UniBoard kick-off meeting, Dwingeloo, 26-27 March 2009 08/09/2018 RFI Mitigation for Pulsar observations R.Weber, University of Orléans D. Ait-Allal, Nançay Observatory G. Kenfack, Nançay Observatory C. Dumez-Viou, Nançay Observatory UniBoard kick-off meeting, Dwingeloo, 26-27 March 2009

Why RFI mitigation By courtesy of I.cognard and G.theureau UniBoard kick-off meeting, Dwingeloo, 26-27 March 2009

RFI Mitigation for Pulsars If coherent de-dispersion |.|2 RFI mitigation 1 RFI mitigation 2 FFT RFI mitigation 3 dedispersion FFT-1 Polyphase filter bank RFI mitigation 1 RFI mitigation 2 RFI mitigation 3 f Control, synchro RFI detector algorithm decision Shift-register Blanking Or flagging N Replacement values (TBD) RFI mitigation 1,2,3 t Blanked t-f slots UniBoard kick-off meeting, Dwingeloo, 26-27 March 2009

Cyclostationary RFI Detectors 08/09/2018 Cyclostationary RFI Detectors  If the cyclic frequency, , is known N=256  If the cyclic frequency, , is not known UniBoard kick-off meeting, Dwingeloo, 26-27 March 2009

RFI Mitigation for Pulsars K channels M channels RDSP Control, synchro Sample clock (If no overlap) Fs Fs/K >Fs/KM Fs/K Number of channels: 1 K >KM DSP ressources x clock (if no overlap) : RDSP RDSP RDSP Memory: N KN KNM N=256, K=1024, M=8192 (complex samples : 2x16bits) 256s 256 Ks 2Gs UniBoard kick-off meeting, Dwingeloo, 26-27 March 2009

Nançay implementations(1) Bande Max = 14 MHz cyclodet En cours R.Weber, C.Viou, A.Coffre, L.Denis, P. Zarka and A.Lecacheux, “DSP Enabled Radio Astronomy: Towards IIIzw35 Reconquest”, Journal of Applied Signal Processing, 16, 2005 , pp. 2686-2693 UniBoard kick-off meeting, Dwingeloo, 26-27 March 2009

implementations : power detectors UniBoard kick-off meeting, Dwingeloo, 26-27 March 2009

implementation : cyclic detector N=2048, K=2048 Operates for INR > -3dB Requires: Memory for transpose One extra FFT Plus a few multipliers UniBoard kick-off meeting, Dwingeloo, 26-27 March 2009