Large reflector antenna profile measurements by phase retrieval techniques: an array processing approach

The determination of the surface quality of large reflector antennas by direct methods like the tape-theodolite method is not accurate enough for millimeter-wave operation. Indirect methods like holographic ones have been widely used. They are based on the Fourier transform (FT) relationship between the far-field pattern and the field distribution in the aperture, whose phase can be used to obtain a map of the axial deformations of the paraboloid by simple ray tracing. Measurement of the pattern phase requires a second antenna-receiver system and is difficult for high frequencies, so the possibility of recovering the aperture field from amplitude-only (or intensity) measurements of its FT (the pattern) has been studied and applied in radio telescope measurement. We present a discrete model for the aperture that enables us to approach this problem from an array processing point of view.