Australian Astronomy MNRF

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Australian Astronomy MNRF

• Development of Monolithic Microwave Integrated
  Circuits (MMIC)
• ATCA Broadband Backend (CABB)

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MMIC DEVELOPMENT
AIM Develop existing ATNF expertise in MMIC
design. Important area for the SKA. Develop MMICs
for use in SKA demonstrators and for new ATNF
receiver systems. TECHNOLOGIES InP, GaAS, SiGe,
RF-CMOS.
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Examples

• Broadband LNAs, e.g. 1-3GHz, 4-12GHz.
• mm-wave LNAs.
• Devices for digital and analogue data
  transmission.
• High speed, high precision samplers/digitisers.
• Integrated receiver systems.

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ATCA BROADBAND BACKEND

• AIM
• To investigate new signal processing
  technologies for the SKA.
• To demonstrate them in a new backend for the
  ATCA
• Increase the maximum bandwidth from 128MHz to
  2GHz.
• Operational in late 2006.
• GAINS
• Enhanced frequency coverage - up by factor 16
• Continuum sensitivity up by at least a factor of
  4
• Increased flexibility - simultaneous spectral
  lines

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COMPARISON At l 3mm
CURRENT FUTURE
Max. velocity coverage 300 Km/s 5000 Km/s
Velocity resolution at max. bandwidth 6.4
Km/s 3 Km/s ( 60 chans ) ( 2000 chans )
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DESIGN PARAMETERS

• 2 frequencies, each with 2 polarisations
• 2 GHz maximum bandwidth
• Full range of lower bandwidths
• 2048 channels on all 4 Stokes parameters
• 8 stations ATCA SKA Demonstrators
• 4 GSample/sec, 6-bit (min.) sampler/digitisers
• FX correlator architecture
• Digital Filter Banks

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SYSTEM COMPONENTS

• Data transmission
• Conversion system
• Sampler/digitisers
• Delay system
• Filter bank / correlator
• Tied array
• Online software

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SYSTEM COMPONENTS (1)

• Data transmission
• New single mode fibre installed.
• Analogue or Digital ?
• Analogue
• 4 to 12GHz band transmitted.
• Digital
• 128GBits/s from each antenna

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SYSTEM COMPONENTS (1)

• Analogue data transmission
• Advantages
• Move all digital electronics away from antennas
• reduced self-generated RFI
• Simplifies antenna electronics
• Cheaper
• Difficulties
• Maintaining dynamic range

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SYSTEM COMPONENTS (2)

• Sampler/digitisers
• Fixed 4GS/s sample rate
• Effective number of bits gt6
• Increased dynamic range
• Correlator efficiency 100

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SYSTEM COMPONENTS (3)

• Conversion system - LO/IF
• Single 2GHz analogue
• anti-aliasing filter
• Interference suppression filters
• where necessary
• Fixed LOs, Sampler Clocks

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SYSTEM COMPONENTS (4)

• Correlator
• Look forward to SKA
• FX architecture
• Using polyphase digital filterbanks

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CORRELATOR ARCHITECTURE

• Polyphase Filterbank
• 32k taps per filter
• Clocked in at 4GHz
• DFB clocked at 2MHz (M2048)
• Field Programmable Gate Arrays (FPGA)
• Commercial devices
• Endlessly configurable

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MODES

• Standard

• Zoom

• nZoom

• nZoomm

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DFB Development

• Development of demonstrator polyphase filterbank
  spectrometers
• Current best performance
• 256MHz BW - 1024 frequency channels
• Using ATNF 4GS/s, 2-bit samplers
• AND
• Lower sample rate 8-bit samplers
• Installed at Mopra in May 2004

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Conventional Channelisation
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Filterbank Channelisation
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CORRELATOR TYPES

• XF
• For each baseline ( N2 )
• Form cross correlation function
• Fourier transform to form spectrum
• FX
• For each signal ( N )
• Form spectrum
• For each baseline ( N2 )
• Multiply corresponding frequencies