Synthesis of Isophoric Sparse Arrays Allowing Zoomable Beams and Arbitrary Coverage in Satellite Communications

In this paper, we address the synthesis of isophoric sparse ring arrays for full Earth coverage from a GEO satellite by means of steerable beams, switchable between two different widths. We show that to achieve such a zooming capability, we cannot simply tailor the array geometry to one of the patterns and then obtaining the beam zooming/shrinking by means of a phase-only control. Hence, we propose a novel synthesis approach that, in order to obtain the required beam zooming/shrinking by means of a phase-only control, tailors the layout geometry simultaneously to both the beams. Numerical results are presented to demonstrate the effectiveness of the proposed approach. The analysis also shows that the required beam re-configurability cannot be achieved for free. In particular, to radiate simultaneously the narrow and wide beams, with a beam-width ratio 1:5, we have to employ a number of control point 80% greater than that necessary to transmit only the narrow beam.