Phased Array Feed Developments for SKA

Stuart HayCSIRO ICT Centre

28th October 2010

Outline

• PAF array analysis, design and measurement• PAF LNAs• PAF cooling• PAF local calibration• PAF sensitivity uniformity and survey speed• PAF optics analysis for SKA

PAF array analysis, design and measurement

- Decrease Tsys - Increase frequency range- Reduce cost- Address SKA requirements

APERTIF Front-end

• Antenna• 121 element dual polarized Vivaldi array, 1 – 1.8 GHz• Laser-cut aluminum plates• Microstrip balun on RO4003• Overall radiation efficiency ~98.5%• Temperature stabilized at 7 °C

• LNA• Room temperature LNA• Noise figure ~0.5 dB (35 K)• Discrete components

test arrays

10 cm

ASTRON Improved Vivaldi/LNA design

• Beamformed sensitivity measurements• Measured Tsys = predicted Tsys=68K (cf 55K APERTIF target)• van Cappellen, BYU workshop May 2010

50% sensitivitycontour

APERTIF front-end as an aperture array

• Hot/cold measurement of APERTIF prototype• System temperature ~50 K at broadside• Very stable over scan range and bandwidth

• More details in presentation of Bert Woestenburg Thursday, 14:30h

Simulations Measurements

Holography

• Very high illumination efficiency, 76 – 78 %• Standing waves are largely eliminated• van Cappellen, BYU workshop May 2010

M33 velocity field

• APERTIF prototype• Single dish, single pointing

• Arecibo (M. Putman)

USA PAF development

2006-2007:7 element array on 3m reflectorRFI mitigation experiments19 element on Green Bank 20m 150 K Tsys

2009-2010:Active matched low noise PAF designsDual polarized 19 element arrayNew 40 channel down converters anddata acquisition systemImproved beamformer methodsProgress towards cryo-cooled arrayDeep nulling interference cancelerAO-40 experiment on the Arecibo dish

2008:19 element dipole array33 K LNAs (room temperature)1.3 – 1.7 MHz tunable bandwidthGoal: highest possible sensitivity66 K Tsys with room temp LNAs

CSIRO Checkerboard analysis

• Extensive EM analysis and measurement of 5x4x2 checkerboard• Mom, MWS, FDTD • Dielectric affects patterns (Mom), fine meshing important (MWS) • Hay et al IEEE APS 2009

−150 −100 −50 0 50 100 150−35

−30

−25

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−5

0

5

θ (deg)

Pow

er (

dB)

9A φ=0 deg1.2GHz

CBFM pol. 1CBFM pol. 2GEMS pol. 1GEMS pol. 2

CSIRO Checkerboard analysis

• Analysis of larger arrays for ASKAP by Mom and MWS• FoV analysis

Signal and noise impacts of mutual coupling

• For checkerboard, max SNR Ymin ~ conjugate of max η Yin

• Ymin = LNA minimum noise figure source admittance

• Yin = LNA input admittance

• When Ymin=conjugate of Yin

21)1/1(min

min <<−×=−

CCT

TThsignalmatc

rec η

• C is a Lange constant (invariant to lossless matching)• C is independent of beamformer weights

• Hay, to appear Intl Journal of Microwave and Optical Technology

0.5 1 1.5 2−200

−100

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Frequency (GHz)

Impe

danc

e (o

hm)

real Zopt

imag Zopt

real Zin

neg imag Zin

Signal and noise impacts of mutual coupling

• Checkerboard DSE sensitivity is within 10-25% of full SE• Hay ICEAA September 2010

ZSE ZSE

Vi+ Vi

-

Patch Patch

Beamformer

A Vi+ A Vi

-

Groundplane

ZSE ZSE

Vi+ Vi

-

Patch Patch

Beamformer

A (Vi+-Vi

-)

Groundplane

ie ZC=ZSE / 2ZD=ZSE x 2

0.5 1 1.5 20

0.1

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Frequency (GHz)

Effi

cien

cy

SE

TotalApertureMatch/Coupling

0.5 1 1.5 20

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Frequency (GHz)

