Analysis of the internal scattering field distribution in an oversized rectangular slotted waveguide

A rectangular parallel-plate slot array fed by a post-wall waveguide is an attractive candidate for high-efficiency and mass-producible planar antennas in millimeterwave applications. The transmission loss is small in the waveguide in comparison with microstrip-type feed lines and the fabrication cost of simple via-holing and etching is low. The design is conducted assuming plane wave propagation, neglecting both the boundary conditions at the narrow walls and the slot coupling perturbation; this is effective only for an extremely large aperture and weakly coupled slots. Since the EM analysis for the actual structure seems too heavy, the key for the advanced design of the parallel plate waveguide arrays is to establish accurate, but still simple models, for the analysis and design. This paper discusses the fast evaluation of slot scattering inside the parallel plate waveguide. It gives the basis for future approximate but accurate analysis/design methods for parallel plate slotted waveguide arrays.