Control of reflection and mutual coupling losses in maximizing efficiency of dense focal plane arrays

The FOV of a radio telescope fed by a cluster of conventional horns in a one-horn-per-beam configuration is limited to a few beamwidths due to the field distortions which appear for off-axis directions of observation. To overcome this limitation, it has been suggested to use dense focal plane arrays (FPAs) of electrically small elements in which several of these elements contribute to each beam. The primary goal of the paper is to investigate the impact of reflection, coupling and dissipation losses in dense FPAs on the total aperture efficiency of the reflector antenna. We present and discuss results obtained for two dense array realizations: one reference realization of miniaturized open-ended hard waveguides, and another practical FPA of Vivaldi elements.