Twin axial electrical cable

Abstract

A high frequency shielded data transmission cable and method of making same are disclosed. Optimal transmission and minimal signal loss are achieved when the conductors of such a cable are maintained in fixed positions relative to one another and relative to the metal shielding. These features are provided by a cable of the instant invention wherein a central core having diametrically opposed spiral grooves hold the insulated conductors in fixed relation to one another. At least one inner layer of dielectric material maintains the insulated conductors within the grooves and provides a fixed spacing between the conductors and the metal shielding. Metal shielding, preferably of braided strips of metal, provides additional strength and flexibility to the cable. The interstitial spaces of the braid may optionally be filled with a filling compound. Likewise, the insulated conductors may be coated with a water-blocking compound to fill any spaces between the conductors and the walls of the grooves. The cable of this invention is suitable for use in harsh environments such as ocean bottom applications where it may be subjected to high pressure and substantial bending. The use of the novel central core of this cable prevents relative lateral movement of the conductors and reduces the volume of interstitial space that might otherwise collapse under such extreme conditions. In addition, a cable of this invention will allow longitudinal movement of the insulated conductors within the grooves thereby allowing the stress and compressive forces that would otherwise fatigue a cable to be relieved.