A two-dimensional slotted array

A two-dimensional slotted array of which the radiating surface is one face of a parallel-plate region is discussed, This configuration differs from others previously reported in that a higher mode is utilized in the parallel-plate region. The array is equivalent thereby to a number of slotted waveguides parallel to each other. The stability of the desired mode requires that the array amplitude be uniform laterally; however, it may have an arbitrary taper longitudinally. The radiation field of the array is discussed with particular regard to the generation of second-order beams. The performance of several such arrays is described.