Reconfigurable Open Architecture Computing Hardware (ROACH board

1. Reconfigurable Open Architecture Computing Hardware (ROACH board Abstract We present the conceptual design for a general-purpose spectrometer system designed to support the Green Bank Telescope (GBT) K band Focal Plane Array (KFPA) project. This design is based on use of reconfigurable computing elements and supporting design tools designed by the Center for Astronomy Signal Processing and Electronics Research (CASPER) at the University of California at Berkeley and collaborators. The CASPER toolset and hardware platforms provide a standard interface to the signal processing power available in today's Field Programmable Gate Array (FPGA) devices. This paper presents an analysis of the projected cost and performance tradeoffs, physical size and weight, and time to deploy for a spectrometer system supporting a seven pixel, dual polarization array receiver, and extends that analysis to a 61 pixel dual polarization receiver. The analysis includes the entire data stream, from digitizer to disk. • The GBT K band Feedhorn Array • 7 Pixels, 18 to 26.5 GHz • 8 GHz RF Bandwidth • Dual Polarizations • 1.8 GHz IF Bandwidth • Expansion plans for up to 60 pixels A General Purpose Spectrometer for a Feedhorn Array Receiver, Paper 2541John Ford , Jason RayNational Radio Astronomy Observatory, PO Box 2, Green Bank, WV 24944, USAjford@nrao.edujray@nrao.edu • New GBT Spectrometer Minimum Specifications • 14 IF channels • 800 MHz bandwidth • 32K spectral channels per IF • 10 ms minimum dump time (4 bins, using cal and sig/ref signalling) • 16 simultaneous 50 MHz sub-bands across the 32K channels • Cross products within each pixel's IF iADC-2 • Basic Spectrometer Requirements for GBT • Wide band modes for searching • Multiple narrow band modes for detailed analysis of spectral lines • Existing Spectrometer modes (Subset of some 800 possible modes) • 16 * 50 MHz BW, 16K spectral channels/IF • 8 * 200 MHz BW, 8K spectral channels/IF • 8 * 800 MHz BW, 2K spectral channels/IF Basic Spectrometer System Design Parameters Per-Pixel Hardware Shared Hardware FFT engines Digitizers Signal Combiner/Accumulator ROACH/ROACH-2 Reconfigurable Compute Engine Fiber to Lab 10 GbE switch iADC2 Backend data storage computer ROACH/ROACH-2 Reconfigurable Compute Engine IF Connections ROACH/ROACH-2 Reconfigurable Compute Engine iADC2 Sampling clock, 1PPS