An apparatus has a permittivity attenuation layer interposed between a substrate and a first conductive trace, wherein the permittivity attenuation layer comprises a resin matrix containing functionalized carbon nanomaterial, such as functionalized single-wall carbon nanotubes (f-SWNTs). In some embodiments, a design structure for designing, manufacturing, or testing the apparatus is tangibly embodied in a machine readable medium. In some embodiments, the apparatus comprises an enhanced laminate core for use in a printed wiring board (PWB) that contains a differential pair having an inner-leg conductive trace and an outer-leg conductive trace. A permittivity attenuation layer is interposed between the inner-leg conductive trace and a laminate core, wherein the loading level of f-SWNTs in the permittivity attenuation layer is selected to attenuate the permittivity of the inner-leg conductive trace to match the permittivity of the outer-leg conductive trace.