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Post-Correlation Interference Mitigation

Post-Correlation Interference Mitigation. M. Kesteven & R. Sault Australia Telescope National Facility mkesteve@atnf.csiro.au. IUCAF – Bonn, March, 2001. Post-Correlation RFI excision. Overview of the scheme Application 1 - Single Dish Application 2 - Synthesis Array Problems/Limitations

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Post-Correlation Interference Mitigation

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  1. Post-Correlation Interference Mitigation M. Kesteven & R. Sault Australia Telescope National Facility mkesteve@atnf.csiro.au IUCAF – Bonn, March, 2001

  2. Post-Correlation RFI excision • Overview of the scheme • Application 1 - Single Dish • Application 2 - Synthesis Array • Problems/Limitations • Comparison with Adaptive Filters • Parametric Filter - Glonass excision

  3. Features • A Post-Correlation equivalent to an Adaptive Filter • Applicable to Single Dish observations • Applicable to Synthesis Array observations • Performance comparable to the Adaptive Filter • Can be implemented with current hardware

  4. Adaptive Filter (schematic)

  5. Post-Correlation Filter

  6. Single Dish - Autocorrelation Reference antenna Parkes 64m

  7. The Reference Antenna

  8. Post-Correlation - Features • Tolerant to small number of sampler bits • Tolerant to multi-pathing interference • Tolerant to significant delays between the reference and the astronomy antenna • Tolerant to offset between the array tracking centre and the interference location • Only one reference antenna required even for an array filter

  9. Post-Correlation Filter

  10. Before and after spectra

  11. ATCA - 1503 MHz; 4 MHz BW

  12. Before and after images

  13. ARRAY - notes • Require one Reference Antenna + conversion chain • Require Additional Correlator resources. Equivalent to adding one extra antenna to the array. • Enjoys all the flexibility of the observatory correlator • Makes no assumption as to similarity between antennas of the array. Interference may enter via different sidelobes in different antennas. • The corrections are based on the correlator output – therefore works with few-bit samplers.

  14. Glonass Excision

  15. Glonass Excision

  16. Glonass excision

  17. Post-Correlation - Theory The correction spectrum Vc(f) is given by:

  18. Post-Correlation Filter

  19. Synthesis Array Filtering

  20. Synthesis Array Filtering

  21. Cleaned spectrum

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