| The purpose of this thesis is driven by the performance and manufacturability of various electromagnetic passive components. These devices are unique in their needs for seemingly arbitrary dielectric properties in seemingly arbitrary spatial locations. The desired properties may or may not exist in conventional material and their corresponding spatial location may not be realizable using conventional fabrication techniques. This thesis addresses these needs by exploiting the effective medium behavior of porous dielectrics. The dielectric properties of porous Titania were characterized for three different pore morphologies: partially sintered pores, 15 micron spherical pores, and 50-70 micron cylindrical pores. Reduction in the dielectric constant, k, was achieved tailoring the volume fraction porosity. The decreasing k vs. porosity behavior is modeled well by the Bruggeman power law independent of pore morphology. Porous dielectric loss behavior is found to more complex. Porous dielectric loss depends on both the inherent loss of the base dielectric and on the pore morphology. Increasing pore size for a given volume fraction porosity decreases dielectric loss. A spatially variable embedded dielectric resonator is fabricated from monolithic Titania. This device exploits effective medium dielectrics by locally controlling the porosity. An artificially anisotropic dielectric is fabricated from Titania with oriented porosity. Using 37% porosity, the dielectric anisotropy is greater than 9:1. A new powder processing method is presented that is capable of realizing complex spatially variable dielectrics or functionally graded ceramics. This new process is called dry powder deposition or DPD. It readily achieves a 3mm level of granularity while maintaining a geometrical tolerance of 0.6% for a 40 mm part size. DPD is applied to the fabrication of a UHF antenna substrate that has a very high degree of dielectric texturization. |
