2-P olarisations A ll D igital

1. 2-Polarisations All Digital 2-PAD 2-PolarisationsAllDigital Dr Georgina Harris / Prof Tony Brown SKADS System Design and Team Leader, University of Manchester Thanks to the 2-PAD Team: ManchesterChris Shenton, Tim Ikin, Aziz AhmedSaid, Richard Whitaker, Tony Brown, Dan Kettle, Mina Panahi OxfordMike Jones, Kris Zarb Adami, Sasha Shidewy Cambridge Andrew Faulkner AstronJan Geralt bij de Vaate, Raymond van den Brink

2. 2-PAD Aims • To produce a flexible platform upon which to test a variety of subsystems for the Aperture Array for the SKA • Digital beamforming • Prove it can be done • Realistic technology projections for cost/ power • Low self induced RFI • Low cost interconnects are feasible • Dual polarisation measurements • Proof of calibration at tile level

3. 2-PAD System Design Bunker RFI Shield Analogue Conditioning 64 dual channels Ant. polarisation 4 off Beamformer. Processors Processor Total 128 inputs ADC Digital Pre- processor PSU Beamformer Processing Beam combiner Processor +ve Reg } ..... ..... ....... PCB Output Beams Analog Conditioning ....... ADC Digital Pre- processor From other beamformer proc. Analog Interconnect CAT7? PSU LNA 64 elements x2 polarisations Time standard Control Processor Up to ~20m Line Tx/Rx Buffers Control Signal Conditioning Rack Processing Rack Outdoors Bunker

4. Antennas • 2-PAD will use 3 sets of array antennas • Each antenna tile will be 16 x 16 dual polarisation elements • The central 8 x 8 elements will be ‘active’, i.e. the signals from these antennas will be amplified and processed • The remaining antennas will be ‘loaded’ elements, i.e. they are present only to reduce the edge effects on the central 8 x 8 • Each antenna type is due to be produced as a passive tile for RF testing • After testing, the active antennas will be used for 2-PAD.

5. Antennas FlowPAD antenna • from our colleagues at Astron • used as a reference design by which to benchmark our other antennas

6. Antennas BECA • (Bunny Ear Combline Antenna) • Designed by the University of Manchester • A development of a Vivaldi Structure

7. Antennas ORA (Octagon Ring Antenna) • Designed by the University of Manchester • New Antenna Design – see talk by David Zhang

8. 2-PAD LNA • The LNA for each antenna must be impedance matched and designed to integrate mechanically with the antenna • There are currently three teams working on LNAs in SKADS for 2-PAD • A completely new single-ended LNA developed in Indium Phosphide in Manchester • A differential LNA designed at ASTRON at 150W impedance for use with FlowPAD and BECA antennas • A differential LNA made up from discrete components in Manchester at 150W for use with FlowPAD and BECA antennas • It is likely that the discrete component LNA will be installed on 2-PAD initially, however, it will be possible for each LNA to undergo validation on the 2-PAD platform.

9. Gain Chain Version 1 Gain = 72dB Designed constructed and characterised by Richard Morrow

10. 2-PAD System Design Bunker RFI Shield Analog Conditioning 64 dual channels Ant. polarisation 4 off Beamformer. Processors Processor Total 128 inputs ADC Digital Pre- processor PSU Beamformer Processing Beam combiner Processor +ve Reg } ..... ..... ....... PCB Output Beams Analog Conditioning ....... ADC Digital Pre- processor From other beamformer proc. Analog Twisted Pair PSU LNA • Signal conditioning module • Analogue signal conditioning on replaceable mezzanine board • Off-the-shelf A/D initially • FPGA for data conversion and initial signal processing 64 elements x2 polarisations Time standard Control Processor Up to ~20m Line Tx/Rx Buffers Control Signal Conditioning Rack Processing Rack Outdoors mini-Bunker

11. Receivers Shielded Bunker Analogue Conditioner And Sampling Rack Processor Rack Front-end Gain. 20Gb Conditioning Module Acquisition &Processing Processor Blade Processor Blade Conditioning Module Acquisition &Processing Processor Blade Processor Blade Processor Blade Processor Blade Conditioning Module Acquisition &Processing Conditioning Module Acquisition &Processing Processor Blade Processor Blade

12. Signal conditioning Midplane Power Module Clock Module 2-channel signal conditioning module 2-channel acquisition and processing module 2 x 10Gb Links Signals from field

13. Analogue Conditioning Board

14. Analogue Conditioning Board

15. DAQ Board

16. DAQ Board

17. 2-PAD System Design Bunker RFI Shield Analog Conditioning 64 dual channels Ant. polarisation 4 off Beamformer. Processors Processor Total 128 inputs ADC Digital Pre- processor PSU Beamformer Processing Beam combiner Processor +ve Reg } ..... ..... ....... PCB Output Beams Analog Conditioning ....... ADC Digital Pre- processor From other beamformer proc. Analog Twisted Pair PSU LNA 64 elements x2 polarisations • Processing Subsystem • 2-PAD Designed to enable the testing of different types of processing • PrepSKA follow-on work to further investigate options Time standard Control Processor Up to ~20m Line Tx/Rx Buffers Control Signal Conditioning Rack Processing Rack Outdoors mini-Bunker

18. Initial Processing for 2-PAD Cyclops processor (IBM) • Cyclops blades in high-bandwidth rack • 80 GFlops/blade • Up to 48 blades/rack • SIMD Architecture • 160 thread units per chip Further Options – see Chris Shenton’s presentation

19. Cyclops frame at Jodrell

20. Cooling System • We have a cooling system for 2-PAD which includes: • A closed-loop controlled water cooling system used to cool the processor chips to keep them running at their most efficient • An air conditioning system used to cool the other electronics in the bunker • The two systems work together to keep the electronics at the correct temperature and humidity without compromising the RFI shielding of the bunker • This cooling system will make use of ‘free’ uncooled air from outside the bunker whenever ambient temperatures permit.

21. 2-PAD System Design Bunker RFI Shield Analog Conditioning 64 dual channels Ant. polarisation 4 off Beamformer. Processors Processor Total 128 inputs ADC Digital Pre- processor PSU Beamformer Processing Beam combiner Processor +ve Reg } ..... ..... ....... PCB Output Beams Analog Conditioning ....... ADC Digital Pre- processor From other beamformer proc. Analog Twisted Pair PSU LNA • Bunker and Shielding • RFI mitigation techniques • Housing and cooling system • ‘Standard’ container structure 64 elements x2 polarisations Time standard Control Processor Up to ~20m Line Tx/Rx Buffers Control Signal Conditioning Rack Processing Rack Outdoors mini-Bunker

22. Processing Bunker Design The processing bunker will be manufactured to the basic pattern of a standard transport container. Dual Function: Provide RFI Shielding Permits the processing bunker to be filled with computers before it is shipped

23. Bunker RFI shielding • Connect via screened sockets • Cables through tube • Wrap foil along cable • >60dB suppression at 1GHz, so far ARJ45 screened connectors

24. Potential SKA Station Layout

25. Software • A highly optimised kernel and software library has been created for the Cyclops processor from scratch in Manchester • A comprehensive MATLAB broadband beamforming model has been developed • We have a vendor developed software simulator for the Cyclops processor and the first version single polarisation beamformer has been implemented (in the simulator environment). This is currently being validated against the MATLAB model (refer to presentation by Aziz AhmedSaid).

26. 2-PAD should be integrated and ready for test by Q1 2009!