电磁干扰的屏蔽方法.doc

电磁干扰的屏蔽方法
Electronic engineering album - the shielding method of electromagnetic interference
June 11, 2003, the firstifferent frequency or electromagnetic energy between a band, and the corresponding circuit will launch this energy to the surrounding environment.
EMI has two ways to leave or enter a circuit: radiation and conduction. Signal radiation is leaked through the seams, slots, open holes, or other gaps. Signal transduction, by coupling to the power supply, signal and control line, leaves the outer shell and emits free radiation in open space, thereby causing interference.
Many EMI suppression using shell screen and aperture combination of screen, most of the time, following the simple principles can help to realize the EMI shielding: from the source to reduce interference: By shielding, filtering, or grounding, the interference can be caused by isolating the circuit and enhancing the resistance of the sensitive circuit. EMI's inhibition, isolation, and low sensitivity should be the goal of all circuit designers, which should be completed early in the design phase.
For design engineers, using masking material is an effective way to reduce EMI. Now has a variety of shell is widely used, shielding materials from metal cans, thin sheet metal and foil to the conductive fabric or volume with spray coating and coating (such as conductive paint, zinc coating, etc.). Whether it is metal or plastic coated with conductive layers, once the designer is identified as a shell material, you can begin to choose the padding.
Metal shielding efficiency
The effectiveness of the shielding mask (SE) is assessed by the effectiveness of the shielding efficiency (SE), which is measured in decibels
SEdB = A + R + B
In which A: absorption loss (dB) R: reflection loss (dB) B: correction factor (dB) (applicable for multiple reflections within A thin mask)
A simple shield will reduce the intensity of the electromagnetic field generated by the amount of electromagnetic fields