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ALMA Technology and RFI Mitigation StrategiesRFI Mitigation Strategies
N.D. WhybornALMA AIV Lead Engineer
CORF meeting, Santiago, 10-11 August 2009
CORF meeting, Santiago, 10-11 August 2009
ALMA System Block Diagram – antenna electronics!
FE
BE
CORF meeting, Santiago, 10-11 August 2009
ALMA System Block Diagram – TB electronics!
Correlator
CentralLO
CORF meeting, Santiago, 10-11 August 2009
LO
Front-end Overview
CORF meeting, Santiago, 10-11 August 2009
Front-end underside
CORF meeting, Santiago, 10-11 August 2009
Band 3 Cartridge: 84 – 116 GHzBand 3 Cartridge: 84 – 116 GHz
Pol 1
OMT
Pol 1Pol 0
2SB Mixer assemblies
Low Noise Cryogenic AmplifiersNanowave Inc. Toronto Canada
Band 3 Cartridge: 84 – 116 GHzBand 3 Cartridge: 84 – 116 GHz
Sid b d S i RFSid b d S i RFSideband Separating RF Hybrid Assembly
Sideband Separating RF Hybrid Assembly
Band 3 Cartridge: 84 – 116 GHzBand 3 Cartridge: 84 – 116 GHz
Feedhorn/Lens
4 K Plate Construction4 K Plate Construction
Feedhorn/Lens, OMT, 2SB Sub-assembly Amplifier
& Isolator
4 K Cold Assembly
& IsolatorSub-assembly
4 K Components4 K Components
Band 6 Cartridge: 211 – 275 GHzBand 6 Cartridge: 211 – 275 GHz4 K Components4 K Components
Sideband separating mixer
mirrors
10
SIS Mixer ChipsSIS Mixer Chips
Band 6 Cartridge: 211 – 275 GHzBand 6 Cartridge: 211 – 275 GHzSIS Mixer ChipsSIS Mixer Chips
/ O /UVML Nb/Al-AlOx/Nb tri-layer process [1][2]
Series array of f j tifour junctions
[1] W. Clark, J.Z. Zhang and A.W. Lichtenberger, "Ti Quadlevel Resist Process for the Fabrication of Nb SISJunctions" IEEE Transactions on Applied Superconductivity, pp 115-118, Vol. 13, 2003.[2] R.B. Bass, L.T. Lichtenberger, and A.W. Lichtenberger, "Effects of Substrate Preparation on the Stress of Nb ThinFilms", IEEE Transactions on Applied Superconductivity, pp3298-3300, Vol 13, 2003.
Band 6 Cartridge: 211 – 275 GHzBand 6 Cartridge: 211 – 275 GHzCooled IF Preamps Integrated with MixersCooled IF Preamps Integrated with Mixers
SIS mixersSIS mixers
3-stage LNA’s
Band 9 Cartridge: 602 – 720 GHzBand 9 Cartridge: 602 – 720 GHz
Optics Assembly
4 K
10 cm
Mixer
50
4 K
SIS Junctions (TU Delft)
50 cm
15 K
110 K
1 cm R. Hesper
300 K
R. Hesper
Band 9 Cartridge: 602 – 720 GHzBand 9 Cartridge: 602 – 720 GHz
C id O i LCartridge Optics Layout
Band 9 Cartridge: 602 – 720 GHzBand 9 Cartridge: 602 – 720 GHz
SIS mixer
Simple constructionEasy to assemble
Front-End under test
CORF meeting, Santiago, 10-11 August 2009
Front-End under test
CORF meeting, Santiago, 10-11 August 2009
Back-end under test
BE IF Processor
Atten AFixed G
AMP
AMP
analog differential to NRAO
diff to NRAOBBA Detector
8 5 . GHz LPFUSB_ Detector
LNA
4- 12 GHzBPF
EqualizerS
R IL
R IL
5 BPF
. - 5 BPF
S
2.1 - 3. 9 GHzNRAO
Anti - alias BPF
2. 1 - 3. 9 GHzNRAO
Anti - alias BPF
0.5 dB step
Atten B
0.5 dB step
Equalizer
AMP
AMP
AMP
AMP
AMP
AMP
AMP
AMP
AMP
AMP S
AMP
AMP
AMPAMP
EqualizerS
diff to NRAO
BBA to NRAO+3dBm
+3dBm
USB IF input4 - 12 GHz
- 37 to - 24 dBmfrom NRAO
BBB Detector
BBB to NRAO
Fixed G
Fixed G
12 GHz LPF 1 5 GHz
1. - 5 GHz
Atten C AMP
diff to NRAO
LSB IF input4 - 12 GHz
8. 5 GHz LPFBBC Detector
Fixed G
S
R IL
R IL
. -BPF
. 5 BPF
2. 1 - 3. 9 GHzNRAO
Anti - alias BPF
2. 1 - 3. 9 GHzNRAO
Anti - alias BPF
0.5 dB step
Atten D
0.5 dB step
AMP
AMP
AMP
AMP
AMP
AMP
AMP
AMP
Equalizer
Equalizer
AMP
AMP
AMP
AMP
AMP
S
S
LNA AMPEqualizer
S
4- 12 GHzBPF
diff to NRAO
