Digital implementation of a robust radio astronomical spectral analyser: Towards IIIZW35 reconquest

In radio astronomy, the radio spectrum is used to detect weak emission from celestial sources. By spectral averaging, noise estimation is reduced and weak sources can be detected. However, more and more observations are polluted by man-made radio frequency interferences (RFI). The impact of these RFI on spectral measurement ranges from total saturation to tiny distortions of the data. To some extent, the final spectral estimation can be preserved by blanking infected channels in real time. With this aim in view, a complete real time processing line has been implemented on a set of FPGA and DSP. The current functionalities of the system are high dynamic range (at least 70 dB), band selection facilities (from 875 kHz to 14 MHz), high spectral resolution through polyphase filter bank (up to 8192 channels with 49152 coefficients) and real time time-frequency blanking with a robust threshold detector.