INTEGRATED COHABITATION OF MULTIPLE MINIATURE...
Transcript of INTEGRATED COHABITATION OF MULTIPLE MINIATURE...
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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
o Location: Australia, New Zealand & South Africa
o Reflector dishes & aperture arrays over 3000 KMs
o Revolutionary discoveries in astronomical science
• Unparalleled Scalability
o Scaling current technology: Not Feasible!!
o 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:
o Adaptive Multi-beam Receiver (Multi-Pixel Feed)
o Complete coverage of available Field-of-View
o Sensitivity & Survey Speed (SVS) greater than Single-Pixel Feed
o 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
o No. of Beams (Nb) Signal Processing : tradeoff relationship
o System Bandwidth (B) Cost : strictly constrained variable
o Beam Solid Angle (b) Field of View : controllable but design-time variable
o Effective Aperture (Aeff) Reflectors & Effective Illumination : controllable variable
o 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)
o Differential Beam-Forming with Common-Mode loading
o Large input mismatch at certain scanning angle
• Scan Blindness: What and When?
o 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-jz U(z) R(z + L) = e-j(z+L) U(z + L)
by Fourier Series l.h.s. becomes
e-jz U(z) = An e-j(2πn/L)z . e-jz
R(z) = An e-jnz : 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
o Tangential dimensions of EBG Layer
o Cavity Height
o Magnitude & Phase of cavity reflection coefficient
o Capacitive/Inductive loading of EBG layers
o Current Issues:
o Narrow radiation bandwidth (~300 – 700 MHz)
o 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)
o Adaptive Multi-beam Receiver & Benefits
o Limitations of PAFs & Current Research Focus
• Objective: Maximize Sensitivity
• Electronic Band Gap (EBG) Structures
o Analytical Models
o 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
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