ALMA Technology and. N.D. Whyborn ALMA AIV Lead Engineer

Transcription

1 ALMA Technology and RFI Mitigation Strategies N.D. Whyborn ALMA AIV Lead Engineer CORF meeting, Santiago, August 2009

2 CORF meeting, Santiago, August 2009

3 ALMA System Block Diagram antenna electronics! FE BE CORF meeting, Santiago, August 2009

4 ALMA System Block Diagram TB electronics! Correlator Central LO CORF meeting, Santiago, August 2009

5 Front-end Overview CORF meeting, Santiago, August 2009

6 Front-end underside CORF meeting, Santiago, August 2009

7 Band 3 Cartridge: GHz OMT Pol 1 Pol 0 2SB Mixer assemblies Low Noise Cryogenic Amplifiers Nanowave Inc. Toronto Canada

8 Band 3 Cartridge: GHz Sideband d Separating RF Hybrid Assembly

9 Band 3 Cartridge: GHz 4 K Plate Construction Feedhorn/Lens, OMT, 2SB Sub-assembly Amplifier & Isolator Sub-assembly 4 K Cold Assembly

10 Band 6 Cartridge: GHz 4 K Components Sideband separating mixer mirrors 10

11 Band 6 Cartridge: GHz SIS Mixer Chips UVML Nb/Al-AlOx/Nb / trilayer process [1][2] Series array of four junctions [1] W. Clark, J.Z. Zhang and A.W. Lichtenberger, "Ti Quadlevel Resist Process for the Fabrication of Nb SIS Junctions" IEEE Transactions on Applied Superconductivity, pp , Vol. 13, [2] R.B. Bass, L.T. Lichtenberger, and A.W. Lichtenberger, "Effects of Substrate Preparation on the Stress of Nb Thin Films", IEEE Transactions on Applied Superconductivity, pp , Vol 13, 2003.

12 Band 6 Cartridge: GHz Cooled IF Preamps Integrated with Mixers SIS mixers 3-stage LNA s

13 Band 9 Cartridge: GHz Optics Assembly Mixer 10 cm 4K 50 cm 15 K 110 K 1 cm R. Hesper SIS Junctions (TU Delft) 300 K R. Hesper

14 Band 9 Cartridge: GHz Cartridge Optics Layout

15 Band 9 Cartridge: GHz SIS mixer Simple construction Easy to assemble

16 Front-End under test CORF meeting, Santiago, August 2009

17 Front-End under test CORF meeting, Santiago, August 2009

18 Back-end under test

19 BE IF Processor LNA USB IF input 4-12 GHz - 37 to - 24 dbm from NRAO 4-12 GHz BPF Fixed G Equalizer S USB_ Detector S 85. GHz LPF analog differential to NRAO R I L GHz BPF R I L 12 GHz LPF GHz BPF GHz NRAO Anti - alias BPF GHz NRAO Anti - alias BPF Atten A 0.5 db step 0.5 db step Atten B Fixed G Equalizer Fixed G Equalizer BBA Detector S BBB Detector S diff to NRAO BBA to NRAO +3dBm diff to NRAO +3dBm BBB to NRAO LSB IF input 4-12 GHz - 37 to - 24 dbm from NRAO LNA 4-12 GHz BPF Fixed G Equalizer S S 8. 5 GHz LPF 12 GHz LPF R I L R I L GHz BPF GHz BPF GHz NRAO Anti - alias BPF GHz NRAO Anti - alias BPF 0.5 db step 0.5 db step Atten C Atten D Fixed G Equalizer Fixed G Equalizer BBC Detector S BBD Detector S +3dBm +3dBm diff to NRAO BBC to NRAO diff to NRAO BBD to NRAO LSB_ Detector diff to NRAO analog differential to NRAO from NRAO 8-14 GHz + 14 to + 18 dbm LO D LO C LO B LO A +17 VDC -17VDC from NRAO DC/ DC Converters Monitor & Control SPI interface to / from NRAO AMBSI - 2 Temperature sensors

