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ICT Centrewww.ict.csiro.au/antennas
Focal Plane Array Related Activities at CSIRO
Trevor S. Bird(1), Douglas Hayman(1), Suzy Jackson(2) & Dick Ferris (2)
(1) CSIRO ICT Centre(2) CSIRO Australia Telescope National Facility
PO Box 76, Epping NSW 1710 AustraliaEmail: [email protected]
www.ict.csiro.au
Focal Plane Array Workshop
Outline of Presentation
Past experience with focal plane arraysCSIRO and other activities related to FPAsAntennas– SKA proposals– FPAs– Line feeds
Integrated receiver systemsHigh-speed digital correlatorsWhat CSIRO brings to collaboration with Europe– Design– Measurement
www.ict.csiro.au
Focal Plane Array Workshop
Parkes Multibeam Receiver SystemMultibeam receiver system sits in the telescope’s focus cabin and receives signals from space
Radio signals from galaxies in space hit surface of telescope and are reflected to focus cabin
Telescope detects faint galaxies
Telescope ‘sees’ 13 patches of sky simultaneously
(Data for the Southern sky)
www.ict.csiro.au
Focal Plane Array Workshop
Arecibo Multibeam Feed System
Successfully installed in April 2004
Feed array (1.225 – 1.525 GHz)under test at CSIRO
Arecibo radio telescope
www.ict.csiro.au
Focal Plane Array Workshop
Arecibo Multibeam Feed Array –Sample Results
Theory
Element 3 : Array reference 45°, OMT horizontal. 135°-plane at 1.225 GHz & distance 3.7m
1
2
3
4
56
7
Theory
www.ict.csiro.au
Focal Plane Array Workshop
Current Australian Radio Astronomy Projects with FPAs
FARADAY and PHAROSMUDDA – multi-use dense digital arrayAustralian SKA Concept Demonstration Projects– MMIC development– Signal processing– Australia Telescope Compact Array Broadband Backend
(CABB)Bandwidth increased from 128MHz to 2GHz
– SKAMP – SKA Molonglo prototype– NTD – new technology demonstrator
Remote and radio-quiet site– Luneburg lens development– Techniques for RFI mitigation
www.ict.csiro.au
Focal Plane Array Workshop
SKA Configurations
Technical and cost assessmentsLuneburg lensCylindrical reflectorWide-field of view (WFOV) reflector
Luneburg lens
Cylindricalreflector
WFOV reflector
www.ict.csiro.au
Focal Plane Array Workshop
Measurement of Prototype Luneburg Lens
Aperture field
Far field
Measured results in S-band
www.ict.csiro.au
Focal Plane Array Workshop
Luneburg Lens with Egg-crate FPA
The ASTRON FARADAY FPA we had on site was used as an illuminator for the Konkur lens.
www.ict.csiro.au
Focal Plane Array Workshop
Cylindrical Reflector
Offset-fed optionsImproved cost modelWideband line-feed development (with Sydney Uni.)
www.ict.csiro.au
Focal Plane Array Workshop
WFOV Reflector
FOV ~10º x 10º~14m diameter reflectorLarge array in focal regionArray is extendableTechnology is well developed and cost known
Three CSIRO MultiBeam antennas at SES-ASTRA, Luxembourg.Each antenna covers a ~40º x 1ºFOV.
www.ict.csiro.au
Focal Plane Array Workshop
Focal-plane Arrays
Prototype focal plane array of Vivaldi elements
All SKA are expected to use focal-plane arraysFocal-plane arrays:– Allow formation of
multiple beams– Correct for errors in
reflectors or lenses– Allow electronic
beam scanning
www.ict.csiro.au
Focal Plane Array Workshop
Approach to Focal Plane Feeds
Compact feed elementsClose packing (max. spacing < 0.9λ)WidebandDual polarizationRigorous analysis including mutual couplingExcitation chosen to maximize secondary antenna Aeff/T (G/T)
www.ict.csiro.au
Focal Plane Array Workshop
Focal Plane Feed Options
Array cluster per beamSingle feed per beam
www.ict.csiro.au
Focal Plane Array Workshop
Cluster Feed Approach
Choose array excitation to maximize G/TAOverlap sub-arrays
– trade-off between number of elements and efficiency
Combine signals at:– RF– IF– M x N processor
www.ict.csiro.au
Focal Plane Array Workshop
Overlapping Sub-arrays
Example: 3 overlapping hexagonalarrays
Efficiency improvement is terraced,for example:
504030201000
20
40
60
80
100
No. of ElementsB
eam
eff
icie
ncy
%
www.ict.csiro.au
Focal Plane Array Workshop
Array Excitation forMaximum G/TA
Antenna gain
G(θ,φ)= GoQ(θ,φ)* Q(θ,φ)
Pf= Go
(cx)† (c x)x† x
c = correlation coefficients between the focal field and co-polar modes in the aperturesx = normalized array excitation coefficient vector
Note: Gain is maximum when x
Zero cross-polarization in beam direction when
where d is similar to c except for cross-polar modes
.= c†
x = c† −d c†
dd† d†
Antenna temperatureTA =
14π
G(θ,φ) T(θ,φ)Ω∫ dΩ = Go
x† B xx† x
For a given beam direction (θ,φ), G/TA is maximum when
x = B−1 c†
Mutual coupling between feed elements is included.
