Arcetri Astrophysical Observatory

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logosmallarcetri Arcetri Technical Reports 2/2011


Test of a real time cyclostationary RFI detector for radio astronomy

A. Tani(1,2), G.Comoretto(1), P. Curioni(1), A. Melis(3), R. Nesti(1), D. Panella(1)

(1) INAF Osservatorio Astrofisico di Arcetri
(2) Università degli Studi di Firenze
(3) INAF Osservatorio Astronomico di Cagliari

Abstract

Radio frequency Interference (RFI) could seriously degrade the observations in the radio astronomy bands, hence suitable methods to detect and mitigate them have to be implemented in the receiver.

In this report the implementation on a FPGA of an RFI detector for radio astronomy based on the cyclostationarity is described. After a brief overview on the basic principles of RFI detection and cyclostationarity, performance in terms of detection and false alarm probability has been derived using a base-band BPSK as a test signal. Moreover the false alarm probability derived by theoretical analysis has been compared to the experimental results.

Finally an uplink GSM signal has been acquired to further test our detection approach. However, the previous method requires the knowledge of the cyclic frequency to be tested and in the GSM case the cyclic frequency depends on the carrier frequency that is unknown. To overcome this issue a more general method, based on the cyclic autocorrelation function (CAF) estimation, is proposed.  In particular, the CAF estimation of the GSM acquired signal is partially carried out in the FPGA, because the FFT is calculated off-line. The comparison between the GSM CAF estimate and the CAF related to a simulated radio source shows that this approach can be employed as detector also with this kind of interference. In the future we will study the real time implementation on a FPGA and performance evaluation of this approach.

Pdf version of this report