Broadband flattened Luneburg lens with ultra-wide angle based on a liquid medium

A two-dimensional flattened Luneburg lens with an ultra-wide viewing angle has been realized based on a liquid medium approach in our present work. A field-of-view angle up to 180° is achieved over the microwave regime. The transformed lens is realized by using a low-loss liquid medium and a large variation of refractive index from 1 to 4.18 is achieved. The non-resonant property of the liquid ensures a broadband and low-loss performance of the lens from 12.4 GHz to 18 GHz. The high directivity and relatively low loss of the proposed lens were demonstrated by simulation and experimental results.