Electrically small antenna elements using negative permittivity resonators

Abstract

We consider the use of materials with negative electric permittivity as a building block for constructing effective small antenna elements. In this paper, we show that negative permittivity alone is sufficient for constructing an effective small antenna element. Further, we clarify, here the issue of the radiation Q: a quasi-static analysis is used to show that a sub-wavelength spherical negative permittivity resonator will have a Q that is a factor of 3/2 above the Chu limit. We demonstrate through finite element simulation a practical antenna geometry composed of a coaxial transmission line coupled to a half-sphere of negative permittivity adjacent to a ground plane. The resonator is impedance-matched to the transmission line, resulting in an antenna Q matching that predicted by the quasi-static analysis.