Low-Frequency Near-Field Interferometry for Characterization of Lossy Dielectric and an Investigation on Sea Ice

The far-field interferometry is a well-established method of subsurface characterization, and it has traditionally been used to determine the dielectric properties and thickness of very low-loss subsurface materials, whose dimensions are comparable to the operating wavelength. However, this method is not very well suited for dielectrics with losses several orders high and, therefore, cannot be considered as a general method of subsurface characterization. In this article, we introduce a new idea of near-field interferometry, which can be used to characterize higher loss dielectrics with dimensions very low compared with the wavelength. It is shown that, in low frequencies, there is a noticeable variation in the field components with different medium dielectric properties and thickness, and these changes can be detected externally from near-field measurements by varying receiver distance and the operating frequency. The proposed method is tested on a lossy sea ice model in the presence of a horizontal electric dipole, and the variation in field magnitudes is observed for thickness up to 5 m. Since practical sea ice bulks have thicknesses of a similar range, the near-field interferometry appears to be a promising approach to determine sea ice thickness from noninvasive measurements.

Automated summary

Far-field interferometry is suitable for small and low-loss dielectrics, while near-field interferometry is suitable for small and high-loss dielectrics. By varying the receiver distance and operating frequency, the near-field interferometry can detect changes in field components externally, allowing for noninvasive determination of sea ice thickness.