Nonlinear two element active antenna array stability analysis

Closed form analytical equations for the stability condition for the two modes available within a two element active antenna linear array as the element separation is increased are presented for the first time. A mathematical explanation to the mode swap characteristics first reported by Stephan and Young (1988) is given with a prediction of within which mode the array will operate as a function of element separation. This knowledge is imperative since the array far-field radiation pattern is different depending on the operating mode, and so a prediction method is desirable (i.e. boresight null or peak). The identical element case is considered, although the analysis can be extended to incorporate similar though non-identical elements