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ALMA Technology and RFI Mitigation StrategiesRFI Mitigation Strategies

N.D. WhybornALMA AIV Lead Engineer

[email protected]

CORF meeting, Santiago, 10-11 August 2009

ALMA System Block Diagram – antenna electronics!

FE

BE


ALMA System Block Diagram – TB electronics!

Correlator

CentralLO


LO

Front-end Overview


Front-end underside


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


Sid b d S i RFSid b d S i RFSideband Separating RF Hybrid Assembly

Sideband Separating RF Hybrid Assembly


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


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


C id O i LCartridge Optics Layout


SIS mixer

Simple constructionEasy to assemble

Front-End under test


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




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



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).


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

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