EP0568048B1 - Data transmission cable - Google Patents

Abstract

Data transmission cable having a standard impedance of 150 OMEGA , having - at least one twisted core pair, the individual cores in each case having one conductor and one insulating sleeve which encloses the respective conductor in the longitudinal direction, - at least one screen which jointly surrounds the cores, - an outer sheath which encloses the screen externally all round, the diameter of the individual cores (2A, 2B, 3A, 3B) being approximately 1 mm or less. <IMAGE>

Description

The invention relates to a data transmission cable with a standard impedance of 150 Ω.

Such data transmission cables are used for example in the "IBM PC world" for data transmission between two devices. In the IBM world, the term "150 Ω impedance standard" stands for the specifically specified parameters - which must be observed precisely by the cable - for example, the impedance or wave impedance, damping, near-end crosstalk attenuation, etc. The term "150Ω" is used here not exactly limited to the numerical value itself, but rather denotes the central value of a tolerance band in the "IBM world" of suitable cable impedances, for example between 135Ω and 165Ω.

In the 150 Ω IBM world there is specifically the so-called "Type 6 cable" for connection to the "IBM Type 1 connector". This data transmission cable ensures the 150 Ω impedance standard of the IBM world and is suitable, for example, for the connection or data transmission between a patch panel device and a computer. By twisting the wires, the electrical properties of the individual Cores of a pair of cores equal to earth. This results, for example, in a pair of wires with a defined capacitance and inductance covering, or with a defined impedance (characteristic impedance).

Although the electrical properties of the known data transmission cable are satisfactory, due to the increasing density of electronic integration, it only partially meets the requirements of the electronics and computer industry. The TYP-1 connector has an external dimension in the order of several centimeters (e.g. 1cm ∗ 4cm), which is too large for many applications.

From FR-A-2 637 117 a television signal transmission cable is known with 2 wires, each consisting of a conductor and an insulating sleeve. The respective conductor has a diameter of less than 1 mm. The 2 wires are wrapped with a shield.

The aim of the present invention is to provide a data transmission cable which at least largely does justice to the increasing integration density of microelectronics.

This goal is achieved by a data transmission cable with a standard impedance of 150 Ω, with four wires, each consisting of a conductor and an insulating sleeve, with diagonally opposite wires forming a pair of wires for the transmission of electromagnetic waves, the wires of the wires forming the corner points of a square and thereby according to Art of a star quad are twisted together, the diameter of the individual cores being approx. 1 mm or less, the geometry of the star quad is fixed by an intermediate sheath formed around the star quad, a shielding foil is wrapped around the four cores on the outside, and the shielding foil is also completely covered by wrapped around an overall screen and finally the overall screen is still completely surrounded by a preferably flexible outer jacket (claim 1). Cables with such thin wires are known in principle. On the other hand, a cable with such thin wires that is adapted to the 150 Ω impedance world is not known. The invention is thus based on the knowledge that, contrary to previous prejudice among experts, with careful design of the cable it is very well possible with reasonable effort to implement a data transmission cable of the 150 Ω impedance world with very thin wires. The type 6 cable described at the beginning has been used in the professional world, although its electrical properties have not given rise to any criticism. Furthermore, the further development of such data transmission cables was neglected.

Basically, the possibilities of a data transmission cable of significantly smaller diameter in this area of technology were clearly recognized for the first time by the invention. The data transmission cable according to the invention enables the use of approximately two to four times smaller plugs. The use of smaller plugs in turn opens the space for a higher integration density of the devices, e.g. in the patch panel area.

In summary, a cable is created that is suitable, for example, for a connection to an AMP connector or RJ-45 connector, so that these connectors can be used for the first time to achieve a high integration density in the 150 Ω world.

The star quad ensures a completely symmetrical structure of the cable, so that the electrical properties of all individual wires to earth are the same. In addition, there is an essentially circular outer shape of the cable, which ensures easy processing: the cable is particularly flexible on all sides. It also ensures that the four wires are within of the data transmission cable are arranged with optimal use of the space available to them. Due to the stranding in the manner of a star quad, the surfaces of the individual insulation of the four wires lie close together. They thus form the spatially least complex solution of an arrangement of four cores and essentially achieve the electrical specifications and values as with a conventional "large" data transmission cable of the 150 ohm impedance standard.

This arrangement of the four wires also provides the most resistant and stable form of wire arrangement with respect to external pressurization. Since the four wires run essentially symmetrically around the longitudinal axis of the cable, each with the same own cross section, the cross section of the data transmission cable has the circular shape already mentioned. In addition to the advantage of a special internal stability compared to external pressurization - and the associated securing of the basic electrical parameters - this construction has the advantage for a data transmission cable of the 150 Ω impedance standard that no spirals occur when the cable is pulled in and the assembly process is not inhibited.

The intermediate sheath ensures a clearly defined guidance of the inner wire pairs and thus contributes significantly to the realization of the data transmission cable according to the invention.

