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Post-Correlation Interference Mitigation Techniques for Radio Astronomy

This paper discusses post-correlation interference mitigation methods utilized in radio astronomy, focusing on their application to both single dish and synthesis array observations. The authors, Kesteven and Sault, present an innovative filter that performs comparably to adaptive filters, yet requires only one reference antenna and can be implemented with existing hardware. They outline the system's capabilities, such as tolerance to sampling bit limits and significant delays, while comparing its performance against traditional techniques. Insights on GLONASS excision further enhance its practical utility in mitigating radio frequency interference.

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Post-Correlation Interference Mitigation Techniques for Radio Astronomy

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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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