Characterization of Variable Density 3D Printed Materials for Broadband GRIN Lenses

In this work we design, simulate, manufacture and measure blocks made of variable density plastic. The density is controlled through varying the size of small cubes at the intersections of a fine grid. This structure is inspired by [1]. Simulations using HFSS show that there is a consistent relation between plastic density and relative permittivity (εr), and this is confirmed by measurements of 24 blocks with different density. Finally, an example design utilizing this is presented; a gradient index lens (GRIN) with continuously varying εr. 3D printed GRIN lens has been presented in [2], but in that case with stepwise varying εr. The GRIN lens was measured in an anechoic chamber, and about 5dB increased gain was demonstrated over the entire bandwidth of 7.5-18GHz.