Transcript Slide 1
Sensitivity, the Challenges Jan Geralt Bij de Vaate Bert Woestenburg Rob Maaskant Laurens Bakker 4th SKADS Workshop, Lisbon, 2-3 October 2008 Sensitivity JGBdV 1 Outline • SKA specification • Aperture Array Noise Analyses • Noise budget • Conclusion 4th SKADS Workshop, Lisbon, 2-3 October 2008 Sensitivity JGBdV 2 SKA, memo100 A • Survey speed ~ eff T sys 2 FoV N B FoV FoV N sa 2 A f c eff FoV m Tsys • E.g. SKA Tsys spec (0.5-1.0 GHz): – If 35K will be 50K, Aeff has to double / Or FoV has to quadruple! Aeff • Sensitivity ~ Tsys 4th SKADS Workshop, Lisbon, 2-3 October 2008 Sensitivity JGBdV 3 SKA • Memo100 4th SKADS Workshop, Lisbon, 2-3 October 2008 Sensitivity JGBdV 4 SKA • Memo100: – Sparse aperture array 70-500MHz • 4000 m2/K, Tsys~1000: 4 km2 – 2 million Antennas – Dense aperture array 500-800MHz • 10.000 m2/K, Tsys=50K: 0,9 km2, nearly 1 km2 – 45 million Antennas » Aperture efficiency 80%, 45 degree scan 4th SKADS Workshop, Lisbon, 2-3 October 2008 Sensitivity JGBdV 5 Costing • A 45 million element system with a total system cost of 250M € can spend: – 4 € per LNA for 50 35 Kelvin • Given a bare die costs of: • 0,5 € for Silicon technologies (only 500 12 inch wafers) • 2 € for GaAs technologies (2000 6 inch wafers) • Low cost technologies cannot compromise on noise! • Also: memo100, 150M€ for AA scenario3 4th SKADS Workshop, Lisbon, 2-3 October 2008 Sensitivity JGBdV 6 Aperture Array Tsys 2 TLNA • Single LNA case s opt 4T0 Rn Tmin Z0 1 2 1 2 opt s • Noise Wave analyses – Optimum Noise match if 4th SKADS Workshop, Lisbon, 2-3 October 2008 opt s Sensitivity JGBdV 7 Aperture Array Tsys s act 4T0 Rn Tmin Z0 1 2 1 opt act 2 TLNA 2 • T=Direct part + Reflected part + coupled part – Optimum Noise match if 4th SKADS Workshop, Lisbon, 2-3 October 2008 opt act Sensitivity See also Arts, today See also Kant, EMBRACE Maaskant APS, 2007 JGBdV 8 Aperture Array Tsys • Extreme example • 2 element dipole array • In principle different matching required for each scan angle 4th SKADS Workshop, Lisbon, 2-3 October 2008 Sensitivity JGBdV 9 Aperture Array Tsys • Clearly low Tmin and RN required • Limited work on RN (process) optimization Simulations Ref. Mateos et.al., 2004/2008 4th SKADS Workshop, Lisbon, 2-3 October 2008 Sensitivity JGBdV 10 Noise budget Aperture Array Spill-over 0K Vivaldi feed loss 9K Low Noise Amplifier 16 K Noise mismatch / coupling /2nd stage 7K Sky 3K Total 35 K • TLNA ~ 50% of noise budget 4th SKADS Workshop, Lisbon, 2-3 October 2008 Sensitivity JGBdV 11 Noise budget APERTIF Focal Plane Array Spill-over 10 K Vivaldi feed loss 5K Single chain receiver 30 K Noise mismatch / coupling 5K Sky 3K Total 53 K 4th SKADS Workshop, Lisbon, 2-3 October 2008 Sensitivity JGBdV 12 AA Tsys characterization • Uniform Test Strategy might be required • Even more importantly error budgets have to be known – And reduced eliminated!! – For example Agilent noise sources are +/-7K • Methods – ‘standard’ noise diode equipment – Hot cold liquid nitrogen loads – Tuner set-ups correction software – Cold noise tests 4th SKADS Workshop, Lisbon, 2-3 October 2008 Sensitivity JGBdV 13 AA Tsys characterization • Action plan.. – Establish available equipment list – Including environment, e.g. Faraday cage – Including noise parameter test sets, tuner set-up / F50 method – Select AA relevant LNA for cross testing – Including approach for differential LNAs – Set-up small working group frequent cross test of new designs • Involvement off all partners working on low noise – UoM, OPAR, FG-IGN, Chalmers, Calgery, ASTRON…..and? – Start with SKADS soon evolving in AAVP 4th SKADS Workshop, Lisbon, 2-3 October 2008 Sensitivity JGBdV 14 AA Tsys characterization • ASTRONs antenna array hot/cold test facility 4th SKADS Workshop, Lisbon, 2-3 October 2008 Sensitivity JGBdV 15 • SKA workshop, in the Microwave Week, Amsterdam, 30th Oct 4th SKADS Workshop, Lisbon, 2-3 October 2008 Sensitivity JGBdV 16 Conclusion • Transistor modeling and optimization (still) crucial! • Noise budget leaves not much room in 35K target • Closer cooperation and system noise tests required • And, Steve T, we indeed want to work in phase! 4th SKADS Workshop, Lisbon, 2-3 October 2008 Sensitivity JGBdV 17