High-speed PCB Design Shielding Method

2016-10-10 15:21:13 Viya 42

Transfer rate speed PCB design wiring system in the steadily accelerating, it also brings a certain anti-interference vulnerability, this is because the higher the frequency of the transmission of information, the stronger the sensitivity to signals, while their energy is increasingly weak, At this point cabling system more susceptible to interference.

Interference everywhere, cables and other components of the device will cause interference or serious interference with other sources of interference, such as: computer screens, mobile phones, electric motors, radio broadcasting equipment, data transmission and power cables. In addition, potential eavesdroppers, hackers and cyber crime is increasing because they UTP cable information transmission interception can cause tremendous damage and loss.

PCB Design

Especially when using high-speed data network, a lot of time to intercept the information they need time to intercept is significantly lower than the low-speed data transmission needs. Data twisted pair twisted pair at low frequencies can rely on its own twisted to resist external interference and crosstalk between pairs, but at high frequencies (especially at frequencies above 250MHz or more), alone wire twisted pair has been unable to achieve the purpose of anti-interference, only to be able to shield against external interference.

The role of cable shield as a Faraday shield, the interference signal will enter into the shield, the conductor but not to enter. Thus, the data transfer can be trouble-free operation. Since the ratio of the shielded cable unshielded cable has a lower radiation sporadic, thus preventing the network traffic was blocked. Shielded network (shielded cables and components) can be reduced significantly into the surrounding environment and may be able to intercept the electromagnetic radiation levels.

Select a different field interference shielding interference fields are mainly electromagnetic interference and radio frequency interference two kinds. Electromagnetic interference (EMI) is mainly low frequency interference, motors, fluorescent lights and power lines are the usual sources of electromagnetic interference. Radio Frequency Interference (RFI) refers to radio frequency interference, mainly high-frequency interference. Radio, television, radar and other wireless communications is the usual sources of RF interference.

For resistance to electromagnetic interference, select the braided shield is most effective because it has a lower critical resistance; for radio frequency interference shielding layer foil the most effective, because the braided shield depends on the change in the wavelength of the gap so that it produces a high-frequency signal can be freely out conductor; and for mixing high and low frequency interference field, will have to use a combination of shielding layer of foil plus braid having broadband coverage function. Generally, the higher the mesh shielding coverage, shielding effect is better.



TAG:   PCB Design

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