Miniaturization of Ultrawideband Monocone Antennas Using Dielectric Loading

Abstract

A so-called intelligent approach for miniaturization of monocone antennas using dielectric loading is presented. Two impedance mismatches causing the degradation in impedance bandwidth due to high permittivity dielectric loading are identified. The input impedance mismatch is addressed by modifying the structure of the antenna feed. Adding a spatial quarter-wave transformer matches the wave impedance of the loading region to that of free space. The feasibility of such a loading scheme is validated by effectively miniaturizing a monocone antenna with a material of ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 9.0. Simulations show the diameter of the ground plane is reduced by 55.2%, while the miniaturized monocone has a relative impedance bandwidth of 106.3%. The proposed dielectric loading concept is further applied to miniaturize three other monocone antennas to show its generality. In addition, the feasibility is further validated through miniaturization of monocone antennas using dielectric materials of various permittivity values. Finally, a miniaturized monocone antenna using a dielectric material of ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 9.0 is fabricated and measured to experimentally verify and validate the concept.