Effect of Source Position on Directive Radiation in EBG Structures With Epsilon-Near-Zero Behavior

This letter shows that the position of a source inside an electromagnetic bandgap material determines how the emission is shaped and focused. Two degenerate electromagnetic configurations, allowed by a square lattice at a given frequency, can be selectively excited by placing the feeding point in specific locations within the building block of the periodic structure. In this way, the radiated energy can be directed toward defined focusing directions, without need to change the lattice and its dispersion diagram. A practical application, where embedded emitters selectively drive single lattice modes, is presented, showing that such a mechanism may open the way to important uses in the microwave domain, e.g., for cell splitting, smart antennas, and multiple-input-multiple-output technology, as well as in terahertz communications and optical applications.