It has been said that there are only two types of electronics engineers in the world: those who have experienced electromagnetic interference and those who have not. With the increase of PCB routing, electromagnetic compatibility design is an issue that we electronic engineers have to consider. Faced with a design, there are five important attributes to consider when conducting an EMC analysis of a product and design:

　　(1) Key device size: the physical size of the emitting device that produces radiation. The radio frequency (RF) current will generate an electromagnetic field, which will leak out of the housing through the housing. The line length on the PCB as a transmission path has a direct impact on the RF current.

　　(2) Impedance matching: the impedance of the source and receiver, and the transmission impedance between the two.

　　(3) The temporal nature of the interference signal: whether the problem is a continuous (periodic signal) event, or only exists in a specific operating cycle (for example, a single keystroke or power-on interference, periodic disk drive operation or network burst transmission).

　　(4) The strength of the interference signal: how strong the source energy level is, and how much potential it has to produce harmful interference.

　　(5) Frequency characteristics of interference signals: the use of a spectrum analyzer for waveform observation, where the observed problem is in the spectrum, easy to find the problem.