A digital correlator upgrade for the Arcminute MicroKelvin Imager

• DOI: 10.1093/mnras/sty074
• Publication Date: 2018-01-09T21:25:46Z
• Authors: Jack Hickish; Nima Razavi-Ghods; Yvette C Perrott; David J Titterington; Steve H Carey; Paul F Scott; Keith J B Grainge; Anna M M Scaife; Paul Alexander; Richard D E Saunders; Mike Crofts; Kamran Javid; Clare Rumsey; Terry Z Jin; John A Ely; Clive Shaw; Ian G Northrop; Guy Pooley; Robert D'Alessandro; Peter Doherty; Greg P Willatt
• Keywords: Upgrade

The Arcminute Microkelvin Imager (AMI) telescopes located at the Mullard Radio Astronomy Observatory near Cambridge have been significantly enhanced by implementation of a new digital correlator with 1.2 MHz spectral resolution. This system has replaced 750-MHz resolution analogue lag-based correlator, and was designed to mitigate effects radio frequency interference, particularly from geostationary satellites that contaminate observations low declinations. upgraded instrument consists 18 ROACH2 Field Programmable Gate Array platforms used implement pair real-time FX correlators -- one for each AMI's two arrays. separates down-converted RF baseband signal AMI receiver into 2.3 GHz-wide sub-bands which are digitized 5-Gsps 8 bits precision. These data streams filtered 2048 channels cross-correlated using FPGA hardware, commercial 10 Gb Ethernet switch providing high-speed interconnect. Images formed show over an order magnitude improvement in dynamic range previous system. ability observe declinations also improved.