Shielded wiring System

Source: Internet
Author: User
Tags ftp reflection
Shielding wiring system from Europe, it is in the general unshielded wiring system outside the metal shielding layer, the use of metal shielding layer of reflection, absorption and skin effect to prevent electromagnetic interference and electromagnetic radiation function, shielding system comprehensive utilization of twisted pair of balance principle and shielding layer shielding role, Therefore, it has very good electromagnetic compatibility (EMC) characteristics. We can see that in the whole of Europe, the majority of end users will choose the shielding wiring system.

At present, the shielding wiring system has been recognized by more and more users, and its good performance in electromagnetic compatibility is also being recognized by more and more people. Therefore, the market's shielding wiring products are not limited to European products, more and more manufacturers to provide shielding wiring products. In the latest North American cabling Tia/eia-568-b Standard, shielded and unshielded cables are also used as a recommended medium for horizontal wiring, thus ending the history of no shielding systems in North America.

Common shielding problems and solutions

Q: What is EMC?

A: EMC is electromagnetic compatibility, refers to electronic equipment or network systems have a certain ability to resist electromagnetic interference, while not producing excessive electromagnetic radiation. In other words, the device or network system is required to work in a relatively harsh electromagnetic environment, while there is no radiation excessive electromagnetic interference around other devices and the network's normal work.

Q: UTP cable is an ideal balance transmission system, why use FTP cable?

A: UTP cables are used to achieve EMC performance through the twisted pair of core wires, which means EMI is first received by UTP Cable and then offset. However, as the frequency increases, the EMC performance of UTP will decrease. The measurement found that the cable pair can only meet the 30MHz of EMC performance, for higher EMI UTP will be powerless. So far, most of the actual network applications have been operating at a lower frequency than 30MHz. --- (computer science)

Also, an ideal equilibrium transmission system does not exist. The balance characteristics of UTP cables are not only determined by the quality of the parts themselves (such as twisted pair), but are affected by the surrounding environment. Because of the metal around UTP, hidden "ground", pulling in the construction, bending and so on will damage its balance characteristics, thereby reducing EMC performance.

In fact, the cable we install is usually put into a metal conduit, a plastic conduit, or other protection with a different grounding impedance. So, there is only one solution to achieve long-lasting ground performance: All cores are grounded with an extra layer of aluminum foil. Aluminum foil provides protection for fragile twisted-pair cores while creating a balanced environment for UTP cables. This means that the shielding solution based on the FTP cable is independent of the environment, which is not related to the environment. FTP is the integration of UTP balance characteristics and construction flexibility and STP shielding effect, that is, balance and shielding principle of the perfect combination.

Q: What is the shielding principle of the FTP cable?

A: Unlike the balance offset principle of twisted pair, the FTP cable is added one or two layers of aluminum foil to the outside of the twisted pair of four pairs of wires. The use of metal to the electromagnetic wave reflection, absorption and skin effect principle (the so-called skin effect refers to the current in the conductor section distribution with the frequency of increase and tend to the conductor surface distribution, the higher the frequency, the skin depth is smaller, That is, the higher the frequency, the more weak the penetration of electromagnetic waves, effectively prevent external electromagnetic interference into the cable, but also to prevent the internal signal radiation out, interfering with other equipment work.

Experiments show that the frequency of more than 5MHz of electromagnetic waves only through 38µm thick aluminum foil. If the thickness of the shielding layer over 38µm, such as Nike Sen's FTP cable for the two-layer 25µm thick aluminum foil shielding, so that can penetrate the shielding layer into the cable inside the frequency of electromagnetic interference is mainly below 5MHz. For low frequency interference under 5MHz, the principle of twisted pair can be effectively offset.

Q: How do we measure performance differences between shielded and unshielded systems?

A: The advantage of the FTP cable shielding system is to provide better EMC performance than UTP Cable, which is based on isolating the system from the external electromagnetic environment. Because the external electromagnetic environment will affect the entire wiring system data transmission. So far, there are no performance metrics or test methods to express or compare EMC performance. It is gratifying to note that the European Committee for Standardization (CENELEC) has started this work (the Nike Integrated Cabling system is involved), coupled attenuation (coupling attenuation) is defined as an indicator for measuring EMC performance. The index is also written into the second version of the international wiring standard iso/iec11801.

Nike Shield Cabling Solution

Nike Sen is the inventor of the FTP series cable and is the leader of shielding technology. Its shielding products have been Denmark independent Electronics Laboratory Delta, the United States Insurance Laboratory UL and the United States ETL testing and certification agencies. The index of series wiring products is much higher than that of ISO/IEC 11801, eia/tia568b and EN50173 standard.

The Nike Sen F2TP Cable uses the world's unique dual-layer longitudinal aluminum foil shielding structure, that is, on the outside of the UTP cable, two layers of 25um thick aluminum foil, this double longitudinal package structure can avoid the cable bending or heating when the shielding layer appeared small gap, but also reduced the transfer impedance, improve the shielding effect, while making the grounding (including shielding grounding and protection grounding) more convenient and reliable. This high-performance shielding cable is also very convenient to install, the outer diameter is only 6.35 mm. For more than 10MHZ of electromagnetic waves, the use of shielding layer of reflection, absorption and skin effect mechanism to offset electromagnetic interference and electromagnetic radiation, the higher the frequency, the effect of shielding layer more obvious. For low-frequency (<5mhz) electromagnetic waves, the balance characteristic of twisted pair is offset. This double-layer aluminum foil shielded cable has the greatest characteristics of two aspects: both excellent shielding performance, but also to maximize the convenience of user installation.

From the EMC aspect, the shielding layer of the cable must be surrounded by a large area of metal surface, known as the 360o grounding (grounding). In the Nike Sen Double-layer aluminum Foil shielding system, simply will inside a layer of shielding card in the Nike Sen patented products Clip-ontm cable wire rack, to ensure that the shielding cable in the distribution frame and information sockets to achieve 360° surround grounding (grounding), will never produce the so-called "antenna effect." This CLIP-ONTM cable lead frame is integrated with the modular wiring tray.

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