Shielded electrical cable

Abstract

A shielded electrical cable includes a conductor set that includes two or more insulated conductors and a ground conductor adjacent to and in the same plane as the insulated conductors. The cable also includes a shielding film disposed around the conductor set, and two non-conductive polymeric layers disposed around the conductor set and the shielding film. The polymeric layers include concentric portions substantially concentric with the ground conductor having a first cross-sectional area and parallel portions where the two non-conductive polymeric layers are substantially parallel to each other. The cable also includes a transition portion providing a gradual transition between the concentric portion and the parallel portion of the two non-conductive polymeric layers. The transition portion has a second cross-sectional area defined as the area between the shielding film and the two non-conductive polymeric layers between first transition points where the two non-conductive polymeric layers deviate from being substantially concentric with the ground conductor and second transition points where the two non-conductive polymeric layers deviate from being substantially parallel. The second cross-sectional area is equal to or smaller than the first cross-sectional area.

What is claimed is: 
     
         1 . A shielded electrical cable comprising:
 a conductor set including two or more substantially parallel longitudinal insulated conductors and a ground conductor adjacent to and generally in a same plane as the insulated conductors;   a shielding film disposed around the conductor set; and   two non-conductive polymeric layers disposed around the conductor set and the shielding film and including a concentric portion substantially concentric with the ground conductor having a first cross-sectional area and a parallel portion wherein the two non-conductive polymeric layers are substantially parallel to each other; and   a transition portion providing a gradual transition between the concentric portion and the parallel portion of the two non-conductive polymeric layers, the transition portion comprising a second cross-sectional area defined as an area between the shielding film and the two non-conductive polymeric layers between first transition points where the two non-conductive polymeric layers deviate from being substantially concentric with the ground conductor and second transition points where the two non-conductive polymeric layers deviate from being substantially parallel, the second cross-sectional area being equal to or smaller than the first cross-sectional area.   
     
     
         2 . The shielded electrical cable of  claim 1 , wherein the second cross-sectional area is smaller than the first cross-sectional area. 
     
     
         3 . The shielded electrical cable of  claim 1 , wherein the second cross-sectional area is substantially the same along the length of the conductor. 
     
     
         4 . The shielded electrical cable of  claim 1  having transition portions positioned on both sides of the conductor set. 
     
     
         5 . The shielded electrical cable of  claim 1  further comprising an adhesive layer disposed between the two non-conductive polymeric layers and bonding the two non-conductive polymeric layers to each other on both sides of the conductor set. 
     
     
         6 . The shielded electrical cable of  claim 1 , wherein the transition portion has a lateral length defined as a length between the first transition points, wherein the lateral length is less than a diameter of the ground conductor. 
     
     
         7 . The shielded electrical cable of  claim 1 , wherein the transition portion has a lateral length defined as a length between the first transition points, wherein the lateral length is less than a diameter of each conductor in the two or more insulated conductors. 
     
     
         8 . The shielded electrical cable of  claim 1  comprising a characteristic impedance that is within 5 to 10% of a target impedance value over a length of 1 meter.