Shielding method in high-speed PCB design
The transmission rate of high-speed PCB design and cabling systems is steadily accelerating, and it also brings about some kind of anti-jamming vulnerability.
This is because the higher the frequency of transmitting information, the higher the sensitivity of signals, and the lower and higher the power of their signals.
The wiring system at this time is more susceptible to interference. Interference is ubiquitous.
Cables and equipment can interfere with other components or be severely disturbed by other sources of interference, such as: computer screens, mobile phones, motors, radio transmission equipment, data transmission, and power cables. In addition, potential eavesdroppers, cybercriminals, and hackers continue to increase because of their enormous damage and loss to UTP cable information interception.
Especially when using high-speed data networks, the time required to intercept large amounts of information is significantly lower than the time required to intercept low-speed data transmissions. The twisted pair in data twisted pair can rely on its own twisting to resist external interference and crosstalk between pairs at low frequencies, but only at high frequencies (especially when the frequency exceeds 250MHz) The twisted pair cannot achieve the purpose of anti-interference, and only the shield can resist external interference.
The cable shield acts like a Faraday shield. Interference signals enter the shield but do not reach the conductor.
Therefore, data transmission can operate without failure. Because shielded cables have lower radiation emissions than non-shielded cables, network transmissions are prevented from being intercepted. Shielded networks (shielded cables and components) can significantly reduce the level of electromagnetic energy radiation that can be intercepted by entering the surrounding environment.
Shielding interference fields of different interference fields mainly include electromagnetic interference and radio frequency interference.
Electromagnetic interference (EMI) is mainly caused by low-frequency interference. Motors, fluorescent lamps, and power lines are common sources of electromagnetic interference.
Radio frequency interference (RFI) refers to radio frequency interference, mainly high-frequency interference. Radio, television transmission, radar and other wireless communications are the usual source of radio frequency interference.
For the resistance to electromagnetic interference, the choice of braided shield is most effective because of its lower critical resistance; for radio frequency interference, the foil layer shield is most effective because the braided shield relies on the change of wavelength, and the resulting gap makes the high frequency signal free In and out of the conductor; and for high and low frequency mixing of the interference field, we must use a wide-band coverage of the foil layer plus woven mesh combination shielding. In general, the higher the mesh shielding coverage, the better the shielding effect.