Patent Publication Number: US-2022215986-A1

Title: Cable

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a cable, and more particularly to a high-speed signal cable used to transmit high-frequency signals. 
     2. Description of Related Arts 
     A high-speed signal cable in the prior art usually includes a pair of signal core wires, a metal shielding layer covering the core wires, an outer insulating layer covering the metal shielding layer, and a pair of signal core wires. Both include an inner insulating layer and an inner conductor covered in the inner insulating layer. The inner conductor and inner insulating layer of each signal core wire are respectively integrally molded, and then the two signal wires are wrapped in the metal shielding layer. The position between the two independently formed signal core wires is relatively unstable, therefore, the electrical characteristics may be unstable. 
     China Patent No. CN108376580, published on Aug. 7, 2018, discloses a cable that comprises a pair of signal core wires and an extruded insulating layer that is simultaneously covered with a pair of core wires. The pair of core wires are respectively formed by extrusion molding, the process is complicated, and the distance between the two inner conductors is large, the insertion loss of the cable is large, and the overall size of the wire is large. 
     Therefore, it is necessary to provide a new type of cable with stable, reliable signal transmission and simple manufacture, which enables the cable to have lower insertion loss under the premise of ensuring the overall impedance matching. 
     SUMMARY OF THE INVENTION 
     A main object of the present invention is to provide a cable which reduces the distance between a pair of inner conductors as much as possible on the premise of ensuring impedance matching so that the cable has lower insertion loss. 
     To achieve the above-mentioned object, a cable comprises: a core wire having a pair of inner conductors and an inner insulating layer extrusion molded around the pair of inner conductors; an insulating layer extrusion molded around the core wire; a shielding layer covering the insulating layer; and a sheath covering the shielding layer. 
     Compared to prior art, the present invention has the following beneficial effects: through the double extrusion molding of the inner insulating layer and the insulating layer, the distance between a pair of inner conductors is reduced, so that the cable has lower insertion loss, and the overall size of the cable is also smaller, and at the same time, the cable of the present invention has a high-speed data transmission capability with a signal frequency greater than 40 GHz. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a cross-sectional view of a first embodiment of a cable of the present invention. 
         FIG. 2  is a cross-sectional view of a second embodiment of the cable of the present invention. 
         FIG. 3  is a cross-sectional view of a third embodiment of the cable of the present invention. 
         FIG. 4  is a cross-sectional view of a fourth embodiment of the cable of the present invention. 
         FIG. 5  is a cross-sectional view of a fifth embodiment of the cable of the present invention. 
         FIG. 6  is a cross-sectional view of a sixth embodiment of the cable of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows the first embodiment of the cable  100  of the present invention. The cable  100  includes a core wire  10 , an insulating layer  20  covering the core wire  10  by extrusion molding, a shielding layer  30  covering the insulating layer  20 , and a sheath  50  covering the shielding layer  30 . 
     In this embodiment, the core wire  10  includes a pair of inner conductors  1  and an inner insulating layer  2  simultaneously covering the pair of inner conductors  1  by extrusion molding. The inner conductor  1  is selected from the group including a copper inner conductor, a silver-plated copper inner conductor, and a tin-plated copper inner conductor. The inner insulating layer  2  is selected from the group including solid PP (polypropylene), solid PE (polyethylene), solid Teflon (polytetrafluoroethylene), foamed PP, foamed PE and foamed Teflon. The insulating layer  20  is selected from the group including solid PP, solid PE, solid Teflon, foamed PP, foamed PE, and foamed Teflon. The cross-sectional profile of the inner insulating layer  2  is glasses-shaped, and the cross-sectional profile of the insulating layer  20  is stadium-shaped. The inner insulating layer  2  is provided with a connecting portion  21 , and the longitudinal dimension of the connecting portion  21  is smaller than the thickness of the inner insulating layer  2  outside the inner conductor  1 . There is no air gap between the inner insulating layer  2  and the insulating layer  20 . 
     The shielding layer  30  includes a first shielding layer  31  and a second shielding layer  32 .The first shielding layer  31  is selected from the group including aluminum foil, copper foil, pure copper tape and silver-plated copper foil. The second shielding layer  32  is selected from the group including bare copper wire, tin-plated copper, silver-plated copper, aluminum foil, copper foil, pure copper tape, and silver-plated copper foil. The first shielding layer  31  may cover the insulating layer  20  in a spiral winding manner or a longitudinal coating manner, the second shielding layer  32  may cover the first shielding layer  31  in a spiral winding manner or a longitudinal coating manner. The sheath  50  is selected from the group including PE, PP, Teflon or PET (polyethylene terephthalate) wrapping tape. The PET wrapping tape can be arranged in one layer or multiple layers. The cable is not provided with a ground wire, but uses the shielding layer as the function of the ground wire. 
       FIG. 2  shows the second embodiment of the cable  100  of the present invention. Compared with the first embodiment, in this embodiment, the shielding layer  30  is only provided as one layer, the shielding layer  30  is selected from the group including aluminum foil, copper foil, pure copper tape and silver-plated copper foil. The shielding layer  30  may cover the insulating layer  20  in a spiral winding manner or a longitudinal coating manner. The sheath  50  is a two-layer PET wrapping tape, of course, it can also be set as a one-layer PET wrapping tape. 
     Referring to  FIG. 3 , which is the third embodiment of the cable  100  of the present invention. Compared with the second embodiment, in this embodiment, a pair of ground wires  70  are added. The pair of ground wires  70  are respectively located on both sides of the core wire, and the ground wire  70  is tightly sandwiched between the shielding layer  30  and the sheath  50 . According to actual requirements, only one ground wire  70  may be added, and the ground wire  70  is located on one of the two sides of the core wire  10 . 
       FIG. 4  shows the fourth embodiment of the cable  100  of the present invention. Compared with the first embodiment, in this embodiment, the upper and lower sides between the inner insulating layer  2  and the insulating layer  20  include air gaps  60 . 
       FIG. 5  shows the fifth embodiment of the cable  100  of the present invention. Compared with the second embodiment, in this embodiment, the upper and lower sides between the inner insulating layer  2  and the insulating layer  20  include air gaps  60 . 
       FIG. 6  shows the sixth embodiment of the cable  100  of the present invention. Compared with the third embodiment, in this embodiment, the upper and lower sides between the inner insulating layer  2  and the insulating layer  20  include air gaps  60 . 
     The dielectric constant of air is smaller than that of insulating materials, and the attenuation during signal transmission is smaller, which makes the electrical performance of the cable better. 
     For the cable of the present invention, the inner insulating layer  2  simultaneously covers a pair of inner conductors  1  in an extrusion molding manner, and after forming a core wire, the insulating layer  20  is then coated to the core wire  10  in an extrusion molding manner. Through two extrusion molding methods, while ensuring the overall impedance matching, only the thickness of the inner insulating layer  2  is isolated between the two inner conductors  1 , and the distance between the two inner conductors  1  is reduced, so that the cable  100  has lower insertion loss, and the overall outer diameter of the cable is also smaller. The cable of the present invention has a high-speed data transmission capability with a signal frequency greater than 40 GHz. It provides more options for the improvement of cable high-frequency characteristics. 
     The above describes only some of the embodiments of the present invention, but not all of the embodiments. Any equivalent changes to the technical solutions of the present invention by those skilled in the art by reading the description of the present invention are covered by the claims of the present invention.