Cable

A cable has a pair of insulated core wires extending parallel to each other in a longitudinal direction. Each of the insulated core wires includes a central conductor and a core insulation layer wrapped around the central conductor in a circumferential direction. A first metal shielding layer is wrapped around the pair of insulated core wires. A second metal shielding layer is wrapped around the first metal shielding layer. An outer insulation layer is wrapped around an outer circumferential surface of the second metal shielding layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Chinese Patent Application No. 202110180885.8 filed on Feb. 9, 2021 in the China National Intellectual Property Administration, the whole disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates to a cable, and in particular to a cable such as a twin-axial cable for enabling data transmission at a high data transmission rate.

BACKGROUND

A conventional high-speed data transmission cable mainly includes a pair of insulated core wires, a drain wire located between the insulated core wires, a metal shielding layer wrapped around the insulated core wires and the drain wire, and an insulation layer wrapped around the metal shielding layer. However, a high-frequency test bandwidth achievable by such the conventional cable is low. Moreover, as the core wires are fixed only by one insulation layer, the insulated core wires, as well as the drain wire, are easily displaced, and have poor performance stability. Further, the metal shielding layer is easily broken during bending movements, resulting in poor high-frequency performance. The electromagnetic shielding effect of one metal shielding layer is also insufficient.

SUMMARY

According to an embodiment of the present disclosure, a cable comprises a pair of insulated core wires extending parallel to each other in a longitudinal direction. Each of the insulated core wires includes a central conductor and a core insulation layer wrapped around the central conductor in a circumferential direction. A first metal shielding layer is wrapped around the pair of insulated core wires. A second metal shielding layer is wrapped around the first metal shielding layer. An outer insulation layer is wrapped around an outer circumferential surface of the second metal shielding layer.

DETAILED DESCRIPTION OF THE EMBODIMENTS

As shown inFIG.1, according to an exemplary embodiment of the present disclosure, a cable100(e.g., a twin-axial, biaxial cable or a differential cable) is configured to transmit data at a relatively high transmission rate, for example a transmission rate higher than 10 Gbps, such as 20 Gbps to 40 Gbps. The cable100according to the exemplary embodiment of the present disclosure includes a pair of insulated core wires110for signal or data transmission. The pair of insulated core wires110extend parallel to each other in a longitudinal direction. Rach of the insulated core wires110comprises a central conductor111and a core insulation layer112wrapped around the central conductor111in a circumferential direction. For example, the core insulation layer112may be in the form of an insulation material strip or tape and wound around the central conductor111in the longitudinal direction. The central conductor may be made of a high-conductivity material such as a copper conductor or a silver-plated wire, and the core insulation layer may be made of an insulation polymer material such as polyolefin.

As illustrated, the cable100according to the embodiment of the present disclosure further comprises a metal shielding layer and an outer insulation layer140. The metal shielding layer is configured to shield signals or data transmitted over the insulated core wires110from an external electromagnetic interference. In an embodiment of the present disclosure, the cable includes two shielding layers, e.g., a first metal shielding layer120and a second metal shielding layer130arranged sequentially from inside to outside. The first metal shielding layer120is wrapped around the pair of insulated core wires110in the circumferential direction to provide an electromagnetic shielding effect. The second metal shielding layer130is wrapped around the first metal shielding layer120in the circumferential direction to provide an improved electromagnetic shielding effect. The outer insulation layer140is wrapped around an outer circumferential surface of the second metal shielding layer130in the circumferential direction. Therefore, the cable is provided with two shielding layers resulting in improved stable bandwidth performance, increased high-frequency bending resistance and better electromagnetic shielding effect.

In addition, in the event of joints or gaps in the first metal shielding layer and the second metal shielding layer, the joint or gap of the first metal shielding layer and the joint or gap of the second metal shielding layer are located at different angular positions with respect to the same core wire. In this way, the joints or gaps of the first metal shielding layer and the second metal shielding layer are staggered or not overlapped with each other in a radial direction. Therefore, even if the joints or gaps of the first metal shielding layer and the second metal shielding layer are separated from or misaligned with each other during bending use, the combination of the first metal shielding layer and the second metal shielding layer still provides a complete or continuous electromagnetic shielding effect.

The first metal shielding layer120may be in the form of a shielding strip and wound around the insulated core wires110in the longitudinal direction. The second metal shielding layer130may also be in the form of a shielding strip and wound around the first metal shielding layer120in the longitudinal direction. The second metal shielding layer130may include a conductive layer partially bonded to an outer circumferential surface of the first metal shielding layer by an adhesive. Alternatively, fillers may be provided between the conductive layer and the first metal shielding layer120, which can further improve the stability of the cable100. As an example, the conductive layer of the metal shielding layer is made of aluminum or copper. For example, the conductive layer may be an aluminum/polypropylene strip. However, it will be understood by those skilled in the art that the conductive layer of the metal shielding layer may also be made of other conductive materials in other embodiments of the present disclosure.

The outer insulation layer140is wrapped around the outer circumferential surface of the second metal shielding layer130. The outer insulation layer may also be in the form of an insulation material strip and wound around the metal shielding layer in the longitudinal direction. The outer insulation layer may be bonded to the outer circumferential surface of the second metal shielding layer through a thermal fusion melting or by an adhesive. The outer insulation layer may be made of an insulation material such as polyester, polypropylene, polyethylene terephthalate (PET). In some examples, the outer insulation layer may be formed by stacking a plurality of sub-insulation layers to enhance a flexibility of the cable during the bending use.

