A Scalable Correlator Architecture Based on Modular FPGA Hardware, Reuseable Gateware, and Data Packetization

Abstract

ABSTRACT.A new generation of radio telescopes is achieving unprecedented levels of sensitivity and resolution, as well as increased agility and field of view, by employing high-performance digital signal-processing hardware to phase and correlate signals from large numbers of antennas. The computational demands of these imaging systems scale in proportion to BMN 2 , where B is the signal bandwidth, M is the number of independent beams, and N is the number of antennas. The specifications of many new arrays lead to demands in excess of tens of PetaOps per second. To meet this challenge, we have developed a general-purpose correlator architecture using standard 10-Gbit Ethernet switches to pass data between flexible hardware modules containing Field Programmable Gate Array (FPGA) chips. These chips are programmed using open-source signal-processing libraries that we have developed to be flexible, scalable, and chip-independent. This work reduces the time and cost of implementing a wide range of signal-processing systems, with correlators foremost among them, and facilitates upgrading to new generations of processing technology. We present several correlator deployments, including a 16-antenna, 200-MHz bandwidth, 4-bit, full-Stokes parameter application deployed on the Precision Array for Probing the Epoch of Reionization.

Project RESUN, a Radio EVLA Search for UHE Neutrinos

“…The down-converted waveform at each antenna were sampled using FPGAbased digital signal processors developed by the CASPER laboratory at U. C. Berkeley (Parsons et al, 2008). Each subsystem module (one per sub-array) consisted of two dual-channel 8-bit analog to digital converters (ADCs) attached to a Internet Break-Out Board (iBOB), which provided Internet Protocol (IP) based configuration and high speed (∼ 5 Mb/s) data transfer to a host computer (see Fig.…”

Hardware Implementation of an SK Spectrometer

“…The implementation is based on the Internet Break-Out Board (IBOB) hardware and firmware tools developed by the Center for Astronomical Signal Processing and Electronics Research (CASPER) [10]. The spectrometer design source files may be downloaded from http://casper.berkeley.edu/wiki/Kurtosis_Spectrometer.…”

Digital Signal Processing

“…Addition of an extra antenna to an FX correlator requires less modification of the reduction procedure than is necessary for a lag correlator. Thus, the FX design is convenient for projects in which the number of antennas is planned to increase over time and is more efficient for larger arrays (Parsons et al 2008). …”