Today, the construction of information highways has become a global industry. As a carrier of information, the Internet has developed rapidly in recent years in China. Light is the first choice for wide-area network (WAN) transmission media because of its fast propagation speed and large information capacity. However, in the building communication integrated wiring system of a local area network (LAN), since the laying cost of the optical fiber cable is too high, and the joint cost and terminal-light-electric conversion cost are expensive, the manufacturing cost is very expensive. For this purpose, a cheap data communication cable must be sought for the final 100m transmission task. In this way, Category 5 / Super Category 5 cable came into being. The so-called category 5 cable (Category5Cable) is a common name for unshielded twisted pair cables for high-speed data transmission (frequency 100MHz). At present, the Category 5 UTP cable is mainly used for the horizontal wiring of the communication terminal of the work area of ​​the building integrated communication wiring system to the communication terminal box of the office area. The so-called horizontal meaning means that the above wiring method is mainly along the horizontal direction of the floor or the ceiling, and is installed in pipes, trunks, and interlayers of floors and ceilings. According to EIA/TIA-568A regulations, horizontal cabling is generally a 4-pair 100 UTP cable. According to statistics, the annual growth rate of demand exceeds 50%, and it is estimated that by the year 2000, the annual demand of the Category 5 system will reach 700,000 km or more.
2 cable structure and raw materials 2.1 Structural Design Category 5 cable in addition to UTP (unshielded pair all), but also includes shielded cable FTP, STP, SUTP, SSTP, the main difference is that there are different shielding structures. Due to 100MHz class 5, the main transmission parameters are attenuation, near-end crosstalk, and structural return loss. Therefore, these parameters should be considered first in the design. Attenuation is a major factor in determining the distance between a LAN design and a signal in a cable. The type and geometry of the conductors and insulation are the main factors affecting the attenuation of the data symmetrical cable. There are several ways to reduce the attenuation in the design.
a) increase the insulation thickness;
b) Use physical foam insulation to reduce dielectric loss;
c) increase the cross-sectional area of ​​the conductor but increase the negative effect of the insulation thickness is to make the cable impedance becomes larger; b) the program can improve the stability of the extrusion to ensure that the high-frequency attenuation of the cable will not be degraded in a long time; c scheme conductor diameter From 0.50mm to 0.511mm. Near-end crosstalk is an important indicator of the transmission quality of the line. It is the crosstalk caused by the electromagnetic field producing voltage and current in adjacent pairs. It is related to the pitch of the pair, the pitch between the pair (cable pitch) and the pitch ratio of each pair. Theoretically, the use of small pitches can fundamentally improve string education. At present, several internationally-used pitches are 16-18-22-24, 17-20-25-30, and 1012-14-16. When designing the pitch, the factor of the greatest common multiple of all pitches should be taken into account. Structural return loss means that the signal transmitted along the line is reflected back when it encounters non-uniform impedance (caused by structural inhomogeneity), and then re-enters the normal transmission signal rank, thereby interfering with the normal signal of the line and causing bit error.
Therefore, the following points should be observed in the design and production:
a) Conductor diameter tolerance should be strictly controlled within 3m. The xy dual-axis laser outer diameter control monitor is used to monitor the outer diameter at any time to ensure the uniformity of the impedance.
b) In the process of pairing and cabling, the consistency of the line pair pitch and the uniformity of the tension of the conductor line on the payout line should be strictly controlled.
2.2 Material selection Conductor material: Annealed copper wire 24AWG (0.511mm) Insulation material: High-density polyethylene sheathing material: Manufacture of low-smoke, low-halogen flame-retardant PVC3 cable 3.1 Extrusion of insulated single wire due to high-speed data transmission cable transmission above 100MHz High frequency, strict requirements on the stability and uniformity of the cable structure size, so each process in the cable production process may bring its own problems to the finished product, and the first process in the manufacturing process insulation single wire extrusion System is the central link of the entire production. Good control of the single-line production process is the basis for the production of high-performance cables. Insulation is not eccentric core core is the premise of impedance stability, but also in the axial requirements to achieve a uniform processing accuracy. In the production, the company adopted the introduction of the wire drawing annealing preheat insulation high-speed serial production line technical system single line.
