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.

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. Examples

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 GAINS: Enhanced frequency coverage - up by factor 16 Continuum sensitivity up by at least a factor of 4 Increased flexibility - simultaneous spectral lines ATCA BROADBAND BACKEND

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

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 DESIGN PARAMETERS

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

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 (1)

Sampler/digitisers – Fixed 4GS/s sample rate – Effective number of bits >6 – Increased dynamic range – Correlator efficiency ~100% SYSTEM COMPONENTS (2)

Conversion system - LO/IF – Single 2GHz analogue anti-aliasing filter – Interference suppression filters where necessary – Fixed LOs, Sampler Clocks SYSTEM COMPONENTS (3)

SYSTEM COMPONENTS (4) Correlator – Look forward to SKA – FX architecture – Using polyphase digital filterbanks

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 FFT FIR Filterbank Fringe Rotators Correlators DMUX CORRELATOR ARCHITECTURE

Standard Zoom n*Zoom n*Zoom^m MODES

DFB Development Development of demonstrator polyphase filterbank spectrometers Current best performance: –256MHz BW 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 ( ~N 2 ) : Form cross correlation function Fourier transform to form spectrum FX –For each signal ( ~N ) : Form spectrum –For each baseline ( ~N 2 ) : Multiply corresponding frequencies