Effi

cien

cy

DSE

TotalApertureMatch/Coupling

CSIRO Checkerboard development

Port Number (symmetric order)

Por

t Num

ber (

sym

met

ric o

rder

)

Simulated Cold Covariance at 1300 MHzNormalised to Hot/Cold Step

5 10 15 20 25 30 35 40

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PAF Port (Symmetric Order)

PA

F P

ort (

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met

ric O

rder

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Measured Cold Covariance at 1320 MHzNormalised to Hot/Cold Step

5 10 15 20 25 30 35 40

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2009 Measured Cold Covariance at 1300 MHzNormalised to Hot/Cold Step

5 10 15 20 25 30 35 40

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2009 measurement• switched power supplies

• planar splitters

• press-fit connectors

2010 measurement• linear power supplies

• transformer splitters

• screw-in connectors

simulation

1300 MHz

CSIRO Checkerboard Tsys measurement

Beamformed on hot microwave absorberMeasuredY-factor from cold sky to hot loadTsys better than PAF operation if all ports used in beamformingPoor Tsys if central 4 ports usedFinite absorber size was accounted for

CSIRO Checkerboard Tsys measurement

• 2009 AA measurements, Chippendale et al IEEE Phased Array 2010• Recent results improved <60K 0.8-1.3GHz• Still measured/simulation differences above 1.2GHz

0.6 0.8 1 1.2 1.4 1.6 1.80

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Frequency (GHz)

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se T

empe

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re (K

)

Prototype Y-factor Measurements

5x4x2 - maxSNRSingle LNA

CSIRO Checkerboard issues and in progress

• Further measurements with improved LNAs• AA and PAF 12m Parkes testbed

• High impedance array/LAN interface• Direct measurements of array or LNA at interface are difficult• Simplified system for interface tests• Vary parameters, see what doesn’t track modelling • Determine unmodelled effects or modelling improvements

PAF LNAs- Decrease Tsys- Increase frequency range- Production

University of Calgary LNA/Receiver Work

• Leo Belostotski’s and Jim Haslett’s teams are working on an astronomy-grade room-temperature CMOS receiver

• Have calibrated noise sources against a precision cryogenic noise source and compared our calibration to Sandy Weinreb’s at Caltech.

Measurements of an LNA made using calibrated noise source, compared with Sandy’s LN2 source.

University of Calgary LNA/receiver work

• Fabricated a gain stage in 90nm and 65nm CMOS.

• Measurement of the 90nm gain stage and a 90nm LNA gives <30K (see figure) of noise temperature at the SMA connector (expect to reduce this by ~7K when the PCB trace and connector are removed)

• The combined gain is >55dB

• Nearly capable of driving our ADCs directly.

• 2 new 65nm LNAs have bee fabricated and 4 others are expected to arrive to our lab shortly.

• Currently starting a new layout of a CMOS receiver in 65nm CMOS for fabrication in February

La Trobe University

• On-chip 0.25µm silicon on sapphire LNA• 0.7-1.8GHz• 20-83 K • H.P. Le et al., Electron. Lett., 45, 18, Aug 2009

CSIRO LNA development

• Input impedance ~300ohm • 0.7-1.8GHz• Teq~40-50K measured with hot/cold 300ohm source• Stable on checkerboard array

ZSE ZSE

Vi+ Vi

-

Patch Patch

Beamformer

Vi

Groundplane

PAF cooling

- PAF Tsys approach SPF Tsys - PAF evolution above 2GHz

NRAO PAF cryostat development

• Sander Weinreb SiGe low-noise amplifiers for 19 dual-polarized antenna elements (not installed in photo)

• Room temp antenna elements• Closed cycle refrigerator is used to cool the LNAs to 15K.• Target Tsys ~ 20-25K

25

Microcoolers - Scope

• Research project with Twente University, Kryoz technologies, ASTRON and CSIRO

• Target: a 100 kelvin microcooler prototype with first stage Low Noise Amplifier

