Low-Frequency Shielding Effectiveness of Magnetic Alloys

This paper presents magnetic alloys’ shielding effectiveness (SE) at low frequencies of (1-50) MHz. The first part of the paper discusses the concept of SE in terms of absorption and reflection loss using a simple analytical model. The second half of the paper demonstrates the SE of magnetic alloys for magnetic field sources using the co-axial and coplanar setups derived from the standards NSA 65-6 and IEEE 299 respectively. Lastly, the study compares the shielding properties of traditional materials such as Copper (Cu) and Nickel (Ni) with Kovar alloys in the frequency range of (1-50) MHz. The SE of high-permeability alloys is found to be superior to Cu and Ni at low frequencies below 7 MHz when the source and victim are in the same plane. Notably, where the source and victim coils are co-axial, the SE of Kovar is better compared to Cu and Ni till 2 MHz according to IEEE 299. Finally, the paper compares two magnetic alloys with a relative permeability of µ r = 300 and µ r = 3000 with various electrical conductivities. This latter comparison indicates that lower electrical conductivity is better in terms of SE for materials with high permeability. On the other hand, higher electrical conductivity materials achieve high SE for magnetic alloys with relatively low µ r .