Design, analysis, application and experimental assessment of algorithms for the synthesis of maximally sparse, planar, non-superdirective and steerable arrays

This thesis deals with the problem of synthesizing planar, maximally sparse, steerable and non-superdirective array antennas by means of convex optimization algorithms and testing their performances on an existing array to assess its far field performances in terms of requirements ful- filment. The reason behind the choice of such topic is related to those applications wherein the power supply/consumption, the weight and the hardware/software complexity of the whole radiating system have a strong impact on the overall cost. On the other hand, the reduction of the number of elements has of course drawbacks as well (loss in directivity, which means a smaller radar coverage in radar applications, loss in robustness, etc.), however the developed algorithms can be utilized for finding acceptable trade-offs that arise, inevitably, when placing advantages and disadvantages of sparsification on the balance: it is only a matter of appropriately translating requirements in a convex way. The synthesis scheme will be described in detail in its generality at the beginning, showing how the proposed synthesis techniques outperform several results existing in literature and setting the bar for new benchmarks. In particular, an important, innovative constraint has been considered in the synthesis problem that prevents selection of elements at distances below half-wavelength: the non-superdirectivity. Moreover, an interesting result will be derived and discussed: the trend of the reduction of the number of elements Versus the (maximum) antenna size is decreasing as the latter increases. Afterwards the discussion will be focused on an existing antenna for radar applications, showing how the proposed algorithms intrinsically return a single layout that works jointly for transmitting and receiving (two-way synthesis). The results for the specific case chosen (mainly the set of weights and relative posi- tions) are first numerically validated by a full-wave software (Ansys HFSS) and then experimentally assessed in anechoic chamber through measurements.