Waveguide slot radiator feeding a parallel plate polarizer

Slotted waveguide linear arrays are quite commonly enclosed in a parallel plate structure, to suppress cross-polar lobes in the case of inclined-slot arrays, and to suppress wide angle grating lobes in the case of shunt slot arrays. However, design equations for such arrays generally assume that the slots radiate into a half space and consequently for arrays designed on this basis significant pattern degradation can occur when the parallel plate structure is introduced. By imaging the slot in the enclosing parallel conducting planes it is shown that the conventional half-space analysis can be enlarged to accommodate the presence of a parallel plate polarizer with very little difficulty, since no more than about ten images are required to model a typical geometry.