Characterization of terminal impedance and radiation properties of a horizontal VLF antenna over Antarctic ice

Measurements of the input impedance of two very low frequency (VLF) transmitters in Antarctica are used to validate existing dielectric models for the ice substrate at these frequencies. Using a finite difference time domain approach, Maxwell's equations are solved in the presence of dispersive media, representing the layers of ice which form the Antarctic ice sheet as a single-pole Debye material. This model provides simulated input impedance values in good agreement with measured data for both the South Pole beacon and the former Siple Station VLF transmitters. Using the validated simulation tool, the radiation characteristics of the South Pole beacon VLF transmitter are characterized. Results for the radiation resistance, efficiency, and far-field pattern are provided for the current South Pole transmitter. The power pattern for a two-element array is also determined.