1. SKAMP Square Kilometre Array Molonglo Prototype
Duncan Campbell-Wilson, School of Physics
Molonglo Radio Observatory, Bungendore, NSW, Australia

2. Cylindrical Antenna 18,0000 m2

3. SKAMP Development Strategy
SKAMP1: Gain experience with FPGA technology, but use existing MOST analogue infrastructure. SPARTAN 2-3 Xilinix FPGAs used for signal processing and complex correlation.
SKAMP 2: Take the lessons learnt from SKAMP 1 to develop a multi-channel correlator system with spectral line and continuum capability. Based on Virtex 4 technology.
SKAMP 3: New feed design with full polarisation and integrated low cost LNAs. Some exploratory work already complete.

4. SKAMP 3 Development Goals ‏
Design a new cost-effective broadband feed system to replace the current mechanically driven beam-steering system.
Frequency agile and compatible with the detector system built for SKAMP 2.
Change the front end receivers to accept bandwidth of 94 MHz within the range MHz

5. SNR1987A

6. SKAMP 2 Design Goals Compatibility with MOST and SKAMP 1.
Major change to digital signal transport on optical fibres and digital signal processing using FPGAs.
368 individual antenna systems: 352 for astronomy and 16 for RFI mitigation and testing

7. Variable Cosmic Radio Sources

8. SKAMP 2-3 Signal Pathway Antenna to Low Noise Amplifier (LNA)‏
LNA to receiver
Receiver fixed 30 MHz BW at 843 MHz; down-converted to baseband (SKAMP 2)
Receiver frequency agile with 100 MHz BW; down-converted to baseband in IQ format (SKAMP 3)
Digitised to 8 bits
Serialised in the Lattice FPGA
Sent on 850 nm optical fibre to the control room for digital signal processing

9. Polyphase Signal Pathway
Optical to electrical conversion
Delay
First level (coarse) FFT performed in the first stage (PFB A)
Second level (fine) FFT produces ~14 kHz frequency channels (PFB B)
Signals aligned to stop the fringes and adjust signal amplitude
Data re-ordered and serialised for transfer to the correlator
Some sections working but full integration is incomplete

10. PFB Output Spectrum (RFI antenna)

11. Correlator 24 boards, each handling approx 4 MHz of bandwidth
48 independent outputs, feeding into a switch
Two computers handle the data reduction, under control of a third computer
Readout every 32 seconds for normal observations

12. SKAMP II correlator board

13. Loaded PFB and Correlator Racks

14. Status: Polyphase Filter and Correlator
All prototype boards completed and tested
26/27 production correlator boards delivered January 2011
27 Correlator Rear Transition Modules (CRTM) and Optical Rear Transition Modules (ORTM) delivered. Front panel fit-off complete
27 production PFB boards complete January 2011.

15. Correlator Status Close to full operation
Long term accumulator is outstanding but underway
System verification is incomplete
Input and output interfaces passing correct test data
About 2 months left to complete the firmware

16. Receiver specifications
Design capable of accepting MHz, with output bandwidth MHz
Analogue input, with digital output in IQ format; fibre optic transmission
Environmental monitoring; local gain and offset control

17. Down-converter Attributes
Wideband input MHz
Gain compensation vs temperature
I/Q outputs
Four receivers per down-converter board
One local oscillator (low phase-noise margin)

18. RX Digitiser Board

19. RX Diagnostics Diagnostic features included as part of the design
Diagnostics along the signal path to allow remote fault-finding
Diagnostic functions kept independent of each other

20. RX System Diagnostics Two Tone test Checker Board test Half Scale
Pseudo random binary sequence
Power supply voltage monitoring
Down-converter temperature monitoring
Digitiser temperature monitoring

21. RX Remote Control
Programmable down-converter; pseudo-logarithmic gain control
Linearly programmable ADC offset control
Linearly programmable ADC voltage reference
System under test for reliability and debugging

22. RX Development Status
Slow firmware development; correlator firmware has priority
Down-converter boards production-ready; assembly underway
Digital RX FPGA boards not yet production-ready
FPGA placement reliability; need for rework

23. RX Diagnostic Spectrum

24. PFB and Correlator Firmware
PFB firmware – still to do: time delay, fringe stopping, amplitude adjustment
Limited testing
Correlator firmware in good shape; long term accumulator incomplete

25. Software Status Data processing pipeline has been tested
Diagnostic software under development
SKAMP2 system control still to be extended from single board to full system
Telescope control computer interface complete
Calibration: no significant work

26. Astronomical Calibration
Selection parameters for calibrators: flux density, spectral index, angular size, variability and declination
Molonglo Southern 4 Jy survey (MS4; Burgess & Hunstead 2006, Table 5) is an excellent starting point for SKAMP2 calibration.

27. Displaying Visibilities

28. System Calibration Temperature dependent gain calibration
Delay calibration
Frequency dependent gain and phase
Fine channel calibration