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Adaptive Filters Revisited - RFI Mitigation in Pulsar Observations
Michael Kesteven (ATNF)
George Hobbs (ATNF)
Ryan Clement

Pulsar detection and timing experiments are applications where adaptive filters seem eminently suitable tools for RFI mitigation. We describe a novel variant which has worked well in field trials - with observations at 700 MHz, 64 MHz bandwidth, 2-bit sampling. Adaptive filters have generally received bad press for RFI mitigation in radioastronomical observations; the most serious drawback is the spectral echo of the RFI which is locked into the filtered signal. Pulsar observations are intrinsically less sensitive to this as they operate in the (pulsar period) time domain. The field trials have allowed us to identify issues which could limit the effectiveness of the adaptive filter.