Metamaterial Integrated Rectangular Waveguide With EM-Wave Localization for Dielectric & Moisture Estimation of Soil.

This paper presents the methodology of EM-field localization in rectangular waveguide using dual layer metamaterial interface for sampling different soil samples. The prototype design consists of WR229 waveguide in which array of metamaterial unit-cell is loaded. A sample loading cell is created in the waveguide where two MTM array layers are kept at $\lambda _{g}/4$ spacing with respect to coaxial feed probe. The metamaterial unit-cell has two open-ring resonators connected with a short stub, and it helps to create a stronger localized resonance in the waveguide. This enables stronger EM field penetration into the soil sample that is under test. The fabricated device has dual resonance at 2.284 GHz and 3.091 GHz. The dielectric characterization of different dry-soil samples like black soil, silt soil, red soil and sand soil is presented. The applicability of the proposed device is also demonstrated for moisture analysis of soil samples with water content ranging from 2% to 14 %. The proposed device yields lower percentage error in extracting the dielectric constant values of the test soil samples. The on-field measurement of the soil sample which is extracted from different depths of soil surface is also presented and analyzed for dielectric estimation. The proposed device can be used in agriculture field testing application for testing properties of soil like dielectric constant and moisture level. [ABSTRACT FROM AUTHOR]