Experimental Demonstration of Active Electromagnetic Cloaking

Active electromagnetic cloaking uses an array of elementary sources to cancel the scattered fields created by an object. An active interior cloak does this by placing the sources along the boundary of the object. This process can be thought of as introducing a discontinuity in the field to cancel out the scattered field by the object. Here, an experimental version of a thin active cloak at microwave frequencies is demonstrated for an aluminum cylinder with a radius of 0.56 lambda. The cloak consists of a 12-element magnetic-dipole array. By controlling the weights of the current on each element of the array, the scattering off of the cylinder is reduced in the backward and forward directions. The ability to disguise the aluminum cylinder as another object by varying the weights of the dipole array is also demonstrated. Finally, potential ways of overcoming the constraint of requiring a priori knowledge of the incident field leading to camouflaging-type behavior are discussed.