Transmission through a bi-planar slot array sandwiched between three dielectric layers

Abstract : This report considers transmission through two metallic surfaces provided with small resonant slots where the two screens are separated by a dielectric slab of relative dielectric constant 2. They ar coated on the outside with dielectric slabs of dielectric constant 1 and 3. It is shown that such a configuration can be disigned to yield a transmission curve with band-pass characteristics, i.e., yielding essentially unity transmission coefficient over a certain frequency range (narrow band) for angles of incidence up to as high as 80 deg from broadside in both the E- as well as the H-plane. The value to the Air Force of such surfaces lies in their potential use in metallic radomes. In this connection, it should be pointed out that metallic radomes possess several inherent advantages such as: (a) lightning protection, (b) reduction of precipitation noise, (c) potentially higher mechanical strength. It is demonstrated that the dielectric on the outside by proper design make the bandwidth almost constant with angle of incidence in both the principal planes, while the dielectric between the two slot arrays provides the proper coupling between the two arrays. (Author)