www.ict.csiro.au
Focal Plane Array Workshop
Potential Elements for Close Packed Arrays
Coaxial waveguide (b/a>0.4)Dielectric rodMicrostrip patchHelicalTravelling-wave slot antennasVivaldi– Balanced– Anti-podal
b
a
(Qassim & McEwan)
x
ychoke ring
input probe
top patch
driven patch
ground plane~0.8λ
~0.25λ
x
ychoke ring
input probe
top patch
driven patch
ground plane~0.8λ
~0.25λ
(after Kiskh & Shafai)
-A
A
truncation limits
y
x
y=±Aexp(Rx)
www.ict.csiro.au
Focal Plane Array Workshop
Arrays of Coaxial Horns
54.0
40.8
40.8
72.0
90.0
Y
X
E1
E2
1
3
2
28.8
-65
-60
-55
-50
-45
-40
-35
-30
-25
-20
3 4 5 6
Frequency GHz
Cou
plin
g co
effic
ient
dB
S12 (theory)S13 (theory)S12 (expt)S13 (expt)
Validation of analysis
Mode matching method for coaxial horns Accurate mutual coupling analysis (Bird, Trans. IEEE, Mar. 2004, pp. 821-829)In compact arrays
where s is the element spacing in wavelengths < 0.9 Example: s < λ/2, b/a > 0.3
80.0
153.0
46.0
3 2 1
Low-loss polystyrene foam spacers
123
Irises
280.0
X
Y
75.0
173.2
86.6150.0
75.076.5
895
514
1
2 3
4
All dimensions in mm
Feed element for Jodrell Bank Lovell radio telescope
2sa
))a/b(1(1
<λ
<+π
www.ict.csiro.au
Focal Plane Array Workshop
Balanced Anti-podal Vivaldi Antenna
E-plane
H-plane
With dielectric Without dielectric
Computations by S. Hanham, CSIROWith CST Microwave Studio Cross-polarization is high
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Focal Plane Array Workshop
Surface Currents on VivaldiElements
Conventional balanced Vivaldi Crossed balanced Vivaldi
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Focal Plane Array Workshop
MUDDA Overview – Frontend
Oversampled Focal Plane Array of 8x8 (nominal) tapered slot antennas for use on Parkes and other large unshaped dishes.RF frequency range 500 – 1700 MHz (nom).Tsys < 50K (uncooled).Instantaneous IF bandwidth 500 MHz.~40dB (6 – 8 bits) dynamic range.Dimensions 1.5m x 1.5m.
www.ict.csiro.au
Focal Plane Array Workshop
MUDDA Overview - Backend
FPGA filterbank on each element.Beamformer for at least four independent beams.Located remotely from feeds – RFI issues.Use technology developed for CABB
www.ict.csiro.au
Focal Plane Array Workshop
Radio on a Chip
Takes advantage of low cost, low power RF-CMOS processes developed for wireless networkingWill integrate Mixer, IF filter, and Sampler, as well as LO distribution.Possibly integrating LNA, RF filter.Design with Cadence toolset (Macquarie Uni.)Integrations issues– CMOS inductor Q < 10 – bulk substrate– FET NFMIN ~40K for 0.25µ, ~20K for 0.18µ (2GHz) –
comparable with GaAs– Broadband LNA noise match.– Gilbert cell mixers.– Active IF filter.
www.ict.csiro.au
Focal Plane Array Workshop
2 GHz Bandwidth Correlator with Polyphase Filterbank
x0(m)
x1(m)
xρ(m)
xM-1(m)
xn
po(m)
p1(m)
pρ(m)
pM-1(m)
M-PointDFTviaFFT
0
1
ρ
M-1
X0(m)
X1(m)
Xk(m)
XM-1(m)
x0(m)
x1(m)
xρ(m)
xM-1(m)
xn
po(m)
p1(m)
pρ(m)
pM-1(m)
M-PointDFTViaFFT
0
1
ρ
M-1
X0(m)
X1(m)
Xk(m)
XM-1(m)
FFT
FFT
FIR
FIR
FilterbankFringeRotators CorrelatorsDMUX
FFT
FFT
FIR
FIR
FilterbankFringeRotators CorrelatorsDMUX
A 2GHz bandwidth polyphase digitalfilterbank with 4096 channels ... ... will fit into four XC2V6000 FPGAs
FPGA hardware may be completely
reprogrammed to produce many
different filterbank configurations, as
different observations may require.
