Active impedance matching, calibration, and interference mitigation for the BYU/NRAO L-band phased array feed

This paper is a summary of recent research progress towards scientifically useful low noise, high sensitivity phased array feeds for radio telescopes. Developments include techniques for designing phased array antennas to realize an active impedance matching condition that minimizes receiver noise over the array field of view, array beamforming algorithms that allow a controlled tradeoff between side-lobe control and peak beam sensitivity, and spatial filtering algorithms that achieve unprecedented levels of interference suppression for moving sources of unwanted radio signals.