© ASTRON On the Fly LOFAR Station Correlator André W. Gunst

© ASTRON LOFAR System Overview

© ASTRON LOFAR Station Locations

© ASTRON Remote Station Architecture MHz MHz Optional 10- … MHz

© ASTRON Receiver Bands

© ASTRON Key Numbers

© ASTRON Top Level Digital Processing Functions

© ASTRON Digital Filter Bank  Sample rate max. 200 MHz  Number of taps:  Number of subbands: 512

© ASTRON Central Beamformer,,, Filter BEAM FORMER Filter ~192 receiver units 8 Gbit/s 200 Gbit/s RCUs

© ASTRON Central Beamformer Add,,, Filter BEAM FORMER beamformer Filter beamformer Filter beamformer Filter beamformer 2 Gbit/s 50 Gbit/s RCUs

© ASTRON,,, Filter beamformer Filter beamformer Filter beamformer Filter beamformer 2 Gbit/s RCUs

© ASTRON Beams Versus Bandwidth Exchange N M M = 165 (200 MHz mode) M = 205 (160 MHz mode) N = 96 beamlet

© ASTRON Remote Station Architecture Receiver Filter Beamformer Buffer Receiver Filter Beamformer Buffer Receiver Filter Beamformer Buffer Receiver Filter Beamformer Buffer 10 GbE 1 GbE Used for 1 beam & station cross correlation

© ASTRON Station Correlator Applications  Station analogue hardware calibration (based on the full cross correlation matrix)  RFI detection  System health management

© ASTRON Overall Ring Structure

© ASTRON + Correlator Beamlets Beam former Antenna data (all subbands) Antenna data (1 subband) Ring 1 0 : : 191 Beamlets Antennas

© ASTRON Board Architecture AP 1 AP 3 AP 2 AP 4 BP RSPRCU 1X RCU 1Y RCU 2X RCU 2Y RCU 3X RCU 3Y RCU 4X RCU 4Y RSP in RSP out LCU WAN

© ASTRON Station Correlator Scenarios  Real-time correlation of 1 subband (2 subbands possible)  Full band correlation with update rates of about 9 minutes  Odd or even subband correlation with update rates of about 4 minutes  Everything in between  Full flexibility in selection of the subbands

© ASTRON Correlator Characteristics Summary (1)  Full dual polarized cross correlator (PFX)  # Signal paths correlated: 192 (96 antennas)  Instantaneous bandwidth 2*195 = 391 kHz  Number of multiplier bits: 18 (set by RFI)  144 multipliers per station 200 MHz for correlator  Station processing: 1.8 Tmul/s (1.6% procent used for correlator)

© ASTRON Correlator Characteristics Summary (2)  Integration time: 1 s  Used technology: 90 ns FPGA technology  Design is scalable, but at some point the ring bandwidth will limit 216 antennas)  Subbands can be selected from a full 100 MHz band  In total 77 stations/correlators in the field

© ASTRON Remote Station Hardware Numbers  96 dual pole low band antennas  96 dual pole high band tiles  192 receiver boards  24 dig. signal processing boards with 5 FPGAs each  12 transient buffer boards  6 backplanes  6 clock boards

© ASTRON Remote Station Numbers  Input data rate: ~ 460 Gbps  Output data rate: ~ 2 Gbps  Processing capacity: ~ 1.8 Tmul/s  Storage capacity: 96 Gbyte

© ASTRON Remote Station Implementation Clock Receiver Filter Beamformer Buffer Receiver Filter Beamformer Receiver Filter Beamformer Receiver Filter Beamformer Buffer

© ASTRON

Remote Station Cabinets

© ASTRON Concluding Remarks  Other way of thinking:  instead of bringing all antenna data traditionally to one point  the antenna data is send to each other and locally processed  Architecture optimized for beam forming used for a distributed correlator

© ASTRON The End