Cables are meant to carry data and signals from one place to another. Often, these signals create an unwanted electromagnetic noise going into the environment. Have you ever wondered what that bead is on your cables? It is a ferrite, meant for suppressing the unwanted noise without affecting the data being transmitted through the cable. To achieve this, two things must happen:
ย ย ย ย 1. Lower frequencies must be able to pass without sufficient ย inductance
ย ย ย ย 2. Higher frequencies must be suppressed
Snoekโs Law is used to govern EMI suppression:
f=ฮณMs /3ฯ(ยต-1) Hz
Where f = Resonant frequency
Ms = Saturation Magnetization
ฮณ = Gyromagnetic Ratio
ยต = Permeability
From this, we find that the lower the resonant frequency the higher the permeability.
In general, ferrites are chosen based on the following parameters:
ย ย ย ย 1. Impedance vs Inductance Ferrites
ย ย ย ย ย – Impedance Ferrites- Used for radiated emissions and every day applications
ย ย ย ย ย – Inductance Ferrites- Very low frequency applications
ย ย ย ย 2. Frequency where maximum attenuation is needed
ย ย ย ย 3. Cable Size and shape
Leader Tech offers a large variety of impedance ferrites to fit many applications. The optimum ferrite profile has the highest attenuation level coinciding with the disruptive frequency. To achieve the range
