Beamformer design for radio astronomical phased array feeds

A major research emphasis in current radio astronomy instrument development is the use of phased array feeds (PAF) to provide radio telescopes with larger fields of view. Statistically optimal beamformers have been shown to provide high sensitivity for PAFs, however, inability to precisely control beampattern details (even in sidelobes) is problematic. Enforcing beampattern structure with a deterministic beamformer is useful. A hybrid beamforming approach is presented in this paper, which offers the best in sensitivity for a desired amount of beampattern control. Designing any beamformer with simulated calibration data is inadequate for PAF operation and introduces distortion in the final beampattern. A transformation step is required to reduce such effects.