Microstrip lines using yttrium iron garnet film

The spectral-domain technique is used to compute the dispersion characteristics and the transverse field distributions of microstrip lines using a yttrium-iron-garnet (YIG) film on a gadolinium-gallium-garnet (GGG) substrate. Numerical results are presented to show a sharp cutoff characteristic for a large thickness of GGG (which is caused by the reduction in the negative permeability range), and to show the effect of YIG film thickness on the nonreciprocal behavior. Experiments are carried out using YIG film a few tenths of a micrometer thick and a 400- mu m-thick GGG substrate. A narrow stopband characteristic of 200 MHz is observed at 6 GHz, which agrees well with theory. The application to a band-rejection filter is briefly discussed.<
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