A 3D-Printed Wideband Sensor for Food Complex Permittivity Estimation Based on Double Ridge Waveguide

Abstract

This work aims to advance the design of a microwave device capable of detecting, through indirect measurements, variations in the permittivity of the food materials. To this aim, a novel sensor based on double ridge waveguide configuration and a specific sample holder, to be 3D-printed, are designed. To numerically study the microwave signal propagation in the designed device and investigate its wideband performance, simulations with different food materials are performed. In particular, the complex dielectric permittivity of Carasau bread doughs, a traditional food product from Sardinia (Italy), and different distilled water-based solutions with various percentage of solutes in them, are measured with open-ended coaxial probe in the range 0.5-8.5 GHz and the acquired data are then used as material under test. The results show a good ability of the device to discriminate variations of the percentage of solute in solutions. Differences of up to 60MHz in the position of the $\vert S_{11}\vert$ peak and 15.8 dB in amplitude are in fact observed between adjacent curves. However, in the case of Carasau bread dough, this device was not capable of clearly discriminating variations in the percentage of ingredients used.