Beamformer Calibration with Distributed Reference Noise for the ALPACA Imaging Array

For wide-field astronomical phased array feeds, accurate beamformer calibration is required. Temperature variations and other environmental factors cause drifts in the phase and amplitude responses of the analog front end and RF- over-fiber signal transport system. To correct for these drifts and eliminate gain reductions and pattern drift in the formed beams, we have developed a distributed noise reference system that allows phase and amplitude recalibration. To validate the system, we use the reference system to correct the phase in a signal transport channel for the Advanced L-band Phased Array Camera for Astronomy (ALPACA) with a length of fiber inserted to mimic phase drifts.