Journal article
Properties of Sub-Wavelength Spherical Antennas With Arbitrarily Lossy Magnetodielectric Cores Approaching the Chu Lower Bound
For a spherical antenna exciting any arbitrary spherical mode, we derive exact closed-form expressions for the dissipated power and stored energy inside (and outside) the lossy magneto-dielectric spherical core, as well as the radiated power, radiation efficiency, and thus the radiation quality factor.
These expressions are valid for the entire range from zero to infinite material loss tangents, with any dispersion of the real parts and an inverse frequency variation of the imaginary parts of permittivity and permeability. For the dipole modes of a sub-wavelength antenna, we demonstrate how an increasing magnetic loss tangent initially leads to a decreasing radiation quality factor, but in the limit of a perfect magnetic conductor (PMC) core the dissipated power tends to zero and the radiation quality factor reaches the fundamental Chu lower bound.
Language: | English |
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Publisher: | IEEE |
Year: | 2014 |
Pages: | 1456-1460 |
ISSN: | 15582221 and 0018926x |
Types: | Journal article |
DOI: | 10.1109/TAP.2013.2293794 |
ORCIDs: | Kim, Oleksiy S. and Breinbjerg, Olav |
Electrically small antennas Energy storage Magnetic losses Quality factor Spherical antennas
Chu lower bound Dipole antennas Dispersion Magnetic cores Magnetic resonance imaging PMC core Q-factor antenna radiation patterns arbitrarily lossy magnetodielectric cores arbitrary spherical mode closed-form expressions dielectric-loaded antennas energy storage inverse frequency variation lossy magneto-dielectric spherical core magnetic losses perfect magnetic conductor core permeability permittivity power dissipation quality factor radiation efficiency radiation quality factor spherical antennas sub-wavelength spherical antenna property zero to infinite material loss tangents