Leaky Wave Enhanced Feeds for Single Aperture Multi Beam Reflectors

This work is the fourth of a series on the use of super-layers to shape the radiation pattern of each of the feeds composing a focal plane imaging array. Using dielectric or frequency selective surface type of super-layers the spill over from the reflectors is reduced without increasing the dimensions of each aperture. This effect is achieved when the inter-element distance between the feeds is 2.4 wavelengths which is typical for satellite based multi beam telecommunication systems. The shaping of the pattern is obtained with the excitation of a pair (TE/TM) of leaky waves, that radiate incrementally as they propagate between the ground plane and the super-layer. The super-layer can be realized with a single dense dielectric slab (epsiv_r = 20.25), a double dielectric slab (epsiv_r = 4.5) or an equivalent frequency selective surface. The maximum edge of coverage enhancement, with respect to reference free space configuration, that can be obtained in these three different cases is equivalent. However, the bandwidth over which the enhancement is maintained depends on how the super-layer is realized. The predicted embedded patterns provide an increase of the edge of coverage gain, with respect to the free space case, of at least 2 dB in an operating bandwidth of ap 1.7%.