Principle of electromagnetic shielding

                                Figure 1 Schematic diagram of electromagnetic shielding principle

Electromagnetic shielding is to limit the transmission of electromagnetic energy from one side of the shielding material to the other side. When the electromagnetic wave reaches the surface of the shielding material, there are usually three different mechanisms for attenuation: one is the reflection attenuation at the incident surface; the other is the attenuation of the electromagnetic wave that enters the shield without being reflected by the material; the third is inside the shield Attenuation of multiple reflections. According to Schelkunoff's electromagnetic wave theory, the total shielding effect of electromagnetic waves passing through the shielding material can be calculated as follows:

(1)

Where: SE is electromagnetic shielding effect, dB; R is surface single reflection attenuation, dB; A is absorption attenuation, dB; B is internal multiple reflection attenuation (only meaningful when A<15dB), dB.