DATA CABLE FOR HIGH SPEED DATA TRANSMISSIONS AND METHOD OF MANUFACTURING THE DATA CABLE

Abstract

A data cable for high-speed data transmissions has a core pair enclosed by a pair shield. The core pair has two conductors each formed by a signal conductor and a conductor insulation surrounding the signal conductor. The conductors of the conductor pair run parallel to one another. An insulating intermediate casing is arranged between the core pair and the pair shield.

Claims

1. A data cable for high speed data transmission, comprising: at least one conductor pair having two conductors each formed by a signal conductor and a conductor insulation surrounding said signal conductor, said conductors of said conductor pair running parallel to one another; a pair shield surrounding said conductor pair; and an insulating intermediate sheath disposed between said conductor pair and pair shield.

2. The data cable according to claim 1, wherein said insulating intermediate sheath is extruded.

3. The data cable according to claim 1, wherein said insulating intermediate sheath is formed in a hose shape.

4. The data cable according to claim 1, wherein said insulating intermediate sheath is composed of a material which is suitable for RF applications and is composed of a solid plastic material.

5. The data cable according to claim 1, wherein said insulating intermediate sheath is formed from a material selected from the group consisting of polyethylene (PE), polypropylene (PP), fluoroethylene propylene (FEP), polytetrafluoroethylene (PTFE) and perfluoroalkoxylalkane (PFA).

6. The data cable according to claim 1, wherein said insulating intermediate sheath has a wall thickness in a range from 0.1 mm to 0.35 mm.

7. The data cable according to claim 1, wherein said signal conductor has a diameter in a range from 0.2 mm to 0.6 mm.

8. The data cable according to claim 6, wherein said wall thickness of said insulating intermediate sheath increases as a diameter of said signal conductor increases, and a ratio of the wall thickness of said insulating intermediate sheath to the diameter of said signal conductor is approximately in a range from 0.4 to 0.6.

9. The data cable according to claim 1, wherein each of said conductors has a conductor diameter which is in a range from 0.4 mm to 1.3 mm, wherein the conductor diameter increases as a signal conductor diameter of said signal conductor increases, and the signal conductor diameter of said signal conductor is in a range between 0.2 mm and 0.6 mm.

10. The data cable according to claim 1, wherein said conductor insulation (8) is composed of a cellular plastic selected from the group consisting of polyethylene (PE), polypropylene (PP), fluoroethylene propylene (FEP) and expanded polytetrafluoroethylene (ePTFE), said cellular plastic has a gas portion of 20-60% by vol.

11. The data cable according to claim 1, wherein said conductor pair is not covered by an insulation film.

12. The data cable according to claim 1, wherein said pair shield has a longitudinally folded shield film.

13. The data cable according to claim 1, wherein said conductor pair is one of a plurality of conductor pairs, each having said pair shield; and a cable sheath surrounding said plurality of conductor pairs.

14. The data cable according to claim 1, wherein the data cable is configured for high speed data transmissions with a data rate of higher than or equal to 25 Gbit/s; wherein said conductor pair is one of a plurality of conductor pairs which have said pair shield that are stranded with one another, wherein said conductor insulation is composed of a cellular plastic, said cellular plastic has a gas proportion of 20-60% by vol; wherein said insulating intermediate sheath is directly extruded on, is in a hose shape and is composed of solid material and has a wall thickness in a range from 0.1 mm to 0.35 mm; wherein said pair shield is a longitudinally folded shield film bearing directly against said insulating intermediate sheath; further comprising an overall shield surrounding said conductor pairs which are stranded to one another and are provided with said pair shield; and further comprising a cable sheath surrounding said overall shield.

15. The data cable according to claim 1, wherein said insulating intermediate sheath has a wall thickness of approximately 0.2 mm.

16. The data cable according to claim 1, wherein said pair shield has a longitudinally folded shield film being a metal lined plastic film,

17. The data cable according to claim 13, further comprising an overall shield disposed between said plurality of conductor pairs and said cable sheath.

18. A method for manufacturing a data cable, which comprises the steps of: surrounding two conductors with an insulating intermediate sheath; and subsequently applying a pair shield to the insulating intermediate sheath.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0034] FIG. 1 is a diagrammatic, cross sectional illustration of a shielded conductor pair, and

[0035] FIG. 2 is a cross sectional illustration of a data cable with a plurality of such conductor pairs.

DETAILED DESCRIPTION OF THE INVENTION

[0036] Identically acting parts are respectively provided with the same reference symbols in the figures.

[0037] Referring now to the figures of the drawings in detail and first, particularly to FIG. 1 thereof, there is shown A shielded conductor pair 2 that has two conductors 4. These are each formed by a central signal conductor 6 and a conductor insulation 8 surrounding the latter. The signal conductor 6 is preferably formed by a solid wire, in particular silver coated copper wire. It has a diameter d1. The latter is, for example, 0.4 mm in the present case. The conductor 4 has a conductor diameter d2, which is approximately 1.0 mm, that is to say approximately 2.5 times the diameter d1 of the signal conductor 6, in the exemplary embodiment.

[0038] The conductor insulation is composed here of a so called cellular plastic which therefore has, in contrast with a solid material, a comparatively high gas portion in the region of 20% by volume. The two conductors 4 bear directly one against the other and are in contact. The distance between the two conductors a therefore corresponds to twice the value of the thickness of the conductor insulation 8 and is therefore 0.6 mm here.

