Time-Gated Free-Space Measurement Signal Processing Method to Estimate Dielectric Constant of 3D Printed Materials

Abstract

In this study, we introduce a technique to eliminate the multiple reflection effects using time gating and calculate the dielectric constant of 3D printed materials using a free-space measurement system. Air, conductor, and MUT signals in the frequency domain obtained using the VNA are acquired and converted into the time domain via the inverse Fourier transform. A window function is applied in the time domain to extract only the reflected signal in the desired area. Subsequently, S 11 and S 21 of the MUT are obtained through calibration, and the dielectric constant of the object is estimated using the NRW method. Consequently, the dielectric constant of PLA, which is often used in FDM printers, is calculated to be 2.788 and the loss tangent is 0.054. Similarly, the dielectric constant and loss tangent for a general resin used in an SLA printer are calculated to be 3.142 and 0.071, respectively.