2-D Sub-Diffraction Focusing with Concentric Circular Arrays in the Microwave Regime

To our knowledge, this work introduces the first method to generate a two dimensional (2-D) circularly symmetric sub-diffraction focus in the microwave regime with concentric circular arrays based on superoscillations. It is demonstrated that an arbitrarily small focus can be theoretically achieved by appropriately exciting two or more concentric circular arrays. Here, two concentric circular arrays are used as a proof-of-concept. Full-wave simulations show that by appropriately exciting the arrays, a focus with 50% the spatial width of the diffraction limited sinc pulse is achieved. The proposed methodology for breaking the diffraction limit in the microwave regime is expected to have important applications, such as, remote sensing and imaging.