Measuring the dielectric properties of wood at microwave frequencies

A method for measuring the dielectric permittivity of thick pieces of wood is presented together with a description of the software required to extract the dielectric parameters from the measured quantities via the solution of a transcendental equation in the complex plane. This specific experimental method was adopted as it is suitable for extension to measurements at elevated temperatures and pressures. The measuring procedure, the numeric scheme, and a general analysis of the solutions are demonstrated by a series of measurements conducted on soda lime glass. First results of Blue Gum (Eucalyptus globulus) wood measurements are also presented and reveal a strong dependence of the dielectric permittivity on the electric field direction and sample moisture content.