Measurement And Influence Factors For Shielding Effectiveness Of Material Based On Shielding Enclosures Method

All kinds of elcetrical and communication devices produce a lot of electromagnetic radiation. The electromagnetic interference is harmfull to human and other devices. Electromagnetic shielding as a important method to solve the electromagnetic interference problem, has attracted more and more concern. The troditional electromagnetic shielding meterials were metal meterials mostly, such as copper and aluminum. These kind of meterials have common features with high electrical conductivity, have good electromagnetic shielding effect. But these meterials are heavy, high cost, and can be oxidated and corroded easily. As the development of material science, nonmetal composite materials, such as conductive rubber, conductive coating,etc., be used as shielding meterial instead of metal meterials. Nonmetal composite materials have advantages like good flexibility and plasticity, portable with low manufacturing cost, and they have unique advantages for some special applications such as electromagnetic sealing. But these meterials have low electrical conductivity, so the testing of electromagnetic shielding effectiveness for these meterials are especially important.Measurements for shielding effectiveness of material mentioned by some relative standards mainly applies to high-frequency section (above 10kHz), and the equipment are expensive and not easy used. An testing method of electromagnetic shielding effectiveness of material in low frequency electric field is given in this thesis, which makes up for the standards. Power source(220V/50Hz), shielding chamber with testing window, self-made plates, electric resistance and multimeter are used in the method. The method is easy used and low cost. Some influence factors for shielding effectiveness of material in low frequency electric field are given based on the experiment.An testing method of electromagnetic shielding effectiveness of material in high frequency electromagnetic field based on the shielding chamber method and the flange coaxial method mentioned on standard GJB 6190-2008 is given in this thesis. Self-made antenna and network analyzer are used in the method, which is easy used and low cost. Some influence factors for shielding effectiveness of material in high frequency electromagnetic field are given based on the experiment.