• Prototype with LNA to be realized in 2011

Frequency range LNA 700MHz – 1700 MHz

Power consumption LNA < 50 mW

Microcoolers - Vacuum chamber

Integrated design of vacuum chamber with gas- and electronic connections

PCB with power and signal lines

Cooling tip with low noise device

27

Vibrationlesssorption compressor

Vacuum chamber containing microcooler

Power supply

13 cm

13 cm

13 cm

High-power: 80 bar to 6 bar, 15.6 mg/s, net cooling power 131 mW

Compressor prototype

Cooler prototype

PAF local calibration

- Sensitivity - PAF stability - Influence of PAF design on requirements

CSIRO local calibration development

• Design of dish-radiator calibration system for Parkes testbed• Initial results of analysis of temperature-induced variations

including LNA impedance and element patterns• Hayman et al ICEAA September 2010

DRAO calibration including polarization

• First steps on challenging PAF calibration for polarization • Orthogonal beamforming on unpolarized source (Sun)• Instrument Q, U and V• Comparison of 2 pol vs 1 pol elements in each beam• Simulation and measurement of gain/phase fluctuations• Veidt et al BYU workshop May 2010

PAF sensitivity uniformity and survey speed

- Requirements (SKA DRM)- PAF performance metric- Compare PAFs and PAF optics- Inform PAF design

ASTRON Beam shaping for mosaic observations

• Optimization constraints are introduced to improve the beam rotational symmetry while maximizing the sensitivity (SNR).

• For the 10% reduction of the MaxSNR• Beam and Gaussian model differences are ∼1% at the beam cross-

over points.• The sensitivity ripple is <20% over a wide frequency bandwidth.

• Ivashina, BYU workshop May 2010, EuCAP2011.

MaxSNR MaxSNR with constraints

CSIRO Optimized interleaving of max sensitivity beams

>< xxee

>ΩΩ< )()( xx ee

PAF 1 PAF 2

Beamformer

Correlator

Optimum linear combiner(mosaic)

Beamformer

>ΩΩ< )()( yx ee >ΩΩ< )()( yy ee

Maximize SNR of each output, subject to zero response to the othersCoefficients depend on direction Ω

Dual-polarization beams

Correlations of parallel and orthogonal beams

Coherency matrixelements

dot dot dot

dot dot dot

Sensitivity / survey speed relation (John Bunton)

2max

2

2pointing

2

pointings

2,,

2

2,

2,

SenSSFOV

)(SenSS

)(Sen1))(Sen(average

)(Senmin)(Sen

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∫∑

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all

all

yxyx

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d

kee

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δ

η

Optimized interleaving

• Maximize SS by optimizing beam sensitivity and spacing

• Fine and coarse mosaic to smooth to within 10%

• Bunton and Hay, ICEAA September 2010.

PAF optics analysis for SKA

- Calibration requirements - Dynamic range- Electronic FoV derotation- PAF size and beamformer cost

- Define SKA upgrade path

Impact of struts on polarization discrimination accuracy

• XPD is defined as the ratio of powers received at the beamformer outputs 1 and 2 due to the same incident field (Eco or Exp).

• Ivashina, BYU workshop May 2010

(XPD)co = 43 dB (XPD)co = 23 dB

Impact of the feed box on PAF patterns

• Pattern ripples cause the increase of Tsys (10-25K for PHAROS)• Neng-Tien Huang et al IEEE APS 2009• Ivashina et al SKA workshop, Perth, 2008.

• PHAROS PAF (2-5 GHz)• PAF is small w.r.t feed box

Marianna’s US optics analysis

• Initial results with Gaussian feeds• Working toward analysis of Vivaldi PAF

CSIRO Analysis of PAF in Parkes testbed

5x4 checkerboard PAF

Diameter of reflector is 12 meters

Antenna Feed and support

• Complete FDTD analysis of 5x4 prototype in Parkes testbed • Collaboration with Raj Mittra (Penn State) • Cavity and scattering effects on sensitivity• All ports scattering parameters and patterns are complete• Beamforming analysis underway

