Wide-Band Electrically Small Antennas Using Active Non-Foster Circuits as Inspired Metamaterial

Using metamaterials in antenna design leads to interesting features includes size reduction, gain or bandwidth enhancement. In this article, the idea of using active circuits to compensate the admittance of electrically small antennas (ESA), in wide frequency range investigated practically. In this article, broadband ESAs based on active metamaterial structures designed, simulated fabricated and tested. To do this, a negative impedance convertor utilized as an active circuit to provide the effective impedance of metamaterial structure. Op-amp based structures as well as BJT transistor based on NICs investigated and discussed. Measurement shows tenfold reduction in resonance frequency while the fractional bandwidth increased up to 65% in BJT transistor based NICs while it enhanced up to 100% in op-amp based structure.