High Frequency Applications For Two-Dimensional Periodic Substrates

The use of advanced ceramic fabrication, specifically, the Indirect Solid Free Form method was utilized to develop high frequency periodic substrates. The electrically thick substrates have reduced substrate modes because of periodic inclusions that are spaced in a two dimensional lattice. The inclusions can serve multiple purposes, to inhibit coupling between elements on the substrate and to control and manipulate the waves as well. As an example, Alumina rods in air have been periodically placed to block the formation of parasitic parallel plate modes. The periodic arrangement creates a two dimensional spatial filter in that fields evanesce in the substrate in all directions. The ceramic substrates block energy in the range of 30 to 40 GHz by using inclusions 1.05 mm wide in a lattice of 3.2 mm. The evanescent nature of the high frequency substrate is then utilized to create a high quality defect mode resonance with a Q of 1308 at 34.48 GHz that can be utilized for high-Q filters embedded in the substrate.