Software beamforming with network defined apertures

Abstract

Ever since the first astronomical observation of radio waves by Karl Jansky in 1933, the field of radio astronomy has been rapidly advancing. Nowadays, astronomers can use antenna arrays to generate synthesised images of the sky at continually increasing angular resolutions and with faster survey speeds. New radio instruments which are in their design phase such as the Low Frequency Aperture Array (LFAA), part of the Square Kilometre Array (SKA), will generate vast amounts of data for astronomers to process and analyse. To combine the output of each antenna from the aperture array one can use the beamforming process. This process generates steerable beams which can be focused on different parts of the sky thus eliminating mechanical parts and storage of raw data from each antenna. The work carried out for this masters thesis concentrates on the design of a novel software beamformer using network defined apertures. The beamformer was devel oped for the new Field Programmable Gate Array (FPGA) board named the Tile Processing Module (TPM). The beamformer can process of a group of 16 dual polarisation antenna inputs using just two FPGAs. A high-speed Ethernet network was utilised to synchronously connect several TPMs together to form a larger processing system. This networking aspect allowed for a network configurable and scalable beamformer. The developed beamforming pipeline is capable of initialising within 12 clock cycles and produces a beam product every 256 clock cycles. The beamformer was successfully tested and mitigated with the digital backend firmware tor the LFAA in collaboration with the University of Oxford and the Instituto Nazionale di Astrofisica