Parasitic Element Time-Modulation for Enhanced Effective Inter-Antenna Coupling: Utilization for Improved Gain-Bandwidth

Time variation has been recently introduced as an additional degree of freedom for wave engineering, that enables going beyond the performances that are expected by linear time-invariant (LTI) systems. In this paper, we introduce the concept of indirect time-modulation of antennas using an add-on time-varying scatterer (parasitic element) that gives rise to an inherent feedback mechanism via the airborne wave system. As opposed to a direct modulated system where a time-dependent element is in contact with the other elements, in an indirect time modulation scheme \emph{no} direct physical contact between the original LTI network and the time-varying add-on scatterer is needed, thus leading to additional flexibility in the design. Using indirect time modulation we demonstrate enhanced effective coupling between remote antenna elements, and the possibility to outperform the gain-bandwidth achieved for the same antenna structure but without time-modulation.