Preliminary Design of a Double Ridge Waveguide Device for Monitoring the Complex Permittivity of Carasau Bread Doughs

The Industry 4.0 paradigm calls for engineering solutions for monitoring the industrial production and quality of food products. Microwave devices can be powerful tools in this scenario. This work deals with the preliminary design of a double ridge waveguide device to perform indirect measurements of the complex permittivity of a traditional food product from Sardinia (Italy), i.e. the Carasau bread, in the case of a small bakery industry. To this aim, the complex dielectric permittivity of doughs was measured with open-ended coaxial probe in the range 0.5–8.5 GHz. The dielectric spectra were fitted to a third-order Cole-Cole model. Then the data were used to numerically study the microwave signal propagation in the double ridge waveguide investigating different sample positioning and configurations. With our full-wave simulations, the thickness of the sample holder, the occupation length of the sample in the waveguide, as well as the inclination angle were determined to achieve suitable transmission performance.