Abstract

The Advanced L-Band Phased Array Camera for Astronomy (ALPACA) is a phased array feed instrument designed for the Green Bank Telescope. It is capable of producing 40 real-time beams on the sky, widening the telescope's field of view and significantly increasing survey speed. ALPACA employs an RF-over-fiber (RFoF) signal transport system from the phased array feed front end to the digital backend. This RFoF link is expected to introduce phase delays and changes in gain through out the course of an observation, invalidating the beamformer weights previously calculated. This work presents rapid beamformer weight calibration updates for ALPACA, a method that estimates changes in the fiber link and mitigates their effects on the beamformer. The design and fabrication of a custom calibration injection distribution system, which facilitates rapid calibration updates, is detailed. Finally, initial results, derived from the use of rapid calibration updates on ALPACA, show that the system successfully restores beamformer weights and prolongs their use without having to perform lengthy on-sky calibration.

Degree

MS

College and Department

Ira A. Fulton College of Engineering; Electrical and Computer Engineering

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2025-06-17

Document Type

Thesis

Handle

http://hdl.lib.byu.edu/1877/etd13735

Keywords

radio astronomy, phased array feed, beamforming, phased array calibration

Language

english

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