CSIRO PAF optics comparisons

• Compare 9x10x2 checkerboard PAF in various optics• ASKAP front-fed paraboloid (f/D=0.5)• Offset-fed paraboloid (fe/D=0.575)• Offset-fed shaped reflector (US SKA proposal)• Offset-fed dual-shaped reflector (US SKA proposal)

Comparison metrics: SS and SSFOV

2max

22

2max

22

2

Sen/||Sen||SSFOV

SenSSFOV

||Sen||

)(SenSS

=

×=

=

ΩΩ∝ ∫Ωall

dspeedSurvey

Comparison metrics: SignalFOV

csys

phyt

TkPnoise

SAPsignalPnoisePsignal

Sk

η

η

=

=

=Sen

• To compare signal differences:

2max

22 /||||SignalFOV tt ηη=

Front-fed paraboloid f/D=0.5 (ASKAP)

• FOV based on sensitivity (SSFOV) less than that of signal power alone• 1.25GHz, single linear x polarization

Front- vs offset-fed paraboloid (fe/D=0.575)

• Front-fed (left) vs offset-fed (right) • 1.25GHz single linear x polarization

Shaped reflector (US 12m)

• Array position optimized for SS• 1.25GHz x and y polarizations

Dual-shaped reflector (US 12m)

• Array centre at DR focus• 1.25GHz x and y polarizations

Dual-shaped reflector (US 12m)

• Array centre at DR focus• 1.25 GHz x and y polarizations• Subreflector diameter increased from 58.4 to 62.5 degrees

Summary

Configuration SignalFOV (deg2) • Front-fed 40 • Offset-fed paraboloid 30• Shaped reflector 27• Dual shaped 25

Optics in progress and recommended

In progress:• Prime vs secondary focus PAF in dual-offset optics

• Closer look at spillover impacts • FoV de-rotation in offset-fed reflectors (no 3rd axis)

• Synthesis of beams invariant to rotation about FOV centre• SP technique devised • Impact on sensitivity and survey speed

• Scattering effects in front-fed reflectors (ASKAP and Westerbork)Future steps:

• PAF/optics co-design• PAF/optics costing• PAF offset- vs front-fed (with 3rd axis): which is best?

Acknowledgements

• Much appreciated input from PAF workers • Neil Roddis for comments

Contact UsPhone: 1300 363 400 or +61 3 9545 2176

Email: enquiries@csiro.au Web: www.csiro.au

Thank you

CSIRO ICT CentreStuart Hay

Phone: +61 2 9372 4288Email: Stuart.Hay@csiro.auWeb: www.csiro.au/group

Bibliography

• [1] K.F. Warnick, B.D. Jeffs, J. Landon, J. Waldron, D. Jones, J.R. Fisher and R. Norrod, “Phased Array Antenna Design and Characterization for Next-Generation Radio Telescopes”, IEEE International Workshop on Antenna Technology, 2-4 March, 2009.

• [2] K.F. Warnick, B.D. Jeffs, J. Landon, J. Waldron, D. Jones, J. R. Fisher and R. Norrod, “Beamforming and Imaging with the BYU/NRAO L-Band 19-Element Phased Array Feed”, 13th International Symposium on Antenna technology and Applied Electromagnetics and the Canadian Radio Science Meeting, 2009.

• [3] D.A. Jones, K.F. Warnick, B.D. Jeffs, J. Landon, J. Waldron, J. R. Fisher and Roger Norrod, “Modelled and Measured Mutual Impedances, Element Patterns and Sensitivity for a 19 Element Focal Plane Array”, IEEE International Symposium on Antennas and Propagation, 2008.

• [4] M.V. Ivashina, O.A. Iupikov, R. Maaskant, W.A. van Cappellen, L. Bakker and T. Oosterloo, “Off-axis Beam Performance of Focal Plane Arrays for the Westerbork Synthesis Radio Telescope – Initial Results of a Prototype System”, IEEE International Symposium on Antennas and Propagation, 2009.

• [5] W.A. van Cappellen, L. Bakker and T.A. Oosterloo, “Experimental Results of a 112 Element Phased Array Feed for the Westerbork Synthesis Radio Telescope”, IEEE International Symposium on Antennas and Propagation, 2009.

