atca l/s c/x receiver upgradel/s receiver becomes a 1‐3 ghz receiver amplifier • upgrade...
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ATCA L/S C/X Receiver UpgradeProject Overview
The Australia Telescope Compact Array (ATCA) L/S C/X upgrade is a program to upgrade the existing ATCA cm‐wave receiver systems.g y
The complete upgrade will:
Provide almost complete frequency coverage from 1.1 ‐12GHz.
Improve the system noise performance by 25% ‐ 50%.
Enable maximum use of the Compact Array Broadband Backend (CABB) at cm wavelengths ‐ instantaneous bandwidths of up to 4GHz.
The AAL EIF funding of $1.471M enables the completion of the C/X receiver upgrade ‐ the third and final phase of the upgrade program.
The C/X upgrade makes extensive use of capability developed during the L/S receiver system upgrade.
L/S Receiver becomes a 1‐3 GHz ReceiverAmplifier
• Upgrade completed on all ATCA antennas in
December 2010.
Amplifier
Receiver assembly
• Delivered a 25% ‐ 30% reduction in system
noise and doubled the available bandwidth.
assembly
• 3 stage 1 ‐ 3GHz, InP, HEMT LNA was
developed by CASS as part of the upgrade.
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60LS System Performance
System
RF module
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e Te
mpe
ratu
re (K
) Receiver (without feedhorn)
Amplifier
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0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2
Noi
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Frequency (GHz)
First paper
Complex Faraday depth structure of Active Galactic Nuclei as revealed by broadband radio polarimetry
Authors: S. P. O'Sullivan, S. Brown, T. Robishaw, D. H. F. M. Schnitzeler, N. M. McClure‐Griffiths, I. J. Feain, A. R. Taylor, B. M. Gaensler, T. L. Landecker L Harvey Smith E CarrettiLandecker, L. Harvey‐Smith, E. Carretti
(Submitted on 16 Jan 2012 (v1), last revised 10 Feb 2012 (this version, v2))
Abstract: We present a detailed study of the Faraday depth structure of four bright (> 1 Jy), strongly polarized, unresolved, radio‐loud quasars The Australia Telescope Compact Array (ATCA) was used to observe these sources with 2 GHz of instantaneous bandwidth fromquasars. The Australia Telescope Compact Array (ATCA) was used to observe these sources with 2 GHz of instantaneous bandwidth from 1.1 to 3.1 GHz. This allowed us to spectrally resolve the polarization structure of spatially unresolved radio sources, and by fitting various Faraday rotation models to the data, we conclusively demonstrate that two of the sources cannot be described by a simple rotation measure (RM) component modified by depolarization from a foreground Faraday screen. Our results have important implications for using background extragalactic radio sources as probes of the Galactic and intergalactic magneto‐ionic media as we show how RM ti ti f b d idth b ti i lt i th f lti l i t f i F d testimations from narrow‐bandwidth observations can give erroneous results in the presence of multiple interfering Faraday components.
We postulate that the additional RM components arise from polarized structure in the compact inner regions of the radio source itself and not from polarized emission from Galactic or intergalactic foreground regions. We further suggest that this may contribute significantly to any RM time‐variability seen in RM studies on these angular scales. Follow‐up, high‐sensitivity VLBI observations of these sources will directly test our predictions.
New and old compared
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Comparison Plot
160
180New Receiver
Old L‐band Receiver
100
120
140
mpe
rature (K
)
Old S‐band Receiver
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System
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01000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000
Frequency (MHz)
ATCA C/X Receiver Upgrade4 – 12GHz receiver development
3 t 4 12GH I P HEMT LNA• 3 stage 4-12GHz, InP, HEMT LNA wasdeveloped by CASS as part of the upgrade utilising device measurement in cryogenic conditionsy g
• A new 4-12GHz Ortho-mode transducer (OMT) was vital to meet th f ifi ti f th
Cryogenically cooled amplifier development probe station
the performance specification for the new frequency band. It has exceeded those specs making the extension of the frequency band to a higher limit a amplifierq y gconsideration.
Ortho mode transducer
ATCA 4 – 12GHz ReceiverStatus
• Australian Astronomy Ltd. funded program ‐ upgrade f d lfunding continues until June 2013.
• The manufacture of hardware and components for the spare receiver and system spares is nearing completion.p y p g p
• The first two receivers (production) were installed on the ATCA during Aug – Sep 2012.
• Installation of receivers 3 and 4 completed end of November 2012.
• All six ATCA antennas outfitted in Mar 2013. ScienceAll six ATCA antennas outfitted in Mar 2013. Science commenced.
• A spare receiver and spares /documentation will complete th j tthe project
4 – 12GHz Receiver – old and new comparedThe greater bandwidth and sensitivity of the new receivers (lower twotraces) is in stark contrast to the piecemeal performance of the originalATCA receivers
The project received the Highly Commended A d t th S d E i i E llAward at the Sydney Engineering Excellence Awards 2012
(L R) M k B Al D i(L-R) Mark Bowen, Alex Dunning and Henry Kanoniuk accepted the award on behalf of the team
4.0 – 12.25GHz Feed Horn DevelopmentStatus
• Existing C/X feed horn does not work above 10.8GHz.
• Two prototype 4.0 – 12.25GHz feed horns were delivered by BAE Systems in Jul – Aug 2012.
• Feed tested on the ICT Centre antenna range during• Feed tested on the ICT Centre antenna range during Aug – Sep 2012.
• Single feed installed on the ATCA (CA03) for evaluation during September 2012.
• Preliminary Tsys results (up to 12GHz) are promising.promising.
• Evaluation of beam patterns, polarisation performance, sensitivity, etc. underway.
• Evaluation of performance above 12GHz requires modification to CABB.
Prototype 4 – 12.25GHz Feed ‐ Performance
The new feed extends the high sensitivity performance past 11 GHzp p