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SKA-TDP AWG Antenna Workshop San Francisco, March 13-14, 2008. SKA TDP Antenna Optics. By Germán Cortés M. Cornell University Ithaca NY 14853, USA. National Astronomy and Ionosphere Center. Overview. Introduction SKA TDP Dishes + WBSPF Optics Design Plan

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SKA-TDP AWG Antenna Workshop

San Francisco, March 13-14, 2008

SKA TDP Antenna Optics

By Germán Cortés M.

Cornell University

Ithaca NY 14853, USA

National Astronomy

and Ionosphere Center


Overview

  • Introduction

  • SKA TDP Dishes + WBSPF Optics Design Plan

  • SKA TDP Antenna Work Breakdown

  • SKA TDP Baseline Antenna Optics.

  • Summary


Current SKA TDP Antenna


Current SKA TDP Antenna


SKA TDP Dishes + WBSPF Optics Design Plan


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


WBSP Feed Far Field Radiation Pattern 10 GHz

Co-Pol

Dir = 10.11 dBi

X-Pol

-1.08 dBi


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

    • Matching Optics Parameters


The SKA TDP Reflectors

Possible Configurations

Gregorian is Preferred

Symmetric Reflector

Off-Axis Reflector


SKA TDP Reflector + WBSP Feed Optics Design Plan

  • 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


8m Reflector+Baseline FeedFar Field Radiation Pattern at 700 MHz

Symmetric Reflector

Co-Pol

Symmetric Reflector

X-Pol


6m Offset Reflector+Baseline FeedFar Field Radiation Pattern at 500 MHz

Off-Axis Reflector

Co-Pol

Off-Axis Reflector

X-Pol


SKA TDP Reflector + WBSP Feed Optics Design Plan

  • 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

  • Matching Optics for Different Configurations

    • Prime Focus

    • Secondary Focus Solutions

    • Multiple Focus Solutions


SKA Offset Design Prime Focus: Wide Pattern Wide Band FeedFreq= 1.400 GHz, f=5.2m

