SKA TDP Antenna Optics

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© Germán Cortés M 2008SKA-TDP AWG Antenna Workshop

San Francisco, March 13-14, 2008

SKA TDP Antenna Optics

By Germán Cortés M.

Cornell Cornell UniversityUniversity

Ithaca NY 14853, USA

National Astronomy and Ionosphere Center

SKA-TDP AWG Antenna WorkshopSan Francisco, March 13-14, 2008

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Overview

• Introduction

• SKA TDP Dishes + WBSPF Optics Design Plan

• SKA TDP Antenna Work Breakdown

• SKA TDP Baseline Antenna Optics.

• Summary

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Current SKA TDP Antenna

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SKA TDP Dishes + WBSPF Optics Design Plan

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SKA TDP Reflector + WBSP Feed Optics Design Plan

• Detailed WBSP Feed characterization– Co-Pol and Cross-Pol Radiation Patterns– Gain– Input Matching– Losses– Phase Center Variations

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WBSP Feed Far Field Radiation Pattern 10 GHz

Co-PolDir = 10.11 dBi

X-Pol-1.08 dBi

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• Detailed WBSP Feed characterization– Co-Pol and Cross-Pol Radiation Patterns– Gain– Input Matching– Losses– Phase Center Variations– Matching Optics Parameters

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The SKA TDP Reflectors

Symmetric Reflector Off-Axis Reflector

Possible Configurations

Gregorian is Preferred

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• Antenna Analysis and Design Optimization– Co-Pol and Cross-Pol Radiation Patterns– Aperture Efficiency– Antenna Temperature vs. elev & freq– Aeff/Tsys Optimization

• Matching Optics for Different Configurations– Prime Focus– Secondary Focus Solutions– Multiple Focus Solutions

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8m Reflector+Baseline Feed Far Field Radiation Pattern at 700 MHz

Symmetric ReflectorCo-Pol

Symmetric ReflectorX-Pol

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6m Offset Reflector+Baseline Feed Far Field Radiation Pattern at 500 MHz

Off-Axis ReflectorCo-Pol

Off-Axis ReflectorX-Pol

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• Antenna Analysis and Design Optimization– Co-Pol and Cross-Pol Radiation Patterns– Aperture Efficiency– Antenna Temperature vs. elev & freq– Aeff/Tsys Optimization– Dynamic Range Issues: Far Side Lobe Levels


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SKA Offset Design Prime Focus: Wide Pattern

Wide Band Feed Freq= 1.400 GHz, f=5.2m

Co-Polar Wide Pattern

X-Polar Wide Pattern

-33.9 dB

-14.2 dB

-42.9 dB

-42.9 dB

-40.8 dB

-39.1 dB

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Far Field Radiation Patterns including Quadrupod Strut Diffraction Effects

Wide Pattern 1.3 GHz

Wide Pattern 32 GHz

-46 dB-126 dB=178° =82°

-45 dB=14°

-85 dB=106°

-46 dB-152 dB=180° =82°

-73 dB=14°

-123 dB=106°

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• Antenna Analysis and Design Optimization– Co-Pol and Cross-Pol Radiation Patterns– Aperture Efficiency– Antenna Temperature vs. elev & freq– Aeff/Tsys Optimization– Dynamic Range Issues: Far Side Lobe Levels


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The SKA TDP Reflectors

Possible Configurations

Gregorian Off-Axis

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• But,… In order to do this we need to agree in some initial parameters….

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SKA TDP Antenna Work Breakdown

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Mount


Reflector

Pedestal

Foundation

ScienceData

Transport

Optics

UWB Feeds

Monitoring&

Control

Power

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Reflector

Pedestal

Foundation

Mount

UWB Feeds

Optics

ScienceData

TransportMonitoring&

Control

Power

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Foundation

Reflector

UWB Feeds

Optics

Pedestal

Mount

Monitoring&

ControlPower

ScienceData

Transport

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UWB Feeds

Optics

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SKA TDP Antenna OpticsSpecification

Frequency

Aeff/Tsys

Diameter

Optics

UWB Feeds

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SKA Dishes+WBSPF Technology Paths

