In an embodiment, a dielectric substrate comprises an unsintered polytetrafluoroethylene; and a high dielectric constant filler, wherein the dielectric constant of the high dielectric constant filler is greater than or equal to 35; wherein the dielectric substrate has a specific gravity of greater than or equal to 90% of a calculated theoretical density of the dielectric substrate, wherein the theoretical specific gravity is calculated based on a measured specific gravity of the high dielectric constant filler, the specific gravity of the unsintered polytetrafluoroethylene, and the relative weight fractions of the unsintered polytetrafluoroethylene and the high dielectric constant filler; and wherein the dielectric substrate has a dielectric constant of greater than or equal to 11.5 as determined at a frequency of 10 GHz.