Measurement of Complex Permittivity of Cylindrical Objects in the E-Plane of a Rectangular Waveguide

Remote sensing of dielectric properties is used for numerous applications such as the field evaluation of soil water, salinity, or the organic matter content. The objective of this study is to measure dielectric properties of cylindrical shaped samples for the previously specified applications. The proposed method employs an analytical approach for determining the complex permittivity of cylindrical dielectric objects placed in the E-plane of a rectangular waveguide. The overall procedure is based on the measurement of reflection and transmission coefficients of the test specimen by placing it inside a section of rectangular waveguide. The reconstruction of dielectric properties of the test sample from the measured scattering coefficients is carried out using the newly proposed closed-form expressions, which are derived by transforming the actual circular cross section of the cylindrical sample into the equivalent multilayered rectangular cross sections. The dielectric properties of a number of specimens, including typical plastics and vegetation samples, are determined using the proposed approach. The typical error in the reconstruction of the dielectric constant of these samples having moderate permittivity values is found to be less than 5%.