[0039] The two conductors 4 are, in particular, surrounded directly by an intermediate sheath 10. The latter is preferably composed of a solid plastic material, that is to say, in contrast to the conductor insulation, is not composed of a cellular plastic or of other foamed or expanded plastic. It is embodied as an extruded sheath, that is to say is applied to the two conductors 4 by an extrusion process. The intermediate sheath 10 is here a hose shaped structure which therefore has a constant wall thickness w circumferentially, and around the two conductors 4. Free interstice regions, in which there is no plastic material, are therefore formed between the two conductors 4 within the intermediate sheath 10.

[0040] The wall thickness w of the intermediate sheath is approximately 0.2 mm in the selected exemplary embodiment.

[0041] The intermediate sheath 10 is surrounded in turn by a shield film 12, which bears directly on the intermediate sheath 10 and forms a pair shield. The shield film 12 is preferably embodied as a longitudinally folded shield film 12 and is therefore not wound. The shield film 12 is preferably a conventional shield film, specifically an aluminium lined (plastic) film. The latter typically has a film thickness of typically several 10 m to several 100 m. The shield film 10 can be a single layer or double layer shield film (metal coating applied to only one side or both sides of the carrier foil). The shielded conductor pair 2 which is illustrated in FIG. 1 is expediently formed exclusively by the elements illustrated in FIG. 1. Therefore, no filler wire is provided. As an alternative to this, such a filler wire can be arranged. In such a case it forms contact with the electrically conductive layer of the shield film 12. Such a filler wire can be provided running, for example, between the intermediate sheath 10 and the shield film 12 or else on the outside of the shield film 12. The filler wire serves to form electrical contact with the shield film 12 in a plug connecting region.

[0042] In particular, an otherwise customary intermediate film which is wound around the two conductors 4 is dispensed with. The intermediate film is replaced by the extruded intermediate sheath 10 with the comparatively large wall thickness w compared to conventional shielded conductor pairs. A particular advantage here is the fact that the distance between the signal conductor 6 and the shield film 12 is, as it were, increased and therefore the two signal conductors 6 move closer together, considered in relative terms. Compared to conventional shielded conductor pairs 2, the distance a is therefore reduced. Overall, this also reduces the length to width ratio, with the result that overall the shielded conductor pair 2 is rounded in comparison with conventional shielded conductor pairs. This is advantageous for later assembly.

[0043] As a result of the comparatively large intermediate sheath, it is therefore possible overall to reduce the thickness of the conductor insulation 8 while maintaining the distance between the signal conductor 6 and the shield film 12. Overall, this gives rise to relatively thin conductors 4 and correspondingly also to the reduced distance a between the two signal conductors 6. Owing to this reduced distance a, the two conductors 4 are overall coupled more firmly to one another, since the pair shield which is formed by the shield film 12 is now further away from the respective signal conductor 6 compared to the distance a between the signal conductors 6. Undesired asymmetries, which cannot be completely avoided during manufacture, therefore have fewer effects overall. The so called mode conversion performance is significantly improved as a result. The short distance a also improves the insertion loss compared to conventional shielded conductor pairs. Investigations have shown an improvement by 15%.

[0044] Finally, it is also to be noted that the electrical field of the differential useful signal is located and propagates predominantly in the (highly cellular) material of the conductor insulation 8, that is to say between the signal conductors 6. On the other hand, the field of the undesired common mode signal has to propagate through the intermediate sheath 10 which is composed of solid material. Overall, this slows down the propagation speed of the undesired common mode signal in comparison with that of the differential useful signal. The common mode signal is therefore not superimposed, or at least no longer to such a large degree, on the useful signal at the end of a transmission link, with the result that better evaluation of the differential useful signal is made possible.

[0045] Overall, a differential data signal with high data rates of, for example, >25 Gbit/second can be transmitted at transmission frequencies of >25 GHz in a reliable and safe fashion via the conductor pair 2.

[0046] FIG. 2 also shows a possible configuration of a data cable 14 in which a plurality of conductor pairs 2 which are shielded in such a way are combined with one another. Basically, the data cable 14 can also have just one shielded conductor pair 2. The data cable 14 preferably has two, four, sixteen or, as illustrated in FIG. 2, eight shielded conductor pairs 2. The individual conductor pairs 2 are usually stranded with one another here and form a transmission core. In the exemplary embodiment, two internal conductor pairs 2 are stranded with one another and form an inner transmission core. Six further shielded conductor pairs 2 are arranged, in particular, stranded, around the latter. The conductor pairs 2 form here, as it were, an external (cable) layer. The transmission core which is formed by the shielded conductor pairs 2 is surrounded by an overall shield 16. In the exemplary embodiment, an intermediate film 18 composed of plastic is arranged between the transmission core and the overall shield 16. The overall shield 16 can have a customary design. The overall shield 16 is formed here by an inner shield film 20 and an outer shield mesh 22. Other combinations of shield films 20 with C, D shields or with a plurality of shield films etc., are basically possible. Finally, an outer cable sheath 24 for protecting against environmental influences is applied around the overall shield 16. This cable sheath 24 is, in particular, also extruded.