Using high permeability shells to improve the Q of electrically small electric-dipole antennas

In this paper, we illustrate for the first time how a thin shell of high relative magnetic permeability can be used to improve the quality factor Q of an electrically small electric-dipole antenna. In particular, a thin shell of permeable material surrounding a top-loaded electric-dipole antenna produces magnetic polarization currents that reduce the stored electric energy inside the antenna volume, lowering the Q. We study antennas confined to a cylindrical volume and compare simulated quality factors to the general lower bounds in order to assess the optimality of the designs.