The development of a CSIRO MKIII wideband phased array feedAlex Dunning, Mark Bowen, Henry Kanoniuk, Jeganathan Kanapathippillai, Doug Hayman, Rob Shaw, Sean Severs, and Aaron Chippendale
PAF workshop, Cagliari, 24th August 2016
CSIRO ASTRONOMY AND SPACE SCIENCE
Introduction
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 2
The motivation for this design was to develop a 40 element array as a technology demonstrator for SKA survey
It has also become a demonstrator for a possible future upgrade of ASKAP and a potential cryogenic PAF for the Parkes Radio Telescope
Frequency range optimized for 0.65-1.65GHz
We have not considered coolingThis design was intended for a low RFI environmentThe LNAs use commercial HEMT transistors
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 3
The RF signal path
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 4
Amp1LNA
Dig.AttnPadRFoF
Tx Amp2 Amp3
RFDetector
Digital attenuator control RF level detection
RFoF Tx card
Coupler
HPF
LPF
3dB ±7dBG=28dB G=22dB G=16dB G=16dB
Full Bandwidth to here
~70dB gain to here
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 5
PEEK Support
Aluminium Element
180ΩDifferential LNA inputs
HDPE probe support
‘The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 6
The design process
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 7
• Constrain the length of the elements to ensure low loss
• With an infinite array, optimize the element geometry to achieve maximum boresight return loss
• Design the edge elements such that the impedance at the edges resembles that of an infinite array
• Check infinite array performance is acceptable over angles required for good dish illumination
• Check array/LNA noise match
Dual ModedFloquet Port
Master/Slave Boundaries
Dual ModedLNA port
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 8
E
0.55 1.9
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 9
E
0.55 1.9
Simulated Element Loss (HFSS)I’m not convinced this is realistic!
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 10
Full 5x4 PAF simulation
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 11
A full 80 port EM simulation of the 5x4 PAF was performed in order to accurately model finite size effects.
This simulation was combined with a Microwave Office simulation of the LNA to model noise covariance matrices and embedded element patterns
The noise simulation exhibits very close agreement with the infinite array simulation for most of the band.
Simulated Array Performance on a Parkes Like Dish
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 12
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 13
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 14
-100 0 100-30
-20
-10
0
10
200.500GHz :0.71
-100 0 100-30
-20
-10
0
10
200.600GHz :0.69
-100 0 100-30
-20
-10
0
10
200.700GHz :0.63
-100 0 100-30
-20
-10
0
10
200.800GHz :0.60
-100 0 100-30
-20
-10
0
10
200.900GHz :0.58
-100 0 100-30
-20
-10
0
10
201.000GHz :0.59
-100 0 100-30
-20
-10
0
10
201.100GHz :0.65
-100 0 100-30
-20
-10
0
10
201.200GHz :0.71
-100 0 100-30
-20
-10
0
10
201.300GHz :0.73
-100 0 100-30
-20
-10
0
10
201.400GHz :0.70
-100 0 100-30
-20
-10
0
10
201.500GHz :0.64
-100 0 100-30
-20
-10
0
10
201.600GHz :0.62
-100 0 100-30
-20
-10
0
10
201.700GHz :0.63
-100 0 100-30
-20
-10
0
10
201.800GHz :0.63
-100 0 100-30
-20
-10
0
10
201.900GHz :0.62
-100 0 100-30
-20
-10
0
10
202.000GHz :0.63
Dire
ctiv
ity (d
Bi)
θ (degrees)
PAF modelled beam patterns using on dish Max SNR weights
The LNA design
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 15
LNA noise temperature measurements
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 16
The Analogue Beamformer
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 17
The analogue beamformer consists of a simple summing network to simulate an equal weights beamformer
Analogue beamformer measurements with the liquid Nitrogen load did not prove very successful
To determine whether the load or the beamformer was to blame we decided to try the analoge beamformer in the Parkes aperture array setup
Analogue Beamformer Noise Temperature
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 18
ΣΔ
Σ
×10
×10
Calibration Plane
0.5 0.75 1 1.25 1.5 1.75 2
Frequency (GHz)
0
5
10
15
20
25
30
35
40
Noi
se T
empe
ratu
re (K
)
Rocket Array Pol A
Rocket Array Pol B
ASKAP ADE 5x4
Rocket Array Simulation
Change in noise from uniform to dish weights
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 19
Results using the Parkes aperture array digital backend
Installing the PAF on the Parkes 64m
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 20
The array was installed on the Parkes 64m antenna in May for a three day measurement campaign
We used Virgo to derive MaxSNRbeamforming weights and to measure Tsys/η
Using pyramidal absorber as a hot load and the sky as a cold load we measured the system temperature
We would have liked to use an adjacent 12m antenna as a reference for holography. However due to the large delay between signals the phase wrap in the 1MHz frequency bins was too great.
A vertex radiator was used as a channel to channel calibrator.
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 21
On dish measurements
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 22
On dish measurements: Intermodulation products, the culprit?
Summary
The CSIRO MKIII Phased Array Feed Design | Alex Dunning | Page 23
The PAF seems to be functioning as expected in aperture array tests however more work need to be done on reconciling the on dish measurements with simulation
At the moment our major effort is aimed towards improving post LNA dynamic range in order to tolerate high levels of RFI
We aim in the near future to start working towards a cryogenic array for the Parkes telescope as well as working with a semiconductor foundry to produce custom LNA MMICs
Thank youCSIRO Astronomy and Space ScienceAlex DunningFront End Technologiest +61 2 9372 4346e [email protected] www.csiro.au
CSIRO ASTRONOMY AND SPACE SCIENCE
