Directive EBG Antennas Based on Lattice Modes

The emission of radiators can be shaped by means of electromagnetic bandgap (EBG) materials exploiting proper Bloch waves supported by the lattice rather than its bandgaps. So far, such a method has relied only on the dispersion diagram of the periodic structure, i.e., on the eigenvalues of the lattice, neglecting the particular configuration of the associated eigenfunction. This paper explores the radiation mechanism under a novel viewpoint, which is mostly focused on the electric field pattern of lattice modes, allowing a deeper understanding of the underlying physics. Such an approach is profitably used here to improve the performance of antennas based on different Bloch waves by reducing spurious lattice modes. Geometrical configurations coupled to a line source are provided with little adjustments, getting EBGs to work at a frequency where they had no bandgap originally. As a proof-of-concept of the proposed perspectives, a compact antenna using a cheap low-permittivity dielectric is conceived, fabricated, and successfully tested.