Time-Modulated EM Skins for Integrated Sensing and Communications

An innovative solution, based on the exploitation of the harmonic beams generated by time-modulated electromagnetic skins (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TM-EMS</i>s), is proposed for the implementation of integrated sensing and communication (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ISAC</i>) functionalities in a Smart Electromagnetic Environment (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SEME</i>) scenario. More in detail, the field radiated by a user terminal, located at an unknown position, is assumed to illuminate a passive <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TM-EMS</i> that, thanks to a suitable modulation of the local reflection coefficients at the meta-atom level of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">EMS</i> surface, simultaneously reflects towards a receiving base station (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BS</i>) a “sum” beam and a “difference” one at slightly different frequencies. By processing the received signals and exploiting monopulse radar tracking concepts, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BS</i> both localizes the user terminal and, as a by-product, establishes a communication link with it by leveraging on the “sum” reflected beam. Towards this purpose, the arising harmonic beam control problem is reformulated as a global optimization one, which is successively solved by means of an evolutionary iterative approach to determine the desired <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TM-EMS</i> modulation sequence. The results from selected numerical and experimental tests are reported to assess the effectiveness and the reliability of the proposed approach.