What are Ferrite Devices?

What are ferrite devices? Why are Isolators and Circulators made from ferromagnetic materials?

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Editorial Team - everything RF

Jun 13, 2021

Ferrite electrical devices are devices that are constructed using Ferromagnetic materials. Ferromagnetic materials are ceramic materials which are made by mixing iron oxide with other metallic elements. These materials are electrically non-conductive, and have useful magnetic properties. They also allow Electromagnetic waves/signals to pass through at high frequencies with negligible attenuation. The non-conductive nature of these materials makes them resistant to current flow which leads to reduced eddy currents.

The combination of low attenuation of EM waves and reduced eddy current makes ferrites a suitable material for various microwave devices. Ferrites are used to construct isolators, circulators phase shifters, variable attenuators, modulators and switches in microwave systems. They are also used as a component of radar-absorbing materials or coatings used in stealth aircraft and in the absorption tiles lining the rooms used for electromagnetic compatibility (EMC) measurements.

Ferrites are ferrimagnetic materials – meaning they can be attracted to a magnet – made by mixing iron oxide with one or more additional metal (or metal oxide) such as Manganese, Zinc, Nickel, etc. They are low cost and have excellent corrosion resistance, which add to the benefits of using ferrite materials.

Ferrite devices are divided into two categories based on their resistance of being demagnetized (magnetic coercivity):

Soft Ferrites: Soft ferrites have low coercivity, which means they can be easily demagnetized, or they can absorb magnetic energy without retaining it. They are used to make efficient magnetic cores called ferrite cores for high-frequency inductors, transformers and antennas, and in various microwave components such as circulators, isolators, phase shifters, and high-speed switches. Magnetically soft ferrites are used to make RF & Microwave components.

Hard Ferrites: Hard ferrites have high coercivity, which means they are hard to demagnetize, or they can retain strong magnetic energy even after the source of the magnetic field is removed. They are used to make permanent magnets for applications such as loudspeakers and storage media in magnetic recording devices.

Why are Ferrites used to make Isolators and Circulators?

  • They allow high-frequency EM Signals to pass through them with low losses.
  • They are cost-effective
  • They are rugged

Here is an article that talks about how Isolators, attenuators and phase shifters are made out of ferromagnetic materials.

Here is a detailed article on ferrite materials and their Applications.

Click here to read about Ferroelectric Phase Shifters on our partner website.

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