Istituto di Radioastronomia INAF -Italy-

Transcription

1 S. Montebugnoli, G. Bianchi, C. Bortolotti, A. Cattani, A. Cremonini, A. Maccaferri, F. Perini, M. Roma, J. Roda, P. Zacchiroli. Istituto di Radioastronomia INAF -Italy-

2 The planned re-instrumentation of of the Northern Cross large array will quickly lead to to a % SKA-A2 (300 ( MHz) MHz) demonstrator based on on cylindrical reflectors, allowing to: to:.. Investigate the use of of cylindrical concentrators for SKA Investigate on on Multibeaming, adaptive beamforming and RFIs mitigation algorithms, imaging of of large FOV and handling of of large array Obtain low risk, medium cost large SKA demonstrator (planned to to be be ready late 2007).

3 BEST-, 2 and 3 a modular SKA experimental prototype A- BEST-: A first single N/S cylindrical reflector test bed (4 Rx) -A g =76 m 2 - ready early 2005, - National funds allocated. 4 Receivers BEST- 4

4 B- BEST-2: A second test bed equipped by 8 N/S cylindric reflectors (32 Rx) -A g = 40 m 2 - ready early 2006, - National funds allocated. BEST-2

5 C- BEST-3: An almost % SKA-A2 demonstrator obtained with the re-engineering of 8000 m 2, (A gtotal = m 2 ) - ready late Cost about 250 /m 2 (Geometrical area is considered) BEST-3

6 Front-End G: ~63 db OIP3: 33.5 dbm Tsys : ~30 K Cost: 25 (electronic) 5 (housing) BEST- construction The Front End during the installation phase on the cylidrical concentrator focal line. In order to increase the reliability and maintainability the only outdore electronic is the LNA and the analog TX optical link.. Optical link LNA

7 low cost analog optical links are a crucial block for the SKA telescope.. link optimised at 6MHz BW Gain Gain Flatness Input Return Loss Output Return Loss Input IP3-22.9dB <0.dB >28.6dB >30.9dB +32.8dBm Noise Figure 3dB link (not optimised) in the MHz band Gain min -23.7dB Gain max -22.dB Input Return Loss >9.5dB This Optical link is a thesis of a student from the local College of Engineering (Bologna) Planned cost: 500 Output Return Loss Input IP3 >24.2dB >+30dBm Noise Figure <3.25dB

8 First observation of the transit of Cassiopea with BEST- BEST- IF Old Cross hardware detector & chart recorder 5.6 deg. 7. deg. (.7 deg.) Rx=¼ of cylinder 4 receivers= cylinder

9 Direct imaging of the FOV with BEST- BEST- A/D A/D A/D A/D Digital Multibeam-forming Beams Beam i 4 (Multiplications / sample) / Rx 2 (Sum / sample) / Rx 2(N Rx -) (Sums / sample) / beam

10 Imaging: F FX Correlator X D.Rx DFT Frequency channel Ch- FPGA FPGA (DSP) (DSP) clock D.Rx clock N N Polyphase filter DFT Polyphase filter FPGA FPGA (DSP) (DSP) D.Rx DFT FPGA FPGA (DSP) (DSP) clock N CORNER TURNER MEMORY

11 Imaging: XF Correlator LO A D A D A D A D Sync. DDC DDC DDC DDC 2 Sample 024 X X T r +j i r 2 +ji 2 r 3 +j i 3 r 4 +j i CORRELATOR X X T Σ Correlation matrix average <X X T > Adaptive Adaptive Beamformer Beamformer Adaptive Beamformer SVD (RFI DOA) d (θ ), d 2 (θ 2 ).. Multibeamin y n =X(n) W * (n) W= R- d 0 (θ 0 ) Radiosource (tracking) d H 0 (θ 0 ) R - d 0 (θ ) d 0 (θ 0 ) Calibration AIPS (Imaging)

12 Best- (and the following Best-2 & 3) will play an important role in the simulation of the real-life of the next generation very large radiotelescopes - It will investigate many aspects of the Architecture of large array: - Achromatic Adaptive Beamforming: large demonstrator introduces high delays. Low cost precise digital delay banks are required to properly form a certain amount of wide band adaptive beams. - Facing the design and the handling of large array infrastructures. - Design of XF and/or FX correlators. - Wide band optical fibre (analog) - RFI handling in a large array. - Reliabilty and Risk analysis evaluation exercise for large radiotelescope. 2- Verify the concepts related with the mechanical construction of a large array with cylinder reflectors 3- An almost complete instantaneous u-v coverage SKA large demonstrator. 4- A large demonstrator (8.000 m 2 ) able to quickly generate science