Frequency

3cPH

AS

E

II AA’s

1.5 GHz 10 GHz

3a

3b

1

2

0.07 0.2 0.5 0.8 1.5 10 GHzAA’s Dishes

Ø15m+ WBSPF

PAF’s

Preliminary Specifications for the Square Kilometer Array v2.7.1 Dec. 4 2007

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Frequency

3cPH

AS

E

II

AA’s

AA’s

1.5 GHz 10 GHz

0.8 GHz 10 GHz

3a

3b

1

2

0.07 0.2 0.5 0.8 1.5 10 GHzAA’s Dishes

Ø15m+ WBSPF

PAF’s


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Frequency

3cPH

AS

E

II

AA’s

AA’s

1.5 GHz 10 GHz

0.8 GHz 10 GHz

0.5 GHz 10 GHz3a

3b

1

2

0.07 0.2 0.5 0.8 1.5 10 GHzAA’s Dishes

Ø15m+ WBSPF

PAF’s


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Frequency

3cPH

AS

E

II

AA’s

AA’s

1.5 GHz 10 GHz

0.8 GHz 10 GHz

0.5 GHz 10 GHz3a

3b

1

2

0.07 0.2 0.5 0.8 1.5 10 GHzAA’s Dishes

Ø15m+ WBSPF

PAF’s

70%

70%

70%

A

30K

30K

30K

Tsys

2400

3000

2000

NII


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0

2000

4000

6000

8000

10000

12000

14000

0.1 1 10 100

Frequency [GHz]

3A. 15m, Nd=3000+WBSPF

3B. 15m, Nd=2000+WBSPF+PAFs

3C. 15m, Nd=2400+WBSPF+DAA

SKA TDP Antenna OpticsAeff/Tsys Point Source Sensitivity

Aef

f/T

sys

[m

2 /K

]

0.5 0.7 1.5 3.0

10.0

0.2


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0

2000

4000

6000

8000

10000

12000

14000

0.1 1 10 100

Frequency [GHz]

3A. 15m, Nd=3000+WBSPF

3B. 15m, Nd=2000+WBSPF+PAFs

3C. 15m, Nd=2400+WBSPF+DAA

0.5 0.7 1.5 3.0

10.0

0.2

SKA TDP Antenna OpticsAeff/Tsys Point Source Sensitivity

Aef

f/T

sys

[m

2 /K

]

SKA TDP

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0

10

20

30

40

50

60

70

80

90

100

0.1 1 10 100Frequency [GHz]

Req

uir

ed T

sys

[K]

3A. 15 m, 70%, 3000 Ant, WBSPF

3B. 15 m, 70%, 2000 Ant, WBSPF+PAFs

3C. 15 m, 70%, 2400 Ant, WBSPF+DAA

SKA TDP Antenna OpticsTsys for a 15m Ø Dish, A =70%

0.5 0.7 1.5 3.0 10.00.2

SKA TDP

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0

10

20

30

40

50

60

70

80

90

100

0.1 1 10 100Frequency [GHz]

Req

uir

ed T

sys

[K]

3A. 15 m, 70%, 3000 Ant, WBSPF

3B. 15 m, 70%, 2000 Ant, WBSPF+PAFs

3C. 15 m, 70%, 2400 Ant, WBSPF+DAA

Sky Brightness (60°) [K]

SKA TDP Antenna OpticsTsys for a 15m Ø Dish, A =70%

0.5 0.7 1.5 3.0 10.00.2

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Frequency

Aeff/Tsys

Diameter

Optics

Frequency

0.07 0.2 0.5 0.8 1.5 10 GHz

0.5 GHz 10 GHzUWB Feeds

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Frequency

Aeff/Tsys

Diameter

Optics

Frequency

0.5 GHz 10 GHz

UWB Feeds0.07 0.2 0.5 0.8 1.5 10 GHz

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Frequency

Aeff/Tsys

Diameter

Optics

Frequency

1.0 GHz 10 GHz

0.3 3 GHzRoom Temp

Cooled

0.5 GHz 10 GHz

UWB Feeds0.07 0.2 0.5 0.8 1.5 10 GHz

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Frequency

Aeff/Tsys

Diameter

Optics

Frequency

1.0 GHz 10 GHz

0.3 3 GHzRoom Temp

Cooled

0.5 GHz 10 GHz

UWB Feeds0.07 0.2 0.5 0.8 1.5 10 GHz

6 8 10 12 14 16 Ø [m]

10 m 16 m

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Frequency

Aeff/Tsys

Diameter

Optics

Frequency

1.0 GHz 10 GHz

0.3 3 GHzRoom Temp

Cooled

0.5 GHz 10 GHz

UWB Feeds0.07 0.2 0.5 0.8 1.5 10 GHz

6 8 10 12 14 16 Ø [m]

10 m 16 m

Survey SpeedPoint Source

Sensitivity

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0

1000

2000

3000

4000

5000

6000

7000

8000

0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70

Frequency [GHz]

To

tal

Aef

f /T

sys

[m2 /K

]

6m, -10dB@60°6m, -11dB@60°6m, -12dB@60°6m <Aeff/Tsys>8m, -10dB@60°8m, -11dB@60°8m, -12dB@60°8m,<Aeff/Tsys>12m, <Aeff/Tsys>

