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The design and manufacture of symmetric communication cable

Information Source:Henan Huadong Cable Co., Ltd Release date:2014-02-20

Key points in manufacturing digital communication cable

Improve and ensure the cable manufacturing precision and stability, uniformity is to manufacture high performance data cable key. Lay on back twist, is actually pre twist, twist twist in the front, give some twisted pair line reverse, the variation curve of characteristic impedance and frequency is more gentle. Back twist rate can improve the electrical performance, but also brings side effect -- single structure has been part of the destruction. So back twist rate should be controlled at about 10%, preferably not more than 35%.

The performance index is difficult to pass through the digital communication cable technical indicators are: attenuation, near end crosstalk attenuation. By increasing the diameter of wire and selection of insulating material more excellent can improve cable attenuation performance; the four on line to design reasonable twisted pitch, can make the cable near end crosstalk and far end crosstalk can reach a best effect, stable relative positions of the four lines on the line, and the mutual isolation, reduce the crosstalk interference, high transmission quality, ensuring that the electrical properties of stable and reliable. The 4 pairs of relative position will change because of external force, affect the crosstalk of the finished cable attenuation performance, cause electrical performance than the skeleton type, so the control of the production process, equipment performance requirements are higher, and then is the design of cable, to consider the margin index should be larger, in order to ensure construction still to meet the requirements, therefore, the cable now few people use.

Design features of digital communication cable

Shielding and wiring system originated in Europe, the shielding twisted pair twisted balance and metal shielding layer, effectively prevent external electromagnetic interference electromagnetic and leakage from the cable internal signal into radiation, electromagnetic compatible with very good properties and confidentiality. Shielded cable each wire pair or four pairs of lines can be used metal shield alone, because of the skin effect and the reflective metal shielding layer and absorption, electromagnetic field can be better separated around and reduce individually shielded the crosstalk between four lines or on the line between.

The development of digital communication cable

Attenuation and crosstalk is one of the two most important transmission parameters, increasing the copper wire diameter, can reduce the attenuation. The physical foaming skin foam skin insulation can reduce 2 of the 2 outer diameter of cable and to reduce the capacitance, attenuation is also decreased. For each line of aluminum foil shield alone, can eliminate the crosstalk between lines and can eliminate and reduce electrical interference environment, improve the electromagnetic compatibility. Longitudinal coated aluminum foil should avoid wrinkling, to ensure that the shielding effect and transmission performance. Using a large pitch on the ground, and the pitch difference is small, can reduce the cable change

Shape, reduce the delay and delay difference. Twisted pair to match group; a time should be extruded minimize wire core stranded at the point of contact on the ground; tension should be the same, in order to reduce the resistance, capacitance unbalance value; cutter can be improved by single eccentric or wire diameter is not uniform and the back twist impedance fluctuation, make the transmission more stable performance. Cable back twist can prevent twisting on the transmission performance degradation line due to torsion deformation caused by. The copper wire braid or aluminum foil shielding at the outside of the cable core, can reduce the transfer impedance, eliminate or reduce electromagnetic interference environment, so that the cable structure and transmission parameter stability.

Process control and equipment requirements of digital communication cable

Digital communication cable production high performance, structure design only precision is not enough, each procedure strict process control and superior equipment performance guarantee is an important condition for satisfaction indicators qualified.

Single line

Copper conductor resistance coefficient does not have significant differences; annealing to equilibrium, elongation should be controlled within ± 1%; conductor diameter tolerances should be restricted within, ± 0.002 mm diameter insulation is limited within ± 0.01 mm coaxial capacitance, restricted to ± 1.5 pFPm; concentric degree should be greater than 96%; conductor pre heat temperature fluctuations small, to the copper wire and insulation layer between the bond, equivalent dielectric constant on the whole line must be uniform. Foam extrusion should be uniform, change, gas injection pressure screw speed changes, take-up tension change should be as small as possible, foaming agent layer should be uniform.

Twisted pair and shielding

We must keep the tension change line less than ± 10% in ground of in the whole process. Bending radius of single wire must be greater than 50 mm, in order to avoid reducing copper wire and bonding properties of insulating layer. Equipped with twisted back the appropriate device can solve the problem of uneven coating concentricity and insulation, ground on the pitch tolerance limit within ± 0.5 mm. Symmetry properties and the axial distance between the two wires is poor in production must remain unchanged, in order to prevent twisting asymmetry. In the whole process of tension variation range shielding shielding belt should be small
To ± 10%. All of the ground for screening line must use compression equal.

Cable and shielding

The cable must ensure geometric stability lay on the line, back twist is a practical choice. In the whole process of twisted cable tension on line should be kept within ± 10%, the bending radius of the cutter line should be more than 75 mm. 4 pair of on line reverse tension should be the same to ensure good geometric properties of cable. In the process of aluminum foil shielding shielding belt tension should be maintained, should prevent the cyclical fluctuations in the range of tension, tension should be less than ± 10%. The braided copper tension and density control of copper wire braid shield process should be. A cable containing 4 twisted pair on the line, the bending radius should be greater than 150 mm.

Digital communication cable equipment selection

As everyone knows, digital communication cable has two kinds of manufacturing methods: one step and two step, therefore in the selection of equipment should be fully taken into account the following factors:
A normal to shield only with a band of. A line of intermediate storage is saved, can save labor. In case of meeting the same production capacity, one step lower than the two step investment cost, which is suitable for digital communication cable in the production of standardized, more professional, more efficient. But it also means giving up the process route diversity. The two step is optional on the line device with adjustable back twist function, back twist regulation in the range of 0% ~ 50%. Simple single line route the wire releasing tension control better, for shielding cable shielding bag can make the design more flexible, can be more than one line on the package shielding belt. The same cable can also match with adjustable line device back twist function, the adjustment in the range of 0% ~ 100%, in order to prevent twisting on line structure change, make the cutter on line in the cable when the cutter on the pitch and shielding will not change. By regulating the release of tension, to ensure the electrical

Cable length of line tension winch. If the plan for future production of digital cable is more advanced, and intends to cable using frequency extending to 10 GHz or higher, then it should choose a flexible, to meet the two step various production line update request.

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