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21 BE Data Transmission System TRANSMITTER MODULE Digitizer iti Formatter Monitor Control / Fiber Optic Assembly Power Supply Transmitter From Baseband Processors P0 P1 3 bit A/D 4Gb/s (1bit) 3 bit A/D 1:16 Demux 1:16 Demux 1:16 Demux 1:16 Demux 1:16 Demux 1:16 Demux 250 Mb/s Rate Adjst Rate Adjst Rate Adjst Prtcl Encr Prtcl Encr Prtcl Encr Mux Mux Mux MC / PS 10 Gb/s (1bit) Fiber Optic Controller Laser Laser Laser Keep Alive 10 Gb/s (1bit) (16bits) 250 MHz From DGCK 4 GHz 125 MHz From LORR Hz From ABM CANH, L

22 Baseline Correlator 1 correlator plane: 64stn x 64stn x 256 lags at 125MHz (2-bit words) One quadrant: 32 planes processes 2GHz x 2 polarisations from 64 antennas Four quadrants: processes 8GHz x 2 polarisations from 64 antennas Total million lags Total 1.68*10^16 multiply-accumulations per sec Built with custom ASIC s ~70 different resolution-bandwidth combinations possible 4GHz at 976 khz resolution with all polarisation products 31.25MHz at 7.6 khz resolution with no polarisation X-products

23 P Correlator AT ANTENNA CORRELATOR STATION ELECTRONICS ONE BASEBAND POLARIZATION PAIR POL 1 POL 2 4 GHz DIGITIZER 4 GHz DIGITIZER DATA TRANSMITTER DATA RECEIVER TUNABLE FILTER BANK CARD TUNABLE FILTER BANK CARD STATION CARD 32-PARALLEL OUTPUTS X 2-BITS PER SLE X 2-POLARIZATIONS 4 GHz DIGITIZER 4 GHz DIGITIZER 4 GHz DIGITIZER 4 GHz DIGITIZER DATA TRANSMITTER DATA TRANSMITTER 12:1 OPTICAL COMBINER 1:12 OPTICAL SPLITTER DATA RECEIVER DATA RECEIVER TUNABLE FILTER BANK CARD TUNABLE FILTER BANK CARD TUNABLE FILTER BANK CARD TUNABLE FILTER BANK CARD STATION CARD STATION CARD 4 GHz DIGITIZER DATA TRANSMITTER DATA RECEIVER TUNABLE FILTER BANK CARD STATION CARD 4 GHz DIGITIZER TUNABLE FILTER BANK CARD DIGITIZES ANALOG SIGNALS AND APPLIES ULTRA FINE DELAY THREE OPTIC CARRIERS THREE OPTIC CARRIERS FINE DELAY AND SELECTS BANDWIDTH BULK DELAY, RE-ORDERS AND PACKETIZES SLES CORRELATOR BASELINE ELECTRONICS CORRELATOR ARRAY (ONE OF 4 IN SYSTEM SHOWN) 32-PARALLEL OUTPUTS X 2-BITS PER SLE X 2-POLARIZATIONS ANTENNA PARALLEL OUTPUTS X 2-BITS PER SLE X 2-POLARIZATIONS HORIZON NTAL DRIVE TO CORRELA ATOR MATRIX 63 PLANE 0 PLA ANE 1 PLANE 2 PLANE 31 LTA LTA ADDER TREE INTRA-QUADRANT RESULTS CROSS BAR AND REAL TIME COMPUTER INTERFACE REAL TIME COMPUTER SYSTEM ANTENNA PCB 0 VERTICAL DRIVE TO CORRELATOR MATRIX Figure 1 Correlator Block Diagram

