Power densities in the near field of a large antenna focused to infinity

At low-beam elevation angles, measurements of microwave propagation from satellite to ground have exhibited large variations in signal strength under clear weather and cloudy conditions. Large nonuniformities in the three-dimensional (3-D) near-field region of an antenna focused to infinity have been computed. These field nonuniformities interacting with a dynamic turbulent troposphere can introduce phase errors at the antenna aperture, resulting in signal scintillation and loss.