• [6] J.G. Bij de Vaate, L. Bakker, E.E.M. Woestenburg, R.H. Witvers, G.W. Kant, W. van Cappellen, “Low Cost Low Noise Phased Array Feeding Systems for SKA Pathfinders”, 13th International Symposium on Antenna Technology and Applied Electromagnetics and the Canadian Radio Science Meeting, 2009.

Bibliography (cont)

• [7] B Veidt, T. Burgess, R. Messing, G. Hovey and R. Smegal, “The DRAO Phased Array Feed Demsonstaror: Recent Results”, 13th International Symposium on Antenna technology and Applied Electromagnetics and the Canadian Radio Science Meeting, 2009.

• [8] O’Sullivan, J., Cooray, F., Granet, C., Gough, R., Hay, S., Hayman, D., Kesteven, M., Kot, J., Grancea, A., and Shaw, R., “Phased Array Feed Development for the Australian SKA Pathfinder”, URSI General Assembly, Chicago, 2008.

• [9] Leonid Belostotski and James W. Haslett, “Sub 0.2dB Noise Figure Wideband Room-Temperature CMOS LNA with Non-50ohm Signal-Source Impedance”, IEEE Journal of Solid State Circuits, 42, 11, November 2007, pp. 2492-2502.

• [10] Leonid Belostotski and James W. Haslett, “A Technique for Differential Noise Figure Measurements of Differential LNAs”, IEEE Transactions on Instrumentation and Measurement, 57(7), July 2008, pp. 1298-1303.

• [11] K.F. Warnick, B. Woestenburg, L. Belostotski and P. Russer, “Minimizing the Noise Penalty Due to Mutual Coupling for a Receiving Array”, IEEE Trans. Ant. Prop. 57(6), June 2009, pp. 1634-1644.

• [12] S.G. Hay, “Ray Transformation Conditions and Shaped Reflector Solutions for Three Reflector Optics without Cross Polarization”, IEEE Trans. Ant. Prop., 55(8), 2007, pp. 2174-2184.

• [13] A.P. Chippendale, T.M. Colegate and J.D. O’Sullivan, “SKAcost: a Tool for SKA Cost and Performance Estimation”, SKA Memo 92, June 2007.

Bibliography (cont)

• [14] R.T. Schilizzi, P. Alexander, J.M. Cordes, P.E. Dewdney, P.J. Hall, J.L. Jonas, K.I. Kellermann, “Preliminary Specifications for the Square Kilometre Array”, SKA Memo 100, December 2007.

• [15] B. Veidt “Focal-Plane Array Architectures: Horn Clusters vs. Phased-Array Techniques”, SKA Memo 71, February 2006.

• [16] Karl F. Warnick, Marianna V. Ivashina, Rob Maaskant amd Bert Woestenburg, “Unified Definitions of Efficiencies and System Noise Temperature for Receiving Antenna Arrays”, IEEE Trans. Ant. Prop., 58, 6, June 2010, pp. 2121-2125.

• [17] Neng-Tien Huang, Raj Mittra, M. Ivashina and R. Maaskant, “Numerical Study of a Dual-Polarized Focal Plane Array (FPA) with Vivaldi Elements Placed in the Vicinity of a Large Feed Box using the Parallelized FDTD code GEMS”, IEEE International Symposium on Antennas and Propagation, 2009.

• [18] Hay, S., Cooray F., O’Sullivan, J., Neng-Tien Huang and R. Mittra, “Numerical and experimental studies of a dual-polarized planar connected-array antenna for the Australian Square Kilometer Array Pathfinder”, IEEE International Symposium on Antennas and Propagation, 2009.

• [19] Rob Maaskant, Dave J. Bekers, Michel J. Arts, Wim A. van Cappellen and Marianna V. Ivashina, “Evaluation of the Radiation Efficiency and the Noise Temperature of Low-Loss Antennas”, IEEE Antennas and Wireless Propagation Letters, Vol. 8, 2009, pp. 1166-1170.

