Synthesis of phased array far-field patterns by focusing in the near-field

A phased-array focusing technique is described that results in far-field antenna patterns being formed at distances as close as one array diameter. This will allow experimental verification of adaptive-array far-field performance in an anechoic chamber of reasonable size. This phased-array focusing technique accounts for parallax effects by matching the null locations of the actual far-field pattern with null locations created in the antenna pattern at close range. In this manner, the gain, beamwidth, and sidelobe behavior of the antenna pattern observed in the near field can be matched exactly to the corresponding far-field pattern. The required array excitation function is determined by inversion of the array pattern matrix. The near-field focusing technique was experimentally verified using a 32-element, linear, L-band phased array. The focused antenna patterns were measured directly by a probe on a linear scanner running parallel to and an array diameter away from the ground plane. Very good agreement with theoretical predictions was achieved