Bluering Prototype System Results G. Hampson, W. Cheng, D. - PowerPoint PPT Presentation

Bluering Prototype System Results G. Hampson, W. Cheng, D. Humphrey, J. Bunton, P. Roberts, K. Bengston, R. Beresford, Y. Chen, R. Chekkala 22 nd September 2020 RadioNet Workshop: Future Trends in Radio Astronomy Instrumentation

Bluering Aims ● To develop a generic receiver ○ Using “RFSOC” = Radio Frequency System On Chip ○ Tailored RF front end to suit most types of astronomy antenna systems ○ Coax connected to enable high dynamic range RF front ends that can be operated with RFI ● RFSOC signal processing capabilities - a powerful DSP FPGA too ○ Can beamform at the antenna (if only limited # of beams) ○ Can calculate correlations, time pulsars, and RFI mitigation ● Integration results in a cost, size and power efficient receiver ● Optical connectivity to backend ○ Optical clocks and control ○ Optical data path out ● This presentation shows how far we have come ...

Bluering System View ● Each Bluering system contains a number of “Razorbacks” (containing the RFSOC), plus supporting equipment ● There are few central services required to operate the Bluering systems White AC-to-48V Rabbit Razorback Master (RFSOC) Razorback Cooling Coax (RFSOC) Fibre M&C # Server WR Slave (2 per (WR, antenna) 1GbE, * GbE) Optical Circuit Irukandji Link to DSP 19” Rack Backend Remote Systems

Bluering = Taipan + Razorback + Irukandji ● Taipan is a customisable RF module ● Razorback contains the Xilinx RFSOC plus: ○ Synthesizer for ADC sample clock and LO generation ○ DDR4 for transient data capture (raw, filterbank, beam, …) ○ MBO for 10GbE ring/star beamformer data, 1GbE, timing and calibration signals ○ Q/SFP for beam output (short or long distance) To beamformer/ ● Irukandji distributes correlator/ ○ Timing, Calibration, 1GbE (M&C) capture Network, Timing, RAZORBACK Calibration Synth Q/SFP 32 RF Chains Taipan 32 RF DC/DC Irukandji MBO RFSOC Optical Signals Beamformer (coax) 48/ Network 12V DDR4 48V (Isolated)

Razorback Board ● Clock and LO generation x8x2 and distribution ● RF inputs (Taipan) ○ 16 RF customisable modules (coax/RFOF, frequency, gain, etc.) ● Optical outputs ○ 40/100GbE QSFP ○ 10/25GbE SFP ○ 12x10GbE MBO ● RFSOC FPGA ○ 2560 channel oversampled filterbank ○ 2GSPS results in 781kHz channels (926kSPS) ● Optical inputs ○ 1GbE M&C (SFP) ○ Reference (125MHz) ○ 1 pulse-per-second ○ Calibration signal ● 8GB DDR4 memory ○ Also SDcard and 8GB iNAND ● 48V power

Taipan RF Card for MWA antenna ● Very simplified (!!!) RF signal chain diagram shown below ● Taipan powers each antenna’s LNA - no extra cables Taipan ● 22dB of sky brightness slope is partially compensated to extend dynamic range - a 12dB improvement ● All 12 RFSOC ADC bits processed in beamformer DSP ● The cost per RFSOC ADC input is halved by using a mixer architecture to sample both polarisations in the same ADC 125MHz Reference PLL PLL 875MHz 2000MHz Calibration Signal C LPF BPF RFSOC To Dual Pol Antenna (power over coax) ADC 12-bits C LPF to DSP Taipan RF board x16 for RFSOC

Taipan RF Module ● Taipan module is 101.5mm x 30.5mm ○ (purple hashed section in drawing) ● Several ports around the module provide RF, LO, control, 5V and ground ● 4-bits of attenuator control are provided for each polarisation ● Soldered in place Y-attenuator LO 5V-LO RF X 5V-RF Taipan 5V-LNA RF out (to final RF Y amplifier and ADC) Cal X-attenuator

MWA Taipan Module ● Prototype version ● Two low cost shields ($1) for first and second stage amplification ● Razorback contains final amp and balun

Taipan Signal Levels ADC Full Scale +1dBm ● RFSOC ADC performance ○ SNR is -150dBFS/Hz or 32dB -150+90 = -60dBFS/300MHz Average ADC SNR 60dB 17dB RFI ○ SFDR is 85dB ○ https://www.xilinx.com/support/docu ADC IM3 78dB ADC SFDR 85dB Sky noise Slope ADC IM2 85dB mentation/data_sheets/ds926-zynq- (300MHz BW) Sky 1MHz ultrascale-plus-rfsoc.pdf RFI IM2 spurious -50dBc RFI IM3 spurious -89dBc ● ADC similar to RF 25dB 32dB spurious Cal Signal ○ IM2 just as important as IM3 Sky (1MHz BW) ADC Noise ● Attenuator set to 17dB so ADC input level for 13dB 300MHz Sky is -33dBm ADC Spurious ○ Can still adjust up and down RFI Spurious further with attenuator depending on RFI

