PCB Design Solution to Field Effect
PCB design will have an impact on the following three effects, they are electrostatic field before static discharge effect, charge injection effect due to discharge, and field effect due to electrostatic discharge current. This article will give some design guidelines for the issues field effect caused by electrostatic discharge current.
In general, the coupling of the field from the receiving circuit can be reduced in one of the following ways:
1.Use filters at the source to attenuate the signal;
2.Use filters at the receiving end to attenuate the signal;
3.Increase the distance to reduce the coupling;
4.Reduce the antenna effect of the source and/or receiver circuitry to reduce coupling;
5.Place the receive antenna perpendicular to the transmit antenna to reduce coupling;
6.Shield the receiving antenna and the transmitting antenna;
7.Reduce the impedance of the transmitting and receiving antennas to reduce the electric field coupling;
8.Increase the impedance of one of the transmit or receive antennas to reduce magnetic field coupling;
9.Coupled with a consistent, low-impedance reference plane (as provided by a multilayer PCB design) to keep them in common mode.
In specific PCB designs, when electric or magnetic fields dominate, methods 7 and 8 can solve the problems. However, electrostatic discharge may produce electric and magnetic fields, indicating that method 7 will improve the immunity of the electric field, but at the same time will reduce the magnetic field immunity. The effect brought by method 8 is the opposite of method 7. Therefore, methods 7 and 8 are not perfect solutions.
Regardless of the electric field or the magnetic field, the use of methods 1 to 6 and 9 will achieve some results, but the solution of PCB design mainly depends on the combined use of methods 3 to 6 and 9.