In a particularly preferred development of the invention, the intermediate jacket consists of a plastic foam, in particular a frangible plastic foam, or a solid material (claim 2). This creates an intermediate sheath that, on the one hand, enables clearly defined guidance. In addition, the cable designed in this way is also particularly easy to install. After easy assembly and processing, there is in particular This is a great need for extremely thin cables, because the technician has to work very precisely and, for example, take special care when stripping. The present variant of the invention does justice to this fact. The intermediate sheath no longer has to be cut out and cut out, but can simply be "broken up" or "broken off" during installation on site, if necessary. This results in a noticeable simplification and shortening of the work required for installation. Especially in view of the often very large number of device connections to be made, the savings made on this work step requiring great attention should not be underestimated.

The flexibility of the entire cable is well guaranteed by the insulating sleeves of the individual wires and by the outer jacket. The idea of the intermediate sheath described here takes advantage of this fact in that, contrary to the usual way - to make all cable sheaths and insulating sleeves of the data transmission cable flexible - the intermediate sheath, for which a slightly lower flexibility is sufficient, is made of a breakable plastic foam.

According to an advantageous variant of the invention, the data transmission cable has a plastic film arranged on the inner wall of the intermediate sheath (claim 3). The plastic film lying on the inside of the intermediate sheath is placed around the wires during cable production before the intermediate sheath is applied. It facilitates the application of the intermediate sheath during manufacture and serves to ensure that the intermediate sheath sticks to the wires.

In a particularly advantageous development of the invention, the individual conductors consist of flexible seven-fold or multiple strands, in particular of bare, tinned or galvanized copper strands (claim 4). The use of individual strands contributes significantly to achieving flexibility.

Contrary to previous assessments, such a data transmission cable of small diameter can achieve good values for near and cross talk attenuation even when using the star quad geometry. The quadruple coupling and the crosstalk effects between the different wires are surprisingly manageable.

According to another advantageous variant of the invention, two pairs of wires are twisted together (claim 8). The twisted pair ensures the symmetry of the single wire pair against earth with a higher operating capacity.

An embodiment of the invention is shown in the drawings and will be described in more detail below.

Fig. 1

einen Querschnitt durch ein erfindungsgemäßes Datenübertragungskabel;

Fig. 2

einen Querschnitt durch einen Zwischenmantel des Datenübertragungskabels aus Fig. 1; und

Fig. 3

eine Längsansicht untereinander nach Art eines Sternvierers verseilter Adern.

Show it:

Fig. 1

a cross section through an inventive data transmission cable;

Fig. 2

a cross section through an intermediate sheath of the data transmission cable of Fig. 1; and

Fig. 3

a longitudinal view of each other in the manner of a star quad stranded veins.

There follows the explanation of the invention and its further advantages with reference to the drawings according to structure and, if appropriate, also according to the mode of operation of the illustrated invention.

1, a data transmission cable 1 according to the invention consists of four wires 2A, 2B, 3A, 3B, the diagonally opposite wires 2A and 2B as well as 3A and 3B each forming an associated wire pair 2, 3 for transmitting electromagnetic waves. The individual wires 2A, 2B, 3A, 3B have a diameter of approximately 1 mm. Their respective diameter is preferably less than 0.99 mm.

The data transmission cable 1 is thus particularly advantageously suitable for small plugs - for example “RJ45” or AMP plugs. Such plugs for penetration technology - for cords with Lahn or mixed strands - can be used for round or flat-oval cords or cables. A one-piece housing with pre-assembled contacts is standardized according to FCC guidelines and the telephone industry. The plugs are available with different numbers of poles and in different versions. In addition, semi or fully automatic processing is possible (UL listed under E-81956 specification; technical data: product specification: 108-1163 or 1173; processing specification 114-6016). The plugs typically have external dimensions of approx. 10 mm ∗ 5 mm, the distance between the individual plug contacts being approx. 1 mm. The individual wires are adapted to this distance. The diameter of the cable core is on the order of a few mm. The data transmission cable according to the invention is easily adaptable to the geometries of these connectors.

As is known, each wire 2A, 2B, 3A, 3B consists of a metallic conductor 4, which is used for the transmission of electrical charge carriers, the individual conductors 4 having a diameter which is much smaller than 1 mm. The structure of the individual conductors from braided strand, in particular from seven-fold copper strand (skin effect) is not shown. Furthermore, it is known that the individual wires 2A, 2B, 3A, 3B each have an insulating sleeve 5 surrounding the conductor 4. The wires 2A, 2B, 3A, 3B are equidistant from a central longitudinal axis C of the data transmission cable 1. In this case, the wires 2A, 2B, 3A, 3B with surface sections of their respective insulating sleeves 5 abut one another in a line in the cross section of FIG. 1.

The conductors 4 of the wires 2A, 2B, 3A, 3B form the corner points of a square. They are twisted together like a star four. This is shown in addition in FIG. 3.

The geometry of the star quad is fixed by an intermediate jacket 7 formed around the star quad, which ensures additional mechanical protection of the thin wires 2A, 2B, 3A, 3B. The intermediate jacket 7 is advantageously made of a foamed plastic. The foamed plastic lies tightly around the cable core during the manufacture of the cable. The resulting advantages in the installation of the cable have already been explained in detail above. On the inside of the intermediate jacket 7 there can additionally be a thin plastic film 6, which facilitates the stripping of the intermediate jacket 7. The intermediate jacket 7 is also shown separately in FIG. 2 for the sake of clarity.

