This application relates to a flexible cable for a portable electronic device, where the portable electronic device includes operational components having connectors that are capable of being electrically coupled to the flexible cable. The flexible cable includes a dielectric substrate having a generally planar shape, an upper grounding plane, a lower grounding plane, and a first signal transmission line that is separated by the upper and lower grounding planes, where the dielectric substrate is capable of electromagnetically shielding the first signal transmission line.