Journal article
Minimum Q Electrically Small Antennas
Theoretically, the minimum radiation quality factor Q of an isolated resonance can be achieved in a spherical electrically small antenna by combining TM1m and TE1m spherical modes, provided that the stored energy in the antenna spherical volume is totally suppressed. Using closed-form expressions for the stored energies obtained through the vector spherical wave theory, it is shown that a magnetic-coated metal core reduces the internal stored energy of both TM1m and TE1m modes simultaneously, so that a self-resonant antenna with the Q approaching the fundamental minimum is created.
Numerical results for a multiarm spherical helix antenna confirm the theoretical predictions. For example, a 4-arm spherical helix antenna with a magnetic-coated perfectly electrically conducting core (ka=0.254) exhibits the Q of 0.66 times the Chu lower bound, or 1.25 times the minimum Q.
| Language: | English |
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| Publisher: | IEEE |
| Year: | 2012 |
| Pages: | 3551-3558 |
| ISSN: | 15582221 and 0018926x |
| Types: | Journal article |
| DOI: | 10.1109/TAP.2012.2201096 |
| ORCIDs: | Kim, O. S. |
Chu lower bound Circular polarization Electric dipole Electrically small antennas Fundamental limitations Magnetic dipole Quality factor
Dipole antennas Energy storage Magnetic cores Magnetic resonance Materials Permeability Q-factor circular polarization closed-form expressions electric dipole electrically small antennas fundamental limitations helical antennas internal stored energy magnetic dipole magnetic-coated metal core magnetic-coated perfectly electrically conducting core minimum radiation quality factor multiarm spherical helix antenna quality factor self-resonant antenna spherical electrically small antenna vector spherical wave theory
