Detection and excision of radio-frequency interference in radio arrays

@misc{ravi2026detection,
  title = {{Detection and excision of radio-frequency interference in radio arrays}},
  author = {Vikram Ravi},
  howpublished = {arXiv},
  year = {2026},
  month = nov,
  doi = {10.48550/arxiv.2611.01308},
  eprint = {2611.01308},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2611.01308},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Detection and excision of radio-frequency interference in radio arrays
AU  - Vikram Ravi
PY  - 2026
DA  - 2026/11/01
PB  - arXiv
DO  - 10.48550/arxiv.2611.01308
UR  - https://arxiv.org/abs/2611.01308
AB  - The detection and excision of radio-frequency interference (RFI) is usually approached by asking how best to identify RFI within a given data product. I address a prior question: which data product is a given RFI emitter is most detectable in? I develop a model for the suppression of RFI in visibilities and tied-array beams by the antenna primary beam, near-field wavefront curvature, bandwidth smearing, and fringe tracking. The comparison between antenna-based and array-based detection reduces to a single quantity related to the mean per-baseline RFI coherence. Cross-correlation detection is preferred only above a coherence threshold of (N−1)^−1/2, where N is the number of antennas. I evaluate this model for four array configurations (the Very Large Array A and D configurations, and the fixed MeerKAT and Deep Synoptic Array / DSA configurations) and five representative RFI emitters spanning distances of 5\,km to medium-Earth orbit. Compact, filled, arrays favor the cross-correlations for stationary terrestrial emitters, whereas extended sparse arrays do not. RFI emitters with significant motion relative to radio arrays, in particular aircraft and low- and medium-Earth-orbit satellites, favor the sum of antenna autocorrelations everywhere by one to seven orders of magnitude, because their coherence is destroyed by rapid fringe rotation. For RFI below the single-antenna noise, no phase-unknown cross-correlation statistic is more sensitive than the autocorrelation sum. Tied-array beams are the least sensitive data product of all: the array factor supplies no suppression of terrestrial RFI, so a beam sees an emitter as a single antenna does. I describe a real-time, GPU-based implementation of autocorrelation-based excision for the 110-antenna Deep Synoptic Array, and outline the design implications for upcoming arrays.
ER  -