Australian Astronomy MNRF Development of Monolithic Microwave Integrated
Australian Astronomy MNRF Development of Monolithic Microwave Integrated Circuits (MMIC) ATCA Broadband Backend (CABB) 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. 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. 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 COMPARISON: At = 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 ) 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
SYSTEM COMPONENTS Data transmission Conversion system Sampler/digitisers Delay system Filter bank / correlator Tied array Online software
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 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 SYSTEM COMPONENTS (2)
Sampler/digitisers Fixed 4GS/s sample rate Effective number of bits >6 Increased dynamic range Correlator efficiency ~100% SYSTEM COMPONENTS (3) Conversion system - LO/IF Single 2GHz analogue anti-aliasing filter
Interference suppression filters where necessary Fixed LOs, Sampler Clocks SYSTEM COMPONENTS (4) Correlator Look forward to SKA FX architecture Using polyphase digital filterbanks
CORRELATOR ARCHITECTURE Polyphase Filterbank 32k taps per filter Clocked in at 4GHz DFB clocked at 2MHz (M=2048) Field Programmable Gate Arrays (FPGA)
Commercial devices Endlessly configurable DMU X FIR FF T
FIR FF T Filterban k Fringe Rotator
s Correlator s MODES Standard Zoom n*Zoom
n*Zoom^m 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
Conventional Channelisation Filterbank Channelisation 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
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