Radio Interferometric Imaging Under Satellite-induced ADC Saturation via Modulo Sampling

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Abstract
Radio interferometric imaging is sensitive to front-end dynamic-range limitations as it relies on antenna visibilities formed from digitized samples. Under strong satellite interference, conventional finite-dynamic-range analog-to-digital converters (ADCs) used for digitization can saturate, introducing nonlinear distortion in the samples. The resulting bias in visibilities undermines interference cancellation, leading to severe imaging artefacts. To address these limitations, we develop a modulo-sampling-enabled interferometric imaging framework. Unlike conventional ADC, modulo sampling is a new data acquisition scheme that folds out-of-range signals into the dynamic range. Within this framework, imaging is carried out either through a reconstruction-based approach, which first reconstructs antenna-level observations from the modulo samples and then applies an ambiguity-correction step, or through a direct-imaging alternative that bypasses reconstruction and operates on differenced modulo samples. Interference is suppressed via visibility-domain eigen-subspace projection, and a temporal smoothing step compensates for projection-induced bias by exploiting the rapid variability of satellite interference. Simulations on synthetic and real Very Large Array data demonstrate that, in contrast to conventional sampling, which is severely affected by interference-induced saturation, the proposed modulo-enabled framework effectively avoids saturation-related imaging artefacts and enables reliable recovery of weak astronomical sources approaching the ideal imaging benchmark.