If an antenna is small relative to a wavelength it will have a low radiation resistance and a high reactive component, both indicative of high non-propagating energy resulting in poor radiation efficiency. With impedance matching, the reactive component can be cancelled over a limited bandwidth. Even with bandwidth limitations and low radiation resistance, the small loop antenna is desirable for mobile applications, particular for HF military communications on-the-move. Electrically small antennas are difficult to emulate by numerical techniques due to inaccurate boundary conditions, resulting in inaccurate current distributions and input impedances. However, electrically small antenna simulation is now possible with the increase in computational power, non-uniform meshing algorithms, and finite element techniques. This paper discusses the detailed computational electromagnetic analysis of an electrically small HF half-loop antenna system mounted on a flat conductive plate. The numerical data was validated by empirical techniques for both impedance and far field performance.
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