Excitation of line and point defect modes in two-dimensional electromagnetic bandgap structures for microwave frequencies

We report on the controlled excitation of line and point defect modes in a two-dimensional hexagonal electromagnetic bandgap structure made of rods of dielectric material (aluminium oxide). We have investigated the coupling from external waveguides to line defects and subsequent coupling to resonant modes by numerical field simulations and experiments at microwave frequencies. We have demonstrated that an impedance matching to external transmission lines can be achieved for a line defect of a certain width. We have furthermore demonstrated that the excitation of localized defect resonances can be tuned by the variation of certain single lattice elements, affecting the transmission behaviour and quality factor of the resonant modes. Finally, the quality factors of the point defect modes are analysed and a possibility of creation of similar structures for the millimetre wave regime is shown.