Dual frequency antenna integration using invisible grating structures

In many applications, particularly on aircraft, the integration of two or more antennas into the same physical area is desirable. A technique, using compensated grating structures, is described which offers the opportunity of constructing radiating elements and feeds which are `invisible¿¿ at a second frequency. This technique is described in detail and its application to microstrip and other similar media is discussed. Particular attention is given to the edges of the structures, and measured results clearly showing the `invisibility¿¿ are presented. An array of `invisible¿¿ microstrip radiators has been mounted in an existing primary aperture. Primary radiation patterns are given, which show the very small degradation introduced by the secondary array.