- 37 to - 24 dBmfrom NRAO
12 GHz LPF
+3dBm
+3dBmBBD to NRAO
BBC to NRAO
BBD Detector
Fixed G
Fixed G
1 5 - GHz
1 5 5 GHz
DC/ DC Converters
Monitor & Control
SPI interfaceLSB_ Detector
Anti alias BPF
AMP
-
-17VDC
+17 VDC
from NRAO
from NRAO8- 14 GHz
+ 14 to + 18 dBm
diff to NRAO
analog differential to NRAO
Temperature sensors
LO B
to / from NRAO AMBSI 2LO A
LO DLO C
BE Data Transmission SystemDi iti F tt Fib O iM i C l /
TRANSMITTER MODULE
P0From Baseband Processors
Digitizer Assembly
Formatter Fiber Optic Transmitter
MC / PS
Monitor Control / Power Supply
Rate Adjst
PrtclEncr Mux Fiber Optic
Controller3 bitA/D
1:16Demux
1:16Demux
Keep Alive
250 Mb/s
10 Gb/sP1
Processors
10 Gb/s
(1bit)
(1bit)
Laser
Laser
Laser
(16bits)
3 bitA/D
1:16Demux
1:16Demux
1:16Demux
(1bit)
1:16Demux
4Gb/s Rate Adjst
Rate Adjst
PrtclEncr
PrtclEncr
Mux
Mux
250 MHz
20.833 Hz
4 GHz
125 MHz
From LORR
From DGCK
CANH, LFrom ABM
Baseline Correlator
1 correlator plane: 64stn x 64stn x 256 lags at 125MHz (2-bit words)
One quadrant:One quadrant: 32 planes processes 2GHz x 2 polarisations from 64 antennas
Four quadrants: processes 8GHz x 2 polarisations from 64 antennas
Total 134.2 million lagsTotal 1 68*10^16 multiply accumulations per secTotal 1.68*10^16 multiply-accumulations per secBuilt with custom ASIC’s~70 different resolution-bandwidth combinations possible70 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
Correlator
CORRELATOR STATION ELECTRONICSAT ANTENNA
TUNABLE FILTER BANK CARD32-PARALLEL OUTPUTS X 2-BITSPER SAMPLE X 2-POLARIZATIONSSTATION CARD
4 GHz DIGITIZERDATA
ONE BASEBAND POLARIZATION PAIR
TRANSMITTER
POL 1
DATARECEIVER PER SAMPLE X 2 POLARIZATIONS
STATION CARD
STATION CARD
4 GHz DIGITIZER
4 GHz DIGITIZER
4 GHz DIGITIZER
4 GHz DIGITIZER
4 GHz DIGITIZER 1:12 OPTICAL SPLITTER
12:1 OPTICAL COMBINER
POL 2 TUNABLE FILTER BANK CARD
TUNABLE FILTER BANK CARD
TUNABLE FILTER BANK CARD
TUNABLE FILTER BANK CARD
TUNABLE FILTER BANK CARD
TRANSMITTERDATA
TRANSMITTERDATA
DATA
RECEIVERDATA
RECEIVER
CORRELATOR BASELINE ELECTRONICS
DIGITIZES ANALOG SIGNALS ANDAPPLIES ULTRA FINE DELAY
FINE DELAY ANDSELECTSBANDWIDTH
BULK DELAY, RE-ORDERSAND PACKETIZESSAMPLES
STATION CARD
4 GHz DIGITIZER
4 GHz DIGITIZER
THREE OPTICCARRIERS
THREE OPTICCARRIERS
TUNABLE FILTER BANK CARD
TUNABLE FILTER BANK CARD
TRANSMITTERDATA
RECEIVERDATA
PLANE 31
PLANE 2
ANE 1
E 0
ANTENNA 63
32-PARALLEL OUTPUTS X 2-BITSPER SAMPLE X 2-POLARIZATIONS
LTA ADDER TREE
CORRELATOR BASELINE ELECTRONICS
REAL TIMECOMPUTERSYSTEM
LTA
CORRELATOR ARRAY
63
(ONE OF 4 IN SYSTEM SHOWN)
HORIZON
CORRELA
INTRA-QUADRANTRESULTS CROSSBAR AND REALTIME COMPUTERINTERFACE
PPLA
PLANE
ANTENNA 0
32-PARALLEL OUTPUTS X 2-BITSPER SAMPLE X 2-POLARIZATIONS
0
VERTICAL DRIVE TOCORRELATOR MATRIX
0 63
NTAL DRIVE TO
ATOR MATRIX
4 PCB
Figure 1 Correlator Block Diagram
Central LO System
Master LaserMaster LaserDistribution
fiber
RF
SwitchingFiber Optic
Patch
MicrowaveSynthesizer
4 unitsLaser Synthesizer
CTNLL(T bl L )
1 unit 4 units
12-20 GHz
Photonic Distribution
4 units
Line LengthCorrection
64 units
SwitchingModule
1 unit
Patch Panel
1 unitHydrogen Maser
Laser Tx
CRG
CRD
1 unit 1 unit
Low Frequency and Timing References
(Tunable Laser)
4 units
4 unitsRF reference
Low Frequency Reference
Laser Tx
RF Power Divider
CRD
Laser TxDistribution
1 unit 1 unit
1 unit1 unit
25 MHz
Photonic LO Reference - Central Building
64 outputs64 outputs
Optical Diplexer
64 units
LO Photonic Receiver
64 units
Photomixer Assembly
