Multiplicative arrays in radio-astronomy and sonar systems

The paper is concerned with gathering together, and extending, some ideas on multiplicative receiving arrays as applied to radio-astronomy and sonar. The main emphasis is on systems using coherent-tone signals an(j designed for direction-determination. It is shown that, using arrays in which the outputs from the two halves are multiplied together, the accuracy of determination of target bearing may be increased by a factor of ¿2 up to 2 as compared with ordinary arrays of the same size; split-beam systems have no theoretical advantage over full-beam systems. Using arrays in which the two portions have the same centre-point, some new and attractive directional patterns are developed (including pencil beams) in which secondary responses may be almost eliminated over a considerable range of bearing.