Tunable electrically small antenna for next generation ionospheric heating



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An efficient, metamaterial inspired electrically small antenna with the capability of frequency reconfiguration is evaluated for potential future use in Transportable Ionospheric Heating. Consisting of a Small Loop Antenna (SLA) inductively coupled to a Capacitively Loaded Loop (CLL) this design provides a high Q, natural match to a 50 Ω source. The resonant frequency of this antenna, being dependent upon the capacitance and inductance of the CLL, may be adjusted to match the frequency range required for ionospheric heating in the range of 2 – 10 MHz. The High Frequency Active Auroral Research Program (HAARP) array in Gakona, Alaska occupies approximately 1.2x105 m2 of land with 180 elements each 440 m2 in area. To match HAARP performance in a transportable array each antenna element must be miniaturized with increased power capability. The antenna design presented, at 2.5 x 1.2 x 3 m in size, is a factor 60 times smaller than a HAARP element at 21 x 21 m in size and a factor 5 to 10 times smaller than a dipole at an equivalent frequency in linear dimension. Tuning range, power handling, and radiation characteristics are evaluated for two antenna designs and three tuning methods.



Electrically Small Antenna, Tunable Antenna, Reconfigurable Antenna, Antennas