Validation of a Long-Wavelength, Near-Field Scattering Simulator Based on Boundary Relaxation

This article presents a numerical model that calculates radio wave scattering from electrically small perfect electric conductors in the near-field of the scattering bodies. The tool is referred to as the long-wavelength, near-field scattering (LWNFS) model, and it is based on electrostatic and magnetostatic field solutions calculated using a boundary-relaxation technique at the edge of the numerical grid space. Electrostatic and magnetostatic solutions are used to approximate the solutions in the slow-time-varying limit. Field tests are performed and analyzed to assess the accuracy of the LWNFS model using measurements of very-low-frequency (VLF) transmitter signals scattered by electrically small metallic boxes with different shapes. Because the amplitudes of the VLF transmitter signals can vary over time, a validation technique using normalized field values is employed: measurements are interpreted using the normalized Stokes parameters of the VLF transmitter signals. Excellent agreement between experimental observations and the predictions of the LWNFS model is demonstrated for a variety of cases. Cases where the LWNFS model is not accurate are highlighted and sources of error are considered.