An Efficient, Electrically Small Antenna with Large Impedance Bandwidth Simultaneously with High Directivity and Large Front-to-Back Ratio

Non-Foster element-augmented, electrically small electric and magnetic antennas have been designed, characterized numerically, fabricated and tested. Specifically tailored broad bandwidth inductive and capacitive devices were introduced into the near-field resonant parasitic (NFRP) components of their narrow bandwidth counter-parts. This internal non-Foster element approach led to nearly complete matching of the entire system to a 50 Omega source without any matching network and high radiation efficiencies over a 10dB fractional bandwidth that surpasses the fundamental passive bound. By including additional resonant parasitic elements, one can also enhance the directivity. Further augmentation of those parasitic elements with a non-Foster device leads to a large directivity bandwidth. A 300 MHz design with ka = 0.94 is reported which simultaneously achieves high radiation efficiencies (>81.63%), high directivity (> 6.25 dB) and large front-to-back-ratios (> 26.71 dB) over a 10.0% fractional bandwidth.