3D-Printed Inhomogeneous Dielectric Lens Antenna Diagnostics: A Tool for Assessing Lenses Misprinted Due to Fabrication Tolerances

Abstract

It is difficult to manufacture 3D-printed voxelized inhomogeneous lens antennas exactly to specifications due to fabrication tolerances. Here, we define fabrication tolerances as the sum total of voxelization errors plus printing errors. In this article, we show that the aperture phase is a sensitive function of these fabrication tolerances. A conservative estimate of ±0.127-mm error in the amount of material specified to be printed leads to a 1.63° phase error per cell. This error accumulates, as a voxelized lens is generally made of many cells. We present a novel method for diagnosing misprinted lenses and reverse engineering the true permittivity inhomogeneity profile of a lens fabricated within specified tolerances. The technique is based on an inverse-scattering tool that uses geometrical optics (GO) and particle-swarm optimization (PSO). Once the actual permittivity profile is found with our method, a new optimal focal point can be calculated by using the same GO-PSO optimization tool to determine where to best feed the misprinted lens. Both numerical and measured examples are given to validate the process. The measured results show that at the new optimal focal point, the measured directivity has been restored to that of the original design specifications.