Electromagnetic Interference Shielding Fabrics for use with Soft Walled Shelters

Traditionally, highly flexible EMI shielding fabrics have failed to block EMI in LF (30 150 kHz) range. This proposal will demonstrate a flexible polyester cloth with a copper and NiFe layer (best suited as an inner liner) that provides effective broad-spectrum EMI shielding that includes the LF frequency range for minimal added cost, weight, and technological risk. To accomplish this feat, we will first use existing technology to electrolessly deposit a 300-nm-thick copper layer onto a polyester cloth without significant reduction in tensile yield strength to provide a seed layer and high frequency (f>300 MHz) shielding, and then electroplate an additional layer of 200-nm-thick high permeability NiFe 80/20 (80% Ni, 20% Fe) to absorb LF EMI (essentially near-field magnetic fields). Magzor Corp. engineers will use thier expertise in electroplating extremely high permeability (r=8500) NiFe (also known as Permalloy) to ensure that the shielding has substantially better attenuation at LF than a conductive non-magnetic material such as Cu or carbon nanotubes technologies that are typically not even tested in the 30 150 kHz range. The permeability of the Permalloy (r=8500) alloy is much higher than that of other electroplated metals such as Ni (r=12) (10), which greatly improves the magnetic shielding capability. However, the permeability of our material is not high enough to be saturated by the earth"s magnetic field. This technique provides a minimum electromagnetic interference shielding effectiveness (EMISE) of 50 dB at 30 kHz, while only adding 11.5 g (0.41 oz) in weight and $1.5 in added cost for a square yard of material. This technique can also be used to metalize hook and loop connections (Velcro) to provide a quick and easy method of electrically connecting seams to minimize the maximum opening of the shield.