Shielding improvement by multi-layer design

Experimental data are presented comparing the combined effectiveness of magnetic alloys and copper as single sheets and in two-, three- and five-layer composites. The two-layer structure shows a small but unmistakable increase in shielding factor, while the three- and five-layer composites increase effectiveness by as much as fifty percent. The increased shielding factor of multilayer designs is also predicted by Schellkunoff´s surface impedance theory (1934). It is noted that, while shielding effectiveness can be further increased by the use of five, seven or more layers, the additional cost of such constructions probably precludes their selection over the more conventional three-layer copper-magnetic-copper high-performance clad shielding