Design of Grain Powder Dielectric Constant Detection Device Based on Microwave Transmission Method

A miniaturized rapid detection device for relative dielectric constant of grain powder is designed for the need of rapid measurement of grain properties. An innovative double heterodyne mixing structure is proposed. The relationship between the microwave phase shift and the relative dielectric constant of grain powder is established based on the free-space method. The relative dielectric constants are calculated by measuring rice flour, barley flour and glutinous rice flour in the frequency range from 4.5 GHz to 11.5 GHz, and the random forest algorithm is used for species identification. The experimental results show that the average relative error of the relative dielectric constant does not exceed 3.5%, the sample prediction accuracy is 96.7%, and the detection device has good repeatability and practicability.