A Coordinate Transformation-Based Broadband Flat Lens via Microstrip Array

A conventional convex lens is compressed into a flat one based on a so-called discrete coordinate transformation technique. While maintaining a good performance of the original lens, such a transformed flat lens only requires a few blocks of isotropic dielectrics. Physical realization via multiple transmission lines is then demonstrated, and it shows an alternative approach to achieve the desired spatially varying dielectric constant across the lens aperture. The full-wave simulation shows that the proposed microstrip array mimics the original convex lens nicely and can function well over a broad frequency band while possessing the merits of a flat profile and small volume.