A circuit structure that comprises a substrate and one or more conductive elements disposed on the substrate is provided. The substrate comprises a polymer composition that comprises an electrically conductive filler distributed within a polymer matrix. The polymer matrix contains at least one thermoplastic high performance polymer having a deflection under load of about 40° C. or more as determined in accordance with ISO 75-2:2013 at a load of 1.8 MPa, and the polymer composition exhibits a dielectric constant of about 4 or more and a dissipation factor of about 0.3 or less, as determined at a frequency of 2 GHz.