Two-Material Ridged Substrate Integrated Coaxial Line for Monomode Bandwidth Improvement

The ridged substrate integrated coaxial line (RSICL) supports transverse electromagnetic (TEM) wave with small size, broadband, and good shielding performance. This article presents a two-material RSICL, which has two different dielectric materials filled in its substrate layers. Compared with the conventional RSICL with only one dielectric material, the two-material RSICL shows a higher cutoff frequency of the first higher order mode. Hence, the monomode bandwidth of the two-material RSICL can be improved accordingly. Based on the printed circuit board (PCB) process, the two-material RSICL with feeding structures is designed and fabricated. In the experiment, the first two-order modes of the two-material RSICL are excited with two types of transitions. The measured monomode bandwidth of the two-material RSICL is from dc to 44 GHz, which is 14.9% wider than that of the one-material RSICL.