1) The production line speed is 800m/min, with xy two-wheel automatic closed-loop external feedback control system, real-time monitoring of the deviation of the outer diameter, coaxial capacitance closed-loop control system synchronous detection of capacitance, precision tension automatic control system to ensure the outer diameter of the wire The uniformity, concentricity is controlled above 95%, copper wire diameter deviation within 3m, capacitance fluctuations in 1pF/m.
2) The masterbatch should be added less, and the color of the insulated wire should be as light as possible. Because any color is an impurity to the medium, the darker the color, the greater the attenuation.
3) The elongation of the conductor is another important indicator of the conductor's quality. The wire is slightly harder or the elastic modulus is larger, so that the wire is not easily deformed during the subsequent processing, which is favorable for the uniformity of the impedance. In addition, the control range of the wire elongation is small, which can avoid the non-uniformity of the two hard and soft uneven core pairs, thereby reducing the structural return loss. In actual production, the elongation of the wire is controlled at 15% to 22%, as far as possible after the completion of each process, the elongation remains basically unchanged.
3.2 Stranding process Stranding consists of two processes: pairing and cabling. At present, internationally popular group stranding machines complete these two steps in one step. The advantage of this type of cluster machine is that it combines the two processes of the system and the line into one, eliminating the need for rewinding after twisting and releasing the cable, reducing the repeated bending of the wire and contributing to the stability of the electrical performance of the cable. . Provincial manpower, small footprint. The biggest drawback of this group of renewal machines is that it is not easy to retract the twisted wires, and the force uniformity of the wire is less than a single process, and the investment is large. Based on the transformation of existing equipment and some equipment, the company adopts a two-step approach to integration and line-up.
1) The paired twisting a) has a great influence on the pitch of the standard pitch cable pair and the near-end crosstalk. Compared with the ordinary class 2 and 3 class lines, the class 5 class cable has a much smaller pitch, and the minimum The pitch can be 10mm. But not the smaller the pitch, the better, because the small pitch will cause slower production, increased material usage, increased DC resistance of the copper wire, and increased cable attenuation. Practice has proved that the pitch is 1012-14-16 is not optimal, and select the appropriate four pitches in the range of 12 to 22, in order to obtain better attenuation and near-end crosstalk.
b) Faster and more uniform performance for continuing equipment requirements. The domestically produced high-speed stranding machine, which usually produces communication cables, has been restructured so that the pitch is in the range of 10 to 50 mm, which can meet the requirements for the production of Category 5 cables. The pay-off device adopts active pay-off. Before the two single-wires enter the pairing unit, the synchronization belt must be pressed up and down so that the two lines entering the pair of renewal machines have even tension. Tension is too large to pull the copper wire. When it is too small, the core wire is slack and bouncing. After the pitch is formed, a shaping device is added so that the wire pair is in a perfect spiral shape. At the same time, the machine is equipped with a sensitive tension feedback system. The quality requirement for the pair is that the length of the two insulated conductors should be equal after the pair is twisted.
2) In actual production, in order to make full use of the existing equipment and reduce the production cost, the system will carry out technological transformation on the existing cabling equipment. The main contents of the technical transformation are: the payoff frame adopts active payoff; the four pairs of lines must have a timing belt to press up and down before entering the cable machine, so that the four pairs of lines are subjected to even force; the guide wheel is as large as possible, so that the pair of guide pitches is maintained Stable, with tension feedback. The cable pitch is controlled below 180mm and the cable pitch is small, which is beneficial to the stability of the unit core structure. The quality requirements for cable installation are that the core structure is stable and compact, the pitch is not easy to loose, and the impact on the impedance non-uniformity is minimal.
3.3 The minimum thickness of sheath UTP4 to category 5 cable jacket is 0.50mm, the maximum outer diameter of the cable is less than 5.8mm, and a torn rope is placed in the middle. The outer sheath surface is round and smooth with an elongation of 125% and a tensile strength of more than 12.5 MPa. The sheath is wrapped around the core of the cable, and neither the cable core nor the core can be pressed to prevent the electrical performance from being affected by environmental changes. Our extrusion jacket was carried out on a conventional 45 single-screw extruder, but an active payoff, laser diameter gauge and ink jet printing equipment were added.
