Efficient calculation of radiation patterns for reactively-steered array antennas

There is growing interest in the use of directive antennas in wireless systems. An alternative approach to traditional designs, such as mechanically-rotatable reflector antennas and phased arrays, is the reactively-steered array (Gyoda, K. and Ohira, T., 2000; Thiel, D.V. and Smith, S., 2002), in which only a single array element is excited by the RF source, and the other elements are parasitically excited. The parasitic elements are loaded by reactances that can be varied to adjust the relative phases of the element excitations. Through an appropriate selection of reactive loads, the main beam of the array, or a , can be scanned to any desired direction. These arrays have the advantage of electronic pattern control without the complicated, expensive, and heavy feed network associated with traditional phased arrays. The paper presents a method that permits the fast calculation of radiation patterns of reactively-steered arrays for new sets of reactive loads applied to the parasitic elements. It is a much faster approach than applying full-wave analysis every time the load reactances change. The scan element pattern matrix and the mutual impedance matrix used in the method incorporate all of the effects of nearby scatterers to the extent that they are accurately modeled, but the matrices are computed only once for a given array geometry.