All-Dielectric Wet Sandy Soil Broadband Tunable Absorber Based on Interference Theory

A broadband tunable absorber based on the periodic structure array (PSA) of wet sandy soil (WSS) is investigated numerically, experimentally and theoretically at microwave frequencies. Simulated and measured results show that the simple PSA absorber with the water content of 30% reaches over 90% absorption in the 10.92-GHz wideband ranging from 6.24 GHz to 17.12 GHz. The absorption mechanism is illustrated by electric field (E-z), magnetic field and current distributions. The high absorption in the wide-frequency region originates from the mixtures of the electric and magnetic resonance. Further simulated results reveal that the absorption performance can be adjusted by changing widths, thicknesses and water contents of WSS. The high absorptivity can remain unchanged when the incident angle for both transverse electric and transverse magnetic modes goes up to 60 degrees. The interference theory is used to analyze the physical mechanism of broadband absorption under different water contents. It provides a convenient and cheap path for designing a broadband absorber.