EMC Design Classic Q & A Ⅳ

Q1:How to avoid high - frequency interference in PCB design?

A basic idea to avoid high frequency interference is to minimize the interference of high frequency signal electromagnetic field, that is, crosstalk. It can increase the distance between high speed signal and analog signal, or add ground guard/shunt traces next to analog signal. It also should pay attention to the digital noise interference to the analog ground.
Q2:How to resolve the conflict between high - speed cab ling and EMI in the PCB design ?

Some electrical characteristics of the signal due to the resistance capacitance or ferrite bead, added by the EMI do not conform to the specification. Therefore, it is best to solve or reduce EMI problems by arranging wiring and PCB stacking techniques, such as high-speed signals to the inner layer. Finally, resistive capacitance or ferrite bead is used to reduce the damage to the signal.

Q3:Can ground wire be added to the middle of the differential signal line in the PCB design?

In general, the ground line can not be added in the middle of the differential signal. The most important point in the application principle of differential signal is to utilize the benefits of coupling (coupling) between differential signals, such as flux cancellation, anti-noise (noise immunity) ability. If the ground line is added in the middle, the coupling effect will be destroyed.