Finite planar array of coupled rectangular waveguide apertures of different size

A combined modal expansion and moment method is described for analyzing finite planar arrays of rectangular waveguides of different size in an infinite ground plane including reactively loaded waveguide elements. Mutual aperture coupling, cross-polarization effects, and the influence of higher-order modes are rigorously taken into account by orthogonally polarized rooftop expansion functions in the apertures, and by modal expansion into the full set of eigenmodes in the waveguide elements. Design examples demonstrate that beamforming and improvement of the cross-polar suppression are achieved by the electromagnetically excited waveguide elements of optimized aperture size and location. The theory is verified by measurements.<>