Analysis and treatment of edge effects on the radiation pattern of a microstrip patch antenna

Microstrip antennas have many applications on structures where size and weight constraints are critical. Because of their low profile and conformal nature, they are especially useful for airborne and spacecraft systems. When designing these antennas, it is often assumed that the microstrip elements are mounted on infinitely large ground planes so that the diffraction from the edges of the ground plane are neglected. In practical applications, however, the diffraction from these edges can have a significant affect on the radiation pattern. It would be desirable to have an analytical model that can be used to understand exactly how great this affect is. Treatment of these edges may be necessary to control their effect on the radiation pattern, which can often be accomplished by placing lossy materials in the vicinity of the edges to minimise the fields which diffract from them. Such a technique has been previously successfully applied to control the scattering from the vertex of a wedge using resistive cards, and will be extended here for the problem of controlling radiation patterns.