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AA signal processing

AA signal processing

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AA signal processing

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  1. AA signal processing Andrew Faulkner

  2. Discussion Signal processing is at the heart of SKA Aperture Arrays • Ingredients: • Distribution • The core • Digitisation • Communications • Data rates • Beam precision • Noise insertion? • UNIBOARDx • CASPER • AAVSx processing • Scaleability • RF over fibre • Algorithm development • Programming tools

  3. An AA-low station layout

  4. “Advanced”AA-low Station Cooling Stand-alone Elements Self powered element Fibre Station Processing RFI shielded Station Beams Control & Monitoring ...... Element Data ….... ...... C & M Clock ...... System clock Single or multiple fibres To Correlator & Services Power Grid

  5. Core Design Core for SKA1AA-low becomes virtually fully filled. More so for SKA2. Core “stations” are not separated – there is a “sea” of elements Design options/considerations to be made: Implies interconnected “station processing”, especially for SKA2 • Non-circular “stations” easier? e.g. Square or hexagonal? • Maximising the sensitivity from each element: • overlapping “stations”? • smaller “stations” (how small) with more correlation? • Apodising element density within areas of the core: • Benefit? Save money? Correlation goes up as n2, post processing nx … Incoming data rate is constant

  6. AA-low signal path

  7. Where to digitise?

  8. Standalone SKA-low element(option) Elements: 70-450MHz Solar panel ADC: 1GS/s Processing 50-100m all optical e/o Data e/o Control Power conditioning Analogue Energy storage Sync. e/o Benefits: Integrated single unit No copper connection Easy to deploy Minimum RFI Lightning “immunity” Challenges: Low total power Integration Manufacturability Packaging No need for digitisation boxes

  9. AA-low element: RF on Fibre Elements: 70-450MHz e/o Data Pol1 e/o Power conditioning Data Pol 2 Analogue Still no need for digitisation boxes! Power over copper

  10. Beamforming Processing 1st stage beamformer size: No. of elements to combine 1st stage o/p data rate: precision of station beams Digitisation resolution: From RFI environment Technology: AAVSx →SKA1→SKA2 Level of programmability: How much is “fixed” RFI excision: Algorithms and where Flexibility: Bandwidth/beams/bits etc. Inter-station comms: Variable station “sizes”, core Is Analogue beamforming a sensible consideration?

  11. AA-mid Array

  12. 1st stage Beamforming: AA-mid

  13. AA-mid signal path Front-end Tile Processing Station Processing ADC – Processor comms Analog Cond. ADC Antenna Tile Digital Processing Primary Station Processing Secondary Station Processing RF Beamforming To Correlator Gain Block LNA Signal Transport Clock Distribution Tile – station processor optical comms optical interconnect Wide area optical comms

  14. Possible AA-mid construction ...... ...... ...... ...... Top View ...... ...... Non-conducting Guideframe Membrane Guideframe Beamformer Beamformer Ground plane The join! Tile support Ground

  15. Station processing Similar for AA-low and AA-mid: • Station level beamforming on all the tiles • Distributes the clock information for all the tiles • Station calibration calculations and corrections (using the tile processors) • Transmits observation beams to the correlator • Station monitoring and control functions

  16. Station processor Requirements: • High bandwidth in • High bandwidth out • Largely cross connected • Scaleable at various levels • Programmable beamforming

  17. Communications

  18. Two stage beamforming Filling “Tile beams” with station beams leads to discontinuities in the beamforming for off-centre beams Can be resolved with higher data rate Tile to station processor

  19. AA Demonstrators Simple processing UNIBOARD? UNIBOARD2?

  20. Discussion Signal processing is at the heart of SKA Aperture Arrays • Ingredients: • Distribution • The core • Digitisation • Communications • Data rates • Beam precision • Noise insertion? • UNIBOARDx • CASPER • AAVSx processing • Scaleability • RF over fibre • Algorithm development • Programming tools