A finite array of ring-slot elements in a ground plane

A ring-slot element excited by a zeroth order mode (no angular variation) E-field across the slot behaves as a monopole. It is a duality of a loop antenna with constant current distribution. A study of monopole array was reported by Fenn (1985). A monopole array is suitable for applications that require a null at broadside and a higher gain beyond 50/spl deg/ and towards endfire. For example, a low profile belly-mounted airborne terminal designed for naval communications can make use of such an element. However, the lack of mechanical rigidity of a monopole array makes it less desirable for a highly vibrating environment compared to all equivalent flush mounted ring-slot array. The characteristics of a finite array or ring-slot elements are presented and they are compared to that of a monopole array.