Design, Additive Manufacturing, and Electromagnetic Characterization of Alumina Cellular Structures for Waveguide Antenna

In this work, a design and additive manufacturing approach is successfully implemented to print via digital-light-processing cubic cellular alumina structures for antenna waveguides. Cellular structures’ porosity is varied during the design phase and different dielectrics are finally produced and inserted in antenna waveguides with the aim of decreasing the cutoff frequency in the range from 1 to 10 GHz. In parallel, the electromagnetic behavior of the cellular alumina structures into the antenna waveguide as the structure porosity varies is simulated. Printed samples are then tested in a laboratory setup. In the results obtained, it is shown that the antenna cutoff frequency increases as the porosity of the alumina cellular structures increases, also evidencing a linear correlation between their average dielectric constant and porosity. In this study, it is demonstrated that the dimensional accuracy achieved after the sintering process is essential because even a small (1%) deviation of the sintered sample size from the nominal ones, due to nonlinear shrinkage, highly affects their cutoff frequencies.