Time-Modulated Arrays for Physical Layer Secure Communications: Optimization-Based Synthesis and Experimental Assessment

The synthesis of time-modulated arrays (TMAs) for physical layer secure communications is carried out in this paper. The problem is cast as the transmission from the TMA of a signal undistorted within a desired angular region, while the signal distortion is maximized elsewhere. Toward this aim, a customized optimization strategy based on a binary genetic algorithm is proposed to define the optimal ON-OFF sequence controlling the radio-frequency switches modulating the signal transmitted by the elements of the TMA. An ad hoc fidelity factor metric is used to quantify the signal distortion as a function of the angular direction. A set of numerical examples is reported and discussed to illustrate the behavior of the proposed synthesis approach as well as to give some insights on its potentialities and achievable performance. Moreover, this paper shows, for the first time, the results of an experimental validation when considering a real TMA.