In the process of custom PCB board making, electromagnetic radiation is a problem that needs great attention. These electromagnetic radiations cannot exceed a limit, and the signal integrity of the system will be affected if the limit is exceeded that causing major quality problems. So, how should we deal with the electromagnetic radiation problem of custom made circuit boards?
In the eyes of SI engineers, the use of microstrip lines or strip lines in PCB board making is to provide a low impedance transmission path for the signal. This is also the need for electromagnetic shielding in the eyes of EMC engineers. After using the microstrip line or stripline, the electromagnetic energy is controlled in the medium between the conductors. Why are most of the electromagnetic energy trapped in the medium after the use of microstrip lines and strip lines? The main reason is that the signal path is closer to the return path, so the inductance of the entire loop is reduced.
Under high-frequency conditions, if the signal has a good return path, the loop inductance it feels will be small, and the signal will be transmitted from the transmitter to the receiver according to people's wishes. If the signal feels the loop inductance is very big, it will cause radiation problems.
At low frequencies, electromagnetic interference can be ignored. Under the low frequencies, the electromagnetic field around the wire does not change so strongly, and the inductance effect of the wire is not so obvious. However, at high frequencies, the electromagnetic field changes drastically. The coupling between the signal path and the return path in PCB board making should be fully considered. The coupling between the signal path and the return path is used to reduce the inductance of the entire loop and control the electromagnetic energy emitted by the wire into space.