Broadband microwave wheat permittivity measurements in free space

Use of broadband horn/lens antennas with a collimated beam in a free-space measurement set-up with a network analyzer operating between 3 and 13 GHz and applying time-domain gating improved the accuracy of permittivity (dielectric properties) measurements on grain. Measurements were taken in the transmission mode on samples from five different classes of wheat over ranges of moisture content, temperature, and bulk density. Dielectric properties were divided by bulk density of the grain for comparison of different wheat lots. No differences in permittivity data were noted among the different wheat classes, so data were combined for presentation. The new data agree well with those reported previously. For further research, to provide dielectric properties over a very broad frequency range for a given grain sample, use of time-domain spectroscopy is suggested.