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SKA AIP Meeting, ASTRON, 8-9 June, 2017

MID-FREQUENCY APERTURE ARRAY

Front-End Design for Mid-Frequency Aperture Array

David Zhang, A. K. Brown, Ming YangThe University of [email protected]

Severin Barth, S. Bosse, S. R. HarisonObs. de Paris, Nancay

Rui CaoKLAASA, CETC-38Pieter Benthem, David PrinslooASTRON, the Netherlands

E. de Lera-AcedoUniversity of Cambridge



Outline• Full Differential Front-End Development

– Review of C-ORA (Crossed Octagonal Ring Antenna)– Prototype investigation– Active C-ORA array measurements– System integration with time delay based beamformer

• Single-Ended Front-End Development– ASTRON

• Active Vivaldi Antenna Array• Integration with phase shifter based beamformer

– KLAASA• Front-End solution and back-end processing

• Sparse Array Design for MFAA



Review of Crossed Octagonal Ring Antenna (C-ORA) Design



C-ORA Design



The Layered Structure



Metamaterial performance in C-ORA



Prototyping and Active ORA Array Measurements



The 1 m2 ORA prototype facts

10x10 elements(1.25m x 1.25m) Dual-polarised for each element Frequency 400MHz to 1450MHz Element separation: 125mm Low profile (array thickness



Gain measurements at field

0.5 1 1.50

5

10

15

20

25

30

35

40

45

50

Frequency(GHz)

Gai

n(dB

)

Simulated Gain 1x1 ORA without LNASimulated Gain 4x4 ORA without LNASimulated Gain 8x8 ORA without LNAMeasured Gain 4x4 with LNASimulated Gain 4x4 ORA + Measured Gain of LNA



Gain comparison for 4x4 Arrays



Raw cross polarisation – XPD

900MHz 1200MHz



Calibration Error and IXR

𝑓𝑓𝑝𝑝𝑓𝑓𝑞𝑞

=𝐽𝐽𝑝𝑝𝑝𝑝 𝐽𝐽𝑝𝑝𝑝𝑝𝐽𝐽𝑞𝑞𝑝𝑝 𝐽𝐽𝑞𝑞𝑝𝑝

𝑒𝑒𝑝𝑝𝑒𝑒𝑝𝑝

𝑓𝑓 = 𝐽𝐽𝑒𝑒

𝑒𝑒 = 𝐽𝐽−1𝑓𝑓𝑓𝑓 + ∆𝑓𝑓 = (𝐽𝐽 + ∆𝐽𝐽) 𝑒𝑒 + ∆𝑒𝑒

∆𝑒𝑒𝑒𝑒

≤ 1 +2𝐼𝐼𝐼𝐼𝐼𝐼

∆𝑓𝑓𝑓𝑓

+∆𝐽𝐽𝐽𝐽

Raw voltageMeasured

voltage

An IXR of 25 dB limits the potential increasein the relative Stokes error during reconstruction to 22%



900MHz 1200MHz

The IXR (Intrinsic Cross-Polarisation)



The radiation pattern measurement



-50

-40

-30

-20

-10

0

10

20

-70

-65

-60

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

900MHz,4x4 beamformed, D-Plane

Co-Pol X-Pol

-35-30-25-20-15-10-505

10

-70

-65

-60

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

1400MHz, 4x4 beamformed, D-plane

Co-Pol X-Pol

The 4x4 beamformed patterns, measured



Measured immersed element patterns

900MHz, E-plane 1400MHz, E-plane

900MHz, H-plane 1400MHz, H-plane



The System Integration With Time Delay based beamformer


MID-FREQUENCY APERTURE ARRAYBeamformer board

ORA filtering board

Quad board

X-pol antenna inputs Y-pol antenna inputs

Beam A output

Beam B output

Time delay based beamformer solution for dual polarisation with two beams

Beam A output

Beam B output

All boards are developed at Nançay



Beamformer Chip Performance



Front-End R&Dat

Station de Radioastronomie de NançayObservatoire de Paris



Adjustable time delayASIC 4 channelsTime delay = 1,2ns * 2 = 2,4 nsStep = 20 ps * 2Error pĥase = ±10 degreesFreq bandwidth = [400-1500 MHz]

4 TD / QuadBoard→ 8 TD for 2 m2

Quad Board

X-pol, Beam A&B

Y-pol, Beam A&B



NEW LNA Topology



Single-Ended Front-End DevelopmentASTRON



Vivaldi Tile for MFAA



Active array with low noise solution

LNAs are integrated at the feeding points, SATA interface to the beamformer board



Dual polarisation two beams beamformer

8 elements beamformer PCB for dual polarisations2 beams for X polarisations2 beams for Y polarisations



Single-Ended Front-End DevelopmentKLAASA



Architecture



4x4 to 1 analogue beam configuration

• 4x4 output 1 analogue beam• 16x16x2 tile will generate 32

beams• 1 CTPM can process 512

antenna elements



4x4 to 16 analogue beams configuration

• 4x4 output 16 analogue beam• 16x16x2 tile will generate 512

beams• 16 CTPM can process 512

analogue beams



CTPM with three layered structure



Prototyping

32 channels with optical receivers

32 AD channels Processing

KLAASA has completed the test of V1.0For LFAA



CTPM for MFAA



Log-Periodic Dipole Antenna for SKA-AAMid(Sparse Array)



Log-Periodic Dipole Antenna for MFAA



LPDA for MFAA and LNA



Tile demonstrator at Lord’s Bridge



Summary

• Different front-end technologies become more mature• Dual polarisation with dual beams per polaristation can

be realised with phase shift or time delay based analogue beamforming

• High polarimetry performance can be achieved• Irregular distribution of elements in the array, random

thinning techniques can be explored to further reduce the total number of elements


MID-FREQUENCY APERTURE ARRAYThank you

Front-End Design for Mid-Frequency Aperture ArrayOutlineReview of Crossed Octagonal Ring Antenna (C-ORA) DesignC-ORA DesignThe Layered StructureMetamaterial performance in C-ORAPrototyping and Active ORA Array MeasurementsThe 1 m2 ORA prototype factsGain measurements at fieldSlide Number 10Slide Number 11Calibration Error and IXRSlide Number 13Slide Number 14Slide Number 15Slide Number 16The System Integration With Time Delay based beamformerSlide Number 18Beamformer Chip PerformanceFront-End R&D�at �Station de Radioastronomie de Nançay�Observatoire de ParisSlide Number 21Slide Number 22Slide Number 23Slide Number 24Slide Number 25Single-Ended Front-End Development�ASTRONVivaldi Tile for MFAAActive array with low noise solutionDual polarisation two beams beamformerSingle-Ended Front-End Development�KLAASAArchitecture4x4 to 1 analogue beam configuration4x4 to 16 analogue beams configurationCTPM with three layered structurePrototypingCTPM for MFAASlide Number 37Log-Periodic Dipole Antenna for MFAALPDA for MFAA and LNATile demonstrator at Lord’s BridgeSummarySlide Number 42

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