Discrete Fourier Transform and Minimum Variance Distortionless Response Beamforming Algorithms for Searching for Transients in Radio Interferometers that Experience Radio-frequency Interference

Searching for transient wireless signals like fast radio bursts (FRBs) in radio interferometer data can be accomplished with beamforming algorithms. Radio-frequency interference (RFI) can significantly hamper the search since it causes a loss of bandwidth that can reach 40% for a telescope like the Canadian Hydrogen Intensity Mapping Experiment. In this work, we propose a new beamforming algorithm that combines the discrete Fourier transform and the high-resolution adaptive minimum variance distortionless response beamformers for RFI-free and RFI-inflicted channels, respectively. Our method operates on the baseband data after the transient has been detected. We deploy the beamformer first to produce cleaner dynamic spectra of the FRBs, and second to localize them spatially under high-power RFI. Our simulation results show that even when a fraction of 20% of the channels are contaminated with RFI, we have an increase in localization accuracy, especially in the low signal-to-noise ratio regime.