256 units
Photonic LO Reference - Antenna
pp
CLO Racks Installed at AOS
FE Band 9 Photomixer – converts photonic b t t t 100GH tbeat note to ~100GHz tone
RFI Threats and Susceptibility LevelNot clear if spectral-line or continuum single-dish is
ALMA RFI suceptibility levels (spectral line)
Not clear if spectral line or continuum single dish is the worst case for ALMA
60−
40−
2nd IF
100−
80−
/ dB
[W/m
^2]
1st IF
140−
120−
FI th
resh
old
/
Ku DBS
1st IF
180
160−
RF
Bands 1 - 10
1 10 100 1 103×180−
frequency / GHz
RFI ThreatsDirect Broadcast Satellite to FE IF system
Ku band ~12GHzNo relief from coordination: above horizon, on all the time
Cloudsat (satellite with high-power 94GHz nadir-looking cloud radar)Infrequent and predictableProtect receivers by automatic shutter closure near zenith
Point to point linksPoint to point linksTopography shields from nearby linksSUBTEL agreement
No licensed emission in ALMA bands within 30kmCoordination of applications out to 120kmRestrict pfd < 2 x 10-6 W/m2 within AOS zone
Collision avoidance radar Prevalence low at present but expected to riseOnly threat is from Paso Jama international highwayOnly threat is from Paso Jama international highwayTopography shields most if not all of ALMA arrayAtmospheric attenuation removes fundamental tone (60GHz only)Harmonics and spurs may cause problems
RFI Mitigation
Antenna required cabin shielding 20dBRF gaskets around doorsNo relief if antenna pointed towards e g satellite !No relief if antenna pointed towards e.g. satellite !
FE chassis sealed with RF gaskets, apertures covered with copper meshcovered with copper mesh
Expect 20dB shielding
IF systems designed with maximum practical shielding
Expect >60dB shielding
Overall we can expect 80dB of shieldingOverall we can expect 80dB of shielding67dB is required to suppress known DSB below interference threshold
Interferometric techniques can raise the system thresholdLO offsetting: apply different LO1 and LO2 offsets for different antennasLO offsetting: apply different LO1 and LO2 offsets for different antennas.
ConclusionAlmost all technology development is completeHardware is in production 3 antennas are equipped and under test3 antennas are equipped and under testPreparations at AOS in full swing ACA correlator installed at AOS1 t d t f BL l t i t ll d t AOS1st quadrant of BL correlator installed at AOSCLO being installedFirst antenna expected to go to AOS mid September, p g p ,next two in October.
Attention has been paid to RFI issues during the designAttention has been paid to RFI issues during the design phaseNo EMC qualification so far: CDR FE & BE pending We do not expect problems but remain vigilant !We do not expect problems but remain vigilant !
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 Nationalcooperation 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, 10-11 August 2009
BE:DTS T ittDTS Transmitter
Digitizer Assembly
Formatter Fiber Optic Transmitter
Monitor Control / Power Supply
TRANSMITTER MODULE
P0
To / From WDM
From Baseband MC / PS
Rate Adjst
PrtclEncr Mux Fiber Optic
Controller3 bitA/D
1:16Demux
1:16Demux
Keep Alive
10 Gb/sP1
From Baseband Processors
10 Gb/s
(1bit)
(1bit)
Laser
Laser
Controller
3 bitA/D
A/D Demux
1:16Demux
1:16Demux
1:16Demux
(1bit)4Gb/s Rate
Adjst
Rate Adjst
PrtclEncr
PrtclEncr
Mux
Mux
250 Mb/s
250 MHz4 GHz
From DGCK
Laser
(16bits)
1:16Demux
Adjst Encr
20.833 Hz
125 MHz
From LORR
CANH, LFrom ABM