Reactively steered adaptive array using microstrip patch elements at 4 gigahertz

A reactively steered adaptive array (RESAA) has one element connected by a transmission line to a receiver and a number of closely spaced parasitic elements, each of which is terminated by an adjustable reactive load. The pattern is formed by adaptive control of the reactive loads. A five element linear RESAA fabricated from microstrip patch antennas was evaluated at 4.0 GHz. Manual adaptive control was used to form a pattern with a minimum in the direction of an interference signal. A minimum could always be formed in the direction of the interference that had a depth (relative to the pattern maximum) of 30 dB and a width of 25 degrees. The theory of the array was developed using an N-port network formalism, and simulations with this theory reproduced the essential features of the experimental measurements. The potential advantages of a RESAA, as compared with a conventional adaptive array, include the elimination of the mixers and other hardware needed to perform the complex weighting of the output of each element at an intermediate frequency, greater dynamic range, and smaller overall size.