Radio Frequency Interference Mitigation In FRB Detection

As a kind of astrophysical explosion phenomenon with huge energy release,fast radio burst is an important research direction in astrophysics.Since the discovery of the first case of fast radio burst,many radio telescopes at home and abroad have observed fast radio burst in the frequency range of 400MHz-800 GHz.The duration of the burst is very short,generally in the order of milliseconds.In the early observation,because of its extremely high dispersion,the dispersion is 10-20 times more than that in the Milky way,so it is supposed to come from extragalactic galaxies.With the rapid development of astronomical radio telescopes,the performance of radio telescopes has been greatly improved,and some progress has been made in the research of fast radio burst.As of July2020,118 cases of fast radio bursts have been detected,but at the same time,the field of radio business is also expanding,which makes the astronomical radio telescopes inevitable to be detected Non astronomical pollution leads to the decrease of the quality of the observation data,and is limited by the storage space of the observation equipment and the occasional and aperiodic fast radio burst.Therefore,the interference signal in the detection of fast radio burst is eliminated,so that the number of samples can be improved and the detailed information can be obtained for more related research.In this paper,according to the characteristics of fast radio burst,based on Nanshan26 m radio telescope,after analyzing different RFI mitigation strategies,two interference mitigation methods are proposed.Firstly,an interference cancellation method based on adaptive filtering is proposed.By adding a low gain reference antenna,astronomical signal extraction in complex noise environment can be realized.It adopts adaptive transverse filter and least mean square error algorithm by changing the step size and order to optimize the filtering effect The evaluation criteria are systematic error and convergence performance.The simulation results show that the filter can effectively extract the signal while ensuring the convergence of the algorithm.In order to test the effectiveness of the algorithm,the observation data recorded by Nanshan 26 m radio telescope and Parkes 64 m radio telescope are selected,and the designed filter is used to test different measured data to verify the effectiveness of the filter.The agreement between theoretical analysis and experimental results shows that this method can effectively eliminate the interference signals in astronomical observation and has certain practicability.Secondly,the signal smoothing method of curve fitting,namely S-G filter,is realized.By adjusting the parameters,the signal-to-noise ratio is improved to a certain extent.