3.4 Looping and Packaging The traditional loop-forming process makes the cable easy to twist when it is released, making the cable core twist back and twisted. When this happens, the impedance of the cable will change and cause the problem of return loss of the structure, and at the same time reduce the stringing performance of the cable within a 90m segment. We self-made a simple cross-wound drawing machine, after the ring was arranged in a #-type line, when the line is put on the use of the international popular 匣 æ— æ‰ twist free line, will not be distorted. The standard package is 304.8m (or 1000 feet) and the small package is 100m or 91.44m (300 feet). Special carton packing. 4 Test results 4.1 Test standards Based on what criteria to measure the size and performance of Category 5 cables is critical. At present, the following international standards for Category 5 cables are available for reference:
1) LAN communication cable system standards of IEC1156, -1 (1994) and IEC1156.2 ~ 4 (1995);
2) ISO/IEC, 11801 (1995) standards;
3) the EIA/TIA-568 standard promulgated by the American Electronics Industry Association in January 1991, and subsequently modified and replaced by the former and the EIA/TIA-586-A standards of TSB-36, TSB-40, and TSB-58;
4) The corresponding standards issued by NEMA and UL in the United States in 1994 respectively. There are two national standards for China's Category 5 cable:
1) YD/T926.1 ~ 21997 building integrated wiring system standards;
2) YD/T838.1～41996 symmetric/cable symmetric cable standard for mathematical communication. The company uses the above two national standards as corporate standards.
4.2 Test Equipment and Results The test equipment used the United States DCMCMS-2XLD network analysis tester. The company designs according to the above specifications, and the mass-produced cables are tested with Type 5 cables with a length of 304.8m and are packaged at a frequency of 1 to 350 MHz. 5 Conclusions The electrical performance of high-frequency digital symmetrical cables is closely related to the geometry and stability of the pairs, and the effect of each tiny link on the geometric dimensions should be considered in production. For the cable to work at higher frequencies, such as 350 to 622 MHz, the pair must be individually clad and shielded. The 622Mb/S Super 7 cable has been developed abroad. In addition to using a single wire pair to shield it, the single wire pair is also fixed in the mesh skeleton slot, and the structure is very stable. For example, the NETLink GXTM 550 MHz type 7 light-shielded UTP4 pair cable produced by Prestolitewire of the United States uses a mesh skeleton structure, and its near-end crosstalk and structural return loss performance is quite good at high frequencies. Existing domestic equipment has not yet been able to produce this type of Super 5 system, but from the perspective of large-capacity information on the channel bandwidth requirements, ultra-high frequency (above 350 MHz) digital symmetric cables must replace the existing high frequency ( 100MHz) digital symmetric cable.
2 cable structure and raw materials 2.1 Structural Design Category 5 cable in addition to UTP (unshielded pair all), but also includes shielded cable FTP, STP, SUTP, SSTP, the main difference is that there are different shielding structures. Due to 100MHz class 5, the main transmission parameters are attenuation, near-end crosstalk, and structural return loss. Therefore, these parameters should be considered first in the design. Attenuation is a major factor in determining the distance between a LAN design and a signal in a cable. The type and geometry of the conductors and insulation are the main factors affecting the attenuation of the data symmetrical cable. There are several ways to reduce the attenuation in the design.
a) increase the insulation thickness;
b) Use physical foam insulation to reduce dielectric loss;
c) increase the cross-sectional area of ​​the conductor but increase the negative effect of the insulation thickness is to make the cable impedance becomes larger; b) the program can improve the stability of the extrusion to ensure that the high-frequency attenuation of the cable will not be degraded in a long time; c scheme conductor diameter From 0.50mm to 0.511mm. Near-end crosstalk is an important indicator of the transmission quality of the line. It is the crosstalk caused by the electromagnetic field producing voltage and current in adjacent pairs. It is related to the pitch of the pair, the pitch between the pair (cable pitch) and the pitch ratio of each pair. Theoretically, the use of small pitches can fundamentally improve string education. At present, several internationally-used pitches are 16-18-22-24, 17-20-25-30, and 1012-14-16. When designing the pitch, the factor of the greatest common multiple of all pitches should be taken into account. Structural return loss means that the signal transmitted along the line is reflected back when it encounters non-uniform impedance (caused by structural inhomogeneity), and then re-enters the normal transmission signal rank, thereby interfering with the normal signal of the line and causing bit error.
