wave effects occurring in overmoded layered waveguide transitions. Particularly, this is related to the coupling of waveguide modes to surface waves propagating in the transverse direction. This is demonstrated for the example of an aperture-coupled patch amplifier array in the N-port waveguide transition, although the analysis is applicable to other waveguide-based antenna structures, which allow for the propagation of surface waves.