John Hogden, Scott Vander Wiel, Geoffrey C. Bower, Sarah Michalak, Andrew Siemion, Daniel Werthimer
Impulsive radio-frequency signals from astronomical sources are dispersed by
the frequency dependent index of refraction of the interstellar media and so
appear as chirped signals when they reach earth. Searches for dispersed
impulses have been limited by false detections due to radio frequency
interference (RFI) and, in some cases, artifacts of the instrumentation. Many
authors have discussed techniques to excise or mitigate RFI in searches for
fast transients, but comparisons between different approaches are lacking. This
work develops RFI mitigation techniques for use in searches for dispersed
pulses, employing data recorded in a "Fly's Eye" mode of the Allen Telescope
Array as a test case. We gauge the performance of several RFI mitigation
techniques by adding dispersed signals to data containing RFI and comparing
false alarm rates at the observed signal-to-noise ratios of the added signals.
We find that Huber filtering is most effective at removing broadband
interferers, while frequency centering is most effective at removing narrow
frequency interferers. Neither of these methods is effective over a broad range
of interferers. A method that combines Huber filtering and adaptive
interference cancellation provides the lowest number of false positives over
the interferers considered here. The methods developed here have application to
other searches for dispersed pulses in incoherent spectra, especially those
involving multiple beam systems.
View original:
http://arxiv.org/abs/1201.1525
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