Therefore, the following points should be observed in the design and production:
a) Conductor diameter tolerance should be strictly controlled within 3m. The xy dual-axis laser outer diameter control monitor is used to monitor the outer diameter at any time to ensure the uniformity of the impedance.
b) In the process of pairing and cabling, the consistency of the line pair pitch and the uniformity of the tension of the conductor line on the payout line should be strictly controlled.
2.2 Material selection Conductor material: Annealed copper wire 24AWG (0.511mm) Insulation material: High-density polyethylene sheathing material: Manufacture of low-smoke, low-halogen flame-retardant PVC3 cable 3.1 Extrusion of insulated single wire due to high-speed data transmission cable transmission above 100MHz High frequency, strict requirements on the stability and uniformity of the cable structure size, so each process in the cable production process may bring its own problems to the finished product, and the first process in the manufacturing process insulation single wire extrusion System is the central link of the entire production. Good control of the single-line production process is the basis for the production of high-performance cables. Insulation is not eccentric core core is the premise of impedance stability, but also in the axial requirements to achieve a uniform processing accuracy. In the production, the company adopted the introduction of the wire drawing annealing preheat insulation high-speed serial production line technical system single line.
1) The production line speed is 800m/min, with xy two-wheel automatic closed-loop external feedback control system, real-time monitoring of the deviation of the outer diameter, coaxial capacitance closed-loop control system synchronous detection of capacitance, precision tension automatic control system to ensure the outer diameter of the wire The uniformity, concentricity is controlled above 95%, copper wire diameter deviation within 3m, capacitance fluctuations in 1pF/m.
2) The masterbatch should be added less, and the color of the insulated wire should be as light as possible. Because any color is an impurity to the medium, the darker the color, the greater the attenuation.
3) The elongation of the conductor is another important indicator of the conductor's quality. The wire is slightly harder or the elastic modulus is larger, so that the wire is not easily deformed during the subsequent processing, which is favorable for the uniformity of the impedance. In addition, the control range of the wire elongation is small, which can avoid the non-uniformity of the two hard and soft uneven core pairs, thereby reducing the structural return loss. In actual production, the elongation of the wire is controlled at 15% to 22%, as far as possible after the completion of each process, the elongation remains basically unchanged.
3.2 Stranding process Stranding consists of two processes: pairing and cabling. At present, internationally popular group stranding machines complete these two steps in one step. The advantage of this type of cluster machine is that it combines the two processes of the system and the line into one, eliminating the need for rewinding after twisting and releasing the cable, reducing the repeated bending of the wire and contributing to the stability of the electrical performance of the cable. . Provincial manpower, small footprint. The biggest drawback of this group of renewal machines is that it is not easy to retract the twisted wires, and the force uniformity of the wire is less than a single process, and the investment is large. Based on the transformation of existing equipment and some equipment, the company adopts a two-step approach to integration and line-up.
1) The paired twisting a) has a great influence on the pitch of the standard pitch cable pair and the near-end crosstalk. Compared with the ordinary class 2 and 3 class lines, the class 5 class cable has a much smaller pitch, and the minimum The pitch can be 10mm. But not the smaller the pitch, the better, because the small pitch will cause slower production, increased material usage, increased DC resistance of the copper wire, and increased cable attenuation. Practice has proved that the pitch is 1012-14-16 is not optimal, and select the appropriate four pitches in the range of 12 to 22, in order to obtain better attenuation and near-end crosstalk.
b) Faster and more uniform performance for continuing equipment requirements. The domestically produced high-speed stranding machine, which usually produces communication cables, has been restructured so that the pitch is in the range of 10 to 50 mm, which can meet the requirements for the production of Category 5 cables. The pay-off device adopts active pay-off. Before the two single-wires enter the pairing unit, the synchronization belt must be pressed up and down so that the two lines entering the pair of renewal machines have even tension. Tension is too large to pull the copper wire. When it is too small, the core wire is slack and bouncing. After the pitch is formed, a shaping device is added so that the wire pair is in a perfect spiral shape. At the same time, the machine is equipped with a sensitive tension feedback system. The quality requirement for the pair is that the length of the two insulated conductors should be equal after the pair is twisted.
