An Empiric Mathematical Models to Predict Electrical Properties of Natural Juniper Wood Samples by Using Non-Distractive Methods

This study focused on determining electrical parameters, both complex dielectric permittivity and tangent loss coefficients, for Juniper wood in its natural form. Therefore, enough rendered samples were selected and kept in the room where the temperature was around $23{{}^{\circ}\mathrm{C}}\pm 2$. Between 2.17 GHz and 6 GHz, three standard waveguide adaptors were used to cover the whole band. Measurements were conducted and repeated considering moisture content variation to express an empiric mathematical model which will allow calculating electrical parameters of natural woods without any $S-\text{parameter}$ measurements (will not require VNA-like equipment for future). The Juniper sample was subjected to $S-\text{parameter}$ measurements, and 500 data were recorded for the prescribed moisture content value. The selected specimens were three softwood and six hardwood species since comparison can be meaningful for industry. A total of 54 empirical models have been generated, 3 for the dielectric constant of individual tree species and 3 for the loss tangent values of particular tree species, and these models are supported by their density values. A total of 16500 data generated from $S-\text{parameter}$ measurements were used in the analysis, in which each measure contains 500 raw data. The proposed mathematical models allow for predicting the electrical properties of selected natural wood samples without requiring any microwave measurements, which is the novelty of this study.