N=4500 N=4500

Prime Focus Aeff/Tsys vs. Frequency

for Na=4500

Reflector 12m

Reflector 6m

Reflector 8m

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SKA TDP Baseline Antenna Optics for Dishes + WBSPF

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SKA TDP Reflector + WBSP Feed Baseline Optics Design Plan

• Baseline Optics Designs that uses WBSPF• Diameter: 12 m to 16 m• Frequency: < 0.5 GHz to 10 GHz• 1st Step: Optimized Aeff/Tsys Optics Design

for a Symmetric Configuration:– Prime Focus WBSPF: 0.3 GHz to 3 GHz– Secondary Focus WBSPF: 1 to 10 GHz

• 2st Step: Optimized Aeff/Tsys Optics Design for a Off-axis Configuration

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SKA TDP Reflector + WBSP Feed Optimized Prime Focus

16 m

• Diameter: 16 m• WBSPF 0.3 to 3 GHz• f1/D Optimized for for

Aeff/Tsys

12 m

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SKA Symmetric AntennaAeff/Tsys Prime focus Optimization using UWB FeedSKA Symmetric Antenna

TRW Aeff/Tsys Prime Focus optimization (Ta at 45°, Trx=10K, Freq: 0.5 GHz to 2.5 GHz)

-8

-7

-6

-5

-4

-3

-2

-1

0

0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70

Paraboloid f/D

Ap

ert

ure

Eff

icie

nc

y [

dB

]

Aperture Efficiency (Freq Ave)

gcm

(TA@45°, Trx=10K, Freq: 0.5 GHz to 2.5 GHz)

53°

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SKA Symmetric AntennaTRW Aeff/Tsys Prime Focus optimization

(Ta at 45°, Trx=10K, Freq: 0.5 GHz to 2.5 GHz)

-8

-7

-6

-5

-4

-3

-2

-1

0

0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70

Paraboloid f/D

Ap

ertu

re E

ffic

ien

cy [

dB

]

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Aef

f/T

sys

[m

^2/

K]

Aperture Efficiency (Freq Ave)Aeff/Tsys at 1.4 GHzAeff/Tsys (Freq Ave)

gcm

SKA Symmetric AntennaAeff/Tsys Prime focus Optimization using UWB Feed

(TA@45°, Trx=10K, Freq: 0.5 GHz to 2.5 GHz)

53°64°79°

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SKA TDP Reflector + WBSP Feed Optimized Prime Focus

16 m

• Diameter: 16 m• WBSPF 0.3 to 3 GHz• Optimized for for

Aeff/Tsys: f1/D ~ 0.38

12 m

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SKA TDP Reflector + WBSP Feed Optimized Secondary Focus

12 m

• Diameter: 12 m• WBSPF 1 to 10 GHz• Optimized for for

Aeff/Tsys: f2/D > f1/D

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SKA TDP Reflector + WBSP Feed Optimized Secondary Focus

12 m

• Diameter: 12 m• WBSPF 1 to 10 GHz• Optimized for for

Aeff/Tsys: f2/D > f1/D• Shaped Optics is also

an option for this frequency band.

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SKA TDP Reflector + WBSP Feed Optimized Multiple Focus

16 m12 m

• Prime Focus Ø16 m• WBSPF 0.3 to 3 GHz• Optimized for for

Aeff/Tsys: f1/D ~ 0.38

• Secondary Focus Ø12 m• WBSPF 1 to 10 GHz• Optimized for for

Aeff/Tsys: f2/D > f1/D

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SKA Technology Path

TDP WBSP Feeds

Wide Band Feeds

Sinuous/Gnd

QSC Feed

Chalmers

Quad-Ridge

ATA

-7 dB

-6 dB

-14 dB

InputMatch

-8 dB

-10 dB

62°

66°

43°

10dB

65°

65°

30K

45K

TN

4 - 12 GHz

1 - 7 GHz>20:1

~10:1

~8:1

~10:1

~15:1

5:1 10:1 20:1

Bandwidth

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Summary

• We are proposing a Frequency coverage for the SKA TDP that goes from < 0.5 to 10 GHz, and that uses WBSPF + Dishes.

• TDP is going to provide two WBSP feeds that demonstrate the performance of these feeds: – One at room temperature from 0.3 to 3 GHz.– One Cooled feed from 1 to 10 GHz.

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Summary Cont…

• We proposed a dish diameter between 12m to 16 m. And still have to agree in a dish diameter for the electromagnetic analysis.

• We are going to provide an antenna analysis and optimization for baseline symmetric and off-axis prime focus configurations that uses WBSP feeds.

• We are going to analyzed options for secondary or multiple focal point configurations.

• We are going to assess the issue of the far SLL for Dynamic Range.

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End

SKA TDP Antenna Optics

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