Microwave properties of composite ceramic phase shifter materials

The microwave properties of bulk ceramic barium strontium titanate and non-ferroelectric oxide composites are measured at X-band with a cylindrical mode-filtered resonant cavity. A helical wire-wound waveguide makes up the cavity´s cylindrical wall, which permits the use of high-purity TE_01p resonant modes for high accuracy permittivity measurements. Measurement results at 300 K show that microwave dielectric losses increase as the stoichiometric percentage of barium increases. The real relative permittivity increases with decreasing weight percent of added non-ferroelectric low-loss oxide. Dielectric losses rapidly decrease with the addition of a relatively small amount of non-ferroelectric oxide