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

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

4. Our first DSP system

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

7. 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 & 20 MHz

8. RFIMS

9. Processor Board Layout

10. A fancy processor

11. RFI time-frequency domains

12. Thresholding in Time Domain

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

14. Adaptive Filtering with WSRT

15. 2004 Adaptive Filtering - Proposed

16. Adaptive Filtering - Ultimate

17. Dual Channel FPGA Layout

18. FPGA layout with Reference antennas

19. 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

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

21. Cross Corr Amp 5X6X b0 & b1

22. Cross Corr Func 5X6X b0 & b1

23. RFIMS 4X & 5X

25. DA240 field

27. 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

28. 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 ? Conclusions