Parametric Enhancement of Radiation from Electrically Small Antennas

Electrically small antennas are characterized by large quality factors, which yield limited gain-bandwidth products, as a result of the Bode-Fano limit. This bound implies a trade-off between the antenna's footprint and radiation features, hindering wireless applications that require compact, broadband, and efficient antennas. Here, building on a previous theoretical analysis of parametric matching networks [H. Li, A. Mekawy, and A. Alù, Phys. Rev. Lett. 123, 164102 (2019)], we demonstrate how parametric phenomena can overcome this trade-off, offering a pathway to realize stable non-Foster wideband antennas that go beyond the restrictions of passive systems. We demonstrate our approach in a planar small loop antenna loaded by a time-varying capacitor that oscillates around twice the radiation frequency, showing that it can result in wideband radiation enhancement, exceeding the limitations of passive scenarios.