Realizing Flat-Top Radiation Pattern with Sharp Cutoff for Reducing Lobing Fades

In this paper, synthesis of the flat-top radiation pattern with sharp cutoff for reducing the lobing fades due to the presence of the earth is investigated. To this end, first the propagation factor is investigated. Then based on the propagation factor, the antenna pattern is examined at different levels of the cutoff to achieve a flat-top radiation with low level of lobing fades. Finally, synthesizing the desired radiation pattern is investigated through Woodward-Lawson method. Our studies reveal that that antenna with large length (> 12A) provides the desired flat-top pattern with the appropriate cutoff. The aperture distribution of the desired pattern is provided and discussed.