Electrically small magnetic dipole antennas with magnetic core

This work extends the theory of a spherical magnetic dipole antenna with magnetic core by numerical results for practical antenna configurations that excite higher-order modes besides the main TE10 spherical mode. The multiarm spherical helix (MSH) and the spherical split ring (SSR) antennas are considered. It is shown that one should be particularly aware of the TM11 and TM20 modes, whose resonances spoil the Q in a range of permeability of the core predicted to be optimal by the single-mode theory. Practical ways of suppressing these higher-order modes are presented.