1. 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, March 2009

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

3. 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, March 2009

4. 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, March 2009

5. 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, March 2009

6. 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
UniBoard kick-off meeting, Dwingeloo, March 2009

7. implementations : power detectors
UniBoard kick-off meeting, Dwingeloo, March 2009

8. 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, March 2009