24 Central LO System fiber RF Master Laser Master Laser Distribution 1 unit 4 units Microwave Synthesizer 4 units Low Frequency and Timing References Hydrogen Maser CRG 1 unit 1 unit GHz RF reference Laser Synthesizer CTNLL (Tunable Laser) 4 units 4 units Photonic Distribution 4 units Switching Module 1 unit Line Length Correction 64 units Fiber Optic Patch Panel 1 unit CRD Laser Tx Low Frequency Reference 1 unit 1 unit 25 MHz Laser Tx Distribution 1 unit RF Power Divider 1 unit Photonic LO Reference - Central Building 64 outputs 64 outputs Photomixer Assembly LO Photonic Receiver Optical Diplexer 256 units 64 units 64 units Photonic LO Reference - Antenna

25 CLO Racks Installed at AOS

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27 FE Band 9 Photomixer converts photonic beat note to ~100GHz tone

28 RFI Threats and Susceptibility Level Not clear if spectral-line line or continuum single-dish is the worst case for ALMA ALMA RFI suceptibility levels (spectral line) 2nd IF RF FI threshold / db[w/m^2] st IF Ku DBS 160 Bands frequency / GHz

29 RFI Threats Direct Broadcast Satellite to FE IF system Ku band ~12GHz No relief from coordination: above horizon, on all the time Cloudsat (satellite with high-power 94GHz nadir-looking cloud radar) Infrequent and predictable Protect receivers by automatic shutter closure near zenith Point to point links Topography shields from nearby links SUBTEL agreement No licensed emission in ALMA bands within 30km Coordination of applications out to 120km Restrict pfd < 2 x 10-6 W/m 2 within AOS zone Collision avoidance radar Prevalence low at present but expected to rise Only threat is from Paso Jama international highway Topography shields most if not all of ALMA array Atmospheric attenuation removes fundamental tone (60GHz only) Harmonics and spurs may cause problems

30 RFI Mitigation Antenna required cabin shielding 20dB RF gaskets around doors No relief if antenna pointed towards e.g. satellite! FE chassis sealed with RF gaskets, apertures covered with copper mesh Expect 20dB shielding IF systems designed with maximum practical shielding Expect >60dB shielding Overall we can expect 80dB of shielding 67dB is required to suppress known DSB below interference threshold Interferometric techniques can raise the system threshold LO offsetting: apply different LO1 and LO2 offsets for different antennas.

31 Conclusion Almost all technology development is complete Hardware is in production 3 antennas are equipped and under test Preparations at AOS in full swing ACA correlator installed at AOS 1st quadrant of BL correlator installed at AOS CLO being installed First antenna expected to go to AOS mid September, next two in October. Attention has been paid to RFI issues during the design phase No EMC qualification so far: CDR FE & BE pending We do not expect problems but remain vigilant!

32 The Atacama Large Millimeter/sub millimeter Array (ALMA), an international astronomy facility is partnership among Europe, Japan, and North America, in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO); in Japan by the National Institutes of Natural Sciences (NINS) in cooperation with the Academia Sinica in Taiwan; and in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC). ALMA construction and operations are led on behalf of Europe by ESO, on behalf of Japan by the National Astronomical Observatory of Japan (NAOJ), and on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI). CORF meeting, Santiago, August 2009

33 BE: DTS Transmitter TRANSMITTER MODULE Digitizer Assembly Formatter Monitor Control / Power Supply Fiber Optic Transmitter From Baseband Processors P0 P1 3 bit A/D 3 bit A/D 4Gb/s (1bit) 1:16 Demux 1:16 Demux 1:16 Demux 1:16 Demux 1:16 Demux 1:16 Demux 250 Mb/s Rate Adjst Rate Adjst Rate Adjst Prtcl Encr Prtcl Encr Prtcl Encr Mux Mux Mux MC / PS 10 Gb/s (1bit) Fiber Optic Controller Laser Laser Laser Keep Alive 10 Gb/s (1bit) To / From WDM (16bits) 250 MHz From DGCK 4 GHz 125 MHz From LORR Hz From ABM CANH, L