Dongguan XSD Cable
Technology Co., Ltd.
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The more difficult performance indicators in digital cable technical indicators include: attenuation, near-end crosstalk attenuation, etc. Cable manufacturers can improve the degradation performance of cables by increasing the diameter of the conductors and selecting higher quality insulators.
It is the key for cable manufacturers to improve and ensure the manufacturing accuracy, stability and uniformity of cables to manufacture high-performance data cables. Twisting and untwisting are actually pre-twisting, that is, before twisting, a certain amount of twisting is given to a single wire in the opposite direction, so that the change curve between characteristic impedance and frequency tends to be smooth. The increase of the twist rate can improve the electrical performance, but it also brings a side effect - the single wire structure is partially destroyed. Therefore, the reverse torque rate should be controlled at about 10%, preferably not more than 35%.
Among the technical indicators of digital signal cables, the performance indicators that are difficult to pass include attenuation and near-end crosstalk attenuation. The attenuation performance of the cable can be improved by increasing the wire diameter and choosing a better insulation material. By designing a reasonable lay distance for the four pairs of wires, the near-end crosstalk and far-end crosstalk of the cable can be achieved to the best effect, and the relative position of the four pairs of wires can be stabilized. The cable manufacturer should isolate them from each other, reduce crosstalk interference, and improve transmission. Quality, to ensure stable and reliable electrical performance. 4 The relative position of the wires will change due to external force, which will affect the crosstalk attenuation performance of the finished cable, resulting in poorer electrical performance than the skeleton type. Therefore, the requirements for production process control and equipment performance are higher. Moreover, when cable manufacturers design cables, they need to consider that there must be a large margin in all indicators to ensure that the requirements can still be met after construction. Therefore, this cable is rarely used at present.
Shielded cables originated in Europe. Cable manufacturers use the twisted pair balance and the shielding effect of the metal shielding layer to effectively prevent the intrusion of external electromagnetic interference signals and the leakage of electromagnetic radiation from the inside of the cable. It has very good electromagnetic compatibility and confidentiality. Each pair or four pairs of conductors of a shielded cable may be individually shielded with metal. Due to the skin effect, reflection and absorption of the metal shielding layer, it can better isolate the surrounding electromagnetic field and reduce the crosstalk between a single shielded pair or four pairs of wires.
Attenuation and crosstalk are the two most important transmission parameters. Cable manufacturers increase the diameter of the copper wire to reduce attenuation. The outer diameter and capacitance of the cable can be reduced by using physical foam skin-2 foam-2 skin insulation, and the attenuation can also be reduced. Providing individual foil shielding for each pair can eliminate crosstalk between pairs, eliminate and reduce environmental electrical interference, and improve electromagnetic compatibility. The vertical aluminum foil should avoid warping to ensure the shielding effect and transmission performance. Large pitch, small pitch difference torsion, cable manufacturers can reduce cable deformation and delay, delay difference. The torsion should be matched; when twisting, the extrusion deformation of the torsional contact point of the core should be minimized. The torsional tension should be consistent to reduce the unbalanced value of resistance and capacitance; twisting and untwisting can improve the impedance fluctuation caused by single wire eccentricity or uneven wire diameter, and make the transmission performance more stable. Cable unwinding prevents the transmission performance of the twisted pair from deteriorating due to torsional deformation. Using copper wire braiding or aluminum foil shielding outside the cable core can reduce the transmission impedance, eliminate or reduce environmental electromagnetic interference, and stabilize the cable structure and transmission parameters.
Precise structural design is not enough to produce high-performance digital signal cables. Strict process control and superior equipment performance guarantee are important conditions for meeting the continuous qualification of various indicators.
There should be no significant difference in the resistivity of the copper. The retreat should be balanced, and the elongation should be controlled at 1%. The conductor diameter tolerance should be limited within 0.002mm, the outer diameter of the insulation should be limited within 0.01mm, the coaxial capacitance should be limited within 1.5pFPm; the concentricity should be greater than 96%; the fluctuation of the conductor preheating temperature should be small, so that the copper wire and The insulation layer is well bonded, and the equivalent dielectric constant of the insulation must be uniform throughout the entire single wire. The cable manufacturer should extrude the foamed material evenly during production, the changes of gas injection pressure, screw speed and retraction and release tension should be as small as possible, and the bubbles in the foaming layer should be uniform and small.
During the entire production and processing process of the cable manufacturer, the tension change of the single wire must be kept within 10%. The bending radius of the single wire must be greater than 50 mm, so as not to reduce the bonding performance of the copper wire and the insulating layer. The concentricity and non-uniformity of the insulation layer can be solved by a proper untwisting device. The pitch tolerance of the twisted pair is limited within 0.5 mm. The cable manufacturer must make the symmetrical performance and the axial distance difference between the two wires Must remain constant in production to prevent asymmetric twisting. During the entire shielding process, the variation range of the shielding tape tension should be less than 10%. All twisted pairs must be shielded with the same stress.
The cable manufacturer must ensure the geometric stability of the twisted pair when the product is cabled, and the untwisting is a practical choice for the cable manufacturer. During the entire wiring process, the tensile tension of the twisted pair should be kept within 10%, and the bending radius of the twisted pair should be greater than 75mm. 4 The reverse tension of the twisted pair should be the same, and the cable manufacturer should ensure the good geometric performance of the cable. During the aluminum foil shielding process, the tension of the shielding tape should remain constant, and periodic fluctuations in tension should be prevented, and the variation range of the tension should be less than 10%. In the copper braided shielding process, the tension and braiding density of braided copper wires should be effectively controlled. The bending radius of the 4-pair twisted-pair cable should be greater than 150mm.
There are two manufacturing methods for digital signal cables: one-step method and two-step method, so the following factors should be fully considered when selecting equipment:
One step normal pair shielding can only be done with one tape. Intermediate storage of twisted pairs is eliminated, saving labor. When cable manufacturers meet the same production capacity, the investment cost of the one-step method is lower than that of the two-step method. It is suitable for the production of digital signal cables that have been finalized, and it is more professional and efficient. But it also means giving up a variety of process routes. The two-step method can be equipped with a pay-off device with an adjustable back-twist function, and the back-twist adjustment range is between 0% and 50%. Cable manufacturers need a simple single-wire pay-off method to better control the pay-off tension. For shielded cables, the shielding tape can be designed to be softer, and the wire pair can be wrapped with more than one shielding tape. The cable can also be equipped with a pay-off device with adjustable back-twisting function. The adjustment range is 0%~100%, so as to prevent the structure of the twisted pair from changing, so that the twisted pair pitch and The shielding will not change; by adjusting the pay-off tension, the tension of the twisted pair wires is guaranteed to be consistent throughout the cable length.
If the cable manufacturer plans to produce more advanced digital cables in the future, and intends to extend the cable use frequency to 10GHz or even higher, then it should choose a two-step production line with flexibility and variety that can meet various update requirements.
