Increasing the Efficiency-Bandwidth of Small Antennas by Coupling Radiative and Non-Radiative Modes Using Time-Variation

Time-variation is one possible method that may be used to contravene the Chu limit, which constrains the bandwidth of electrically-small antennas. Here, insights gained from the analysis of parametric circuits are applied to the design of a time-varying antenna in such a way that the antenna exhibits an increased efficiency-bandwidth product over the matched linear time-invariant (LTI) benchmark antenna. Both the time-varying antenna and the benchmark LTI antenna are a sectored version of the common top-hat loaded monopole antenna. The methods demonstrated in this work rely upon coupling radiative (bright) modes of the antenna to poorly radiating (dark) modes of the antenna through spatio-temporal modulation. By confining intermediary frequencies from the parametric processes in the dark modes, their radiation is suppressed.