19 July 2016 FPGA-based digital signal processing for the next generation radio astronomy instruments: ultra-pure sideband separation and polarization detection
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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.
© (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Andrés Alvear, Andrés Alvear, Ricardo Finger, Ricardo Finger, Roberto Fuentes, Roberto Fuentes, Raúl Sapunar, Raúl Sapunar, Tom Geelen, Tom Geelen, Franco Curotto, Franco Curotto, Rafael Rodríguez, Rafael Rodríguez, David Monasterio, David Monasterio, Nicolás Reyes, Nicolás Reyes, Patricio Mena, Patricio Mena, Leonardo Bronfman, Leonardo Bronfman, } "FPGA-based digital signal processing for the next generation radio astronomy instruments: ultra-pure sideband separation and polarization detection", Proc. SPIE 9914, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VIII, 99141E (19 July 2016); doi: 10.1117/12.2233090; https://doi.org/10.1117/12.2233090
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