Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.atnf.csiro.au/whats_on/workshops/mm_science2001/talks/Wilson.pdf Дата изменения: Tue Apr 23 11:34:14 2002 Дата индексирования: Wed Dec 26 09:06:36 2007 Кодировка: Поисковые слова: освещенность

ATCA Broadband Backend
Warwick Wilson CSIRO Australia Telescope National Facility


ATCA BROADBAND BACKEND
AIM: To increase the maximum instantaneous bandwidth of the ATCA from 128MHz to 2GHz. GAINS: · Enhanced frequency coverage - up by factor 16 · Continuum sensitivity up by at least a factor of 4 · Increased flexibility - simultaneous spectral lines


COMPARISON: At = 3mm
CURRENT Max. velocity coverage: 300 Km/s 4800 Km/s NEW

Velocity resolution at max. bandwidth: 6.4 Km/s ( 60 chans ) 1.5 Km/s ( 4000 chans )


INITIAL DESIGN PARAMETERS
· · · · · · · · 2 frequencies, each with 2 polarisations 2 GHz maximum bandwidth Full range of lower bandwidths 4096 channels on all 4 Stokes parameters 8 stations 4 GSample/sec 4 -bit samplers FX correlator architecture Digital Filter Banks Total component costs: $A3.1M


MNRF2001
ATNF Component : · Total capital : $A11.8M
­ SKA Prototype development ­ SKA Technology development

· 5 year project lifetime
­ Completion 2005/6


SYSTEM COMPONENTS · · · · · · · Conversion system - LO/IF Samplers Data transmission Delay system Correlator Tied array Online software


SYSTEM COMPONENTS · Conversion system - LO/IF ­ Single 2GHz analogue anti-aliasing filter ­ Interference supression filters where necessary


SYSTEM COMPONENTS · Samplers ­ Fixed 4GS/s sample rate ­ Number of bits - 6 or 8 ??? ­ Increased dynamic range ­ Correlator efficiency ~100% ­ Photonic sampling techniques ???


SYSTEM COMPONENTS · Data transmission ­ ~128GBits/s from each antenna ­ New single mode fibre installed · Correlator ­ Look forward to SKA ­ FX architecture


FX CORRELATOR
· Use filter bank to produce a spectrum of each IF signal. · Cross Multiply corresponding frequency channels from all antennas/ polarisations .


CORRELATOR ARCHITECTURE
· Polyphase Filterbank ­ 64k taps per filter ­ Clocked at 4GHz ­ FFT Clocked at 0.5MHz · COTS FPGAs ­ Endlessly reconfigurable
DMUX

x0(m) x1(m) xn x?(m) xM-1 (m)

po(m) p1(m)

0 1

X0(m) X1(m)

p?(m)

M-Point DFT ? via FFT
M-1

Xk (m) XM-1(m)

pM-1(m)

FIR

FFT

FIR

FFT

Filterbank

Fringe Rotators

Correlators


ZOOM
· Standard · Zoom · n*Zoom · n*Zoom^m
32kchannels 4k channels 2GHz 4k channels

4k channels 4k channels

4k channels