Analysis of inner fields and aperture illumination of an oversize rectangular slotted waveguide

Parallel plate waveguide arrays are promising candidates for high gain and low loss millimetre-wave antennas. The design theory of these oversize waveguide arrays is not yet mature, although system applications are already underway. The key difficulty is to predict the inner field in the slotted oversize waveguide, which is perturbed by its narrow walls and the coupling of slots. The paper provides a simple analysis model of these unique arrays, to enhance the quality and accuracy of the design. Effective approximations are introduced which dispense with large matrix inversion, and determine the slot excitation coefficients. Overall, the measured aperture illumination shows good agreement with prediction by the proposed method. Illumination defects peculiar to antenna polarisation are clearly demonstrated.