A shielding film 8 is wound around the four wires on the outside. It is used to shield high frequencies. This shielding film 8 is furthermore completely surrounded or wrapped by an overall shield 9, in particular made of copper braid. This overall screen 9 serves to shield the low-frequency range. Finally, the entire screen 9 is completely enclosed by a preferably flexible outer jacket 10. The diameter of the entire cable is typically 5 to 6 mm.

With this construction, it is possible to implement a data transmission cable with the following specific properties with a wire diameter of less than 1 mm: an impedance between 135 Ω and 165 Ω in the frequency range between 3 Mhz and 20 Mhz, an impedance between 200 Ω and 270 Ω in the frequency range 38.4 kHz, an insulation resistance greater than 16000 MΩ * km with a DC voltage 500V and an earth asymmetry (capacitive unbalance) less than 1500 pF / km at a frequency of 1kHz.

The data transmission cable shown schematically in cross section in FIG. 1 also has the following near-cross talk characteristic: at a frequency of 9.5 kHz:> 80dB, at a frequency of 38.4 kHz:> 75dB, at a frequency of 3 to 5 MHz:> 58dB, and at a frequency of 12 to 20 MHz:> 40dB. The following damping characteristics can also be implemented: at a frequency of 9.6 kHz: <10 dB / km, at a frequency of 38.4 kHz: <15 dB / km, at a frequency of 4 MHz: <76 dB / km, at a frequency of 16 MHz: <150 dB / km.

However, the following attenuation values are typical: at a frequency of 9.6 kHz: approximately 5.6 dB / km, at a frequency of 38.4 kHz: approximately 8 dB / km, at a frequency of 4 MHz: approximately 38 dB / km km, at a frequency of 16 MHz: <approximately 75 dB / km. With a test voltage of 900V / 50Hz, no breakdown occurs at 1 min.

Despite the small cable diameter, the data transmission cable according to the invention thus ensures excellent electrical characteristics.

Claims (8)

1. Data transmission cable (1) with a standard impedance of 150 Ω, with four cores (2A, 2B, 3A, 3B) each consisting of conductor (4) and insulating sheath (5), wherein in each case diagonally opposed cores (2A, 2B; 3A, 3B) form an associated pair of cores (2, 3) for the propagation of electromagnetic waves,

   - the conductors (4) of the cores (2A, 2B, 3A, 3B) form the corner points of a square and at the same time are twisted together in the manner of a star quad cable, wherein the diameter of the individual cores (2A, 2B, 3A, 3B) is about 1 mm or less,

   - the geometry of the star quad cable is fixed by an intermediate casing (7) formed around the star quad cable,

   - a shielding film (8) is wrapped on the outside around the four cores (2A, 2B, 3A, 3B) and

   - the shielding film (8) is furthermore completely wrapped by an overall shield (9) and the overall shield (9) lastly is also completely surrounded by a preferably flexible outer casing (10).
2. Data transmission cable according to claim 1, characterised in that the intermediate casing (7) is made of a plastic foam, in particular a brittle plastic foam, or a solid material.
3. Data transmission cable according to one or more of the preceding claims, characterised by a plastic film (6) arranged on the inner wall of the intermediate casing (7).
4. Data transmission cable according to one or more of the preceding claims, characterised in that the individual conductors (4) consist of a flexible sevenfold or multiple stranded conductor, in particular a bare, tin-plated or galvanised copper stranded conductor.
5. Data transmission cable according to any of claims 1 to 4, characterised by the following electrical properties:

   - an impedance of between 135 Ω and 165 Ω in the frequency range between 3 MHz and 20 MHz,

   - an impedance of between 200 Ω and 270 Ω in the frequency range around 38.4 kHz,

   - an insulation resistance of > 16·10⁹ Ωkm with a d.c. voltage of 500 V,

   - a capacitive unbalance of < 1500 pF/km at a frequency of 1 kHz.
6. Data transmission cable according to claim 5, characterised by the following near-end crosstalk characteristic:

   - at a frequency of 9.5 kHz: > 80 dB,

   - at a frequency of 38.4 kHz: > 75 dB,

   - at a frequency of 3 to 5 MHz: > 58 dB,

   - at a frequency of 12 to 20 MHz: > 40 dB.
7. Data transmission cable according to either of claims 5 or 6, characterised by the following attenuation characteristic:

   - at a frequency of 9.6 kHz: < 10 dB/km, in particular approximately 5.6 dB/km,

   - at a frequency of 38.4 kHz: < 15 dB/km, in particular approximately 8 dB/km,

   - at a frequency of 4 MHz: < 76 dB/km, in particular approximately 38 dB/km,

   - at a frequency of 16 MHz: < 150 dB/km, in particular approximately 75 dB/km.
8. Data transmission cable according to any of claims 1 to 4, characterised in that two pairs of cores (2, 3) are stranded in pairs.

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