Comparison of RFI Mitigation Strategies for Dispersed Pulse Detection

TL;DR

This paper compares various RFI mitigation techniques for detecting dispersed astronomical pulses, finding that combining Huber filtering with adaptive interference cancellation reduces false positives effectively.

Contribution

It develops and evaluates RFI mitigation methods tailored for dispersed pulse searches, highlighting the effectiveness of combined approaches over individual techniques.

Findings

Huber filtering effectively removes broadband RFI.

Frequency centering best mitigates narrowband RFI.

Combining Huber filtering with adaptive cancellation yields fewer false positives.

Abstract

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.