Improved microwave devices using narrow linewidth garnets

Two materials have been developed in a new class of polycrystalline microwave garnets with linewidth less than 10 oe. The compositions are Y2.9Ca0.1Fe4.2Ge0.1In0.7O12 and Y1.6Ca1.4Fe3.9V0.7In0.4O12. These new materials were used in coaxial and waveguide circulators, in different frequency bands between 3.7 and 8.5 GHz. The figure of merit of these circulators is about 600, to be compared with 200 for circulators equipped with classical garnets. As expected, the insertion losses have been lowered, typically they are less than 0.1 db. These circulators, in a four-port configuration, are very attractive for parametric amplifiers applications. The feasibility of magnetically tunable pass-band filters employing these polycrystalline materials is demonstrated