| This thesis presents a theoretical model and experimental verifications of resonance cone radiation in hyperbolically anisotropic metamaterials. The material under consideration consists of a planar square-celled wire grid, series-loaded with orthogonal inductors and capacitors. Depending on the polarization of the propagating wave, the metamaterial may be either electrically or magnetically anisotropic. It is shown that under certain excitations, resonance cones emerge as conical high-field regions whose cone angle is a function of the frequency and the material parameters. The currents flowing in the high-field regions are parallel to the cones and possess a uniform phase progression transverse to the cone. The far field radiation pattern due to these currents is unidirectional and has its maximum broadside to the resonance cone. Since the resonance cone angle is a function of the material parameters, it is therefore possible to control the direction of maximum radiation by varying the permittivities or the permeabilities. To verify the aforementioned concepts, a proof-of-concept beam-steerable antenna realised on a tunable hyperbolically anisotropic metamaterial is designed, built, and tested. The metamaterial on which the antenna is realised is magnetically anisotropic. The permeability can be adjusted by varying a DC bias voltage. Near-field measurements of the antenna show resonance cone formation and the near fields possess a uniform phase progression transverse to the cone. Far-field measurement demonstrates the unidirectional radiation pattern with the maximum being broadside to the resonance cone. Theoretical and experimental results are in good agreement with each other. |
