Frequency-Domain Permittivity Extraction Method for Soil Samples by Free-Space Measurements

A frequency-domain de-embedding extraction methodology is proposed for relative permittivity εrsdetermination of soil samples poured into a container using time-gated free-space measurements. Different from previous works, this methodology has the following unique features. First, it uses calibration-independent algorithm, thereby eliminating calibration errors arising from improper calibration standards. Second, it does not require exact location of the container with a sample, thus giving flexibility of freely locating the container anywhere between reference planes. Third, it retrieves unique and ripple-free εrsowing to the implementation of time-gating procedure. Objective functions are derived to facilitate εrsdetermination. Numerical analysis is implemented to validate whether one solution for εrsis feasible. Free-space measurements at X-band (8.2 − 12.4 GHz) of two different soil samples were performed, and their εrsvalues are extracted by different frequency- and time-domain methods for validation and accuracy comparison.