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RFI Mitigation at Westerbork: algorithms, test observations, system implementation

RFI Mitigation at Westerbork: algorithms, test observations, system implementation. Willem Baan, Peter Fridman & Rob Millenaar. Implementing Mitigation Hardware in the WSRT system 3 locations in data flow of system different algorithms at different stages stapling of methods

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RFI Mitigation at Westerbork: algorithms, test observations, system implementation

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  1. RFI Mitigation at Westerbork:algorithms, test observations, system implementation Willem Baan, Peter Fridman & Rob Millenaar

  2. Implementing Mitigation Hardware in the WSRT system 3 locations in data flow of system different algorithms at different stages stapling of methods AI decision-making subsystem for control

  3. Our first DSP system

  4. WSRT RFIMS • Main goal RFIMS is to recover (full) sensitivity of WSRT across all observing bands with hostile RFI environment • Three year implementation plan • System scalability and upgradeability • RFIMS pre-processing 14 x 2 x 20 MHz FPGA hardware • Possible implementation of 10msec sampling at WSRT correlator for on-line processing • Envisioned implementation on other telescopes

  5. WSRT RFI Mitigation System Real-time pre-detection and pre-correlation baseband processing a) 12bit ADC b) Altera Stratix FPGA c) 14bit DAC d) VME control e) 40Msamples/sec 14 RTs & 2pol & 20 MHz

  6. RFIMS

  7. Processor Board Layout

  8. A fancy processor

  9. RFI time-frequency domains

  10. Thresholding in Time Domain

  11. Thresholding in Frequency Domain Reference power spectrum Median Filtering of spectrum

  12. Adaptive Filtering with WSRT

  13. Adaptive Filtering - Proposed 2004

  14. Adaptive Filtering - Ultimate

  15. Dual Channel FPGA Layout

  16. FPGA layout with Reference antennas

  17. T-f thresholding First trial of 14 RT system 20 MHz 5X band cleaned All other 7 bands at same frequency 10 hr synthesis of DA240

  18. Auto Corr Amp 5X5X b0 & b1 RT 5X, 6X, 7X, 9X

  19. Cross Corr Amp5X6X b0 & b1

  20. Cross Corr Func5X6X b0 & b1

  21. RFIMS 4X & 5X

  22. DA240 field

  23. Short Term Plans • Persuade astronomers to use the system • Use RFIMS with new 14 RT LFFE system in LOFAR band 110- 180 MHz • Implement adjacent RT for reference antenna • Introduce separate Refants • Apply ANC for pulsar operations (PuMa I & II) • Implement HOS for blanking • Evaluate efficiency and impact on the imaging and spectrum data

  24. Conclusions 1. Single dishes and connected radio interferometer 2. Evaluate algortihms for RFI environments 3. Implement in ALL new RTs ( multi-bit ADC (>14)), short averaging intervals, higher order statistics, auxiliary reference channels). 4. Number crunching aspects 5. Dedicated devices ?

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