YIG_sphere
YIG sphere
Magnetic device
Yttrium iron garnet spheres (YIG spheres) serve as magnetically tunable filters and resonators for microwave frequencies. YIG filters are used for their high Q factors, typically between 100 and 200.[1][2] A sphere made from a single crystal of synthetic yttrium iron garnet acts as a resonator.
The field from an electromagnet changes the resonance frequency of the sphere and hence the frequency it will allow to pass. The advantage of this type of filter is that the garnet can be tuned over a very wide frequency range by varying the strength of the magnetic field. Some filters can be tuned from 3 GHz up to 50 GHz.