2) In actual production, in order to make full use of the existing equipment and reduce the production cost, the system will carry out technological transformation on the existing cabling equipment. The main contents of the technical transformation are: the payoff frame adopts active payoff; the four pairs of lines must have a timing belt to press up and down before entering the cable machine, so that the four pairs of lines are subjected to even force; the guide wheel is as large as possible, so that the pair of guide pitches is maintained Stable, with tension feedback. The cable pitch is controlled below 180mm and the cable pitch is small, which is beneficial to the stability of the unit core structure. The quality requirements for cable installation are that the core structure is stable and compact, the pitch is not easy to loose, and the impact on the impedance non-uniformity is minimal.
3.3 The minimum thickness of sheath UTP4 to category 5 cable jacket is 0.50mm, the maximum outer diameter of the cable is less than 5.8mm, and a torn rope is placed in the middle. The outer sheath surface is round and smooth with an elongation of 125% and a tensile strength of more than 12.5 MPa. The sheath is wrapped around the core of the cable, and neither the cable core nor the core can be pressed to prevent the electrical performance from being affected by environmental changes. Our extrusion jacket was carried out on a conventional 45 single-screw extruder, but an active payoff, laser diameter gauge and ink jet printing equipment were added.
3.4 Looping and Packaging The traditional loop-forming process makes the cable easy to twist when it is released, making the cable core twist back and twisted. When this happens, the impedance of the cable will change and cause the problem of return loss of the structure, and at the same time reduce the stringing performance of the cable within a 90m segment. We self-made a simple cross-wound drawing machine, after the ring was arranged in a #-type line, when the line is put on the use of the international popular 匣 æ— æ‰ twist free line, will not be distorted. The standard package is 304.8m (or 1000 feet) and the small package is 100m or 91.44m (300 feet). Special carton packing. 4 Test results 4.1 Test standards Based on what criteria to measure the size and performance of Category 5 cables is critical. At present, the following international standards for Category 5 cables are available for reference:
1) LAN communication cable system standards of IEC1156, -1 (1994) and IEC1156.2 ~ 4 (1995);
2) ISO/IEC, 11801 (1995) standards;
3) the EIA/TIA-568 standard promulgated by the American Electronics Industry Association in January 1991, and subsequently modified and replaced by the former and the EIA/TIA-586-A standards of TSB-36, TSB-40, and TSB-58;
4) The corresponding standards issued by NEMA and UL in the United States in 1994 respectively. There are two national standards for China's Category 5 cable:
1) YD/T926.1 ~ 21997 building integrated wiring system standards;
2) YD/T838.1～41996 symmetric/cable symmetric cable standard for mathematical communication. The company uses the above two national standards as corporate standards.
4.2 Test Equipment and Results The test equipment used the United States DCMCMS-2XLD network analysis tester. The company designs according to the above specifications, and the mass-produced cables are tested with Type 5 cables with a length of 304.8m and are packaged at a frequency of 1 to 350 MHz. 5 Conclusions The electrical performance of high-frequency digital symmetrical cables is closely related to the geometry and stability of the pairs, and the effect of each tiny link on the geometric dimensions should be considered in production. For the cable to work at higher frequencies, such as 350 to 622 MHz, the pair must be individually clad and shielded. The 622Mb/S Super 7 cable has been developed abroad. In addition to using a single wire pair to shield it, the single wire pair is also fixed in the mesh skeleton slot, and the structure is very stable. For example, the NETLink GXTM 550 MHz type 7 light-shielded UTP4 pair cable produced by Prestolitewire of the United States uses a mesh skeleton structure, and its near-end crosstalk and structural return loss performance is quite good at high frequencies. Existing domestic equipment has not yet been able to produce this type of Super 5 system, but from the perspective of large-capacity information on the channel bandwidth requirements, ultra-high frequency (above 350 MHz) digital symmetric cables must replace the existing high frequency ( 100MHz) digital symmetric cable.
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