Isophoric Sparse Arrays Ensuring Global Coverage in Satellite Communications

Non-periodic, sparse Direct Radiating Arrays employing equi-amplitude (isophoric) radiators represent an appealing solution to meet the requirements of next satellite services. In this work we address the synthesis of isophoric sparse arrays capable of radiating highly steerable pencil beams, in order to meet the requirement of full Earth coverage from GEO orbits. To this aim, we first of all perform an analytical study that allows assessing the geometrical constraints that the desired beam steerability puts on the design of the array layout. Starting from such results, in the second part of the work we address the actual synthesis of the sparse array. The proposed strategy consists in the synthesis of the optimal radiating feed followed by the synthesis of the array layout capable of taking into account the aforementioned geometrical constraints as well as the feeds´ pattern, in such a way to guarantee satisfaction of the side lobe level constraint for every steered beam. Numerical examples demonstrate the effectiveness of the proposed synthesis strategy.