Shielding method of high-speed PCB design

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

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

Especially when using high-speed data network, the time of intercepting a lot of information is significantly lower than the time of intercepting low-speed data transmission.

Faraday shield

The role of cable shield is like a Faraday shield.The interference signal will enter into the shield,but can not enter the conductor. Thus, the data transfer can be trouble-free operation. Since the shielded cable has a lower radiation sporadic than unshielded cable ,which prevent the network traffic was blocked.

Shield select interference fields of different interference fields are mainly two kind:electromagnetic interference and radio frequency interference. 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, and it is mainly high-frequency interference. Radio, television, radar and other wireless communications are the usual sources of RF interference.

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

Source from http://www.ifastpcb.com/blog/158-2/