A large antenna array for millimeter wave propagation studies

An antenna array has been constructed for reception of line-of-sight, ground-to-ground transmissions at 35 GHz over a 28-km path. It measures, individually, the amplitude and the relative phase of the arriving wave at each of eight antenna elements spaced horizontally over a distance of 24 m transverse to the path. Preliminary observations have shown perturbations in amplitude which appear at one end of the array and progress sequentially in a matter of seconds from element to element across the array. Similar traveling perturbations occur in the phase measurements. Variations in tilt of the wave front are observed, usually amounting from a few to tens of seconds of arc. In addition, changes in wave-front curvature have been measured corresponding to an apparent shrinkage or expansion of path length on the order of ten percent. Other capabilities of the array as a propagation-research tool are mentioned.