Flat Luneburg Lens via Transformation Optics for Directive Antenna Applications.

The great flexibility offered by transformation optics for controlling electromagnetic radiation by virtually re-shaping the electromagnetic space has inspired a myriad of dream-tailored electromagnetic devices. Here we show a 3D-transformed microwave Luneburg lens antenna which demonstrates high directivity, low side-lobe level, broadband response and steerable capabilities. A conventional Luneburg lens is redesigned accounting for dielectric materials that implement a coordinate transformation, modifying the lens geometry to accommodate its size and shape for easy integration with planar microwave antenna applications. An all dielectric lens is manufactured following a thorough holistic analysis of ceramic materials with different volume fractions of bi-modal distributed titanate fillers. Fabrication and measurements of a 3-D flat Luneburg lens antenna validate the design and confirm a high-directivity performance. A directivity of 17.96 dBi, low side-lobe levels for both main planes \sim -26~dB, excellent directivity performance within the X-band and beam-steering up to 34^\circ were achieved. [ABSTRACT FROM PUBLISHER]