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Schediwy: Advantages and Disadvantages of Sparse Aperture Arrays Fermilab: October 2009.

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Presentation on theme: "Schediwy: Advantages and Disadvantages of Sparse Aperture Arrays Fermilab: October 2009."— Presentation transcript:

1 Schediwy: Advantages and Disadvantages of Sparse Aperture Arrays Fermilab: October 2009

2 Schediwy:  Introduce some of the concepts of mid-frequency, sparse aperture arrays  Show that 2-PAD is the perfect test-bed for experimentally investigating these concepts  Aperture Array Review  Sparse Aperture Array Concepts  Effective Area  High-Gain Antenna Strategy  Instantaneous Field of View  Sky Coverage  Dynamic Range  Computational Complexity  2-PAD Sparse Configuration Motivation and Contents Fermilab: October 2009

3 Schediwy: Aperture Arrays Fermilab: October 2009

4 Schediwy: beamformer Aperture Arrays Fermilab: October

5 Schediwy: d  Dense: d ≤ λ/√2, Sparse: d > λ/√2 Sparse Aperture Arrays Fermilab: October 2009

6 Schediwy:  Dense: A eff = λ c 2 /2, Sparse: A eff = λ 2 /2  Critical frequency f c sparse limit Effective Area per Element [SKA Memo 100] dense up to f c = 700MHz dense up to f c = 1000MHz fcfc fcfc f c = 300MHz Effective Area Fermilab: October 2009

7 Schediwy:  “The total cost of aperture array is strongly correlated with number of receiver chains”  If each antenna element has more forward gain, you can use less antennas while still maintaining comparable effective area, but make drastic cost savings due to the reduction in receiver chains S = A eff /T sys SS FoM = (A eff /T sys ) 2 ∙ FoV  Therefore maintain target SKA sensitivity and survey speed while decreasing cost [SKA Memo 100] High-Gain Antenna Strategy Fermilab: October 2009

8 Schediwy: Instantaneous Field of View  Fully Digital Dense A. Array  120deg  10,000deg 2  18deg  250deg 2  Hybrid Dense A. Array  120deg  10,000deg 2  28deg  625deg 2  18deg  250deg 2  60m Dish + Phased Array Feed  120deg+  10,000deg 2 +  18deg  250deg 2  Sparse High Gain A. Array  36deg  1,000deg 2  18deg  250deg 2 Fermilab: October 2009

9 Schediwy:  Earth rotation gives full coverage in RA  Trick: 3-way 36° switching mechanism to get a 108° of declination  Karoo SKA site (SA) 30.5°S  Murchison SKA site (WA) 26.5°S Overall Sky Coverage Fermilab: October 2009

10 Schediwy:  Which key science projects require pointing in opposite parts of the sky?  1 – The Dark Ages  2 – G. Evolution, Cosmology & Dark Energy  3 – Cosmic Magnetism  4 – GR using Pulsars & Black Holes  Search  4a – Gravitational Waves  4b – BH Spin  4c – Theories of Gravity  5 – Cradle of Life  5a – Proto-planetary Disks  5b – Prebiotic Molecules  5c – SETI  6 – Exploration of the Unknown      Sascha Schediwy: Instantaneous Sky Coverage Fermilab: October 2009

11 Schediwy: Dynamic Range  Station beam pattern Antenna Element Separation Station Beam Pattern  Antenna separation: dense (f < 1)nominal (f = 1)sparse (f > 1)random (f > 1) [SKA Memo 87] Beam Power Fermilab: October 2009

12 Schediwy:  For a constant processed FoV, the digital processing complexity increases as the square of the sparseness factor [SKA Memo 87] Computational Complexity Fermilab: October 2009 

13 Schediwy: OSKAR Simulator Fermilab: October 2009

14 Schediwy:  Dual-Polarisation All Digital Aperture Array  Dual Polarisation plug and play antennas  4x4 antenna array  Various interchangeable antennas  MHz RF range  Digital backend processing  Multi-FPGA boards, Multi-ASIC boards  200MHz processed bandwidth  Multiple independent beams  No. of Beam vs. Bandwidth trade-off  Demonstrate upgrade path to the AAVP 2-PAD Aperture Array Fermilab: October 2009

15 Schediwy: 2-PAD Aperture Array Fermilab: October 2009

16 Schediwy:  Log-periodic dipole array (LPDA) antenna  Frequency range = MHz 2-PAD High Gain Antenna Fermilab: October 2009

17 Schediwy:  Beam-width = 34.5° (Field of View = 928deg 2 )  Gain = 13.2dBi (20.9x isotropic) 2-PAD High Gain Antenna Fermilab: October 2009

18 Schediwy: ROACH Correlator Fermilab: October 2009

19 Schediwy: Jodrell Bank RFI Winterhill (500kW) Moel-y-Parc (100kW) The Wrekin (100kW) Sutton Coldfield (1000kW) Emley Moor (870kW) Fermilab: October 2009

20 Schediwy: Jodrell Bank RFI Fermilab: October 2009

21 Schediwy: Future Deployment Fermilab: October 2009

22 Dual Polarisation All Digital Aperture Array

23 Schediwy: Schediwy – Danny Price Antenna (ANT) & Balun (BAL) BECA ORA FlowPADLPDA LNASRCFILCXA GCM ANT CATSPL CXBCXC BAL SCMMIDTLB

24 Schediwy: Schediwy – Danny Price Low Noise Amplifiers (LNA) LNASRCFILCXA GCM ANT CATSPL CXBCXC BAL SCMMIDTLB

25 Schediwy: Schediwy – Danny Price Filter Module (FIL) LNASRCFILCXA GCM ANT CATSPL CXBCXC BAL SCMMIDTLB

26 Schediwy: Schediwy – Danny Price Gain Chain Module (GCM) LNASRCFILCXA GCM ANT CATSPL CXBCXC BAL SCMMIDTLB

27 Schediwy: Schediwy – Category-7 Cable (CAT) LNASRCFILCXA GCM ANT CATSPL CXBCXC BAL SCMMIDTLB

28 Schediwy: Schediwy – Danny Price Splitter Balun (SPL) LNASRCFILCXA GCM ANT CATSPL CXBCXC BAL SCMMIDTLB

29 Schediwy: Schediwy – Danny Price Signal Conditioning Module LNASRCFILCXA GCM ANT CATSPL CXBCXC BAL SCMMIDTLB

30 Schediwy: Schediwy – Danny Price Translator Board (TLB) LNASRCFILCXA GCM ANT CATSPL CXBCXC BAL SCMMIDTLB

31 Schediwy: Schediwy – Danny Price Coaxial Cables SRC CXA CXBCXC LNASRCFILCXA GCM ANT CATSPL CXBCXC BAL SCMMIDTLB


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