Abstract: A frequency selective surface includes resonators (104) which are spherically shaped and have an arrangement which defines a periodic array (103) of rows (112) and columns (114). The periodic array extends in at least two orthogonal directions. A registration structure (602) is provided and arranged so that it at least partially maintains a position of each of the resonators in a predetermined spatial relationship with respect to adjacent ones of the plurality of resonators to define the array. Each of the resonators is formed of a conductive material and is electrically insulated from adjacent ones of the resonators forming the array by an insulator material.