RFI measurements ● North of Sydney (Wamberal) ● Near Australia Telescope (Yarrie Lake) ● Greatest concern (in band) is FM radio ○ Seems to be everywhere - even the MWA site has FM at times Spatial filtering experiment with the Murchison Widefield Array - G.Hellbourg & I. Morrison, URSI GASS 2020

Razorback RFSOC Firmware ● “Standard” Bluering firmware and software ● Can be customised for any application Test Test Signals Packets Coarse Quantise, 2GS 10/100 16-RF Filter Select & Beamformer ADC GbE bank Packetise 1pps /BAT ADC ADC FB Sync Capture Capture 128MHz To ADC Spectrum SysMon PLL Statistics Maxhold monitoring Irukandji Attenuators Processor IO 1GbE & AXI IF

Bluering RFSOC Synchronisation High ECUO Calibration Isolation Firefly Taipan Resistive Rx RF RF Splitter Receivers LMX2594 125MHz 875 SC4PS-33+ RF MHz RF Splitter Synthesizer ECUO LMK04610 125MHz 125MHz Firefly Clock Jitter Rx Cleaner 125MHz LMK00304 LMX2594 ZU29DR 2GHz Differential RF ADC Clock 125MHz Synthesizer Clocks Buffer CVHD-950 Ultra-Low LMK00304 ZU29DR Sync Phase Noise Differential SysRef Pulse Oscillator Clock & Logic ECUO Sync 1pps Buffer ZU29DR Firefly Manchester Pulse Decode Rx Encoded

Filterbank Compute ● 2560 point filterbank, oversampled by 32/27, with 16x2560 FIR taps ○ Using sample clock 2000MHz results in 721kHz channels ○ Can be modified to suit your application ● Filterbank FPGA resources ○ LUTs : 122911 (29%) ○ DSPs : 2112 (49%) ○ 36K BRAMs : 568 (53%) ● Filterbank use about ~40W ○ Measure slightly less (data dependent)

Liquid Cooling ● EMI shielding combined with liquid cooling ● Encouraging results so far - no leaks - good performance

EMI Shielding ● A critical aspect of Bluering is EMI shielding as its only ~1m from an antenna. ● This box achieves >90dB shielding effectiveness in the single shielded side and >150dB in the double ○ Gets very hard to measure ● 48V power is filtered many times

First RFSOC ADC samples ● The RFSOC has an endless number of configurations - so getting the first ADC samples out is a particularly pleasing moment in time! ● Here an unfiltered 200MHz signal (that is locked to the 125MHz reference clock) is input into the ADC ● The location of the noise is ~right ○ RF in is -20dB and ADC SNR is 60dB, so 80dB about 40dB above noise floor ○ But processing gain reduce level of noise by 10log10(16384) = 42dB ○ So peak to noise floor is 40+42=~82dB ○ Measure 155-75=80dB so levels close to right for a first measurement

Upgrades being made now ● As with all prototypes there a few bugs! ○ Wrong values, wrong side, or just missing ● Major upgrades for the optics ○ Originally MBO + QSFP + SFP cages ○ Moving to quad QSFP - similar to Jimble (another CSIRO RFSOC receiver) ○ Enables more data output options ○ QSFP’s are lower cost than MBO now - as it's more of a COTS product ● RF connector ○ Moving away from ganged RF connector to SMA ○ Using a surface mount connector to improve RF over wider frequency range ● Taipan module ○ Originally soldered in and potentially difficult to replace ○ Now moving to MMBX solution to enable easy replacement/upgrades ● Second version available for Christmas

Prototyping Continues Many thanks to Wan, Keith and David

What are we planning at CSIRO? ● After completing the second revision of boards we intend to do installation at the Australia Telescope ● We have two MWA tiles (each MWA tile requires one Razorback) to install ● Hoping to use power and fibre connections available at positions along the array arms

Summary & Conclusions ● Only a small team of people work on Bluering - but it has come a long way ● Steady progress on RF side - greatest concern is FM radio ● RFSOC software and firmware has come along way ● First ADC results are very promising ● We still have a lot to do! ● Really looking forward to demonstrating all aspects of Bluering at the Australia Telescope https://i-love-png.com/images/octopus-tentacles-png-photos.png