• [20] M. Arts, M. Ivashina, O. Iupikov, L. Bakker, R. van den Brink, “Design of a Low-Loss Low-Noise Tapered Slot Phased Array Feed for Reflector Antennas”, Proceedings of the Fourth European Conference on Antennas and Propagation (EuCAP) 2010.

Bibliography (cont)

• [21] A. Chippendale, J. O’Sullivan, J. Reynolds, R. Gough, D. Hayman, S. Hay, R. Shaw, R. Qiao, “Chequerboard Phased Array Feed Testing for ASKAP”, International Workshop on Phased Array Antenna Systems for Radioastronomy, Provo, UT, 2010. [Online] Available: http://csas.ee.byu.edu/docs/Workshop/

• [22] Wim van Cappellen, “APERTIF phased array feed development for the Westerbork synthesis radiotelescope”, International Workshop on Phased Array Antenna Systems for Radioastronomy, Provo, UT, 2010. [Online] Available: http://csas.ee.byu.edu/docs/Workshop/

• [23] K.F. Warnick, D.E. Carter, T. Webb, B.D. Jeffs, R. Norrod and J.R. Fisher, “Active impedanced matched dual-polarized phased array feed for the GBT”, International Workshop on Phased Array Antenna Systems for Radioastronomy, Provo, UT, 2010. [Online] Available: http://csas.ee.byu.edu/docs/Workshop/

• [24] Ivashina, M., “Numerical approach to the analysis and optimization of phased array feed systems”, International Workshop on Phased Array Antenna Systems for Radioastronomy, Provo, UT, 2010. [Online] Available: http://csas.ee.byu.edu/docs/Workshop/

Bibliography (cont)

• [25] R. Norrod, J.R. Fisher, B.D. Jeffs and K.F. Warnick, “Steps toward a cryogenic L-band phased array feed for reflector antennas”, International Workshop on Phased Array Antenna Systems for Radioastronomy, Provo, UT, 2010. [Online] Available: http://csas.ee.byu.edu/docs/Workshop/

• [26] K.F. Warnick, B.D. Jeffs and T. Webb, “Calibration and beamforming for polarimetric phased array feeds”, International Workshop on Phased Array Antenna Systems for Radioastronomy, Provo, UT, 2010. [Online] Available: http://csas.ee.byu.edu/docs/Workshop/

• [27] Stuart Hay, Raj Mittra, Neng-Tien Huang and Wenhua Wu, “Analysis of reflector and feed scattering and coupling effects on the sensitivity of a phased array feed”, International Workshop on Phased Array Antenna Systems for Radioastronomy, Provo, UT, 2010. [Online] Available: http://csas.ee.byu.edu/docs/Workshop/

• [28] Bruce Veidt, “Polarimetry with phased array feeds”, International Workshop on Phased Array Antenna Systems for Radioastronomy, Provo, UT, 2010. [Online] Available: http://csas.ee.byu.edu/docs/Workshop/

Bibliography (cont)

• [28] Hayman, D. et al. International Conference on Electromagnetics in Advanced Applications, Sydney, Australia, September 2010.

• [29] Bunton, J. and Hay, S., “Achievable field of view of checkerboard array feed”, International Conference on Electromagnetics in Advanced Applications, Sydney, Australia, September 2010.

• [30] Hay, S., “Connected array sensitivity matching with single-ended loading and differential beamforming”, International Conference on Electromagnetics in Advanced Applications, Sydney, Australia, 2010.

• [31] Ivashina, M., International Conference on Electromagnetics in Advanced Applications, Sydney, Australia, 2010.

• [32] Aaron Chippendale, John O’Sullivan, John Reynolds, Russell Gough, Douglas Hayman and Stuart Hay, “Phased Array Feed Testing for Astronomy with ASKAP”, Proceedings of the 2010 IEEE International Symposium on Phased Array Systems and Technology, Boston, 2010.

• [33] W.A. van Cappellen, L. Bakker, "APERTIF: Phased Array Feeds for the Westerbork Synthesis Radio Telescope", Proceedings of the 2010 IEEE International Symposium on Phased Array Systems and Technology, Boston, 2010.