In some embodiments, as shown inFIGS.1-3, the cable100further comprises a drain wire150. The drain wire150is, for example, disposed between the first metal shielding layer120and the second metal shielding layer130and adapted to be pressed against the outer circumferential surface of the first metal shielding layer120by the second metal shielding layer130. As an example, the drain wire150may be in electrical contact with at least one of the first metal shielding layer120and the second metal shielding layer130, for example in electrical contact with the conductive layer of the metal shielding layer.

FIGS.1and2illustrate an embodiment wherein the drain wire150is located at a radial outer side of the pair of insulated core wires110. In the embodiment illustrated inFIG.1, the cable includes two drain wires150, which are located at opposite radial outer sides of the pair of insulated core wires110, respectively. In the embodiment illustrated inFIG.2, the cable includes a single drain wire150, which is located at an outer side of one of the pair of insulated core wires110facing away from the other of the pair of insulated core wires in the radial direction. For example, a center of the central conductor111of each of the pair of insulated core wires110is located in the same radial plane as a center of the drain wire150, and the center of the drain wire150is located outside of the center of the central conductor111of a corresponding one of the pair of insulated core wires110in the radial direction.

In the embodiment illustrated inFIG.3, the cable100comprises a single drain wire150. The drain wire150is located between the centers of the two central conductors111of the pair of insulated core wires110in a first direction parallel to a virtual line extending between the centers of the central conductors111of the pair of insulated core wires110. For example, the single drain wire150is centered relative to the centers of the two central conductors111of the pair of insulated core wires110in the first direction. The single drain wire150shown inFIG.3is located at the same side of the two insulated core wires110. It will be understood that in other embodiments, in addition to the drain wire150shown inFIG.3, another drain wire may be provided at the opposite side of the two insulated core wires. That is, the cable may include two drain wires respectively located at two opposite sides of the two insulated core wires in a second direction perpendicular to the first direction.

In some embodiments of the present disclosure, at least one of the second metal shielding layer130and the first metal shielding layer120may be used as a drain wire suitable for electrical connection with an external ground. For example, as shown inFIG.4, the cable is not provided with a separate drain wire, and the second metal shielding layer130or the first metal shielding layer120can also serve as the drain wire, thereby providing a cable with a more regular outer contour. As an example, the second metal shielding layer may be directly wrapped around the outer circumferential surface of the first metal shielding layer. Alternatively, an adhesive or fillers may be provided between the second metal shielding layer130and the first metal shielding layer120.

In some embodiments of the present disclosure, the cable100may further include an inner insulation layer160. The insulation layer160may be wrapped around the core insulation layers112of the pair of insulated core wires110, for example, partially wrapped around outer circumferential surfaces of the core insulation layers112. The insulation layer160fixes the pair of insulated core wires110, such that the core insulation layers112of the pair of insulated core wires110abut against each other on outer circumferential surfaces thereof at sides facing toward each other. As illustrated, the first metal shielding layer120is wrapped around the inner insulation layer160, for example, wrapped around an outer circumferential surface of the inner insulation layer160in the longitudinal direction. Compared with a conventional cable, as the inner insulation layer is additionally provided between the metal shielding layer and the insulated core wires to fix the insulated core wires, the insulated core wires can be protected from being displaced during use, for example during the bending use, so as to improve the performance stability of the cable.

For example, the inner insulation layer160may be in the form of an insulation material strip and wound around the core insulation layers112of the pair of insulated core wires110in the longitudinal direction. For example, the inner insulation layer may be bonded directly to portions of outer circumferential surfaces of the core insulation layers of the pair of insulated core wires, for example, through the thermal fusion. In other examples, the inner insulation layer may be bonded to the portions of the outer circumferential surfaces of the core insulation layers of the pair of insulated core wires, for example, by an adhesive. The inner insulation layer is made of an insulation polymer material. For example, the inner insulation layer may be made of an insulation material such as polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET). In some examples, fillers may be provided within a space defined between the core wire insulation layers112of the pair of insulated core wires110and the inner insulation layer160so as to provide a flexibility of the cable during the bending use and to further avoid the insulated core wires from being displaced during use.

The presence of the inner insulation layer160can prevent the metal shielding layer from entering a gap between the insulated core wires. For example, the first metal shielding layer may be directly bonded to the outer circumferential surface of the inner insulation layer through thermal fusion, or it may be bonded by an adhesive. For example, the first metal shielding layer may include a conductive layer bonded to the inner insulation layer by an adhesive, or fillers may be provided between the conductive layer and the inner insulation layer, which can further improve the stability of the cable. In some embodiments, as shown inFIG.5, such an inner insulation layer is not provided, and the first metal shielding layer120may be wrapped directly around the core wire insulating layer.

In the illustrated embodiments, the various layers/wires of the cable100are shown to be separated from each other or spaced apart from each other by a predetermined gap for the purpose of clearly illustrating the various layers/wires. In fact, the layers/wires of the cable are at least partially closely attached or directly bonded with each other, or suitable fillers or adhesive are provided between the layers/wires.

In addition, those areas in which it is believed that those of ordinary skill in the art are familiar, have not been described herein in order not to unnecessarily obscure the invention described. Accordingly, it has to be understood that the invention is not to be limited by the specific illustrative embodiments, but only by the scope of the appended claims.