  Radio Frequency Interference (RFI) of impulsive nature is created by sources
like sparking on high-power transmission lines due to gap or corona discharge
and automobile sparking, and it affects the entire observing frequency bands of
low-frequency radio telescopes. Such RFI is a significant problem at the
Upgraded Giant Metrewave Radio Telescope (uGMRT). A real-time RFI filtering
scheme has been developed and implemented to mitigate the effect on
astronomical observations. The scheme works in real-time on pre-correlation
data from each antenna and allows the detection of RFI based on median absolute
deviation statistics. The samples are identified as RFI based on user-defined
thresholds and are replaced by digital noise, a constant or zeros. We review
the testing and implementation of this system at the uGMRT. We illustrate the
effectiveness of the filtering for continuum, spectral line and time-domain
data. The real-time filter is released for regular observations in the bands
falling in 250 - 1450 MHz, and recent observing cycles show growing usage.
Further, we explain the relevance of the released system to the Square
Kilometer Array (SKA) receiver chain and possible ways of implementation to
meet the computational requirements.
