RFI mitigation at WSRT: algorithms, test observations, system implementation
W. Baan (ASTRON)
P. Fridman (ASTRON) fridman@astron.nl
R. Millenaar (ASTRON)

An RFI mitigation subsystem (RFIMS) based on real-time digital signal processing is proposed here for the Westerbork Synthesis Radio Telescope (WSRT). RFIMS is based on a powerful field programmable gate array (FPGA) processor Altera Stratix S80. In this system the radio astronomy signals polluted by RFI are "cleaned" with the RFIMS before the routine backend correlation processing takes place. The high temporal and frequency resolution of the RFIMS allows the detection and excision of RFI better than do standard radio telescope backend configurations.

For WSRT the minimum number of channels is 28 with 14 antennas and 2 polarizations. In the first instance, just one of the eight 20 MHz-bandwidth frequency channels will be processed before correlation. The full system consists of 28 separate processing channels (ADC -> FPGA -> DAC). The structure of RFIMS, the used RFI mitigation algorithms and some results of radio astronomy observations made with RFIMS are given. Eventually the system could be expanded up to 224 channels up to cover eight 20 MHz frequency bands from each antenna.