Real-time RFI Mitigation

Status: Mature

Introduction

One of the hardest problem modern radio telescopes face in present days is dealing with radio frequency interference (RFI). RFI is most commonly generated by telecommunication system and equipment and its power is many orders of magnitude higher that the astronomical signals. Some common ways to mitigate RFI in observatories is the implementation of Radio Quiet Zones (RQZ) and the offline software tools to flag and blank data. However, more powerful mitigation techniques exist were the interference can be eliminated in real time, without incurring in the loss of valuable astronomical data.

In this project a real-time adaptive filter is implemented in ROACH2 for RFI mitigation in radio telescopes. The filter requires a reference antenna to take a second measurement of the interference, and then automatically adjust its internal parameters in order to perform an perfect subtraction between the telescope and the reference interference.

Documentation

• Overview of many RFI mitigation techniques:https://www.itu.int/pub/R-REP-RA.2126-1-2013

• First proposal and implementation of frequency domain adaptive filter for RFI mitigation:

  • https://iopscience.iop.org/article/10.1086/316861

  • https://pos.sissa.it/107/023/pdf

• Franco Curotto's (me!) M.Sc. thesis on frequency domain adaptive filter for RFI mitigation in ROACH2: http://www.das.uchile.cl/lab_mwl/publicaciones/Tesis/tesis_franco_curotto.pdf

• Following papers on RFI Mitigation in ROACH2:

  • https://ui.adsabs.harvard.edu/abs/2018PASP..130b5002F/abstract

Code and Models

• RAOCH1 and ROACH2 models, bofs, and scripts: https://github.com/FrancoCalan/simulink_models/tree/master/RFI_Mitigation