Array pattern estimation from amplitude measurements on arbitrary near-field surfaces

A new method is presented for determining far-field radiation patterns of an array by means of amplitude-only measurements performed on arbitrary surfaces in the array´s near field. Based on the method of successive projections, it is a significant generalisation of existing techniques where measurements are restricted to equally spaced points on canonical surfaces. The method has particular application to the airborne measurement of the large low-frequency arrays used in OTHR (over-the-horizon radar) systems, where direct determination of the far field is difficult if not impossible. Two examples illustrate the technique, showing its efficacy for both smooth and gross variations in array excitation