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Proceedings Paper

FPGA-based digital signal processing for the next generation radio astronomy instruments: ultra-pure sideband separation and polarization detection
Author(s): Andrés Alvear; Ricardo Finger; Roberto Fuentes; Raúl Sapunar; Tom Geelen; Franco Curotto; Rafael Rodríguez; David Monasterio; Nicolás Reyes; Patricio Mena; Leonardo Bronfman
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Paper Abstract

Field Programmable Gate Arrays (FPGAs) capacity and Analog to Digital Converters (ADCs) speed have largely increased in the last decade. Nowadays we can find one million or more logic blocks (slices) as well as several thousand arithmetic units (ALUs/DSP) available on a single FPGA chip. We can also commercially procure ADC chips reaching 10 GSPS, with 8 bits resolution or more. This unprecedented power of computing hardware has allowed the digitalization of signal processes traditionally performed by analog components. In radio astronomy, the clearest example has been the development of digital sideband separating receivers which, by replacing the IF hybrid and calibrating the system imbalances, have exhibited a sideband rejection above 40dB; this is 20 to 30dB higher than traditional analog sideband separating (2SB) receivers. In Rodriguez et al.,1 and Finger et al.,2 we have demonstrated very high digital sideband separation at 3mm and 1mm wavelengths, using laboratory setups. We here show the first implementation of such technique with a 3mm receiver integrated into a telescope, where the calibration was performed by quasi-optical injection of the test tone in front of the Cassegrain antenna. We also reported progress in digital polarization synthesis, particularly in the implementation of a calibrated Digital Ortho-Mode Transducer (DOMT) based on the Morgan et al. proof of concept.3 They showed off- line synthesis of polarization with isolation higher than 40dB. We plan to implement a digital polarimeter in a real-time FPGA-based (ROACH-2) platform, to show ultra-pure polarization isolation in a non-stop integrating spectrometer.

Paper Details

Date Published: 19 July 2016
PDF: 14 pages
Proc. SPIE 9914, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VIII, 99141E (19 July 2016); doi: 10.1117/12.2233090
Show Author Affiliations
Andrés Alvear, Univ. de Chile (Chile)
Ricardo Finger, Univ. de Chile (Chile)
Roberto Fuentes, Univ. de Chile (Chile)
Raúl Sapunar, Univ. de Chile (Chile)
Tom Geelen, Technische Univ. Eindhoven (Netherlands)
Franco Curotto, Univ. de Chile (Chile)
Rafael Rodríguez, Univ. de Chile (Chile)
David Monasterio, Univ. Chile (Chile)
Nicolás Reyes, Univ. de Chile (Chile)
Patricio Mena, Univ. de Chile (Chile)
Leonardo Bronfman, Univ. de Chile (Chile)

Published in SPIE Proceedings Vol. 9914:
Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VIII
Wayne S. Holland; Jonas Zmuidzinas, Editor(s)

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