-42.9 dB

-42.9 dB

-39.1 dB

-33.9 dB

-14.2 dB

-40.8 dB

Co-Polar Wide Pattern

X-Polar Wide Pattern


Far Field Radiation Patterns including Quadrupod Strut Diffraction Effects

-126 dB

-46 dB

-152 dB

-46 dB

=178°

=82°

=180°

=82°

-85 dB

-123 dB

-45 dB

-73 dB

=106°

=106°

=14°

=14°

Wide Pattern 1.3 GHz

Wide Pattern 32 GHz


SKA TDP Reflector + WBSP Feed Optics Design Plan

  • 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

  • Matching Optics for Different Configurations

    • Prime Focus

    • Secondary Focus Solutions

    • Multiple Focus Solutions


The SKA TDP Reflectors

Possible Configurations

Gregorian

Off-Axis


SKA TDP Reflector + WBSP Feed Optics Design Plan

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


SKA TDP Antenna Work Breakdown


SKA TDP Antenna Work Breakdown

Science

Data

Transport

Monitoring

&

Control

UWB Feeds

Power

Optics

Reflector

Mount

Pedestal

Foundation


SKA TDP Antenna Work Breakdown

UWB Feeds

Science

Data

Transport

Optics

Monitoring

&

Control

Power

Reflector

Mount

Pedestal

Foundation


SKA TDP Antenna Work Breakdown

UWB Feeds

Optics

Reflector

Mount

Monitoring

&

Control

Power

Science

Data

Transport

Pedestal

Foundation


SKA TDP Antenna Work Breakdown

UWB Feeds

Optics


SKA TDP Antenna OpticsSpecification

UWB Feeds

Optics

Aeff/Tsys

Frequency

Diameter


SKA Dishes+WBSPF Technology Paths

Frequency

0.07 0.2 0.5 0.8 1.5 10 GHz

1

AA’s

Dishes

Ø15m

+ WBSPF

2

AA’s

PHASE II

3b

1.5 GHz 10 GHz

PAF’s

3c

3a

Preliminary Specifications for the Square Kilometer Array

v2.7.1 Dec. 4 2007


SKA Dishes+WBSPF Technology Paths

Frequency

0.07 0.2 0.5 0.8 1.5 10 GHz

1

AA’s

Dishes

Ø15m

+ WBSPF

2

AA’s

PHASE II

3b

1.5 GHz 10 GHz

PAF’s

3c

AA’s

0.8 GHz 10 GHz

3a

Preliminary Specifications for the Square Kilometer Array

v2.7.1 Dec. 4 2007


SKA Dishes+WBSPF Technology Paths

Frequency

0.07 0.2 0.5 0.8 1.5 10 GHz

1

AA’s

Dishes

Ø15m

+ WBSPF

2

AA’s

PHASE II

3b

1.5 GHz 10 GHz

PAF’s

3c

AA’s

0.8 GHz 10 GHz

3a

0.5 GHz 10 GHz

Preliminary Specifications for the Square Kilometer Array

v2.7.1 Dec. 4 2007


SKA Dishes+WBSPF Technology Paths

Frequency

0.07 0.2 0.5 0.8 1.5 10 GHz

1

AA’s

Dishes

Ø15m

+ WBSPF

2

A

Tsys

NII

AA’s

2000

PHASE II

3b

1.5 GHz 10 GHz

70%

30K

PAF’s

2400

3c

AA’s

0.8 GHz 10 GHz

70%

30K

3000

3a

0.5 GHz 10 GHz

70%

30K

Preliminary Specifications for the Square Kilometer Array

v2.7.1 Dec. 4 2007


SKA TDP Antenna OpticsAeff/Tsys Point Source Sensitivity

0.2

0.5

0.7

1.5

3.0

10.0

Aeff/Tsys [m2/K]

Preliminary Specifications for the Square Kilometer Array

v2.7.1 Dec. 4 2007


SKA TDP Antenna OpticsAeff/Tsys Point Source Sensitivity

0.2

0.5

0.7

1.5

3.0

10.0

Aeff/Tsys [m2/K]

SKA TDP


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

0.2

0.5

0.7

1.5

3.0

10.0

SKA TDP


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

0.2

0.5

0.7

1.5

3.0

10.0


SKA TDP Antenna OpticsSpecification

Frequency

0.07 0.2 0.5 0.8 1.5 10 GHz

UWB Feeds

0.5 GHz 10 GHz

Optics

Aeff/Tsys

Frequency

Diameter


SKA TDP Antenna OpticsSpecification

Frequency

UWB Feeds

0.07 0.2 0.5 0.8 1.5 10 GHz

0.5 GHz 10 GHz

Optics

Aeff/Tsys

Frequency

Diameter


SKA TDP Antenna OpticsSpecification

Frequency

UWB Feeds

0.07 0.2 0.5 0.8 1.5 10 GHz

0.5 GHz 10 GHz

Optics

Room Temp

0.3 3 GHz

Cooled

1.0 GHz 10 GHz

Aeff/Tsys

Frequency

Diameter


SKA TDP Antenna OpticsSpecification

Frequency

UWB Feeds

0.07 0.2 0.5 0.8 1.5 10 GHz

0.5 GHz 10 GHz

Optics

Room Temp

0.3 3 GHz

Cooled

1.0 GHz 10 GHz

Aeff/Tsys

6 8 10 12 14 16 Ø [m]

Frequency

10 m  16 m

Diameter


SKA TDP Antenna OpticsSpecification

Frequency

UWB Feeds

0.07 0.2 0.5 0.8 1.5 10 GHz

0.5 GHz 10 GHz

Optics

Room Temp

0.3 3 GHz

Cooled

1.0 GHz 10 GHz

Aeff/Tsys

6 8 10 12 14 16 Ø [m]

Frequency

10 m  16 m

Diameter

Survey Speed

Point Source

Sensitivity


Prime Focus Aeff/Tsys vs. Frequencyfor Na=4500

Reflector 12m

Reflector 8m

Reflector 6m


SKA TDP Baseline Antenna Optics for Dishes + WBSPF


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


SKA TDP Reflector + WBSP Feed Optimized Prime Focus

  • Diameter: 16 m

  • WBSPF 0.3 to 3 GHz

  • f1/D Optimized for for Aeff/Tsys

12 m

16 m


SKA Symmetric AntennaAeff/Tsys Prime focus Optimization using UWB Feed

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

53°


SKA Symmetric AntennaAeff/Tsys Prime focus Optimization using UWB Feed

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

79°

64°

53°


SKA TDP Reflector + WBSP Feed Optimized Prime Focus

  • Diameter: 16 m

  • WBSPF 0.3 to 3 GHz

  • Optimized for for Aeff/Tsys: f1/D ~ 0.38

12 m

16 m


SKA TDP Reflector + WBSP Feed Optimized Secondary Focus

  • Diameter: 12 m

  • WBSPF 1 to 10 GHz

  • Optimized for for Aeff/Tsys: f2/D > f1/D

12 m


SKA TDP Reflector + WBSP Feed Optimized Secondary Focus

  • 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.

12 m


SKA TDP Reflector + WBSP Feed Optimized Multiple Focus

  • 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

12 m

16 m


SKA Technology Path

TDP WBSP Feeds

Wide Band

Feeds

Bandwidth

10dB

TN

Input

Match

5:1 10:1 20:1

62°

Chalmers

~10:1

-7 dB

4 - 12 GHz

66°

30K

Quad-Ridge

~8:1

-6 dB

65°

Sinuous/Gnd

~10:1

-8 dB

65°

QSC Feed

-10 dB

~15:1

1 - 7 GHz

43°

45K

ATA

>20:1

-14 dB


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.


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.


End


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