Outline Introduction: SKA & Phased Array Feeds (PAFs) PAFs: - - PowerPoint PPT Presentation

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Outline Introduction: SKA & Phased Array Feeds (PAFs) PAFs: - - PowerPoint PPT Presentation

May 13, 2023 104 likes •363 views

I NTEGRATED C OHABITATION OF M ULTIPLE M INIATURE A NTENNAS Presented by: Raheel M. Hashmi PhD Student, 42664675 Supervised by: Prof. Karu P. Esselle Department of Engineering Macquarie University, Sydney 13 th June 2012 1/24 Outline

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INTEGRATED COHABITATION OF MULTIPLE MINIATURE ANTENNAS

Presented by:

Raheel M. Hashmi

PhD Student, 42664675

Supervised by:

  • Prof. Karu P. Esselle

Department of Engineering Macquarie University, Sydney 13th June 2012

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  • Introduction: SKA & Phased Array Feeds (PAFs)
  • PAFs: What? Why? Limitations?
  • EBG Structures: A Possible Remedy
  • Research Objectives & Outcomes
  • Project Plan & Progress
  • Conclusions

Outline

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Square Kilometer Array

  • To be the largest Radio Telescope in history
  • Location: Australia, New Zealand & South Africa
  • Reflector dishes & aperture arrays over 3000 KMs
  • Revolutionary discoveries in astronomical science
  • Unparalleled Scalability
  • Scaling current technology: Not Feasible!!
  • High design complexity & cost barriers
  • Main Objectives:
  • Large Collecting Area
  • Greater Field-of-View

ASKAP Antennas at Murchinson Radio Observatory

(Courtesy: ATNF, CSIRO)

Australia’s Telescope Compact Array

(Courtesy: ATNF, CSIRO)

Smart Feeds: Multi-Beam Phased Array Feeds (PAF)

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Artist’s Impression of SKA dishes spread over the Radio-Quiet zone in Western Australia

(Courtesy: Swinburne Astronomy Productions/SKA)

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Phased Array Feeds Designs

BYU/NRAO Dipole Feed

  • BYU/NRAO, USA
  • Thickened Dipoles
  • Linear Polarization
  • Frequency Ratio 1.3:1

Checker-Board Connected Array

  • CSIRO, Australia
  • Planar Connected Arrays
  • Dense Focal Plane Sampling
  • Orthogonal Polarizations
  • Frequency Ratio 2:1
  • Simple & Low-cost Structure

Phased Array Feed Demonstrator

  • DRAO, Canada
  • ASTRON, the Netherlands
  • Vivaldi Elements
  • Dense Focal Plane Sampling
  • Orthogonal Polarization
  • Frequency Ratio 3:1
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  • Introduction: SKA & Phased Array Feeds (PAFs)
  • PAFs: What? Why? Limitations?
  • EBG Structures: A Possible Remedy
  • Research Objectives & Outcomes
  • Project Plan & Progress
  • Conclusions

Outline

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  • Wide-Angle High-Resolution Radio Camera
  • A Phased Array Feed offers:
  • Adaptive Multi-beam Receiver (Multi-Pixel Feed)
  • Complete coverage of available Field-of-View
  • Sensitivity & Survey Speed (SVS) greater than Single-Pixel Feed
  • Improved Radiation and Aperture Efficiencies
  • Governing Factors (B. D. Jeffs et al., 2009):

SVS/unit Cost  max.(SVS) & min.(Cost) SVS  Nb . b . B . (Aeff/ Tsys)2

Why PAFs?

Model of PAF illuminating a Reflector Dish

(B. D. Jeffs et al., 2009)

(a) Primary pattern of reflector (b) Feed pattern by PAF

(B. D. Jeffs et al., 2009)

  • No. of

beams Solid angle per beams System Bandwidth Effective Aperture / System Temperature Sensitivity

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  • Constraints
  • No. of Beams (Nb)  Signal Processing  : tradeoff relationship 
  • System Bandwidth (B)   Cost  : strictly constrained variable 
  • Beam Solid Angle (b)   Field of View  : controllable but design-time variable 
  • Effective Aperture (Aeff)   Reflectors  & Effective Illumination  : controllable variable 
  • System Temperature (Tsys)   Design Complexity  & Cost  : controllable variable  & 
  • Objective

“Maximize Sensitivity of Radio Telescope”

Design Constraints & Objectives

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Mutual Coupling & Tsys

System model of Phased Array Feed based receiver

(K. F. Warnick et al., 2009: BYU/NRAO Arecibo Telescope Progress)

  • LNA’s inherent noise: <50 Kelvin (strictly ) requirement for radio astronomy
  • Inter-Channel mutual coupling
  • Independent LNA design: Insufficient!!!
  • Result: Decreased Sensitivity
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Scan Blindness & Surface Waves

  • Physically: Common-Mode Currents (CMC)
  • Differential Beam-Forming with Common-Mode loading
  • Large input mismatch at certain scanning angle
  • Scan Blindness: What and When?
  • Floquet Mode = Propagation Const. of supported Mode

Common-mode currents on Connected Array at 1.7 GHz (above) and 0.9 GHz (below)

(S. G. Hay and O’Sullivan, 2008)

For a function ‘R’ periodic in ‘z’ with period ‘L’: R(z) = e-jz U(z)  R(z + L) = e-j(z+L) U(z + L)  by Fourier Series l.h.s. becomes e-jz U(z) =  An e-j(2πn/L)z . e-jz R(z) =  An e-jnz : n =  + 2πn/L n  , L   i.e. periodicity breaks

(B. Munk, 2009)

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  • Introduction: SKA & Phased Array Feeds (PAFs)
  • PAFs: What? Why? Limitations?
  • EBG Structures: A Possible Remedy
  • Research Objectives & Outcomes
  • Project Plan & Progress
  • Conclusions

