Antenna arrays emulate metamaterial-based carpet cloak over a wide angular and frequency bandwidth

We present the concept and the design of an antenna-based device for restoring the reflection from a ground plane over a broad incidence angular range, when an arbitrarily large object is placed on it. The proposed device is based on fully passive antenna arrays, whose elements are properly connected to each other by following a mirrored version of the Van Atta configuration used for realizing retroreflective arrays. Thanks to its self-adaptive behavior, the device allows faithfully emulating the reflection from a flat metallic plane, regardless the incidence angle of the illuminating field. However, the antennas reduce the amount of reflected energy due to their intrinsic limits in absorption. Except for this aspect, it acts in a similar fashion as a carpet cloak, restoring the signal reflection from the ground, even in the presence of an extremely electrically large object. The concept is numerically and experimentally verified by covering an electrically large metallic triangular bump (2.8 lambda(0) x 5.6 lambda(0)) with a pair of equal antenna arrays. The proposed design may find application in radar and antenna systems as a thin, lightweight, and easy to design and fabricate solution for concealing electrically large objects over a wide frequency and angular bandwidth.