Resolving ambiguity in broadband waveguide permittivity measurements on moist materials

The dielectric properties of moist materials depend strongly on free water content. Moisture content may be conveniently sensed using microwaves, provided that calibration data is available. One common method utilizes network analyzer transmission measurements on waveguide cells filled with samples of known water content. Since this technique yields multiple solutions for the complex permittivity, a simple procedure has been developed to identify the correct solution. This has proved to be highly reliable and lends itself to measurement automation.