Outline

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  • Engineered materials designed to have structural periodicity

– Originally a domain of Solid State Physics – Composed of metal, dielectrics, or both – Assist/ Impede flow of EM waves of certain wavelengths – Periodicity on the order of half-wavelength or more

  • Applications

– High Gain & Directive Antennas – Frequency Selective Surfaces (FSS) – Waveguides & Filters – High-Impedance Loading

Electronic Band-Gap Structures

1D, 2D and 3D EBG Structures

(Joannopolous et al., 2008)

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Applications

Partially Reflective Surfaces: Metallic Loading

(A. P. Feresidis et al., 2005)

Frequency Selective Surface

(B. Munk, 2000)

High Impedance Ground Plane

(R. F. J. Broas et al., 2005)

Optimized PRS-EBG Resonator Antenna

(Y. Ge et al., 2007)

High Gain 1-D EBG Resonator Antenna

(A. R. Wiley et al., 2005)

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  • Defect-Mode Transmission Model (Jecko B. et al., 2007)
  • Fabry-Perot Cavity Model (Y. Ge et al., 2012)
  • Gain & Directivity Enhancement
  • Tangential dimensions of EBG Layer
  • Cavity Height
  • Magnitude & Phase of cavity reflection coefficient
  • Capacitive/Inductive loading of EBG layers
  • Current Issues:
  • Narrow radiation bandwidth (~300 – 700 MHz)
  • Limited Beam-Steering support (~20-30 degrees)

Band-Gap Theory

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  • Introduction: SKA & Phased Array Feeds (PAFs)
  • PAFs: What? Why? Limitations?
  • EBG Structures: A Possible Remedy
  • Research Objectives & Outcomes
  • Project Plan & Progress
  • Conclusions

Outline

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  • Enhance radiation bandwidth of EBG resonant structures

– Engineering reflection phase gradient of the Partially Reflecting Surface (PRS) by loading – Multivariable Optimization for PRS loading patterns

  • Eliminate Scan Blindness & Mutual Coupling

– Applying high-impedance loading for CMC suppression – Evaluating EBG superstrate effects for distant placement of elements

  • Conserve planar low-cost structural advantage
  • Increase array gain & beam steering angle
  • Extract empirical models to assist design processes
  • Integrating the findings to develop EBG focal plane array prototype

Research Objectives

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  • Wide Radiation Bandwidth of EBG-PRS Resonant Structures
  • Improved Radiation Efficiency
  • Higher Reflector Illumination Effeciency
  • Suppression of Surface Currents  Less Power Transfer Mismatch
  • Reduction of Noise Increased Sensitivity
  • Possibility to use Sparse Arrays for dense sampling

Expected Outcomes

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  • Introduction: SKA & Phased Array Feeds (PAFs)
  • PAFs: What? Why? Limitations?
  • EBG Structures: A Possible Remedy
  • Research Objectives & Outcomes
  • Project Plan & Progress
  • Conclusions

Outline

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Project Milestones

Period Milestones From To

Mar 2012 Aug 2012 Extensive Literature Review & Skill Enhancement Sep 2012 Feb 2013 Achieving Wide Radiation Bandwidth for EBG Structures Mar 2013 Aug 2013 Elimination of Scan Blindness & Mutual Coupling Sep 2013 Nov 2013 Formulating Analytical Basis & Data Reorganization Dec 2013 Mar 2014 Optimizing EBG structures for Gain Enhancement & Beam Steering Apr 2014 Aug 2014 Fully integrated PAF design verification and prototype fabrication Sep 2014 Feb 2015 Experimental measurements of prototype and Thesis development Mar 2015 Thesis submission & Examination

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Delivery Schedule

Deadline Deliverable Aug 2012

Detailed Research Proposal

Feb 2013

Prototype A: Wide Radiation Bandwidth EBG surfaces

Feb 2013

Reporting results in IEEE Conferences

Aug 2013

Prototype B: EBG Focal Plane Array free of Scan Blindness & Mutual Coupling

Dec 2013

Empirical Models for Trend Analysis

Jan 2013

Reporting results in IEEE Letters/Journals

Aug 2014

Prototype C: Fully Integrated and Optimized Focal Plane Array

Dec 2014

Reporting of results in IEEE Conferences/Journals

Mar 2015

Thesis Document

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High-Level Execution Plan

Years

1 2 3

Months 1-3 4-6 7-9 10-12 13-15 16-18 19-21 22-24 25-27 28-30 31-33 34-36 Literature Review Software Training Simulation Development Investigative Analysis Physical Measurements EBG Incorporation Formalization & Optimization Gain Enhancement Prototyping & Fabrication Thesis Development Publication Process

Project Kick-off: 1st March 2012 Project Completion: 30th March, 2015

We are here

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  • Introduction: SKA & Phased Array Feeds (PAFs)
  • PAFs: What? Why? Limitations?
  • EBG Structures: A Possible Remedy
  • Research Objectives & Outcomes
  • Project Plan & Progress
  • Conclusions

Outline

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  • Square Kilometer Array (SKA) & Phased Array Feeds (PAF)
  • Adaptive Multi-beam Receiver & Benefits
  • Limitations of PAFs & Current Research Focus
  • Objective: Maximize Sensitivity
  • Electronic Band Gap (EBG) Structures
  • Analytical Models
  • Planar EBG Structures in PAFs
  • Overcoming limitations, improving performance, conserving cost & simplicity
  • Contribution to Science:

“Better feeds for Astronomy to support precise discovery of evolution of Universe & Life”

Conclusions

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Thank you!

Pulsar orbiting a black hole Cosmic Magnetism by Faraday Rotation SKA dishes night impression

Images Credit: Swinburne Astronomy Productions