Planar YIG filters

A tunable filter is described which uses spherical crystals of magnetic materials such as Yttrium Iron Garnet (YIG) together with photolithographically fabricated coupling structures. Eddy current induced frequency shifts can be completely avoided in this structure and eddy-current induced line-broadening can be reduced to an insignificant level. Precise crystal orientation, required to avoid temperature dependence of the resonant frequency, is achieved by an improved sphere orienting technique.