Australian Astronomy MNRF Development of Monolithic Microwave Integrated Circuits (MMIC) ATCA Broadband Backend (CABB)

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 2006.

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 Filterbank32k taps per filter

Clocked in at 4GHzDFB clocked at 2MHz

(M=2048)

• Field Programmable Gate Arrays (FPGA)Commercial devices

Endlessly configurable

FFT

FFT

FIR

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 - 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