The type of dielectric substrate used has an impact on the size, port, surface, volume, and field properties of the antennas. The dielectric materials have polarized molecules which possess mobility due to presence of electric field. The motion of charged particles results in heat loss which leads to rise in signal attenuation in direct proportion with frequency. Selection of dielectric material impacts the performance of antenna. You can use the dielectric functions to control the relative permittivity, and loss tangent of the substrate. You can design antennas with single or multi-layer substrates.