2GHz
4k channels
4k channels
Multiple Zoom (>2 possible)
2GHz
4k channels
4k channels
Compound Zoom
2GHz
4k channels
Simple Zoom
2GHz
4k channels
Basic Configuration
FPGA hardware may be completely
reprogrammed to produce many
different filterbank configurations, as
different observations may require.
2GHz
4k channels
4k channels
Multiple Zoom (>2 possible)
2GHz
4k channels
4k channels
Multiple Zoom (>2 possible)
2GHz
4k channels
4k channels
Compound Zoom
2GHz
4k channels
4k channels
Compound Zoom
2GHz
4k channels
Simple Zoom
2GHz
4k channels
Simple Zoom
2GHz
4k channels
Basic Configuration
2GHz
4k channels
Basic Configuration
www.ict.csiro.au
Focal Plane Array Workshop
Wideband Correlation
Build wider bandwidths by paralleling 2GHz slices8 GHz (per polarisation) high resolution spectrometer for MOPRA– 2GHz bandwidth per IF, four IFs per antenna
www.ict.csiro.au
Focal Plane Array Workshop
Baseband Receiver / PoC Spectrometer1024 Channel Spectrum, DC-256MHz
www.ict.csiro.au
Focal Plane Array Workshop
Molonglo Observatory Synthesis Telescope
Photo: G. WarrMaterial supplied by Anne Green, University of Sydney
www.ict.csiro.au
Focal Plane Array Workshop
SKAMP - the Molonglo SKA Demonstrator
Two substantial demonstrator projects have been funded for installation on the Molonglo Telescope:– A 96-station, wideband FX correlator – A broad-band line feed system for a cylindrical
paraboloid.
These two projects constitute the SKA Molonglo Prototype – SKAMP. They will result in a significant trial of key SKA engineering elements and enhance the scientific value of the Molonglo TelescopeJoint venture between University of Sydney and CSIRO
www.ict.csiro.au
Focal Plane Array Workshop
SKAMP Science Goals
Low-frequency radio spectrometry (300-1420 MHz)– Selection of objects via their radio spectral shape, e.g. candidate high
redshift (z>3) galaxies with ultra-steep radio spectra, study the formation of galaxies and massive black holes.
Redshifted HI (300-1420 MHz)– HI in absorption against bright continuum sources over a wide redshift
range (z=0 to 3). HI in emission - evolution of the HI mass function from z=0 to 0.5.
Low-frequency Galactic recombination lines– Recombination lines of carbon and hydrogen can be used to probe the
partially-ionized ISM.
Gamma Ray Bursters– Electronic beam steering gives a 5% chance of capturing a random event.
Concurrent SETI search, and Pulsars and Source Flux Monitoring
– 18 to 400 deg2 accessible around main beam. Real time de-dispersion
www.ict.csiro.au
Focal Plane Array Workshop
The SKA Molonglo Prototype (SKAMP)
Collecting area = 1% of SKA (i.e. equivalent to 1 SKA station)
Multibeaming
Wide instantaneous field of view
Digital beamforming
Wide-band FX correlator(2048 channels)
Frequency and pointing agility
Line feed 0.3-1.4 GHz >100 MHz instant BW
Cylindrical antenna prototype
RFI mitigation strategies - adaptive noise cancellation
www.ict.csiro.au
Focal Plane Array Workshop
Progress in Upgrade of Signal Path
Feed Development– modelling– feed synthesis– scan performance
Data Acquisition & Beamforming– Customised A/D
converters– delay & phase
tracking– data acquisition &
beamforming hardware installed in 2004
Correlator Development– Ball grid FGPAs– Testing in progress
Signal Processing– correlator control
computer (CCUBED) with external data interface has been setup
www.ict.csiro.au
Focal Plane Array Workshop
‘Petal’ Line Feed Element
-150 -100 -50 0 50 100 150-40
-35
-30
-25
-20
-15
-10
-5
0
θ (degrees )
Amplitude (dB)
Me asure d Azimuth Patte rns for Ante nna Prototype , F=1539MHz
Co-polarX-polar
Elementpattern
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Focal Plane Array Workshop
SKA New Technology Demonstrator (NTD)Aims:
Antenna, receiver and backend technology for support wide FOV, wideband astronomyOperational facility at a radio-quiet site– Demonstrate radio science opportunities in extremely
low RFI environment
Data transport/processing over long distances– Continent-wide, international connectivity
Remote energy provisionEnvironmental conditioning on a semi-arid remote site