Progress towards an electrically small antenna with high efficiency and large bandwidth simultaneously with high directivity and a large front-to-back ratio

Abstract

Non-Foster element-augmented, electrically small electric and magnetic antennas have been designed, characterized numerically, fabricated and tested. Internal non-Foster elements, which produce specifically tailored broad bandwidth inductive and capacitive devices, are introduced into the near-field resonant parasitic (NFRP) components of their narrow bandwidth counter-parts. This internal non-Foster element approach leads to nearly complete matching of the entire system to a 50 Ω source without any matching network and high radiation efficiencies over a FBW10dB bandwidth that surpasses the fundamental passive bound. By including additional parasitic elements, one can also enhance the directivity of the original passive NFRP antenna. Further augmenting such a parasitic element with a non-Foster element, one can additionally achieve a large directivity bandwidth. A 300 MHz design with ka = 0.94 is reported which simultaneously achieves high radiation efficiencies (>81.63%), high directivities (> 6.25 dB) and large front-to-back-ratios (> 26.71 dB) over a 10.0% fractional bandwidth.