Progress in high sensitivity phased array feeds for large single-dish radio telescopes

Phased array feeds (PAFs) for large telescopes are currently moving from the research stage to prototype instruments with the capability for scientific observations. We report on progress towards an L-band array element design optimized for the Green Bank Telescope, imaging algorithms and real time digital signal processing, and a preliminary PAF front end design for the China Five Hundred Meter Aperture Spherical Telescope (FAST).